biomass instal. scottland

BUILDING STANDARDS DIVISION Low carbon equipment and building regulations A guide to safe and sustainable construction Biomass Installations This guidance document is intended to be read in conjunction with the general introduction to low carbon equipment

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Document Version Control

Title: Low Carbon Equipment & Building Regulations: Biomass Installations

Purpose: To provide a guide to safe and sustainable biomass installations

Version Date Notes

1.0 February 2012 Guidance for the installation of woody biomass equipment taking account of the mandatory building standards set by the Scottish Building Regulations.

We acknowledge with thanks the drawings and photographs kindly provided by others.

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Low carbon equipment and building regulations:

A guide to safe and sustainable installation

This chapter is one of a series that provides a basic introduction to different low carbon technologies and describes their relationship to the building regulations in Scotland. It should be read alongside the general introduction to this guide. Biomass Installations

Section 1 INTRODUCTION

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Section 2 WOOD BIOMASS 6

Section 3 LOG BURNING APPLIANCES 15

Section 4 WOODCHIP APPLIANCES 17

Section 5 PELLET BURNING APPLIANCES 20

Section 6 CHIMNEYS AND FLUES 22

Section 7 HEATING SYSTEM CONTROLS 24

Section 8 BUILDING REGULATIONS 27

Appendix A EXPLANATION OF TERMS 37

Appendix B GOOD PRACTICE ADVICE 39

Appendix C WORK NOT REQUIRING A WARRANT

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Appendix D RELEVANT STANDARDS 44

http://www.scotland.gov.uk/Resource/Doc/217736/0097150.pdf

Low carbon equipment and building regulations Biomass

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BIOMASS 1. Introduction

This guidance is one of a series of chapters that provides a basic introduction to different low carbon technologies and describes their relationship to the building regulations in Scotland. In the energy industry, the term biomass includes a wide variety of materials – not just wood. The UK Biomass Task Force defines biomass as: “literally, any biological mass derived from plant or animal matter. This includes material from forests, crop-derived biomass including timber crops, short rotation forestry, straw, chicken litter and waste material” The use of woody biomass, in the form of wood chips, wood pellets, and logs may offer a viable alternative to fossil fuels, particularly in areas not served by gas mains. Biomass heating systems can be a simple stove used to heat a single room or with a boiler to provide hot water and central heating. Wood logs and wood based products can be included as part of a low carbon emissions strategy for buildings. The majority of biomass boilers on sale in the UK, at the scale appropriate to this document, are designed to run on dry and seasoned logs, woodchips and wood pellets. Appliances should be designed in accordance with the British Standards Institution (BS EN or BS) or the Design Guide produced by the Chartered Institution of Building Service Engineers (CIBSE). The types of wood biomass appliances covered are: x Log boilers x Pellet boilers x Wood chip boilers SCOPE OF GUIDANCE This guidance has been prepared with domestic sized installations in mind, with output ratings not more than 50kW. The guidance therefore, may not be relevant to a biomass appliance with an output rating of more than 50kW. It is also important to note that the wood fuel systems discussed within this guide are only space heating and hot water systems. CARBON MONOXIDE Carbon Monoxide (CO) is an extremely poisonous gas that can be present in the fumes from the combustion of fuel burnt under incorrect conditions. The gas cannot be seen, smelt or tasted, making it difficult to detect. Carbon monoxide can kill or cause permanent damage to a person’s health. Initial symptoms include tiredness, drowsiness, headache, nausea and chest pains (similar to flu). To reduce the risk of carbon monoxide poisoning the following should be checked to ensure that: x there is adequate ventilation x there is correct installation of flue liner and chimney x the draught in the flue meets manufacturers recommendations x the correct fuel for the appliance is being used


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x there is regular maintenance, including sweeping chimney and x there is a carbon monoxide detector to alert occupants. HETAS recommends that a Carbon monoxide detector is installed with every solid fuel appliance including existing ones. However the detector must never be considered as a replacement for correct maintenance or chimney sweeping. CLEAN AIR ACT The Clean Air Act allows local authorities to create smoke control areas in which smoke emission is prohibited unless arising from the burning of authorised fuel or from the use of an exempt appliance. Wood fuel can be burnt in a smoke control area, if you use an “exempt” appliance. An “exempt” appliance is one which is permitted to burn unauthorised fuels in smoke control areas. These appliances have passed tests to confirm that they are capable of burning an unauthorised or inherently smoky solid fuel without emitting smoke. EXEMPT APPLIANCES The following website lists the appliances and fuels that are approved for use in smoke control areas and contacts for local authorities - smokecontrol.defra.gov.uk FUELS To burn wood, wood chips and wood pellets in a smoke control area you must use an exempt appliance, as listed in the above link. It is an offence to acquire any unauthorised solid fuel for use in a building in a smoke control area other than in a building or appliance that is exempt. A definition of terms used in this guide can be found in Appendix A.

http://smokecontrol.defra.gov.uk/


WOOD BIOMASS 2. Wood Biomass

The most common biomass used for domestic sized appliances is wood. When used as an energy source wood can be classed as a low carbon fuel because although it emits CO2 during combustion, it absorbs CO2 during growth. Wood is a very versatile fuel which can be burned in many different forms and in a number of appliances. It can be used to heat one or more rooms, a whole house, or to produce hot water and to cook.

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This guidance document looks at biomass in the form of a wood derived fuel. There are three main forms: logs, woodchips and reconstituted fuels such as pellets.

wood burning releases CO2 back

growing trees convert CO2 into plant material

atmosphere CO2

IS WOOD BIOMASS RIGHT FOR ME? Wood biomass may be suitable for you depending on: x building location x space available x position of the fuel store in relation to the boiler x the availability of fuel. For many people in rural Scotland where a backup source of heating in the event of a power-cut is useful, stoves which can burn logs may provide the ideal solution. THE BENEFITS OF WOOD FUEL The benefits of wood fuel as a renewable energy are: Good for the local economy - wood fuel sourced locally can create business opportunities and contribute to the local economy. Security of supply – using wood to heat our buildings diversifies the fuel sources, decreases dependence upon fossil fuel exporting countries and depending on the amount of wood grown can increase the security of our energy supply. Carbon neutral fuel – wood fuel is considered almost carbon neutral due to the short time span of the carbon cycle if the wood is harvested and replanted. The same quantity of atmospheric CO2 is absorbed when the tree is growing as released when the wood is burned. Low carbon process - the emission of carbon dioxide through harvesting, processing and transportation of wood fuel can be minimised by using local production and distribution networks. Contributing to social amenity - parkland, woodland, forestry and agriculture are generally perceived to be environmentally and socially attractive amenities by the UK population, providing opportunities for recreation and leisure activities. The wood fuel industry invests in these sectors.

Low carbon equipment and building regulations Biomass Avoids landfill - recycling and reuse is generally the best environmental option and should ideally be the first choice for use of wood by-products and waste. Where this is not done, the debris left from processing trees and the waste not used as fuel, generating energy, or some other application are often consigned to landfill. This imposes costs for disposal, additional burden on limited landfill resources and also contributes to climate change by the creating landfill gases. These gases include a high proportion of methane (CH4), which has a much higher global warming impact than carbon dioxide.

FUEL TYPES Wood logs - are easily available and are the most common form of wood fuel. Logs have been used for centuries in open fires and more recently in stoves and boilers. The amount of storage required for logs will depend on whether the owner is splitting their own or buying ready prepared logs from a supplier. Log stores should allow plenty of air flow and be designed to protect the logs from rain. The moisture content of logs can have a considerable effect on the useful heat yield. Between 35% and 60% of the weight of freshly felled (green) wood can be water therefore, it is important that logs are allowed to ‘dry’ or ‘season’ to reduce the moisture content. For successful burning, the moisture content should be below 25% so it is advisable to have covered storage facilities for at least one year's worth of fuel to allow for seasoning. As the moisture content in the wood increases the amount of useful energy available from the wood decreases; as energy is used up to drive off the excess moisture. At 60% moisture, wood can have an energy content of typically 1.7kWh/kg, but at 25% moisture this can increase to 4kWh/kg. Burning wet wood will result in a fire that smoulders and creates a lot of tar, steam and smoke. This can result in corrosion and condensation problems in boilers and flues and reduce the amount of heat produced. This applies to both log burning boilers and stoves. Unburned fuel can result in tar like deposits on the lining of the chimney thus contributing to the risk of chimney fires. It can also be detrimental to the visual look of a stove as burning wet wood can blacken the glass at the front of the stove. Wood Chips - are made from whole trees, branch wood or coppice products which have been mechanically shredded by a chipping machine. Wood chips are bulky and sufficient storage and delivery access needs to be considered when designing a heating system with this type of fuel. They are normally stored in a bunker or silo designed so that the chips can be tipped in. The chips are then fed by an auger to the boiler. Transport costs can be high, but if wood chip is sourced within a 20 miles radius it can be a very cost-effective fuel.

