General Information

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General Information

Below is a wealth of information related to both 'dry' and 'wet'/boiler stoves. Please do not hesitate to get in touch if you cannot find the answer for your question. Details of how to contact us are available on our 'Contact Us' page.

A Glossary of commonly used terms is available here.

What size stove is needed?

Flue, hearth and chimney requirements

Specific Advice for Dry Stoves

Specific Advice for Boiler (or 'Wet') Stoves

Useful Data

Burning Wood and Solid Fuel

Site Search

Efficiencies:


The stove efficiency (Nett or Gross) is the percentage of useful heat generated from the fuel source that is passed into the room or to the boiler jacket.

An average wood burning stove will be between 65 & 80% Gross efficient, an open fire is around 25% efficient. HETAS require minimum Gross of 65% for a dry stove or 67% for a boiler stove to register on their site, CE certification alone requires 50% efficiency for any stove.

All Arada stove efficiencies are listed as Nett not Gross.

The Nett efficiency figure is slightly higher than the Gross figure. The Gross figure is mainly used during the testing process. Most stove manufacturers in the UK list the Nett figure in their marketing literature, HETAS list the Gross figure in their data. The Nett figures are also the most common used and quoted figures by European stove manufacturers. During performance comparisons it is always essential to check that you are comparing directly equivalent efficiency figures.

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What size stove output is needed?


Often a stove is chosen to match the fireplace, hearth or style of room it is to be fitted in. However the most important factor in choosing the right size stove is getting the right output to ensure you will not be too hot! The formula for doing this is to measure the room volume (width x length x height) in metres and divide this by 14.

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Heat Output Example


A room has dimensions of 4.8m x 4.8m x 2.6m. The room has a volume of 59.9m3, which is divided by 14 to calculate an average output requirement of 4.3 kW.

Remember this is an average room. The number of doors and windows in the room and other factors such as stairs leading off the room may increase the heating requirements. Similarly a well insulated house may reduce the heating requirements.

A well-insulated room, central heating, double glazed window – 5kW recommended.

Draughty room, old windows, wooden floor – 7kW recommended.

The examples above show a room as described in the example but with different furnishing and heating with the recommended stove outputs for each.

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Introduction


An existing chimney should be inspected by a HETAS or NACE engineer. A sound chimney does not automatically need lining. A very large internal flue is not well suited to wood burning stoves and should be lined in accordance with Arada’s installation manual. A minimum flue height of 4.5m is recommended although lower overall height may be sufficient, subject to testing for flue draw ( 0.1-0.2mbar/10 -20 pa) See Ref. Document BS EN 13384 1:2005

A 6 inch / 150mm liner is the minimum required diameter for a wood burning or multi fuel stove regardless of proposed fuel type (anthracite etc.)

A 5 inch / 127mm liner is only suitable for a solid fuel stove or DEFRA exempt stove installed in an UK smoke control zone.

Lining generally consists of a stainless steel liner made of two thin layers, an inner and outer layer, sandwiched together. The layers are often made from different grades of stainless steel, i.e. 304, 316 or 904. 304 being the lowest grade and 904 the highest and most corrosion resistant grade.

A minimum of 316/316 stainless steel is recommended, 316/904 is better 904/904 is best. Avoid 304/304 St-steel flue liners, whilst much cheaper they have only around a 5 year guarantee.

Note:

If an installed DEFRA exempt stove is replaced at any time with a NON DEFRA exempt stove, the Liner / Flue must be changed to a 6” diameter liner to conform to Building Regulations when burning wood.

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Chimney Sweeping:


A chimney should be swept at least once a year, preferably by a HETAS or NACE qualified engineer who will provide a certificate on completion covering the visual condition of the flue and compliance with Document J.

A stove used as the main source of heating and burning predominantly wood should be swept twice a year. A HETAS or NACE engineer will be able to offer on site advice on this.

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Ventilation:


All stoves require ventilation to burn safely and correctly. Stoves require considerably less ventilation than open fires and therefore produce very little in the way of room draughts while burning. However, there are still requirements that need to be met when installing a stove, such as allowing for the permeability of the house (air permeability is the general seepage of air into the house via air vents, doors and windows etc.)

