Reasons for regular maintenance of stoves and the risks of neglect.

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Any kind of appliance that does something with moving parts and especially those exposed to high temperatures , will need to be maintained regularly.
When it comes to maintenance people can normally be divided into three kinds:
1. Those that know , understand and appreciate the situation and whom will maintain their devices/appliances.
2. Those that know but think they can ‘risk it’ one more time.
3. Those who are just simply not aware. [Installers to blame here?]

Once you own a wood burning stove you become responsible to ensure it works safely , burns cleanly and hopefully lasts as long as possible. Unfortunately , many stove owners are unaware of the basic requirements needed to ensure it all keeps working correctly.

Wood burning stove maintenance

Stove maintenance can be broken down into three distinct sections. Much of the daily maintenance can be handled by the owner but some of the more complex maintenance will require professional help.

  1. Regular owner maintenance checks and stove servicing.

Ensure the stove is cold with no burning embers before undertaking any of the tasks below which are mostly straight forward , once you get used to them.

  • Clean out the ash on a regular basis. (This may seem obvious but it’s often overlooked and the old adage of a little ash in the fire bed for burning wood is often abused.)
  • Regularly check all controls for smooth movement.
  • Burn only seasoned or kiln dried wood that is the correct size for the firebox. Burning wood that is low quality or high in water content will damage your appliance and liner, may cause a chimney fire and is a nasty air pollutant.
  • Check firebricks for cracks monthly.
  • On a 1-3 monthly basis, the baffle plate should be removed and the flue way checked for soot build-up and potential blockage. If you are not confident with removing and replacing the baffle , get your chimney sweep to show you how or do it for you.
  • Clean the glass. If you cannot see the flames then you do not know how well your fire is burning. Remember moderate flaming combustion is what you need.
  • The last part of owner maintenance is planning regular expert maintenance from your local experienced chimney sweep.

2. Chimney sweeping

Regular sweeping of the chimney is imperative to the correct and safe functioning of all solid fuel appliances. Chimney sweeping is a profession that requires a diversified knowledge skill set , the correct equipment and a lot of experience.

It is widely accepted that all chimneys should be swept annually as a minimum. Some chimneys require sweeping twice per year and rarely some even more frequently, depending on use and a variety of other factors. A professional chimney sweep will also provide important advice and confirm with you the required sweeping frequency for your usage , which with a lot of other information will be recorded in his notes too.

3. Solid fuel servicing

Solid fuel servicing is often an unknown variable when people purchase stoves and similar appliances. Whilst it is true that many stoves often last a very long time, it is also true that their internal components often do not. Owners are often surmised to find many of these items are NOT covered by guarantees and are classified as consumables by manufacturers.

The internal stones and grates of an appliance should be designed to survive the rigors of use however they do decay, wear and occasionally break. Repeated opening and closing of doors degrades rope seals which will eventually require replacing. Controls and hinges can become loose or seize with time. Castings and the main body of the stove itself can warp or even crack.

Door Glass can be broken but more often becomes scratched or milky with use and replacing it is not as straightforward as replacing the glass of a house window. The glass used in stoves is often a clear pyro-ceramic which is held in place with heat proof fixings and sealed with a specially sized fiber glass rope. It is specially treated and pre-cut with beveled or smooth edges to prevent early failure

Many owners find it most beneficial to find a professional sweep who also undertakes servicing as this can save time , money and gives peace of mind. Experience is very important when servicing is involved as there are so many appliances , that only time and practice can teach.

Potential risks of maintenance neglect

There are many possible risks to the stove user who avoids or neglects the necessary maintenance and sweeping intervals:

Carbon monoxide poisoning even death
Chimney fire
House fires
Invalidated warranties**
Invalidated home insures**
Shortened appliance lifespan **
Greatly increased running costs
Excessively polluting our air quality
Angry neighbours

*** These risks are very real and significant ***

If you are unsure of what you must do yourself then call your local chimney sweep and ask to have your stove swept , while he is there you can ask for his advice. Although the advice in this post is good general advice please note it is not specific to your particular appliance.