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Low carbon equipment and building regulations Biomass For most users and suppliers of wood chips the two parameters that are critical to efficient, trouble free operation of the appliance are moisture content and chip sizes. Wet wood chips have a lower energy content (lower calorific value) than dry wood chips. Chips with a moisture content greater than 30% should be stored in a ventilated area to allow for seasoning. The wood species used also has a bearing on the calorific value of the chips, with hardwood chips having a higher calorific value than softwood. Heaps of wood chips can be very difficult to dry and should therefore be ideally dried as logs and chipped once the wood is at the target moisture content. Wood Pellets - are a type of wood fuel generally made from highly compressed waste sawdust. Because they are compressed they need less storage space and are easier to handle. They are usually produced as a by-product of sawmilling and other wood transformation activities. The materials used, include ground woodchips, sawdust and bark however, pellets can be made from practically any biomass material including straws, grasses, energy crops etc. No chemical additives are needed, the properties within the wood itself serves as a binder, although sometimes small quantities of maize starch are added to improve binding. As with logs and chips, storage has to be considered; a whole house size wood pellet boiler uses up to 10m3 or 6.5 tonnes per year. Depending on the heat loss from a house, a stove which heats only one room is unlikely to use more than a tonne a year. Pellets can be delivered in pre-packed bags or by bulk tanker delivery. With bulk storage, dust may accumulate creating health and safety and operational hazards. The pellets are extremely dense and can be produced with a low humidity content (about 6% to 10%) this allows them to be burned with a very high combustion efficiency. There are only minor energy losses due to the need to burn off the moisture content.

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http://en.wikipedia.org/wiki/Wood_fuel

http://en.wikipedia.org/wiki/Sawdust

http://en.wikipedia.org/wiki/Sawmill


CHOOSING THE RIGHT TYPE OF FUEL

Description Storage Advantages Disadvantages

Logs - usually seasoned for up to 2 years to decrease moisture content. Suitable for small to medium appliances

During seasoning store under cover with good air circulation. Keep dry

Familiar fuel, which can be used on domestic fires, stoves and wood burners

Not as suitable for automatic feeds. Log burners require regular de-ashing. Large storage space may be required

Wood Chips - Depending on the moisture the chips can be: wet: moisture content > 30% dry: moisture content < 30% More suitable for larger installations e.g. over 25kW output

Keep dry, store as loose piles Covered open air storage is preferable

More suited to automatic handling More efficient combustion Cheaper than pellets

Moisture content > 30% results in a lower net calorific value. When storing over long periods high moisture wood degrades quickly which can result in risk of self heating and potential spontaneous combustion. Turning over of stockpiles is necessary to avoid build up of heat

Wood Pellets - usually referred to by the diameter of the pellets, typically between 4-10mm. They should be clean, pleasant smelling and smooth to touch Suitable for small to medium appliances

Keep dry, stored under cover, preferably in enclosed areas

Generally good storage characteristics Low moisture content Can be shipped in bulk. Good combustion characteristics

Pellets must be kept dry as exposure to water will breakdown pellets and cause them to swell considerably Can degrade to saw dust as a result of excessive, or poorly designed, mechanical handling processes If breakage of pellets does occur levels of dust can rise dramatically. In the most severe cases this has the potential to create a dust explosion hazard

FACTORS TO BE CONSIDERED When considering what is the most suitable appliance for a particular building there are many factors that will influence the choice, including the location and the need for additional building work. For most houses, equipment and storage space needs to be compact and easy to maintain. Logs or pellets may be best suited as they can be more easily accommodated. Other factors to take into account are: x the source of fuel and the delivery method x installations inside Smoke Control Areas must only be of ‘exempt appliances’ x owners of wood fuel boilers where the burn rate exceeds 45.4kg/hr must apply to

the local authority for chimney height approval x storage facilities x suitably sized log stores will be required to dry wood during the summer x water heating stoves have higher installation costs than room heating stoves. 9

Low carbon equipment and building regulations Biomass COMBINED SYSTEMS (central heating) The most economic and effective system to realise a fully low carbon heating system for single family houses is at present, the combination of a wood biomass boiler, a water tank and solar thermal collectors (2-3m³) (see also the low carbon equipment chapter - Solar thermal systems or solar hot water (SHW)). In summer the solar system provides hot water and stores it in the tank. BOILER SIZING Similar to other solid fuel systems, wood biomass systems do not respond well to varying loads or long periods of low load. Therefore to get the best out of the system it should be operated relatively continuously between 30% and 100% of its rated output. This is because if used as part of a combined heating and hot water system, more energy (heated water) will be produced during the combustion process than may be required at that time. A heat store (highly insulated heat storage tank) is useful for accommodating this excess energy (heated water) for use at different times during the day.

The correct sizing of a wood biomass system is essential in helping reduce waste, cost and providing a comfortable environment. The sizing of an appropriate boiler should be carried out by a qualified heating engineer. However, there are a couple of methods and online calculators for roughly establishing the boiler output required. The following is an example of one of these methods.

To produce a room temperature of around 21º Celsius, when the outside temperature is minus 1º Celsius, you will need about 1kW of heat for every 14 cubic metres of an average insulated space. 1kW is the equivalent of approximately 1 bar of an electric fire.

EXAMPLE To establish the output of the wood burning stove required to heat a room, ascertain the cubic capacity of the room in m3, the kilowatt requirement is then calculated by dividing this figure by 14. VARIABILITY DEPENDING ON INSULATION These calculations are based on heating a room which has been averagely insulated (1990s or earlier). To calculate the kW requirement for a poorly insulated room (1950s or earlier) divide m3/10. To calculate the kW requirement for a room constructed to comply with current energy efficiency standards divide m3/24. Worked example - a room 5 metres wide, 3 metres long and 2.4 metres high will have a cubic capacity of 36m3. The required output in kW for the boiler would be 36/14 = 2.57. A stove with 3 kW output would adequately heat this room.

A higher output stove may be required if the room has, stairs leading off it, is badly insulated, or has lots of windows/external doors. The actual size of the appliance will not only vary depending on the insulation but also, the exposure of the room, the temperature requirements, the geographical 10

http://www.scotland.gov.uk/Topics/Built-Environment/Building/Building-standards/publications/pubtech/techlceqshw

Low carbon equipment and building regulations Biomass location and the amount of time it will be used. Specialist advice should be sought before a final decision is taken. The rated output of each appliance is based on the performance of the appliance when tested using a standard test fuel and with all doors closed. Appliances are tested to BS EN 13240 if they are conventional room heaters/stoves burning wood logs and/or smokeless fuels and to BS EN 14785 if designed to burn mechanically fed wood pellets. STORAGE The storage facilities for the fuel can be a significant proportion of the overall capital cost of a system. It is important that careful consideration is given to the design of such facilities so that there is sufficient storage space for the fuel, appropriate access to the boiler for loading and a local fuel supplier. There is considerable variation between the amount of storage needed depending on the different boiler systems and fuels such as wood pellets. Sufficient storage is needed to avoid frequent transport deliveries which would reduce the carbon savings generated from using biomass. The main factors that influence the choice of storage are: x type of fuel and appliance x quantity of fuel required depending on heat demand x frequency of deliveries x space available and x vehicle and handling equipment available. VOLUME OF STORAGE REQUIRED

Courtesy of Forestry Commission

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Low carbon equipment and building regulations Biomass To calculate the storage area necessary for the particular fuel type, the following information is required: x Energy demand x Calorific Value of the fuel x Density of the fuel Fuel consumption (kg) = Energy demand (kWh)/Calorific value (kWh/kg) Fuel volume (m3) = Fuel consumption (kg)/Fuel density (kg/m3)

EXAMPLE Calculate the storage volume required for wood pellets if: x The annual heat requirement is 24000kWh and the coldest monthly heat

requirement is 4000kWh x Wood pellets density is 600kg/m3 x Wood pellets calorific value is 5kWh/kg x Pellets are delivered on a monthly basis Worked Example: x Calculate the fuel consumption (FC) for the coldest month

FC = 4000kWh/5 kWh/kg = 800kg/ month x Calculate the fuel volume (FV) required

FV = 800kg/600 kg/m3 = 1.33m3

The store volume required would be 1.33m3

OTHER FACTORS Due to the cost of delivery it is usually prudent to order a minimum of 3 tonnes of wood chips. Calculating the storage volume for logs is more problematic as the sizes are not always consistent. If a hopper is used for storing wood fuel, it is best if it can be attached to the outside of the building in an accessible location, or in an underground lined pit. The following table provides details on the size of storage for different fuel types based on a 3 month delivery cycle to minimise the number of deliveries. Advice on the sizing of storage for woody biomass fuel for larger buildings is given in the non-domestic Technical Handbook.

Bulk woody biomass fuel storage: 100% primary heating and DHW Dwelling size Wood pellets Wood chips Logs - stacked

< 80 m² 1.5 m³ 3.5 m³ 3 m³

80 -160 m² 2 m³ 5 m³ 4 m³

> 160 m² 3 m³ 6 m³ 5 m³

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Low carbon equipment and building regulations Biomass In some dwellings the stove may only be used to provide secondary heating. The following table provides details on size of storage based on a 6 month delivery cycle.

