Thursday 8 December 2011

Choosing A Stove - The Guide

As this is a fairly expensive exercise it really does makes sense to get it right first time. Think long term!

Common sense, planning, using quality products and seeking professional advice are paramount to your success when buying and installing a stove. Using solid fuel requires a little effort but the joy of owning a stove during those cold winter months is unbeatable.

A little reading is required, a little legwork, some research and some comparisons will help you make a few key decisions. These actions will help ensure a successful and safe installation and you will have many years of enjoyment and pleasure from your stove.

Stove guide - Building Regulations

Stove installation is covered by building regulations “Document J” Hetas – Heating Equipment Testing and Approval Service. Hetas registered installers are trained to adhere to these building regulations. 

Safety First! - Hetas Certified Engineers

We strongly recommend that you employ the services of a qualified / certified Hetas engineer. Please do not compromise your safety, the safety of your property or your loved ones and neighbours by performing an installation yourself. 

A badly installed stove can lead to an explosion, a fire or a build up of poisonous gasses and any of these events can lead to a loss of life or critical injury.

Stove guide - Important First Things To Consider

Purchasing stoves over the internet can be fraught with danger if you do not do your research before pressing the buy button.
Remember all stove installations are subject to building regulations and come under the control of your local authority. When you buy from a reputable stove retailer you will get the complete package: advice, guarantee and the right stove, if you've done your research! 
Before purchasing a stove, check with your local authority if you are in a smoke control area.  

You should not burn wood or bituminous coal in a smoke control zone unless the stove has been granted Exemption from the Clean Air act by DEFRA, find some DEFRA approved stoves here. You should be familiar too with the Clean Air Act .

Always follow the advice of your stove manufacturer regarding fuels suitable for your appliance. A good stove retailer will be able to advise on how to get the best results when burning these fuels. Remember you will invalidate your appliance guarantee if you burn a fuel that is not recommended by the stove manufacturer.

Stove guide - Chimney Flue – (the engine behind your stove)

All wood burning or multi fuel stoves require a class 1 chimney flue.  As the majority of stoves are more than 78% efficient it is imperative that the chimney flue is better than adequate. 

The chimney flue is what drives the appliance and the more efficient the stove is, the more efficient the flue system has to be in order to exhaust the combustion gasses quickly into atmosphere. 

Wherever possible the stove should be flued from the top of the appliance into the chimney and not from the back. Flue gasses naturally want to rise in a vertical fashion and encountering bends of more than 30 degrees to the vertical will slow and cool the evacuation of these gasses down,  resulting in possible condensation / deposit problems in the chimney flue. If bends are needed then they must be rounded and not sharp.

Flue Liners

It is common for most stove installations to be recommended a double skin, flexible, stainless steel flue liner. 

These come in 2 grades:
316 - with a guarantee of 10 years.
904 - with a guarantee of 20/25 years.

When either system is installed, I would strongly advise that they be insulated with either Vermiculite, Pearlite, Leca or a non combustible wrap in order to maintain the flue gas temperature. It is imperative that a flue liner is fitted to be both water-tight and insulated correctly.

As the guarantee implies, these lining systems are not permanent. If the stove is oversize or not operated efficiently or the liner is not installed correctly, then the life of these liners can be much less than the period of the guarantee. This can often lead to tension between the installer and you the householder as to what is the cause of the failure. 

A more permanent cure for an oversize or inefficient chimney flue is a “cast in situ” system provided by “Shellcast” or “Cico”. Although this may cost a couple of hundred pounds more to install, you will get a more permanent and durable system that will give many years of service.

Be aware that before any lining system is installed you must ensure that the existing chimney flue should be swept clean and pressure tested for air tightness.

Top Tip - For maximum safety chimney flues should be swept twice a year by a competent person registered to the National Association of Chimney Sweeps – NACS - or the Guild of Master Sweeps or be Hetas approved.

National Association of Chimney Sweeps HETAS  Guild of Master Sweeps

Home Is Where The Hearth Is

3. Your Hetas engineer will advise on hearth construction and ventilation requirements as again both are covered by building regulations. As all combustion processes require a supply of oxygen then there is an ongoing need to replenish any oxygen that is used in the process. Stoves with an output of more than 5kw require an additional supply of air from an external source.

The Silent Killer

Carbon monoxide is a product of incomplete combustion and is formed when there is a lack of adequate ventilation or if there is a blockage or restriction in the chimney flue. Carbon monoxide is a gas that kills, so for safety reasons, prior to using the appliance a battery operated carbon monoxide detector should be installed in the room.

Kilowatt Capacity

4. The kilowatt output of the stove should be very closely matched to the kilowatt requirement of the space you are wanting to heat.  For example a standard room of 15ft length by 14 ft wide by 7ft high only needs a stove with an output of 3 kilowatts.  

Installing an oversize stove will result in possible low firebox temperatures which in turn will lead to condensates and deposits forming in the flue system. These, are highly corrosive and can lead to failure of stainless steel flue systems. 

Burning Real WoodThere is a basic difference between a wood burning and a multi fuel stove, and it's all to give the favoured fuel optimum burning conditions. Wood burns best on a bed of ash, whereas solid fuel needs a grate capable of supplying primary / combustion air. If you want to burn a combination of both wood and solid fuel then this can only be done on a multi-fuel stove.

Before burning any wood, it must be either seasoned for a minimum period of 18 months or have been kiln dried down to an ideal of less than 20% moisture – the drier the better! 

Burning non seasoned logs (Green Wood) leads to creosote type condensates in the flue system. These will not only block the chimney flue but are also highly flammable and will lead to destructive chimney fires. We strongly recommend that you do not burn non seasoned wood in your stove.

Do not allow the stove to “tick over” for long periods especially if you have installed any type of flexible stainless steel flue liner. 

Before and after any slumbering or overnight burn you should “open up” the stove for an hour to increase the fire box temperature. This will help to create the correct conditions in the chimney flue to allow the combustion gasses to escape into atmosphere and not to condense on the inner surface of the flue. 

The purchase of a magnetic temperature gauge, to fit on the off-take pipe (the pipe that connects the stove to the chimney flue), will alleviate any low temperature problems. This device shows the best operating temperature at a glance.

Smokeless Fuels

All smokeless fuels used should be Hetas approved for use in a closed appliance and most importantly do not burn “neat” or “raw” petroleum coke as this can cause severe damage to the firebox. This fuel has very little ash content and consequently burns at very high temperatures. The ash content of the fuel is there to protect the fire bars, the grate and the firebox of the stove from the very high temperatures generated during the combustion process.


Natural ventilation is a good thing. Avoid using extract fans in the locality of the stove as this leads to a lowering of pressure in the building which can cause the combustion gasses to be drawn “back down” the chimney flu and into the room.

Stove Buying Golden Rules

Maintain sufficient temperature in the firebox to ensure the combustion gasses can escape into the atmosphere.

  • Follow the stove manufacturer’s guidelines and Stove Retailers advice.
  • Purchase a carbon monoxide detector.
  • Building regulations are there to ensure maximum safety – abide by them
  • Use a certified Hetas Engineer
  • Talk to your local authority before spending your hard earned cash

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