To reduce the risk of a chimney fire you need to;-
- choose an appropriate fuel for your appliance and burn it as efficiently as possible.
- keep the chimney warm.
- inspect and clean the flues and chimney at regular intervals.
You need to minimise the creation of soot, tar and creosote. Damp/unseasoned logs can very quickly create a fire hazard in any chimney, particularly if they are burned slowly. Therefore make a special effort to season your firewood thoroughly before you burn it. This is covered in our Fuel page.
The use of household (“bituminous”) coal in a closed stove can likewise generate high volumes of soot, and will void your stove warranty. You’ll find smokeless fuels are far more satisfactory.
A warm chimney is far less prone to fouling up than a cold one. Therefore chimneys contained within the body of the house work best and those on the end of a building – particularly when fully exposed to the weather – have a built-in disadavantage. In the latter case, it may be possible to boost flue-temperatures by lining the flue with a low-mass flexible liner back-filled with an insulating filler material. A discussion of internal/external chimney placement is on our Chimney Theory page
You should sweep your chimney ‘as often as is necessary’. There is no fixed rule about this since much will depend upon the frequency of use, type of appliance, type of fuels used – etc. If in doubt, call the sweep in sooner rather than later and consult them on their findings. If your usage pattern is fairly consistent it should become fairly easy to judge the intervals at which cleaning is necessary.
Deflector plates are generally made from cast iron or mild-steel. These materials have a high melting point but they are in the hottest part of the fire and should be considered as a ‘sacrificial’ component. How long a deflector plate lasts depends partly on the overall design of the stove and partly on your manner of running the stove. If a deflector burns out at short intervals you should take this as a warning to mend your ways! Either you are burning a fuel with a long flame that actually causes the deflector plate to become red hot for long periods, or you are simply over-running the stove. Either way you are almost certainly losing much of your heat straight up the chimney thereby incurring excessive fuel costs.
A central heating stove does far more work than a ‘dry’ stove that is simply heating one room so it is unsurprising that deflector plates tend to burn out much faster in boilered stoves. All the more reason to choose your fuel carefully when you want to keep a battery of radiators hot for hours at a stretch. Smokeless fuel is by far the best choice in this situation. You should aim to create a fire with plenty of heart in it and even, radiant output. This means keeping the airflow through the stove under tight control and not over-running the stove. If you’re burning wood only, see our Technique page for the right and wrong way to burn wood.
Modern door glasses are made of single-piece ceramic glass which is far more stable than the strips used in early stoves. Nevertheless, glass is funny stuff and sometimes contains invisible stresses that can cause it to crack for no apparent reason. Therefore the occasional crack is to be expected. However if you have frequent problems the most likely cause is that you are over-tightening the glass into the door-frame. Cast iron and glass expand and contract at different rates. When you fit a new glass, renew its compressible gasket at the same time and take care not to over-tighten the attachment bolts. They shouldn’t be much more than finger-tight.
It is unlikely that your door-seals are the only things gumming up! The glass is probably blacking up as well – and perhaps other fire-box components. The use of damp/unseasoned wood is the most obvious cause, coupled perhaps with a tendency to go in for long, slow burns. Take this as a warning that you are almost certainly building up flammable deposits in the chimney – and the prospect of an unpleasant chimney fire. If you must run your stove on a low setting for long periods the use of bone-dry wood becomes absolutely critical and even then, some judgement is needed to ensure you don’t under-run your stove with the consequences illustrated on our Technique page.
In the last few years most stove manufacturers have changed over from the old-style refractory fire-bricks (heavy and brittle) to the new, lightweight insulating firebricks which resemble a light-coloured chipboard which are designed to keep the firebox hotter and reduce emissions further. The new material is more durable than the older but is softer. Like deflector-plates these lining materials should be regarded as sacrificial and will need to be replaced from time to time. And like deflector plates you can shorten the life of your fire-bricks very considerably by running your stove too hard, and by being rough with them.
Most stoves now have steel bodies and cast iron doors, so this is less of a problem nowadays, but older stoves may have cast iron body panels, which are inherently brittle.
You should never fire up a cold stove too fast or you run the risk of creating uneven expansion – the single most common cause of fractures. Also make sure the internal burn-plates or firebrick linings are in sound condition as they are designed to protect the panels from excessive heat. If you study the relevant section on Technique and create burning conditions within your stove that deliver a steady, even radiant output, your cast-iron stove should give many years of trouble-free service. This assumes you have bought a branded product assembled from top-quality casting. Cheap, imported stoves of dubious origin are a different matter and are best avoided.