Bulk woody biomass fuel storage: secondary heating Dwelling size Wood pellets Wood chips Logs - stacked

< 80 m² 0.3 m³ (9 bags) 1 m³ 0.5 m³

80 -160 m² 0.5 m³ (13 bags) 1.5 m³ 1 m³

> 160 m² 0.7 m³ (16 bags) 2 m³ 1 m³

SELECTING THE RIGHT FIREWOOD SUPPLIER Environmentally, it is preferable to select a local supplier as this limits the energy/emissions required to transport fuel. Using a local source where possible, can result in local investment and employment, it also has the potential to create and sustain jobs in rural areas. There are various factors which could influence the choice of supplier: x does the wood supply come from a sustainable source? x what type of wood is being supplied – hardwood, softwood or a mixture of both? x will the wood fuel suit the appliance? x is it possible to buy the wood by volume rather than weight? (as this removes the

influence of moisture content). UNAUTHORISED FUELS Burning certain wood fuel types can affect the amount of tar and deposits which build up on your chimney and release noxious chemicals into smoke. The materials should be avoided for combustion as they can emit unpleasant odours, generate emissions that damage the environment and are harmful to health: x varnished or plastic-coated wood x wood treated with preservatives x household waste x garden waste AMOUNT OF ENERGY (calorific value) Energy density - the term 'energy density' refers to the energy contained in a fuel per unit weight. The energy density of fossil fuels such as coal, oil and gas are considerably higher (up to three times) than that of wood biomass fuels such as pellets or chips.

Indicative Calorific Values of Wood Biomass

Particle size Moisture content (%)

Gross Calorific value (MJ/kg)

60 6 Logs �100 mm 25 15 50 8 Chips from fresh

wood 2 – 25 mm (can be graded) 10 17

Wood Pellets 8-10 mm 10 17.5 13

Low carbon equipment and building regulations Biomass CARBON EMISSIONS Research indicates that using wood biomass for heating can give reductions in carbon emissions compared to using other fossil fuel heating fuels. This is dependent on good practice in fuel production, processing and transport, the efficiency of the heating system and the eventual disposal.

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PERFORMANCE The performance of a wood biomass boiler depends upon the type of fuel used. The relationship between the boiler and the fuel is crucial – boilers are usually designed to burn fuel of a specific type and quality. Deviation from the specification without adjustments to the boiler design can lead to poor efficiency and increased emissions of air pollutants.

Comparison of CO2 emissionsFuel kg CO2/kWh Heating oil 0.274 Electricity (standard tariff)

0.517

Mains gas 0.198 Woodchip 0.009 Wood pellets 0.028 Wood logs 0.008


3. Log burning appliances TYPE OF APPLIANCE

Appliances for burning logs are: x open fires x stoves (includes ranges) x log boilers OPEN FIRES These appliances are the traditional way of burning logs to provide space heating. Although not renowned for their efficiency, they have a strong amenity value as a feature in a room and a modern fireplace with a well designed grate and flue can make a useful contribution to space heating. For example, many modern designs of fireplaces include chimney dampers to control air flow to the chimney increasing the useful heat output. Some also include a convection chamber which pushes hot air into the room which greatly increases their efficiency. A coal grate may not be suitable for an open fire to burn wood, as a solid base to retain an ash bed is required. STOVES A wood-burning stove is often the simplest and the cheapest way of benefiting from efficient wood heating. Stoves are available in a variety of forms, including cast iron, steel and ceramic. This includes kitchen ranges although relatively few are specifically designed for wood-burning and tend to be designed as multi-fuel systems. Although many wood-burning stoves only heat the room they are in, the higher output versions may have an integral back boiler to provide domestic hot water and if required, central heating.

15Courtesy of Biomass Energy Centre

Low carbon equipment and building regulations Biomass An efficient wood burning stove or boiler produces flue gases that are cooler than an open fire. For this reason it is beneficial to install an insulated liner within an existing chimney when a wood burning stove is installed to ensure that there is a sufficient draw of air. If there is no existing chimney, a wood burning stove or boiler installation is normally fitted with a new system chimney, such as the insulated twin wall type. LOG BOILERS While wood logs are often used in stoves to heat the room they are situated in, they can also heat water for central heating systems, either in a stove with a back boiler or a log burning boiler designed for burning logs. Stoves burning logs often have an efficiency of around 65% however, modern wood log boilers when burned at maximum output can have efficiencies of up to 90%. Log boilers are the least 'automated' of all the wood heating options described here and require refuelling every few hours as well as regular de-ashing. Modern boilers have closely controlled combustion and a high level of efficiency. They are often referred to as log wood gasification boilers where the term ‘gasifying’ means that the wood is superheated, resulting in high efficiency ratings. Boilers can be designed with large combustion chambers to minimise how often they need to be stoked. Log systems however, begin to become impractical for heating requirements over 50kW because of the need to regularly re-fuel.

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WOODCHIP APPLIANCES 4. Woodchip Appliances Woodchip burning technology has been widely developed and adopted in the Nordic countries, North America, Austria, Germany and many other countries. Many decades of development have resulted in robust and reliable systems ranging in size from appliances suitable for a 4 bedroom domestic property up to a power-station. Modern woodchip systems are typically used for larger buildings such as schools or community centres but they are available from 20kW which is suitable for about fifteen radiators. This means that the heating of larger homes is perfectly feasible with wood chip. However, as these boilers require automation to feed the fuel to the burner and need up to three times the storage space required for wood pellets, they might not be cost-effective for a smaller home. The space requirements of wood chip systems also means that their incorporation into existing buildings can be difficult, especially where there is limited access for vehicles. TYPES OF WOOD CHIP BOILERS There are different types of woodchip boilers on the market, which are characterised by the type of combustion and feed mechanisms. The main difference between wood chip and wood pellet systems is the way the chips are fed into the boiler. As the chips do not flow as easily as pellets an agitator is needed to stir the chips to keep them moving through the boiler to the burner. Modern small-scale woodchip heating systems are relatively simple in design and generally contain a woodchip storage hopper and a supply pipe to the burner unit attached to the boiler. Domestic sized appliances will normally use the underfeed burner or the horizontal burner. The three types discussed here are: x underfeed burner x horizontal (stoker) burner x moving grate burner UNDERFEED BURNERS In these systems the chips are fed from the bottom up using an auger system. The primary air is supplied through the ring shaped steel grate with secondary air being supplied from above. While fuel should ideally have a low moisture content this type of burner can accept fuels with a moisture content of up to 50%. The removal of ash from the bottom of the combustion chamber is sometimes by manual intervention, but it is more common to have the ash augured from the bottom of the combustion bed to an external ash bin.

Underfeed burner

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Low carbon equipment and building regulations Biomass HORIZONTAL BURNERS Commonly known as the stoker burner this appliance has a small self-contained fire bed at the end of the fuel feed pipe which is fixed into the base of a boiler-water jacket heat exchanger. A small fan blows air under and over the small heap of wood fuel that is fed by the horizontal auger into the fire bed to produce a large flame which heats the boiler surface and heat exchanger. It is cheaper than the moving grate systems because it is less complicated. Ash is usually removed manually especially on smaller units. Horizontal Burner

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MOVING GRATE BURNER The moving grate burner, (also known as step-grate or inclined grate) is similar to furnaces traditionally designed for coal firing. Woodchip fuel is fed via the hopper and feed pipe onto an inclined fire grate. The grate gently oscillates to move the woodchips down and along as it burns and forced combustion air is fed in underneath the grate. Combustion happens at high temperatures within a ceramic chamber, with a boiler heat exchanger above the firebox. Appliances are made in the full range from 20kW upwards. While fuel should ideally have a low moisture content this type of burner allows wet fuel to self-dry before combustion. Therefore it is less sensitive to fuel moisture content and to a degree fuel quality; this allows it to burn a wide range of fuels of varying moisture content. Once the wood has combusted, the remaining ash falls from the lower end of the grate, and is removed mechanically into the ash pan or bin. Of the three general designs the moving grate burner type is the most complex in construction and generally the most costly. Moving grate plants can use pellets or woodchips, although woodchips are used more commonly because of the capacity of the plants to burn wet fuel. There are 3 main types of moving grate burners, these are: x stepped x tipping x rotating

Low carbon equipment and building regulations Biomass Moving Grate Burner

Feed

Combustion Ceramic

3-section reciprocating

Water

Secondary

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Primary WOODCHIP FUEL Woodchip fuel should: x be uniform in shape and size and suited to the heating appliance x be free of oversize slivers or pieces of twig that could block the automatic feed

system x have a low dust/fines content. Small airborne particles are injurious to health,

reduce the airflow through the chips, and tend to create more fly-ash x be of low moisture content. Woodchip systems are not as sensitive to this as log

fuel systems. Woodchip moisture content below 30% are usually fine, but the ability of each appliance to self-dry the fuel should be assessed.


5. Pellet burning appliances PELLET STOVES Pellet stoves are often designed to be a focal point of a room, giving a direct view of the fire. They are efficient and have a high level of control with automatic operation. Rooms are heated radiantly through the glass door and by heat from the body of the appliance and the boiler. They offer the most user-friendly form of wood heating. These appliances generally have an auto-ignition system using a hot air blower, allowing the stove to be used in conjunction with a heating system programmer and boiler interlock. With thermostatic controls it can automatically stop burning when demand is satisfied or when a time clock turns it off. The controls allow an accurate supply of fuel and combustion air in response to the energy demand. Most stoves have an integral hopper which can normally hold enough pellets for several days burning. They are much easier to control than log burning stoves, and can be left to burn all day with little attendance. Domestic sized stoves are filled by hand using bags of pellets of 15kg upwards. Wood pellet appliances should be tested to BS EN 14785 if designed to burn mechanically fed wood pellets. KEY CHARACTERISTICS The stoves are designed to burn quality pellets to an approved standard. Pellet stoves are generally available with heat outputs between 5kW and 18kW. Careful consideration needs to be given to the flues to ensure they satisfy the building regulations (see section 8). OPERATION OF WOOD PELLET STOVE Wood pellet fuel is loaded into the top of the stove, with a pellet feed auger at the bottom of the hopper. The auger turns and pushes the pellets up into the top of the chamber, where they drop down into the combustion chamber. Once in the combustion chamber ignition is usually by a hot air blower which starts the fire automatically. A combustion fan then feeds the fire with the correct amount of air to achieve maximum combustion efficiency and minimum ash. Secondary air is introduced above to create full combustion of volatile gases resulting in low levels of carbon monoxide and unburned gas. The ash generated from combustion falls through the grate into the ash pan below although because of the high efficiency of the appliance the ash pan may only need to be emptied every two months. 20


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Many units have pressure switches in the flue system to prevent or extinguish combustion if the flue becomes blocked. TOP FEED BURNER This system allows for the accurate feeding of fuel to the combustion chamber and is particularly suited to small appliances with on/off operation. After use the ash needs to be cleaned from the grate. If low quality pellets are used clinkering or slagging of the ash can occur. Wood pellet burning stoves and boilers are designed and constructed to be very efficient with low emissions and high levels of automation. COMBINED HEATING Wood pellet stoves with a back boiler can provide convenient hot water and appliances are available that provide central heating and hot water for all building types. These appliances range from simple 8kW boilers upwards to several hundred kWs.