Below is taken from the 'HETAS Guide 2012' (last updated 08/11/12)


For closed appliances without any draught stabiliser fitted installed in a building where the design air permeability is greater than 5.0m3/h.m2, the air requirement is 550mm2 per kW of rated output above 5kW e.g. for 8kW this would be:- (8-5) x 550 = 3 x 550 = 1,650mm2/16.5cm2. If the building's design air permeability is less than 5.0m3/h.m2 the air requirement is 550mm2 per kW of rated output.

If the appliance has a flue draught stabiliser fitted then the following air requirements apply:- Installations in buildings where the design air permeability is greater than 5.0m3/h.m2; For the first 5kW of rated output add 300mm2 per kW and then from 5kW upwards, add 850mm2 per kW. e.g. for 8 kW the air requirement would be: (5x300) + (3x850) = 4,050 mm2/40.5cm2. If the building's design air permeability is less than 5.0 m3/h.m2; add 850mm2 per kW of rated output.

Note: It is unlikely that a dwelling constructed before 2008 will have an air permeability of less than 5.0m3/h.m2 at 50Pa unless extensive measures have been taken to improve air tightness. Appendix F of Approved Document J gives additional details.


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Connecting a stove to a chimney:


There is a distinct difference between a chimney and a flue. A chimney is the permanent structural part of the building, usually brick construction. The flue refers to the inner passage which carries the exhaust gases through the chimney. The stove is connected to the chimney or flue with a short length of Vitreous or stainless steel flue pipe. This connecting flue pipe will either terminate above a register plate or connect directly onto a flue system or liner.

The connection from the connecting flue pipe to the chimney or flue should be done as soon as is practical, generally above the register plate, providing it is not significantly more than 600mm above the stove outlet, into a suitable sized 150mm minimum flue. If no liner is required then the flue pipe can be suitably terminated above the register plate. Access in the register place for cleaning must be provided. Your HETAS fitter should be able to advise further on this.

Stove fitted to a sound with the connecting flue terminating above the register plate.

Stove fitted to a chimney lined with a flexible stainless steel liner.

For rear flue connection, only 150mm of horizontal travel into a sweep-able ‘T’ is allowed under current Building Regulations.

Note:The following factors can affect the flue draught:

  • Wind pressure and direction, low pressure or high wind speeds can lead to over-draught, over firing, higher fuel consumption and lower heat output. High pressure or low wind speeds can lead to under-draught resulting in a less efficient burn.
  • Location of the chimney outlet
  • Adjacent buildings, hills or tall trees, these can affect the exit of flue gases.
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Hearths:


The hearth that the stove sits on is a slab of non combustible material that extends around the stove to protect the floor, carpet etc from the heat and any burning material that may fall from the stove.

The edge of the hearth must be at a different level from the surrounding floor to define a safe perimeter, a 50mm high Fender may be used for this purpose.

For a stove installed into a recess, the hearth must extend 150mm to the sides of the stove and 225mm in front for stove that cannot be operated with the doors open, and 300mm for a stove that can be operated with the doors open.

Many stove suppliers only quote the ‘300mm in front’ dimension to ensure they are covered in the event of a problem.

For a freestanding stove not installed into a recess the hearth size must be at least 840 x 840mm irrespective of the stove dimensions and a minimum of 150mm to the rear and sides or to a suitably heat resistant walling.

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12mm minimum hearth thickness


A free standing stove, independently certified by a competent body, that has an under stove temperature that cannot cause the hearth temperature to exceed 100ºC may stand on an 850 x 850mm minimum non combustible material hearth of a minimum of 12mm thick. The stove must also have a clear surrounding hearth area of 150mm to the rear and sides of the appliance.

The regulations covering constructional hearths are quite complex and are fully covered in Approved Document J.

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Lintels


There are two types of lintels; constructional and throat forming.

Constructional lintels can be made of concrete or steel. They are used to span the top of the opening of a fireplace and bear the weight of the building materials above it.

Throat forming lintels are usually a chamfered block which is designed to provide a flat surface parallel with the upper firebrick in order to form an angled passage (or throat) for the fire exhaust fumes to flow through.