You may simply be over-running your stove. It is a common mistake to allow too much air to enter the stove. The more air you let in, the more heat you let out to the chimney. So aim at a balance and study the general discussions on the Technique page.
Other factors include use of unseasoned wood. The moisture content in logs has huge impact on the actual amount of fuel you have to burn for a given output as is illustrated on the Fuel page.
You may also be expecting too much of your wood if you are trying to obtain sustained high-outputs from a central-heating stove. The burning characteristics of wood are not well suited to driving high-output boilers in modestly proportioned domestic heating appliances. Switching to a smokeless grade of fuel (Like Homefire or Phurnacite) may well solve your problems.
Finally, take a hard look at your installation. A deeply recessed stove is operating at a massive disadvantage and may only be delivering a fraction of its output to the surrounding air. A properly designed and insulated convector-box can overcome this difficulty. To learn more see our Installation page.
Any new stove that has been sprayed with a matt paint will produce fumes for a short period while the volatiles are driven off. This is nothing to worry about – simply open a window and air the room until the process is completed.
You may also want to check that there is no physical blockage in your stove – caused for instance by a badly deformed deflector plate.
Solid fuel cookers – particularly when run on household coal, can clog rapidly in the flue passages around the oven(s) and should be cleaned at regular intervals.
But in the vast majority of cases, the stove is blameless and the real culprit is your chimney which if it is doing its job properly should be generating enough ‘suck’ to remove all fumes. If it is not, check the flue-connector between your stove and chimney first, since this is often a bottle-neck that clogs up first.
If the problem persists even after you have had the chimney inspected and swept, you may have more serious design/structural problems. See our ‘Chimney Theory‘ page for a general discussion on chimneys that may help you trouble-shoot your problem.
Modern stove designs offer an ‘air-wash’ or ‘clean-burn’ option that helps to keep your glass clear. The best designs employ three techniques;-
- The air supply is pre-heated by being passed through a duct in the head of the stove and is then passed over a blade that causes it to spread out and wash the internal surface of the glass.
- The door is double-glazed.
- The fire-box is lined with insulating fire-bricks in the area of combustion.
The effect of these three techniques is to boost temperatures to a level at which smokeless combustion can take place.
If your glass keeps blacking over, your stove may not be a clean-burn model or the clean-burn features may be poorly implemented. High output boilers virtually obliterate the benefits of a clean-burn design by keeping the combustion temperature down at a level at which even the driest wood is likely to produce some smoke and tar.
Positioning fuel too close to the door can disrupt the air-wash system and create sooty marks on the door.
The final and most frequent cause of glass blacking up is use of damp/unseasoned wood – particularly in conjunction with long, slow burns.
You can clean your stove glass using a specialist glass cleaning product, or by using damp kitchen paper or newspaper dipped in some of the stove ash, followed by a clean damp piece of kitchen paper to clean the ash off and finally a dry piece to dry the glass off. Alternatively, for very stubborn deposits a Stanley blade in a plastic holder does the job quickly and efficiently. You should not attempt to clean hot glass!
Grate bars are cast at an extremely high temperature and contain various additives including chromium to make them more durable. This explains their high cost.
If you are burning smokeless fuel with the grate bars open, then the best way to extend the life of your grate bars is to riddle and de-ash at regular intervals. That way the bars are cooled by the air-stream passing through below. If you let ash levels build up, the cooling effect of the air is lost. In extreme cases you may even ‘submerge’ the bars in a bed of red-hot ash. At these elevated temperatures they will distort and quickly burn out.
Some grades of anthracite generate temperatures high enough to shorten the life of your grate bars. Over-running your stove on almost any fuel will have the same effect – a practice that’s all too common when the stove is a boiler model driving several radiators.
Cheap grate bars of dubious origin will nearly always fail prematurely. Buy only branded spares originating from your stove manufacturer.
(Footnote; the above text relates to stoves being fired on solid fuel. If you are burning wood only, you should be burning onto a bed of ash – see here – and your grate (if your stove is equipped with one) should last virtually forever.)
Check your fuel first. Household (“bituminous”) coal produces large volumes of soot and the modest airflow through a closed stove is simply inadequate to carry it clear of the chimney. This is why it should not be used in a stove and will void your stove warranty.
Slow-burning is another area to review – especially if you are burning damp, unseasoned wood. All stove installations need to be burned up brightly at regular intervals to purge condensate and tars from the flue-ways.
Chimneys on the end of a building – particularly those fully exposed to the weather – soot up far more rapidly than a ‘warm’ chimney accommodated within the main body of the house. See our Chimney Theory page for a further discussion on this.