6. Chimneys Hearths and Flues CHIMNEYS The purpose of a chimney is to take the combustion products (smoke and gasses) from an appliance to the outside air and at the same time, to draw air for combustion into the appliance. This movement of combustion air and exhaust is called draught. For wood burning appliances to work successfully they must be connected to a chimney with a correctly sized flue. For a flue to work properly the hot air must rise. Factors such as running an appliance at a very slow rate or cold air leaking into a flue may cool and slow down the combustion gases which will affect the performance of the chimney. For a chimney to operate satisfactorily it should be smooth internally, warm and as straight as possible. The use of the words 'chimney' and 'flue' can be confusing. BS EN 1443 defines a chimney as 'a structure consisting of a wall or walls enclosing a flue or flues' and a flue as 'the passage for conveying the products of combustion to the outside atmosphere’. For the purposes of the building regulations a 'flue pipe' is defined as a pipe that connects a combustion appliance to the flue in a chimney. See diagram below: Open Fire Example

Gather, lintel and throat above the fireplace recess formed by brick / blockwork or a pre-cast chamber

Flue – the passage through which the products of combustion are discharged to the external air.

Flue Liner – the material which forms the passage through which combustion gases pass

Chimney – the structure that surrounds, carries and supports the flue

Constructional Hearth

Superimposed Hearth

Fireplace Recess






Superimposed Hearth






Superimposed Hearth






Superimposed Hearth





Constructional HearthConstructional Hearth

Superimposed Hearth

Fireplace Recess

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Low carbon equipment and building regulations Biomass If the property does not have an existing chimney then one can often be constructed without too much disturbance. CONSTRUCTION MATERIALS Chimney are generally made of brick or stone but other materials such as metal (system chimney) can also be used. By using a double skin insulated chimney system, a stove can be installed practically anywhere, and no existing chimney is needed to fit the flue system. Modern stove / boiler connection to chimney CONNECTION OF THE APPLIANCE The flue connection should be: x vertical for at least 600mm from a top outlet appliance x no more than 150mm long horizontally from a rear outlet appliance x airtight x no more than 450 from the vertical and x easy to sweep both the connecting flue pipe and chimney. HEARTHS A solid fuel appliance (including wood biomass) should be provided with a solid, non-combustible hearth that will prevent the heat of the appliance from igniting combustible materials. Also any part of a dwelling that abuts or is adjacent to a hearth should be constructed in such a way as to minimise the risk of ignition by direct radiation or conduction from a solid fuel appliance located upon the hearth.

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7. Central Heating Systems and Controls CENTRAL HEATING RELATING TO BIOMASS APPLIANCES The boilers discussed here are for central heating. BS EN 303-5:1999 applies to heating boilers for solid fuels, that are hand or automatically fired with a nominal output of up to 300kW. This covers appliance properties such as performance, efficiency, emissions, thermal output, pressure testing, safety measures and testing. ACCUMULATOR TANK A combined system for both space heating and hot water is likely to generate more energy (heated water) than is required. Therefore, to get the most out of the system it is best practice to store the heated water in a highly insulated heat storage tank, called an accumulator. The tank retains the hot water generated by your heating system for use when you need it.

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Log boiler with thermal store (accumulator) for hot water and central heating

This can be used in log, woodchip or pellet boilers to deliver both central heating and domestic hot water to the house for the rest of the day. A further advantage is that an accumulator tank can be integrated for use with different heat sources. For example the water could be pre-warmed by solar panels, or come from other wood burning stoves, a kitchen range, electric immersion heater or an oil-fired boiler which could also provide a backup heating system.

Typical log burning boiler

Cold water feed

Vent pipe

Log Boiler

Hot water cylinder


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The heat from these systems cannot be turned off immediately so require inbuilt safety devices for heat cut-off or ‘heat dump’ to allow them to be used with sealed type heating systems. HEAT CONTROLS Wood biomass heating systems can be fitted with controls that will enable the generated heat to be directed around the system in accordance with the wishes of the building occupant. All new installations must include heat and safety controls to minimise energy consumption and carbon dioxide emissions and to ensure that the risk of harm to users of a building is limited. Systems must be installed in accordance with the building standards requirements of both Section 6: Energy and Section 3: Environment of the building standards Technical Handbooks. Controls for wood burning biomass systems have three functions: x Safety - they provide additional safety in the event of misuse or mechanical failure x Comfort - to control the comfort level in the building x Efficiency - to reduce energy consumption. Safety functions include: x high limit thermostats to activate the pump if the system gets close to boiling. This

will dissipate the heat x a low limit thermostat to switch the pump off to prevent condensation of the water

vapour in the products of combustion within the appliance and x temperature control of stored hot water or water leaving the store.

The other 2 functions of comfort and efficiency are normally considered together and must satisfy both Section 6: Energy and Section 3: Environment of the Technical Handbooks. In the majority of cases the following should be considered: x the optimum temperature of the water distributed around the system x control of the temperature of the stored hot water and/or the temperature of the

water leaving the hot taps x time control for the operation of the heating system x temperature of the space that is heated and x zoning of the heating system for larger properties.

TIME AND TEMPERATURE CONTROL FOR HEATING SYSTEM A full programmer which can be wired to the pump to control the on/off periods for central heating and hot water is recommended. However, the level sophistication of any time controls should be selected to be compatible with the appliance. It can also be linked to temperature sensors to control the level of comfort. The two main ways of controlling room temperature are: x Thermostatic radiator valves (TRV) – it is important NOT to fit thermostatic valves

to any ‘heat leak’ radiator as it must be able to operate at all times. It is recommended that at least one other radiator is NOT fitted with a TRV to allow heat dissipation in an overheat situation.

Low carbon equipment and building regulations Biomass x Room thermostats – an effective control for a wood biomass system is a room

thermostat. This device monitors the temperature in the room and turns the radiators on and off in order to help maintain the desired temperature and efficiency.

Schematic layout of semi-pumped system

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1. Heating boiler2. Circulator and isolating

valves3. Double feed indirect

cylinder4. Hot water draw off5. Cold water storage

cistern6. Feed and expansion

cistern7. Heat leak radiator with

2 full way lock shield valves

8. Two port normally open motorised valves controlled by cylinder thermostat (9)

10. High limit pipe thermostat to bring on circulator in an overheat situation

11. Low limit pipe thermostat to prevent the pump coming on until a minimum temperature is reached

12. Programmable room thermostat

13. Injector tee to pump assist the thermosyphoncircuit when the pump is operating

14. Thermostatic radiator valves to provide temperature zoning

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8. Building Regulations BUILDING REGULATIONS AND BUILDING WARRANTS All wood biomass heating systems serving a building must comply with the requirements of the Building (Scotland) Regulations 2004. The Building Regulations are enforced through the building standards system with the Technical Handbooks providing guidance on how to meet the mandatory building standards. When installing a wood biomass system a building warrant is not normally required in a 1 or 2 storey house but may be required for a 3 or more storey house and a flat or maisonette. A building warrant may be required for works to a 1 or 2 storey building that alter the roof, external walls or elements of the structure of the building (further guidance can be found in clause 0.5.1 of Building Regulation 5).