When installing an inset stove model you will need to take into consideration the depth of the lintel. Depending on the depth you may need to fit a flue gather to your stove. These come in two sizes a short reach (50mm) and a long reach (96mm) flue gather. These will allow you to connect your stove exhaust outlet to a flue pipe.

D = Depth of lintel.

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Some amazing preamble and a link to dynamic minimum distance to combustibles table should go here.


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Air Controls


Primary Air Inlet:The main source of air at the bottom of the stove, used to ignite the stove and control the stove when burning solid fuel. When burning wood, once the fire is lit, the primary air inlet should be fully closed to allow the fuel to burn more efficiently, the main control for this type of fuel is the secondary air inlet. In multi fuel stoves the primary air inlet is the main source of controlling the fire when using solid fuel, opening the primary air inlet will increase the flame size and give off more heat, closing the primary air inlet will decrease the flame size and give off less heat but will increase the burn time of the fuel.

Secondary Air Inlet: An additional source of air into the stove, at the top of the stove door, also known as “secondary burn”. This is the main control of air for burning wood, opening the secondary air inlet will increase the flame size and give off more heat, closing the secondary air inlet will decrease the flame size and give off less heat, but will increase the burn time. The secondary burn feature means more heat and less emissions as the warm air entering the stove at the top mixes with the un-burnt gases that are about to leave the stove and ignites them.

Tertiary Air Inlet: This air inlet is usually at the back of the stove, it is referred to as “tertiary burn”. The air is drawn into the back of the stove and enters the upper part of the fire chamber through small holes. Tertiary air further cleans the emissions as the air from this inlet mixes with and ignites the remainder of the un-burnt gases creating higher efficiency.

Airwash:The warm air coming in from the secondary air inlet flows downwards behind the glass to the fire bed creating a warm air film over the glass which prevents the flames from blackening the glass viewing area. As the temperature of the stove and secondary air increases the hot air visibly cleans the glass which is known as Airwash.

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Over firing


Stoves should be burnt with a bright energetic flame but avoiding a furnace like roaring fire, this is ‘over firing’

Over firing a stove is generally the result of excessive air supply to the stove via the air controls for prolonged periods of time.

Over firing will cause damage to the stove components quite quickly, especially the throat plate and liners. In time the integral features in the stove, such as side landings, rear grate bar support, and fuel retainer will start to deteriorate. Eventually the body of the stove may be severely damaged and any warranty voided.

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High burn rate with controls set low or closed:


If the stove appears to have a high burn rate when the controls are set low or even closed check the controls are closing properly (they will not close air-tight) details of these checks will be found in the product manual. Also check that the door rope is forming a tight seal when the door is closed, and check the rope seal around the door glass for any gaps.

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Excessive Flue Draught:


If a high burn rate persists when all the above checks have been made and any problems rectified, it may be as a result of an excessive flue pull or ‘draught’. The flue draught when warm should be 10-20 pa (0.1-0.2 mbar); if it is found to be much higher then a flue draught stabiliser may be required. This will help to control the pull to reasonable levels and help to cure high burn rates. Consult a HETAS engineer if this is a persistent problem. In some circumstances the HETAS engineer may recommend a flue damper is all that is needed rather than a complete draught stabiliser system.

It should be remembered that the inclusion of a flue draught stabiliser in the chimney will alter the air vent requirements for the stove (See ‘Ventilation’ section).

Note:One often seen feature of a high flue draught is a good flame picture, clean glass together with total fuel consumption producing little ash, but also producing much less heat than would be expected. High flue draughts tend to overcome the capacity of the fire box to retain heat and produces very similar results as running a stove without a throat plate fitted.

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Smoking stoves (burning wood):


When correctly installed and with a flue draught in the 0.1- 0.2mbar range the stove will not smoke back into the room via the primary or secondary air supply inlets.

If smoke is seen to come back into the room, especially when burning at a lower rate the cause should be investigated as a matter of urgency.

Some likely causes are:

  • Poor flue draught (below 0.1 mbar)
  • Insufficient initial flue temperature before loading fuel
  • Low burn rates with wet wood
  • Over loaded fire box laid onto a poor ember bed
  • Insufficient air supply into room
  • Extractor fan fitted in close proximity to stove effecting draw

Solutions:All possible causes must be checked by a HETAS certified engineer to determine the best course of action.