You must take professional advise specific to your particular installation
So Make sure your installer educates you at the time of installation !!! You must also read and follow the guidelines set out by the appliance manufacturer in the instruction manual. You should also be aware of your home insurance company policy regulations and or small print.

Buckled/Broken Baffle Plates

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It almost always comes as a shock to new wood burner or multi fuel stove owners that their baffle plate (also known as a throat or deflector plate) is classed as a stove ‘consumable’ and is therefore NOT covered under their stove warranty in the same way that most of the other components are.

This is because baffle plates are positioned at the top of the fire chamber specifically to deflect flames and heat back into the stove instead of letting them go straight through the flue system. And is partly why stoves are much more efficient at delivering heat to your room than an open fire.
However, it’s also why even on top quality stoves, baffle plates tend to burn out.

The Main Problem

Baffle plates are positioned at the hottest possible part of the stove and take the full brunt of the very high temperatures day-in and day-out. So whether your baffle plate is made of traditional cast iron, heavy steel plate, stainless steel or vermiculite board, you will eventually have to replace it.
How often this needs to happen depends on the type of fuel you burn, the size of the fuel load and how you burn your fuel.

Some stove owners can burn through their stove baffle plate in a matter of months and conversely some owners can make theirs last for years. A baffle plate on a boiler stove for example, will not tend to last as long as a baffle plate on a non-boiler stove. This is simply because boiler stoves generally need to be burned ‘harder’ over longer periods to maximise the heat to the hot water, especially when there are lots of central heating radiators connected to the system.
***As a matter of interest, smokeless mineral fuels (eg Anthracite Ovals) do not have the same flame height as an equivalent wood log load and can therefore be easier on a boiler stove baffle plate (but not necessarily on your CO2 emissions or our faces).***

The Consequences

If you regularly need to replace your stove baffle plate then you should review how you operate your stove by referring to your owners manual. It should contain advice on recommended fuel types and fuel loads, as well as instructions on how to effectively operate your stove. Quickly burning out a baffle plate means that you are probably not only wasting money on replacement baffle plates but also wasting money on fuel for sure.

***Chimney sweeps need to be able to remove the baffle plate so they can use the power sweeping equipment and clean effectively. *** If it is buckled and cannot be removed then I am in the unfortunate situation of having to charge a call out fee and you will need to call your installer out to remove & replace it.

Damaged baffle plates are increasingly more common these days, (which is one of the reasons for writing this article) creating speculation on the quality of metal materials nowadays. Also, often the installers fail to ensure the customer is sufficiently educated in the use and maintenance requirements of their appliance in the first place. Mostly though, it is users over filling beyond the stove load capacity.


The Cure

It is often the case that you are over loading and over-firing your stove and producing excess heat which is wasted through the flue system. An easy to use magnetic flue pipe thermometer will help you to monitor your flue gas temperature and can clearly indicate when you are over-firing your stove.

In my opinion a flue pipe thermometer is one of the best, ‘value for money’ stove accessories you could buy. It helps you to maximise the efficiency of your stove and also alerts you when your stove is potentially dangerous by being over or under fired.

It is very easy to abuse a stove and burn out a baffle plate within a single heating season by simply ignoring the manufacturer’s recommended fuels and operating instructions. Ergo, it’s also easy to see why most manufacturers now exclude baffle plates, fire grates, fire fences and glass from their normal warranty terms.

Figure 1 : Warped , corroded and finally broken Baffle plate

Figure 1 above shows a burned out cast iron baffle plate which is about three years old.

The owner used mainly softwood (it was free) which required a substantially bigger fuel load than the equivalent hardwood load needed to generate the same heat.

***This meant that the fuel and flames were too close to the baffle plate so the extremely high temperatures which were created, caused the baffle plate to warp and eventually fail (there is NO middle left).***

That particular stove had a rear fitted flue and it wasn’t until the owners noticed the flue pipe was glowing red that they realised they had any kind of problem.