Building Standards Division in conjunction with the Scottish Association of Building Standards Managers (principal officers from the Scottish local authorities), have produced a guidance matrix on combustion appliances and associated work not requiring a warrant. This matrix has been reproduced in the table to Appendix C, with information relating to solid fuel appliances highlighted. If you have any doubts you should seek guidance from your local authority. PLANNING PERMISSION Some biomass systems may require the construction of outhouses or areas to store the wood materials. They may also require the construction of a new means of access for service vehicles the provision of which may need planning permission. Guidance is available in Planning Advice Note 45 Annex: Planning for Micro-renewables. TECHNICAL HANDBOOKS Guidance on complying with the building regulations is given in the building standards Domestic and Non-domestic Technical Handbooks 2011. This chapter will highlight the issues in each section of the Technical Handbooks that should be considered when installing a wood biomass heating system. For further advice on specific projects please contact your local authority’s Building Standards office. Contact details can be found in the telephone directory, the local authority website, or from the website of the Scottish Association of Building Standard Managers. GENERAL - SECTION 0 Section 0 explains Regulations 1 to 17. It includes guidance on appropriate standards of durability, workmanship and fitness of materials. A particular consideration for a wood biomass heating system is that there is sufficient space surrounding the system to enable access for maintenance and repair (see regulation 8).

http://www.scotland.gov.uk/Publications/2006/10/03093936/0

http://www.scotland.gov.uk/Publications/2006/10/03093936/0

http://www.sbsa.gov.uk/tech_handbooks/tbooks2009.htm#1

http://www.sabsm.co.uk/

http://www.sabsm.co.uk/

Low carbon equipment and building regulations Biomass STRUCTURE - SECTION 1 Section 1 aims to ensure that the structure of a building does not pose a threat to the safety of people in or around buildings. For biomass heating systems, including associated water storage tanks, the following issues should be considered to avoid damage to the structure of the building: x all loads imposed by the heating system installation on the structure including the

self weight of the appliance, fuel storage units, and radiator units. x the installation of the chimney or flue may require changes to the building’s

structure, all such changes should be assessed by a chartered engineer or other appropriately qualified person.

x where a constructional hearth is being installed it may be necessary (for example where there is a suspended floor) for the trimming of joists and the provision of additional support, which may require the involvement of a structural engineer or other appropriately qualified person.

x water storage vessels may change the loads imposed on the structure of the floors. Changes in loading should be assessed by a chartered engineer or other appropriately qualified person:

o a supporting floor or attic floor needs to be strong enough, or made strong enough, to resist the loads imposed by water storage vessels, including the weight of water;

o for timber floor structures, loads should normally be shared across at least two joists and it may sometimes be necessary to add members to provide sufficient support for water storage vessels.

As with any system that distributes water around a building, consideration must be given to the installation of pipes and ductwork: x the installation of pipework and ductwork must not weaken the structure of timber

roofs, floors, or walls: o notches and holes should not be cut in rafters, roof ties, collars or hangers o notches should not be cut in wall studs, cripple studs or lintels unless a full

structural appraisal has been carried out by a chartered engineer or other appropriately qualified person

o lightweight trussed rafters should not be cut, trimmed, notched or drilled o figure 8 below, shows the safe locations and sizes for notches and holes in floor

joists and studs - if in doubt, ask a chartered engineer to check the proposed installation.

Notches and hole locations in timber floor joists and studs 28


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FIRE - SECTION 2 Section 2 aims to ensure that the risk of fire is reduced. If a fire does occur measures must be in place to restrict the growth and spread of fire and smoke to enable occupants to escape safely and fire-fighters to deal with the fire safely and effectively. Where a biomass system is installed the integrity of any fire rated element must be maintained both during installation and operation of the appliance. Further guidance can be found in Section 2 of the Technical Handbooks. It is important to identify if walls and floors are required to have a fire resistance rating and to ensure that the installation of a wood biomass heating system does not reduce their required performance (i.e. stability, integrity, and insulation). This should include: x separating walls and separating floors which are constructed to prevent the

spread of fire between buildings or between parts of a building, for instance between flats or attached houses

x walls and floors of compartments, which are parts of non-domestic buildings that are constructed to prevent the spread of fire to or from another part of the building

x walls and floors that protect escape routes for example: a protected enclosure or a protected zone.

For wood biomass heating systems, care should be taken to limit the risk of the spread of fire through gaps in walls, floors, or ceilings, between cavities, and between cavities and any other room or space in the building: x walls and floors that are required to have a fire resistance duration and are made

of combustible materials, for instance timber frame separating walls, must not contain any pipes or wiring. Pipes, wiring and ducts (other than a ventilating duct) can pass through walls. However pipes from any solar water system on the roof of a block of flats must not run down through timber frame walls between flats

x cavity barriers must not be compromised by the pipes or ductwork associated with the biomass heating system – particular care should be taken not to disturb cavity barriers separating roof spaces or at the head of a cavity wall, or at the edges of intermediate floors

x pipes of less than 40mm diameter do not require fire stopping where they pass through any wall or floor required to have a fire resistance duration (such as separating walls or floors), or through a cavity barrier. Pipes with diameters of 40mm or more should be fire stopped to preserve the integrity of the wall, floor, or cavity barrier

x if a roof is required to be fire-rated to prevent the spread of fire from one building or part of a building to another, the same limitations on pipe work apply.

In any event, consult the relevant Technical Handbook and in particular for more detailed guidance on service penetrations, see clause 2.2.9 of the Domestic Technical Handbook and clause 2.1.14 of the Non-Domestic Technical Handbook. Wood biomass heating systems must not compromise the fire performance of the roof. For instance, the penetration of the roof by a chimney must not increase the risk of the external spread of fire.

http://www.sbsa.gov.uk/tech_handbooks/th_pdf_2008/domestic/chapters/Section_2_Domestic_2008.pdf

http://www.sbsa.gov.uk/tech_handbooks/th_pdf_2008/domestic/chapters/Section_2_Domestic_2008.pdf

http://www.sbsa.gov.uk/tech_handbooks/th_pdf_2008/non_domestic/chapters/Section_2_Non_Domestic_2008.pdf


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ENVIRONMENT - SECTION 3 Section 3 aims to ensure that buildings do not pose a threat to the environment and that people in and around buildings are not placed at risk from various sources, including combustion appliances and the effects of moisture. For wood biomass heating systems particular care should be taken to avoid moisture damage to the building. To do this: x any pipes, collectors, or fixings that penetrate the roof should be properly weather

protected to prevent the ingress of rainwater or dampness by using flashings x any pipes or fixings that penetrate an external wall should be properly weather

protected to prevent the ingress of rainwater or dampness, for instance by sealing small gaps around pipes

x pipes or fixings that penetrate an external wall should be installed in a way that does not adversely affect any existing damp proof, waterproof or breather membranes. If a membrane is damaged or disturbed, it should be repositioned or repaired.

Safe operation of combustion appliances Where it is intended to install a wood biomass system the building must also be designed and constructed in such a way that each fixed combustion appliance installation operates safely. Where it is intended to install a wood biomass heating system and extract fan, the system should be able to operate safely whether or not the fans are running. However, where possible extract ventilation and biomass systems should not be installed in the same room. Where a hearth, fireplace (including a flue box), or system chimney is provided, extended or altered information essential to the correct application and use of these facilities should be permanently fixed in the dwelling to alert future workmen to the specification of the installed system. Standards applicable to wood biomass systems are: x BS EN 14785: 2006 'Residential Space Heating Appliances Fired By Wood

Pellets' x BS EN 12809: 2001 'Residential Independent Boilers Fired by Solid Fuel' x BS EN 13229: 2001 'Inset Appliances Including Open Fires Fired by Solid Fuels' x BS EN 13240: 2001 'Room Heaters Fired by Sold Fuel' and x BS EN 303 - 5:1999 'Heating Boilers. Heating Boilers with Forced Draught

Burners. Heating Boilers for Solid Fuels, Hand and Automatically Fired, Nominal Heat output of up to 300kW'.

Chimneys and flues generally Where a wood biomass heating system is being installed, the building must be designed and constructed in such a way that any part used for the removal of combustion gases will withstand heat generated as a result of its operation without any structural change, that would impair the stability or performance of the system. The process of burning wood can cause deposits of soot in the flue, chimneys and flue-pipes therefore should:

Low carbon equipment and building regulations Biomass x be swept at least annually where smokeless solid fuel is burnt and more often if

burning wood, peat and/or other high volatile solid fuel such as bituminous coal. Mechanical sweeping with a brush is the recommended method of cleaning

x have such capacity and be of a height and location with an outlet located so that the products of combustion are discharged freely and will not present a fire hazard

x be of a material that will safely discharge the products of combustion into the flue under all conditions that will be encountered

x have outlet locations that are located for safe and efficient working, taking account of height, prevailing wind direction and the following minimum dimensions:

Minimum dimensions to flue outlets`

A 2300mm horizontally clear of the weather skin.

B 1000mm provided A is satisfied or

600mm where above the ridge.

C 1000mm above the top of any flat roof; and

1000mm above any openable rooflight, dormer or ventilator, etc. within 2300mm measured horizontally.

D/E where D is not more than 2300mm, E must be at least 600mm.

Notes: 1. Horizontal dimensions are to the surface surrounding the flue. 2. Vertical dimensions are to the top of the chimney terminal. 3. Specialist advice will be required for roofs with combustible coverings.

Clearance from combustion appliances A flue pipe that passes through a roof space, partition, internal wall or floor must have sufficient clearance from combustible material to avoid raising the temperature of adjacent materials which may result in the possibility of charring or outbreak of fire. These clearance dimensions may also be defined in the appliance or chimney manufacturer’s instructions. A 'flue liner' is used to form the flue passage within the chimney.