A poor flue draught may be as a result of:

  • Condition (leaking air into chimney),
  • Location,
  • Height (less than 4.5m),
  • Restricted gas flow due to poor cleaning regime,
  • Oversized chimney (greater than 12 x 12 inches),
  • Undersized flue liner (less than 150mm)

Always maintain a good burn rate with an energetic flame picture; never burn wet wood (moisture content greater than 20%)

Always re-fuel onto a good red-hot ember bed with small pieces of wood until a lively fire is established, then slowly load with dry hard wood logs as required. This will help to ensure a warm flue with correct draw. As previously stated always ensure a good flue temperature is present before loading new fuel. Ensure an extractor fan is not fitted in the same or adjacent room.

Note:A poorly maintained flue liner (i.e. not cleaned at least annually) is susceptible to a chimney fire. Tar in a flue will burn vigorously and is very hard to extinguish. Tar will burn at over 1000ºC and cause substantial damage to the chimney and stove, and possibly a serious house fire.

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The stove burns well, with bright flame picture - but the stove body appears not to heat up as expected?


The most frequently found causes for this problem are:

  • Excessive flue draught (See ‘Over Firing’ section).
  • Incorrectly fitted, faulty or missing throat plate.
  • Incorrect or wrongly fitted side liners, allowing excessive gap around and above the throat plate.
  • Stove fitted into a tight recess, restricting convection of air around stove body (very common error).
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The stove burns well and heats up as expected, but does not appear to heat the room sufficiently?


Assuming the stove body is heating up correctly:

  • Is the stove fitted into a tight recess? Restricting convection of air around stove body (very common error)
  • It is possible that the stove is undersized for the room, see ‘What size stove output is needed’

If the stove is found to be undersize and a larger replacement is not an option, an alternative may be to burn a high output fuel such as anthracite. The anthracite not only has twice the calorific value of wood but will produce about 20% more heat even when the weight is corrected for calorific value, i.e. half the weight of solid fuel compared to wood fuel should produce the same output. In fact it will produce approximately 20% more heat.

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Space requirements for fitting a stove into an existing fireplace:


Where a stove is being fitted into an existing recessed fireplace allowances should be made for convection air around the stove. This should ideally be 100mm to the sides of the stoves and 200mm to the top. This will allow optimum heat convection into the room. A reduced clearance to non combustible walls is possible but the effective heat output of the stove may be reduced.

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Occasional whistling can be heard when the stove is burning at a medium to low rate?


This is a problem that occurs on occasion and is quite normal. Any wood or solid fuel stove can do this from time to time, and is part of the charm of using a wood burner.

It is as a result of fast moving air being drawn into the stove through a certain size restriction. It will stop if the air control is opened or closed slightly from its current position. It is not a fault.

It can be accompanied by the occasional rattling of the air slider, once again this is quite normal not a fault.

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The controls are very hot?


All controls on the stove can be very hot when the stove is alight and for some considerable time after the stove appears to have gone out. Great care should always be taken when adjusting settings or opening the fire door and a stove glove must always be used. Adjustment of the air controls can be made using the multi-purpose tool but a stove glove must still be worn. This also applies to emptying the ash pan; embers can stay very hot for several days.

Note:The kooler touch spring handle option available for some stoves does not get as hot as the standard handle but still should not be operated without a stove glove.

All controls and surfaces on the stove can be very hot and cause severe burns for a considerable period after the stove appears to have gone out.

A fireguard conforming to BS 8423:2010 should be used in the presence of children and old or infirm people.

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Operating the stove with the fire door open


Stoves in the Aarrow, Hamlet, Stratford & Villager range are not designed to be operated with the doors open as this reduces the appliance efficiency to that of an open fire (25%) and can lead to over firing and increases the risk of a house fire. Even operating the stove with the door slightly ajar will over fire the stove.

The only appropriate time to operate the stove with the fire door/doors open is during re-fuelling and during the initial lighting of the stove to aid the early stages of combustion.