See section above on fumes coming into the room.
A stove that runs out of control in average conditions obviously needs attention. Most likely the door seals are worn and possibly one or more damper-seals (if fitted). If the stove has been over-fired the doors may be warped to the extent that they no longer close properly.
Stoves that are DEFRA exempt are designed to prevent you from shutting them down enough to put the stove into a full slumber and therefore tend to burn quite brightly even when shut down as fully as possible. Also we often suffer from Atlantic gale force winds which can have a considerable impact on a DEFRA exempt stove since you can then find you have much less control over your stove than is ideal when there is a fierce draw due to weather conditions. Stoves that slumber often do not burn wood cleanly and thus produce smoke and various deposits which in an a smoke control area, is deemed illegal.
These are the obvious and cheapest things to check ‘on the ground’.
If you are in a very exposed location, your chimney draught may exceed the values your stove is designed for. A well-engineered stove built to tight tolerances is better able to resist this problem than a leaky appliance with poorly aligned door-hinges and crude air-valves – and thermostatically controlled appliances are more vulnerable than stoves with robust manual controls.
Often it is best to tackle extreme draught problems at their source. Aerocowls have an excellent track-record for both taming excessive draught and helping to eliminate down-draughts.
See above. This problem is related to the problems of a stove running out of control.
A cold chimney doesn’t generate much draught so this problem is most likely to arise when the fire is out. The smells are also associated with moisture so anything you can do to dry out the chimney and warm it up will help. Burning a small quantity of smokeless fuel at low output may be beneficial and if you have to leave the house unattended in wet weather for an extended period you should fit a rain-cap. This won’t afford much protection though when rain is carried under the cap by strong winds. One short-term expedient is to tie a plastic bag over the chimney if it is accessible. But remember to remove it before lighting up your next fire!
The rated output of a boiler is generally only met when the stove is run at its rated output. Therefore if your stove is rated at 4 kW and you run it closer to 2 kW the boiler capacity will drop from 10,000 BThUs to just 5,000 BThUs. It may drop more and it may drop less. Much depends on the design of the stove – but also on the way you run it. Again, a common mistake is to let too much air into the stove. This literally cools the internal surfaces of the appliances and allows most of the heat to rush up the chimney.
The burning characteristics of different fuels can have a major bearing on boiler performance. A fuel with a short flame and high radiant output does best. Smokeless fuels and charcoal cannot be beaten, but once again, damp/unseasoned wood is unsatisfactory.
Poor chimney draught – and even excessive chimney draught can upset boiler performance. A poorly designed system may be ‘robbing’ heat due to lengthy pipe-runs, or circulation may be poor. There is too, the possibility that your boiler has been under-specified for the job it has to do.
Thus there are several variables to be examined and in practice a boiler that is actually defective is so rare as to be almost the last thing to consider!
A useful reference point when outputs are in dispute is to do a test-firing with a ‘benchmark’ fuel. If your principle fuel is wood, try burning a quantity of wood briquettes which have a moisture content of only around 7%. The results may well astound you! If you burn mainly solid fuel, run a test with Homefire. This again will enable you to compare the fuel you are burning against something you can always refer back to.
The most likely cause is that the stove has the wrong output ratio for the job it is doing. Take a situation where your sitting room needs 3 kW of heat and the rest of the house needs 30,000 BThUs. If you now install a stove that delivers 5 kW of heat to the room and 30,000 BThUs to hot water, your sitting-room will receive 2 kW more than it needs.
In the short-term your only option is to attempt to ‘spill’ some of the excess heat from your sitting-room to an adjacent area. In the longer term you should consider replacing you stove with one correctly balanced to your needs.
This most commonly arises when the stove is an ‘inset’ model. These stoves are effectively buried in the wall and deliver only a small fraction of their output to the room they are installed in. Adding a radiator or increasing the size of the one fitted should solve your problem.
There are several possible causes for this;-
- Airlock somewhere in the system.
- Insufficient rise in the pipes between the appliance and the domestic hot water tank.
- Pipes too small in diameter.
- Pipe runs excessively long.
- Boiler over-specified for the job it is doing.
In the first four cases, the time taken to heat up a tank of cold water may be noticeably slow. You need to call in a plumber – unless you have the competence to tackle the issues yourself.
If the boiler is over-specified for its job, one possible solution is to mask part of it off with some insulating fire-brick using adhesive fire-cement. Another possibility is to dissipate the excess heat through a towel-rail or something similar. The third option of course is to replace the boiler with one matching your needs – though this may involve replacing the entire stove.