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Low carbon equipment and building regulations Biomass The guidance to Section 3.19 of the Technical Handbooks (Combustion Appliances-relationship to combustible materials) provides details of acceptable construction clearance dimensions. Relationship of metal chimneys to combustible material

manufacturers declared distance xx

There should also be a separation distance where the metal chimney runs through or is in close proximity to combustible material. The separation distance should be 25mm from the outer surface of a single-walled chimney to the combustible material. A metal chimney should not pass through a separating wall or separating floor. However, when the chimney or a non-combustible fire rated casing totally encloses the chimney and is constructed in such a way that, in the event of a fire, the fire resistance is maintained then a metal chimney can be used. A flue-pipe serving a wood biomass heating system should be non-combustible and of a material and construction capable of withstanding the effects of a chimney fire without any structural change that would impair the stability and performance of the flue-pipe. Combustible material should not be located where the heat dissipating through the walls of fireplaces or flues could ignite it. Generally combustible materials should: x be located at least 200mm from the surface surrounding a flue in a masonry

chimney x have a separation distance where a metal chimney passes through or in close

proximity to combustible material. A fireplace recess should be constructed of solid, non-combustible material in accordance with the recommendations in Clauses 7 and 8 of BS 8303: Part 1:1994 and to the minimum thickness shown in Figure 2 to BS 8303: Part 3:1994. All combustion appliances have the potential to cause carbon monoxide (CO) poisoning if they are poorly installed or commissioned, inadequately maintained or incorrectly used. Any chimney or flue-pipe installed in a building should: x be suitable for use with the type of appliance served

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x have such capacity, be of a height and location and with an outlet located so that the products of combustion are discharged freely and will not present a fire hazard

x have each solid fuel appliance connected to a separate flue x have the outlet from a flue located externally at a safe distance from any opening,

obstruction or flammable or vulnerable material x be surrounded by non-combustible material that is capable of withstanding the

effects of a chimney fire without any structural change that would impair the stability or performance of the chimney.

Access should be provided for inspection and cleaning of the flue and appliance. Air for Combustion An open-flued appliance needs to receive a certain amount of air from outside the appliance dependant upon its type and rating. A wood biomass appliance installed in a room or space should have a supply of air for combustion. This can be provided by way of permanent ventilation either directly from the open air or from adjoining space (including a sub-floor space) that is itself permanently ventilated direct to the open air. As part of the Government’s commitment to reducing carbon emissions, the building regulations are encouraging low air permeability for new buildings. These are designed to have lower levels of uncontrolled air infiltration through gaps and cracks in the building fabric. Care should be taken when installing a biomass system in buildings with very low air infiltration rates (air infiltration rate of less than 5m3/m2.h) to ensure there is sufficient air for combustion. It is also important that installers recognise the need to accurately assess the need for ventilation in any building, but particularly in recently completed buildings or where there is evidence that a building may have been built to higher energy standards on a voluntary basis. Such buildings are more likely to have lower infiltration rates and a means of controlling the exchange of air between the inside and outside of a dwelling by: x mechanical devices such as extract and supply fans x passive stack ventilators using ducts from terminals in the ceiling of rooms to

terminals on the roof that extract air to the outside. Safe Storage of Fuel By its very nature woody biomass fuel is highly combustible and precautions need to be taken to reduce the possibility of the stored fuel igniting. To help ensure maximum energy from the fuel, storage should be designed to be damp free to reduce any increase in the moisture content of the fuel. To inhibit the spread of fire, storage for wood fuels should be in containers constructed in accordance with the guidance to Section 3.23 of the Technical Handbooks.


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Minimise Fuel Deliveries Every building must be designed and constructed in such a way that the volume of wood biomass fuel storage allows the number of journeys by delivery vehicles to be minimised. It is recommended that wood fuel storage provision is of a size that will ensure deliveries need not be made at intervals of less than 3 months for bulk storage and 6 months for small installations. SAFETY - SECTION 4 Section 4 aims to ensure that the risk of harm to users of a building is limited to an acceptable level by identifying hazards in and around buildings. For wood biomass heating systems that use an electricity supply care should be taken to avoid risks of electrocution and fire: x systems using an electricity supply should be installed in accordance with BS

7671, also known as the Institute of Electrical Engineers (IEE) Wiring Regulations 17th edition.

For any wood biomass heating system that incorporates hot water storage care should be taken to avoid risks of scalding and burns from the discharge of steam or hot water: x provision must be made to prevent scalding by limiting the temperature of hot

water delivered to a bath or bidet to 48ºC. This can be achieved by fitting a thermostatic mixing valve (see Domestic Technical Handbook, 4.9.5)

x the fluid in a wood biomass heating collector circuit can reach very high temperatures and where a system includes a means of venting fluid or steam this should not result in the risk of scalding to people or damage to the building fabric:

o temperature and pressure relief valves should vent into pipes or containers that are designed to receive steam

x particular care should be taken with unvented hot water storage (see Domestic Technical Handbook, 4.9.1 - 4):

o unvented hot water storage systems should incorporate appropriate safety devices and controls to regulate temperature and pressures within the system

o installations should be carried out by people with appropriate training and practical experience, usually members of a registration scheme operated by a recognised professional body, including the Scottish and Northern Ireland Plumbing Employers Federation (SNIPEF) and the Construction Industry Training Board (CITB).

Provision should also be made to protect from scalding during maintenance of the system: x a low level drain down facility should be provided to allow the safe draining of

the heat transfer fluid. For any biomass heating system that incorporates a pre-heat cylinder or other hot water storage care should be taken to avoid risks of legionella: x to control the risk of legionella and similar pathogens, a secondary heat source,

typically an immersion heater coil, is needed to raise the temperature of the stored water, once a week for a short time to at least 60qC, in accordance with guidance to the Water Byelaws.


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NOISE - SECTION 5 Section 5 aims to limit the transmission of sound to a level that will not threaten the health of occupants. Sound transmission emanates from within a building as well as from attached buildings and differently occupied parts of the same building. Building service installations in buildings have the potential to cause noise nuisance. For example, common plant such as lifts, air conditioning units, ventilation systems, and drainage pipes running the height of a block of flats have all been known to be a source of complaint. Therefore, it is important that the design of building services, their position in the building and the building structure should be considered at an early stage in the design process. It is worth noting that the only noise from a wood biomass heating system comes from the circulation pump which is probably no louder than a modern central heating pump. Custom-built or system chimneys should not be built into timber-framed separating walls. Only masonry chimneys (including precast concrete flue-blocks) may be included as an integral part of a separating wall. ENERGY - SECTION 6 Section 6 aims to ensure that effective measures for the conservation of fuel and power are incorporated into buildings, and that emissions of carbon dioxide are limited. Minimum efficiency of a biomass heating system An installed biomass heating system is required to meet minimum appliance efficiency. The minimum efficiencies for different appliance types are set out in clause 6.3.2 of the Domestic Technical Handbook. Controls for solid fuel heating systems are set out in clause 6.3.9 and are also discussed in Section 7 of this guidance document. Installation of a wood biomass heating system should not prejudice the energy performance of the building: x if insulation within the walls, ground floor, roof or on pipe work is disrupted it

should be re-positioned or replaced x if membranes or seals that contribute to the air-tightness of the building are

disrupted they should be repaired and the junctions around pipes or ductwork made airtight

x gaps should be filled where any pipes or ducts penetrate external walls, incorporating insulation material to limit thermal bridging.

Various measures can help to ensure that the installation of the wood biomass heating system is energy efficient: x pipes and ducts within the system should be well insulated to minimise heat loss: o BS 5422: 2009 'Methods for specifying thermal insulating materials for pipes,

tanks, vessels, ductwork and equipment operating within the temperature range – 40°C to + 700°C’; for example a 22mm diameter copper pipe should be insulated with a minimum of 18 mm of insulation with a thermal conductivity of 0.035W/mK

o the correct grade of insulation needs to be used to withstand the very high temperatures generated


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o for external pipes and ductwork, the insulation will need to be resistant to the effects of weathering.

Correct use and maintenance of a wood biomass heating system is essential if the benefits of enhanced energy efficiency are to be realised. Therefore: x the whole system, including the auxiliary heating, should be properly

commissioned and tested, taking account of the manufacturer’s recommendations to achieve optimum energy efficiency, and with a view to ensuring safe operation

x written information should be made available for the use of the occupier of the building on the operation and maintenance of the whole system, including the recommended frequency of scheduled maintenance.

MINIMUM CONTROL REQUIREMENTS To satisfy Section 6: (Energy) of the Technical Handbooks the heating system, where appropriate, should incorporate the following: x thermostatic control of the burning rate x boiler interlock (only as advised by manufacturer) x fully pumped circuits where appropriate x dwellings with a floor area more than 150m2 should be divided into at least two

heating zones with independent time and temperature controls x full programmer (7 day for space and hot water), the level of sophistication of time

controls should be selected to be compatible with the appliance. The highest levels should only be used for appliances with automatic ignition

x room thermostats and TRVs (except in rooms where ‘heat bleed’ is required) x a cylinder thermostat. Separately controlled circuits to cylinder and radiators with

fully pumped circulation where appropriate. SUSTAINABILITY - SECTION 7 Sections 1 to 6 of the 2010 Technical Handbooks identify the minimum requirements for satisfying building standards. Section 7 builds on the sustainability aspects already embedded in building standards and aims to encourage the sustainable design and construction of all new buildings. As part of this sustainability labelling has been developed to: x formally recognise the levels of sustainability already achieved in the Building

Regulations, by setting compliance with the 2010 standards as the entry benchmark level

x encourage more demanding sustainability standards through enhanced Silver, Gold and Platinum upper levels and

x identify buildings that incorporate a low or zero carbon generating technology (LZCGT).

Levels of sustainability The specified level of sustainability for a dwelling should be selected from the following: • Bronze or Bronze Active • Silver or Silver Active • Gold The use of biomass is recognised as one of the low and zero carbon generating technologies that can help meet part of the specified upper levels in Section 7.