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Cracked Liners:


The stove liners may become cracked after a long period of heavy use at high running temperatures, or if the liners become damp and are subjected to a high burn rate without a period of slower firing.

Assuming the liners are still in situ and able to support the throat plate correctly there is no need to replace them in the short term. Cracked liners will not in themselves affect the performance of the stove.

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Cracked Glass:


It is not recommended to operate the stove with cracked glass; this can lead to over firing due to air leaks and may fail completely leading to personal injury or a fire.

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Wood tray verses Grate bars:


Burning any type of solid fuel on a wood tray is strongly discouraged. It will cause severe damage to the wood tray and not be covered by our warranty.

Burning wood on the riddling grate is perfectly acceptable and no discernable difference in stove performance will be found. One advantage of the wood tray for burning wood is it will allow a slightly larger fuel load to be used. If the user intends to burn solid fuel at any time a multi fuel riddling grate must be fitted as solid fuel requires an underdraught as provided through the grate in order to burn.

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A typical boiler installation


(1) Boiler Stove | (2) Pump | (3) Radiator | (4) Pipe Thermostat | (5) Indirect Hot Water Tank
(6) Gravity Radiator | (7) Feed & Expansion Tank | (8) Cold Water Tank | (9) Domestic Hot Water

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Open vented system


An open vented system is a wet heating system incorporating a header tank fill system and an atmospheric pressure level vent, (normally vented back into the header tank, or outside the building)

All add in and wrap round boilers available from Arada must be installed in an open vented system.

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Pressurised systems


Our range of stoves are not suitable for use in a pressurised system, and do not incorporate the mandatory safety features required to do so. (Cooling coils etc). It is unsafe to operate our range of stove in a pressurised system and constitutes a serious hazard to do so.

A pressurised system has a normal operation pressure above that of a normal vented system with an atmospheric pressure vent pipe (approximately 1 bar in a typical installation).

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Connecting an Arada boiler stove in conjunction with a pressurised gas or oil boiler


It is possible to use an Arada boiler in conjunction with a pressurised gas or oil boiler as part of a larger system perhaps including Solar or Ground Source Heat Pump (GSHP) but this can ONLY be done with the use of a Thermal Store or equivalent, which will effectively isolate the boiler stove from the other components in the system and provide all the necessary safety elements.

There are many companies offering suitable thermal store systems. Arada cannot recommend any specific models or manufacturers of thermal stores, your installer should be best placed to advise on a suitable model for the intended installation and system.

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Output of DRY heat to the room


The theoretical heat output of a boiler stove is split typically 50/50 heat to water and heat to room when the fire is running at its nominal maximum output. However in daily use the reality is quite different. The ratio will shift significantly more towards heat to water at lower burn rates, and as a result the heat into the room may fall below that required for a comfortable temperature once the output to water is satisfied. This is quite normal and is a result of the thermostat control automatically closing the primary air supply therefore lowering the burn rate. If the heat to room appears to be too low under these circumstances an additional radiator in the same room as the stove may be required. This radiator will also have the effect of calling for more heat to satisfy the water temperature demand, and at the same time boost the dry heat to the room as a result of the increase in burn rate. A Thermostatic Radiator Valve (TRV) is recommended on this radiator to help maintain an even temperature.

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Boiler outer body temperature


Both sides, back and top of the stove are surrounded by a water jacket on the boiler stoves and as such will not reach a temperature in excess of the water temperature leaving the stove output ports. The top of certain models are insulated and the canopy may well be cool enough to touch at times. This is quite normal and is designed to preserve as much heat as possible in the water. The majority of heat into the room from the stove will be via the door and glass window.

During the early stages of initial firing the body may feel quite cool even though the fire burn rate is high. This is due to the main volume of heat going to heat the water. As previously mentioned it may be necessary to fit a radiator in the same room as the stove to regulate the room temperature more evenly.

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Output to the water


The output to water is generally around 50% of the total heat output of the stove. This varies from model to model and the exact ratio can be found in the product manual.

The output to the water can serve two purposes, Hot water and Radiators.

The boiler can be configured as a fully pumped system for radiators only but will still require the header tank and open vent together with a heat leak radiator. The boiler stove is not recommended for a hot water only application as it may be oversized and therefore run at inefficient burn rates for most of the time. Once the cylinder water temperature demand has been satisfied the boiler would close down for long periods causing possible tarring problems particularly if wood is the primary fuel.

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Hot water circuit

The hot water element of the output is installed as a thermosyphon and is often called a gravity circuit.

This is connected with large bore pipe work, usually 28mm diameter but it can be larger. The water on the output side of the stove is much hotter than the input side and therefore less dense. This causes the heavier cold water to pull the hot water up and through the hot water cylinder coil. It is on the output side that the safety features including the heat leak radiator, header tank and open vent, essential in a solid fuel central heating system, should be installed.

The gravity circulation relies on a very small amount of energy to drive it and is therefore easily restricted or stopped. To ensure a reliable gravity circulation circuit it is important to confirm:

  • Large bore pipe work (28mm minimum)
  • No valves or restriction in the pipe work or heat leak radiator
  • So far as is practical continuously rising pipes on the hot side, never falling
  • Short pipe runs
  • The cylinder must be higher than the stove outlet, the higher the better.
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Radiator output circuit


There are a number of common configurations for the radiator side of the boiler output, varying in complexity according to specific installation needs. Some schematic diagrams of typical installations can be seen in the boiler stove product manual.

Additional methods not described in the manual call for the use of a Heat Store or Neutraliser Tank.

The radiator circuit will be pumped and uses different terminals to those used for the hot water gravity circuit. The best installation method can only be determined by a site visit from a suitably qualified (HETAS) engineer.

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Primary air inlet control


The air for combustion enters the boiler stove on the left hand side, towards the bottom, via a temperature controlled mechanical damper (Automatic primary air controller). The air enters under the grate and into the area around the ash-pan.

This area is subject to a build up of ash especially if the ash pan is not regularly emptied. In order for the stove to maintain good control over water temperature it is important to keep this area free from ash and other debris. Consult the manual for detailed procedure.


The damper mechanism is powered by the expansion of oil in a small reservoir, or phial, located at the top of the stove boiler jacket. When the oil in the phial is heated it expands and travels down the thin copper capillary and opens a small diaphragm in the actuator mechanism, pushing the damper closed. The amount of movement is controlled by the setting of the numbered knob on the damper body. The higher the number the hotter the stove / water jacket will need to become in order to close the damper. This will also increase the time taken to automatically close down the boiler when the maximum desired temperature is reached.

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Boiler over-run


Due to the nature of solid fuel boiler stoves in general, the fire box temperature cannot be controlled precisely and once maximum output has been reached it will take time to reduce the output to water even when the damper is full closed. For this reason the heat leak radiator and open vent are essential safety features that cannot be dispensed with. In order to avoid incidents of boiler over-run, opening the thermostat to full and then closing when a desired temperature is reached should be avoided. Set the initial temperature to approximately half way and by trial and error the best position will be found for a consistent temperature level to be obtained. Change the setting in small steps only and wait to see the effect over a period of time.

Once well alight the boiler will take between 20 and 40 minutes to produce reasonable amounts of useful hot water, once the system is up to temperature the damper will maintain a constant temperature by slowly varying the air supply to the fuel, avoid constantly changing the primary air control as the output will lag well behind a change to the setting and will result in the output rising and falling in an undesirable way.

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Fuel Consumption


Initially the fuel consumption in the early stages of firing will appear high as the damper will be fully open, allowing a fast burn rate and rapidly raising the heating circuit water to the desired temperature. Remember during the initial stages of firing the return temperature to the boiler will be low having the effect of maintaining a rapid burn rate.

When the whole system is up to working temperature the return flow water will be high giving only a low differential temperature across the boiler jacket. This will mean the water is up to the desired temperature and the damper will reduce the air to the fire box and the fuel consumption will drop rapidly. As mentioned in the ‘Boiler over-run’ section, setting the thermostat is important to prevent the boiler from cycling high to low and burning fuel very inefficiently. If a boiler is constantly rising to maximum output and falling back again under damper control, large amounts of fuel are wasted. During the period when maximum firing is reached and the damper is throttling back the air, a considerable amount of the heat produced will not be absorbed by the water but rather passed directly into the room or up the flue. This is a result of the maximum heat absorption rate of the water being reached before the fire box temperature can fall back under the influence of the damper closing (Control Lag).