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COMPLIANCE The responsibility to ensure that biomass installations comply with building standards generally lies with the owner of the building. It is therefore important that biomass installations are designed, constructed and installed by persons with relevant professional skills and experience. Using an Approved Certifier is an option open to an owner or developer to gain certification and assurance that building warrant approved work, as constructed, does comply with building standards. Approved Certifiers are members of a scheme approved by Scottish Ministers. Checking procedures adopted by Approved Certifiers will deliver design or installation reliability in accordance with legislation. The Scottish and Northern Ireland Plumbing Employers Federation (SNIPEF) currently operate an approved scheme that includes the certification of fixed solid fuel combustion appliances including biomass installations.


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APPENDIX – A Explanation of terms

ACCUMULATOR OR BUFFER TANK An insulated tank of water plumbed to take heat from the boiler when heat output exceeds immediate demand and to release heat when demand exceeds boiler output. Accumulator tanks avoid excessive modulation of boilers, allows more heat to be supplied by the wood fuel system and allows a reduction in boiler size thus reducing cost.

AUGER A rotating Archimedean screw that pulls wood chip or wood pellet fuel from the fuel store to the drop zone of the boiler. BURNER Is made up of an auger that feeds the fuel directly into the combustion zone. BOILER Conventional boilers similar to those used with gas or oil fire systems. It contains either a simple water jacket or multi-pass fire tube positioned either vertically or horizontally. The boilers are highly efficient with typical efficiencies of 80% to over 90% for woodchip and wood pellet systems. CALORIFIC VALUE The amount of heat released by unit weight or unit volume of the fuel during complete combustion. CHIMNEY The chimney stack has two functions: it draws the flue gases and disperses them to the atmosphere at a safe level. The structure can enclose 1 or more flues, but not a flue-pipe, and includes any openings for the accommodation of a combustion appliance, but does not include a chimney terminal. COMBUSTION GRATE The main point at which combustion starts. COPPICE PRODUCTS A thicket or dense growth of small trees or bushes, regularly trimmed back to stumps so that a continual supply of small poles and firewood is obtained. ENERGY DENSITY This term refers to the energy contained in a fuel per unit weight; figures are usually quoted in Gigajoules per tonne. FLUE Passage for conveying the products of combustion to the outside atmosphere. FLUE LINER Wall of a chimney consisting of different component parts, the surface of which is in contact with products of combustion.


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FLUE-PIPE Is a pipe, either single walled (insulated or non-insulated) or double-walled, that connects a combustion appliance to a flue in a chimney. HEAT EXCHANGER Where an appliance is providing hot water to heat a space, a heat exchanger transfers the heat in the hot combustion gases to the water e.g. via ‘fire tubes’ with a ‘water jacket’. IGNITION SYSTEM Wood-pellet appliances may be ignited automatically using a hot air blower to raise material to ignition point (smaller systems) or electrically ignited gas pilot (larger systems). MODULATION A modulating condensing boiler will adjust flame and pump speed to produce a varying amount of heat depending on the temperature of the room (more heat if room at a lower temperature than if room was near maximum temperature) to achieve a more constant temperature and reduce gas consumption. MOISTURE CONTENT The percentage of the total mass of a fuel that is comprised of water. Expressed as a percentage (30% moisture content) or simply as MC30. SPRING ARM AGITATOR / OUTFEEDER A mechanism involving two metal arms that rotate at the base of the fuel store to funnel the fuel to the auger. In addition to the issues covered by the Technical Handbooks, the following good practice guidance will make the installation of a biomass heating system safer and more sustainable.


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APPENDIX – B Good Practice Advice

IMPORTANT SAFETY INFORMATION Approved appliances are designed and assessed to be safe in use. However, it is essential to refer to the manufacturer's installation and operating instructions and also to any permanent warning label. It is recommended that a permanent warning label along the following lines is attached to approved room heaters. However, it is not mandatory for recently approved appliances under the new BS ENs. Building regulations do not extend to how people use their buildings therefore it is important for owners and occupiers to consider the following: WARNING Safe operation of their appliances: x Fumes from blocked chimneys can kill. x Keep chimneys clear, sweep at least annually. x Keep throat plates and flueways clear; clean at least monthly. x Use only recommended approved fuels. x Read instruction card. Never leave an open fire unattended without a spark guard (to BS 3248) and always use a fire guard (to BS 8423) when children and elderly and/or infirm people are present. INCORRECT BURNING, SMELLS OR FUMES If, for no obvious reason, the appliance starts to burn slowly and you smell or suspect fumes, open doors and windows, extinguish the fire and evacuate the premises. Do not re-light the fire until the cause of the fume emission has been investigated and removed. CARBON MONOXIDE Occupants of a building can be alerted to the presence of carbon monoxide (CO) by the use of detector / alarms. Whilst these devices should not be considered as a substitute for correct installation or regular maintenance of appliances and flues, they can provide warning to the occupants. Many combustion appliance installers recognise the safety benefits of installing CO detectors and currently install them as good practice. The current review of building regulations is considering introducing the requirement for CO detection within buildings. ADEQUATE VENTILATION Remember that the people in the room and also the appliance itself, need air and any draught proofing or double glazing must allow adequate ventilation as required by the Building Regulations. CHIMNEY MAINTENANCE Chimneys and their flues need to be maintained so that the by-products of combustion are safely discharged to the outside air. Maintenance should include: x sweeping and removal of debris from all areas, at least annually, this may need

to be increased depending on type of fuel burnt and local site conditions; x an annual smoke draw test x testing on a programmed basis by both evacuation tests and pressure smoke

tests to BS 6461. Approximately every 5 years during the life expectancy of the


41

flue and more regularly once the expected life of the chimney has been reached and

x regular visual inspections followed by any necessary repairs. APPROVED CHIMNEY SWEEPS The National Association of Chimney Engineers (NACE) was set up to ensure the safety of all fuel users who depend upon a chimney or flue for the operation of a heating appliance. They provide a register of competent and qualified chimney engineers for all types of chimney work. Advice is also available from the British Flue and Chimney Manufacturers’ Association (BFCMA). These organisations do not have a mandatory status. See also the following links:http://www.nace.org.uk/ http://www.feta.co.uk/ Approved chimney sweeps, who have been through NACS, GMCS or APICS induction procedures to confirm their competency and who have attended the National Association of Chimney Sweeps course or the HETAS Solid Fuel Awareness course and passed the assessment, are listed in Part 4, Section E of the HETAS Guide. They will carry a special HETAS approved identity card. The Guild of Master Chimney Sweeps Ltd, 24 Church View, Aveley, Essex, RM15 4LH. Tel: 0800 043 737 Web: www.guildofmasterchimneysweeps.co.uk The Association of Professional and Independent Chimney Sweeps, Bryallen, Hengar Road, St Tudy, Bodmin, Cornwall, PL31 3PL Tel: 0845 604 4327. Web: www.apics.org.uk REGISTERED HEATING ENGINEERS The Heating Equipment Testing and Approval Scheme (HETAS) is an independent organisation which sets standards of safety, efficiency and performance for testing and approval of solid fuels, solid mineral fuel and wood burning appliances and associated equipment and services for the UK solid fuel domestic heating industry. It operates a registration scheme for competent Engineers and Companies working in the domestic solid fuel market. The Official Guide to Approved Solid Fuel Products and Services published by HETAS Ltd contains a list of Registered Heating Engineers deemed competent in the various modules listed, e.g. for the installation, inspection and maintenance of solid fuel appliances. There are other organisations representing the solid fuel industry but neither they nor HETAS have a mandatory status. QUALITY ASSURANCE SCHEMES To assists producers and suppliers to provide quality wood fuel various quality assurance schemes now exist including:

WOODSURE - (www.woodsure.co.uk) has developed a UK quality assurance scheme where wood fuel is assessed by performance testing.

HETAS (www.hetas.co.uk) has a wood fuel quality assurance scheme where producers are assessed against European standards to check that they are meeting a quality standard for solid biomass fuels.

http://www.nace.org.uk/

http://www.feta.co.uk/

http://www.guildofmasterchimneysweeps.co.uk/

http://www.woodsure.co.uk/

http://www.hetas.co.uk/

Low carbon equipment and building regulations Biomass Uk wood pellet producers have also opted to provide quality fuel through the certified processes of the new European standard – ENPlus (www.pelletcouncil.eu) or to have their fuels tested and accredited by Independent test labs that are accredited by the UK Accreditation Service.