Best results are obtained with a high quality anthracite fuel, with around a 20% reduction like for like when burning seasoned hardwood.

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Cold water corrosion


Cold water corrosion is the result of water below around 40ºc being pumped through the boiler jacket.

This causes large quantities of condensation to form inside the fire box which can encourage rusting but more importantly, mix with the products of combustion when coal is burnt and form a sulphuric acid, attacking the steel work. This can result in a water jacket failure surprisingly quickly. For this reason we always specify a pump control pipe thermostat to be fitted on the pumped circuit return flow, set at 45ºC disabling the pump until the correct temperature has been reached. See image below.

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Re-fueling


The most efficient way to re-fuel the boiler stove is not to continuously top-up with fresh fuel, but rather allow the stove to burn back to a bright ember bed and re-fuel with sufficient fuel for the burn period required. Constantly topping up causes the fire box and flue temperature to fall rapidly as the door is opened and the cold fresh fuel load will use a percentage of the original fuel to heat it to combustion temperature. This will reduce the water outflow temp and cause the damper to open and rapidly increase the burn rate wasting fuel.

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Operating a boiler stove as a dry stove


As a rule we will always say we do not recommend using a boiler as a dry stove and can take no responsibility for any resulting problems.

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Fuel calorific value:


The potential energy available in the chosen fuel in measured in calorific value (CV). Typical CV for coal and wood are:


Solid fuel (good quality anthracite) 31000 kJ/Kg (kilojoules per kilogram)
Wood (Dry hard wood) 15600 kJ/Kg
Wood (Dry soft wood) 14400 kJ/Kg
1k/watt hour = 3600 kJ therefore 1 kg of anthracite = 8.6 kwh of energy
1 kg of hard wood = 4.3 kwh of energy

If you multiply the energy value by the stove efficiency percentage you will get the output per kg for the stove, i.e. a stove with an efficiency of 70% burning 1kg of wood will produce 3 kW of heat.

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Fuel usage for stoves:


The typical amount of fuel used by a stove depends on the output required, time period the output is required for and the burn efficiency of the stove.

For example a 75% efficient dry stove producing 2kw of heat for 6 hours will use 3.75kg of wood or 2kg of coal.


For an EB12 HE boiler producing the maximum 40,000 BTU to water output for 6 hours the stove would consume 18kg of coal. (5 x 25kg bags per week) “This is an example only and not representative of typical usage”.

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Operating Temperatures:


One way to assist in the correct operation of your stove is to use a flue pipe thermometer suitably positioned on the connecting vitreous flue pipe. In general use the temperature of the flue would be expected to be in the range of 150°C to 250°C.

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Boiler output measurement:


The output to water from a boiler can be described as BTU or kWh. BTU is a British imperial unit of measure (British Thermal Unit) and 1kW = 3414 BTUs.

Some manufacturers describe the whole output of their boiler stoves (wet and dry heat) in BTU this is possibly misleading, all Arada quoted BTU outputs are purely the outputs to water only.

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Data plates:


Since 2002 it has been mandatory to have a data plate fitted on all new installations or upgrades detailing the chimney and its suitability for specific applications.

Older properties may not have had this plate originally, but if a new stove is fitted with a liner a data plate must be fitted by the installer regardless of the original date of the chimney construction.

If a customer is having difficulties with the performance of a stove and a simple resolution seems to be impossible, ask for the registration number of the HETAS engineer who installed the stove, or if it is a DIY installation, the Building Control sign-off certificate number. This is generated by the completion of The Building Control Consent Checklist.

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Boiler Tappings Measurements:


Below are listed the distances for the location of boiler tappings.

If you cannot find the information which you are looking for please don't hesitate to contact us on support@arada.uk.com

All measurements are supplied in mm.