RELEVANT TRADE ASSOCIATIONS

TRADE ASSOCIATION WEBSITE HETAS www.hetas.co.uk

Scottish and Northern Ireland Plumbing Employers Federation (SNIPEF)

www.snipef.org.uk

Solid Fuel Association www.solidfuel.co.ukChartered Institute of Plumbing and Heating Engineers (CIPHE)

www.cipe.org.uk

Institute of Domestic Heating and Environmental Engineers (IDHE)

www.idhee.org.uk

British Flue and Chimney Manufacturers Association

www.feta.co.uk

National Association of Chimney Engineers

www.nace.org.uk

Association of Professional Chimney Sweeps (APICS)

www.apics.org.uk

Guild of Master Chimney Sweeps www.guildofmasterchimneysweeps.co.uk

42

http://www.pelletcouncil.eu/

http://www.hetas.co.uk/

http://www.snipef.org.uk/

http://www.solidfuel.co.uk/

http://www.cipe.org.uk/

http://www.idhee.org.uk/

http://www.feta.co.uk/

http://www.nace.org.uk/

http://www.apics.org.uk/

http://www.guildofmasterchimneysweeps.co.uk/


APPENDIX – C Work not requiring a warrant [1]

DOMESTIC BUILDINGS WORK TO EXISTING BUILDINGS [2]

Work Activity Type [3] Flat House (up to 2 storeys)

House (3 storeys &

above)

NEW AND REPLACEMENT BOILERS

New gas combustion appliance, not more than 70kW net input [4] 1, 6 Not Required Not Required Not Required

New gas combustion appliance, more than 70kW net input [4] 1, 6 Required Not Required Required

New oil combustion appliance, not more than 45kW output [4] 1, 6 Not Required Not Required Not Required

New oil combustion appliance, more than 45kW output [4] 1, 6 Required Not Required Required

New Solid fuel combustion appliance, not more than 50kW output [4]

1, 6 Not Required Not Required Not Required

New Solid fuel combustion appliance, more than 50kW output [4]

1, 6 Required Not Required Required

Replacement gas appliance, not more than 70kW net input 1, 6 Not Required

[5] Not Required

[5] Not Required

[5]

Replacement oil appliance, not more than 45kW output 1, 6 Not Required

[5] Not Required

[5] Not Required

[5]

Replacement solid fuel appliance 1, 24 Not Required [6]

Not Required [6]

Not Required [6]

Electrical work associated with boiler installation or replacement See separate electrical matrix

CHIMNEYS/FLUE–PIPES

Installation of a new or replacement balanced flue serving a room sealed appliance


Installation of a new chimney or flue-pipe 1 Required Not Required Required

Installation of a flue liner 1, 9 Not Required Not Required Not Required

Alterations to an existing chimney or flue-pipe 1 Required Not Required Required

Repairs to, or replacement of, an existing chimney, flue-pipe or a flue outlet or terminal

1, 24

Not Required [6]

Not Required [6]

Not Required [6]

HEARTHS

New or replacement superimposed hearth (i.e. non-constructional) 1, 6, 24 Not Required

[6, 7] Not Required

[6] Not Required

[6, 7]

New constructional hearth not affecting the floor or wall structure 1, 6 Required Not Required Required

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Work Activity Type [3] Flat House (up to 2 storeys)

House (3 storeys &

above)

FUEL STORAGE (when connected to a combustion appliance for space/water heating or cooking) [8]

Installation of an LPG storage tank, including pipework connecting the tank to a combustion appliance with a net input rating of 70kW or less


Work associated with refillable LPG cylinders serving space/water heating combustion appliance(s) or cooking facilities via fixed pipework


Installation of a fixed oil storage tank with a capacity of more than 90 litres, including pipework connecting the tank to the combustion appliance

1, 6 Required Not Required Required

Repairs to, or replacement of, an LPG or oil storage tank, including associated pipework

1, 24 Not Required

[6] Not Required

[6] Not Required

[6]

Installation of an oil storage tank with a capacity of not more than 90 litres

The building regulations do not cover work of this nature

CENTRAL HEATING AND HOT WATER STORAGE ANCILLARIES

Any work associated with a combustion appliance installation, e.g. pipework, radiators, convector heaters and thermostatic controls


Note 1 Works not requiring a building warrant under the terms of schedule 3 require, in all respects, to meet the requirements of the relevant regulations, except where falling within types 24 to 26, where works constituting replacements must be to a standard no worse that at present. Note 2 Where indicated as not requiring warrant approval, this is on the proviso that no structural works to, or affecting, the roof, external walls or elements of structure, or works adversely affecting a separating wall/floor, are to be carried out to facilitate the installation. This guidance is intended to cover the indicated work activities only, a building warrant may be required for ancillary works. If the work activity is carried out at the same time as works requiring a warrant, the building warrant application should include all works. Note 3 Building work type as referenced in schedule 3. Note 4 Excluding works to a flue-pipe, chimney and/or constructional hearth. Note 5 On condition that the boiler complies with the current technical standards Note 6 If a replacement, on condition that the installation is to a standard no worse than at present. Note 7 Not applicable to solid fuel appliances having an output rating more than 50kW, oil-firing appliances with an output rating more than 45kW or gas-fired appliances having a net input rating of more than 70kW. Note 8 The installation of biomass storage should be discussed with the local authority verifier.

44


APPENDIX – D Relevant Standards

EUROPEAN AND BRITISH STANDARDS CEN Technical Committee 295 produces Standards for residential solid fuel appliances and the current range of Standards represents the broad classifications of appliances in the market (Table 2.1). Residential heating devices, as defined by CEN TC 295, either heat a single room or a single dwelling. European EN standards for residential solid fuel appliances and for independent boilers with nominal heat output up to 300kW. The Standards include minimum requirements for efficiency, construction and safety of appliances. In general residential appliances are less than 50kW output and most direct heating appliances (stoves, fireplaces) have an output of <10kW.

RESIDENTIAL SOLID FUEL APPLIANCES BS EN 303 Pt 5: 1999

Heating boilers - Part 5: Heating boilers for solid fuels, hand and automatically stocked, nominal heat output of up to 300kW - Terminology, requirements, testing and marking.

BS EN 12809: 2001+ A1:2004

Residential independent boilers fired by solid fuel – Nominal heat output up to 50kW - Requirements and test methods.

BS EN 12815: 2001+ A1:2004

Residential cookers fired by solid fuel - Requirements and test methods.

BS EN 13229: 2001 + A2: 2004

Inset appliances including open fires fired by solid fuels - Requirements and test methods.

BS EN 13240: 2001 + A2: 2004

Room heaters fired by solid fuel - Requirements and test methods.

BS EN 14785: 2006

Residential space heating appliances fired by wood pellets - Requirements and test methods.

BS EN 15250: 2007

Slow heat release appliances fired by solid fuel - Requirements and test methods.

prEN 15281 (under development)

Sauna stoves fired by solid fuel - Requirements and test methods.

prEN 15544 (under development)

One off tiled/mortared stoves - Dimensioning.

STANDARDS FOR WOOD BIOMASS HEATING SYSTEMS

45

BS 5615:1985 Specification for insulating jackets for domestic hot water cylinders.

BS EN 13831: 2007

Closed expansion vessels with built in diaphragm for installation in water.

BS 5422: 2009 Method for specifying thermal insulating materials for pipes, tanks, vessels, ductwork and equipment operating within the temperature range -400C to +7000C.

BS EN 12831, Specification of forced circulation hot water central heating


46

BS EN 12828, systems for domestic premises design. BS 5970: 2001 Code of Practice for thermal insulation of pipework and

equipment in the temperature range of – 1000C to + 8700C.

GENERAL STANDARDS FOR HOT WATER STORAGE VESSELS, AND ASSOCIATED FITTINGS

BS EN 1490: 2000 Building valves. Combined temperature and pressure relief valves, tests and requirements.

BS EN 1491: 2000 Building valves. Expansion valves. Tests and requirements. BS 1566: Part 1: 2002

Copper indirect cylinders for domestic purposes – Open vented copper cylinders – Requirements and test methods.

Part 2:1984 (1990) Specification for single feed indirect cylinders. BS 3198:1981 Specification for copper hot water storage combination units for

domestic purposes. BS EN 12897: 2006

Water supply. Specification for indirectly heated unvented (closed) storage water heaters.

BS 7074-1:1989 Application, selection and installation of expansion vessels and ancillary equipment for sealed water systems. Code of Practice for domestic heating and hot water supply.

BS EN 13831: 2007

Closed expansion vessels with built-in diaphragm for installation in water.

STANDARDS FOR WATER HEATING SYSTEMS

BS 6700: 2006 Design, installation, testing and maintenance of services supplying water for domestic use within buildings and their curtilages.

BS EN 15316 Part 1: 2007

Heating systems in buildings. Method for calculation of system energy requirements and system efficiencies. General

Part 3-1: 2007 Domestic hot water systems, characterisation of needs (tapping requirements).

Part 3-2: 2007 Domestic hot water systems, distribution. Part 3-3: 2007 Domestic hot water systems, generation. Part 4-3: 2007 Heat generation systems, thermal solar systems.

http://www.bsi-global.com/en/Shop/Publication-Detail/?pid=000000000030137884



47

PRODUCT AND MATERIALS STANDARDS

BS 7431:1991 Method for assessing biomass heaters. Elastomeric materials for absorbers, connecting pipes and fittings.

BS 3734-1:1997 Rubber. Tolerances for products. Dimensional tolerances. BS 6920: 2000

Suitability of non-metallic products for use in contact with water intended for human consumption with regard to their effect on the quality of the water.

OTHER RELEVANT FUEL STANDARDS AND GUIDANCE

BS 7671 Requirements for electrical installations. BS EN 14419, BS EN 448, BS EN 489

District heating pipes.

BS 8000 Workmanship on building sites. HETAS Solid Biomass Assurance Scheme. DD CEN/TS 14774-2:2004

Solid Biofuels. Methods for the determination of moisture content. Oven dry method. Total moisture. Simplified method.

DD CEN/TS 14588: 2004

Solid Biofuels. Terminology, definitions and descriptions.

DD CEN/TS 14961:2010

Solid Biofuels. Fuel specifications and classes.

CEN/TS 15234-1 General Requirements.

OTHER RELEVANT STANDARDS

BS 7671 Requirements for electrical installations. BS EN 14419, BS EN 448, BSEN 489

District heating pipes.

BS 8000 Workmanship on building sites.



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