Name

Code

A

B

C

Acorn 4ACORN4216191294
Acorn 5ACORN5206210316
Ecoburn 5ECB5MCE, ECB5WCE244210354
Ecoburn 7ECB7MCE, ECB7WCE245264337
Ecoburn 9ECB9MCE, ECB9WCE267369359
Ecoburn 11ECB11MCE, ECB11WCE267459369
Ecoburnplus 4ECB4FPLUS237210347
Ecoburnplus 5ECB5FPLUS265264357
Ecoburnplus 7ECB7FPLUS260264352
Ecoburnplus 9ECB9FPLUS247269390
Ecoburnplus 11ECB11FPLUSTBATBATBA
Sherborne Compact*SHBCM242210352
Sherborne Small*SHBSM243265335
Sherborne Medium*SHBMM256369348
Sherborne Large*SHBLM251459353
Signature 5SIGN5M, SIGN5W234230286
Signature 7SIGN7M, SIGN7W246315301
Signature 9SIGN9M, SIGN9W279460368
Signature 11SIGN11M, SIGN11W302505402
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Solid fuel (Smokeless fuels only not standard house coal):


Solid fuel burning is quite straight forward, the stove must be fitted with a suitable cast iron grate and the burn is controlled with the primary (under grate air) control. A very small amount of airwash air is required only to keep the glass clean and plays no part in the normal burning of coal.

A cast iron grate is required as a steel grate will be quickly damaged by the higher levels of acid produced by burning coal and the tendency of steel to absorb carbon from the coal during the combustion process. Any damage to a wood burning tray caused by burning coal will not be covered by our warranty.

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Wood:


Burning wood correctly requires a little more effort and planning. The wood should be well seasoned hardwood with a moisture content ideally below 20%, and stored dry with good air flow around it.

Sufficient quantities should be stored indoors to allow a ready supply to be at hand.

Avoid burning straight from the outside store if possible as it will probably have a high surface moisture level.

Hard Wood has approximately half the calorific value of coal, so twice as much in weight terms and about six times as much in volume terms will be required to match the heat production of coal.

Wood tends to burn a little less efficiently so output per comparative quantity may be less.

Softwood will burn well but it tends to produce much more impurities and will tar up the flue far more quickly. As softwood has a much lower density than hard wood the volume of fuel will increase significantly, to maybe 8 times the volume for a comparable coal output.

Ideal types to wood to burn are:
  • Beech
  • Birch
  • Elm
  • Hawthorn
  • Hazel
  • Oak

Wood burns best with the air supply coming from above the fuel.

When wood is burnt it is in fact wood gas that burns and it requires a good supply of air from above

The primary air control should be used only during initial lighting or to revive a fire after re-fuelling. Subsequent burning control should be achieved using the airwash and with the primary air control closed. As much as 40% of the heat from burning wood is obtained from secondary combustion and this is severely hampered by air entering the fire box from below, as for example, via the primary air inlet control.

Clean burning stoves such as the Signature SC 5 have only an air supply from above and often the flames can be seen hanging in the air above the fuel and the occasional jet of flame where secondary air is introduced to the fire box.

Wood should be burnt with a clearly visible energetic flame to avoid the window glass from becoming blackened and increased tarring of the flue.

Banking up a wood stove and shutting down overnight is not an efficient way to use fuel and is not good for your chimney.

If the stove is burned at low levels for any period of time it is recommended to burn the stove vigorously for approximately 30 minutes to burn off any deposits from the interior of the stove.

There are many manufactured wood fuels available and most of these are suitable for use in Arada stoves. While these offer a convenient fuel option we cannot test or comment on heat outputs for these products and it will be up to the user to determine the best fuel for their own use.

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General fuel advice:


It is not recommended to burn wood and coal at the same time as burning coal produces sulphuric acid, this mixed with the moisture inevitably released from burning wood, will both coat the inside of your chimney / flue liner and be released into the atmosphere.

The condition required for efficiently burning wood and coal are not the same so overall efficiencies are reduced.

Both coal and wood release carbon dioxide into the atmosphere however wood is considered a carbon neutral fuel because the carbon released when burning wood is the same carbon that was absorbed by the tree while it was growing over the previous few months or years as opposed to the carbon released from fossil fuels which was absorbed millions of years ago. The carbon that is released when burnt is the same amount of carbon it would release if left to decompose naturally.

Never burn any manufactured fuels containing Petrocoke as it will damage the stove and invalidate the warranty.

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