Cool Fuel Rules

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There are many fuel types available to the solid fuel user: coal, peat, wood logs, compressed wood products, smokeless coals. With so much negative information in the press these days … which is the right fuel for you to burn?

Firstly , you must look at your appliance and follow the manufacturer guidelines as burning the wrong fuel type can be dangerous and at the very least invalidate your warranty. Good sweeps are generally a hive of knowledge.

If you care about the environment, then you would want to focus more on renewable fuels such as wood logs.

Selecting and purchasing wood logs

Ash and beech are some of the best woods logs to burn however most logs burn perfectly well (see our burning wood post) if they are dry enough and have been adequately seasoned.

Wood should be purchased from a reputable supplier who should have to comply to regulations and have a vested interest in planting more trees to replace what has been felled.

Wood logs must have less than 20% water content when they are burned. This can ascertained several ways, (see our post on moisture meters) but the easiest and probably most reliable at a price is to purchase logs from woodsure who will have done all checks and tested the moisture content in random batches. You will also be able to complain if the wood you purchased is too high in water content.

If you choose to purchase unseasoned logs then you must season them (typically for 18 months or more) and after seasoning you must test the moisture content with an electrical conductivity moisture tester prior to using them. (again for more on this see our post on moisture meters) Users burning wet wood are one of the biggest problems and challenges our industry faces but it is one of the easiest fixes too.

Why mixing fuels is a problem

Wood and coal burn quite differently. Wood burns through a process of gasification where the volatile oils within become heated, turn to a gas, mix with oxygen above the log and then eventually combust as a mixture of gases.

Coal on the other hand is primarily a carbon, to burn efficiently oxygen must enter and mix from below the fuel. Combustion takes place inside and not above the coal itself.

There are also distinct differences between wood and coal burning types of appliances, such as a grate below or just flat metal base.

Some issues associated with the incorrect use of fuels

  1. Wood on top of coal

If you try to burn wood on a bed of coal you would need to open the top air intake, thus drawing air above the coal and not through it from below. Therefore, the coal would burn poorly and produce high levels of carbon monoxide and carbon dioxide, which acts as a fire suppressant/extinguisher and the effect is compounded by the inadequate heat from the coal.
Wood burns by first emitting volatile hydrocarbons which then become gaseous.
Normally these hot gasses mix with oxygen and burn with the yellow flame we associate with wood. However, in the reduced oxygen environment above a coal bed the volatile gas emitted by the wood log will instead travel into the chimney where it then deposits as a flammable creosote.
Another issue is when combustion temperatures and oxygen levels are too low, then the later hotter stages of gaseous combustion will not effectively take place. During these later phases, carbon soot particles should be burned.
If these particles are not burned they will then exit the chimney as fine dust pollution harming our air quality with all the associated risks.

2. Coal on top of wood

So we understand that coal requires oxygen from below to burn effectively, think bellows in a foundry. If we burn wood below a coal bed we will have a situation where our coal is bathed in carbon dioxide leaving an incomplete burn. The second issue here is that wood produces lots of ash which in turn blocks the ash grate, further lowering the amount of available oxygen to the coal.
If the coal used is smokeless, such as anthracite then high levels of sulphurous compounds will also be emitted. These compounds are highly corrosive and will eat through stainless steel liners and most pot coverings in next to no time. The one exception to the wood underneath coal scenario, is when kindling a fire with wood. Here it is very likely that the air intakes or even the door will be open in order to provide enough oxygen for both fuels for a limited time.

Slumbering

The term slumbering describes the process of the user loading the already burning appliance and then closing down the air supply. This is in an attempt to make the fire burn for long periods, typically overnight.

The big problem here is the fact that fuel requires oxygen for combustion. When oxygen is limited in a combustion reaction, there are several results that occur as are shown below.

  • Much of the volatile content within the fuel is emitted due to the reduced heat but it does not combust. It rises up the flue coating the chimney with volatile fuel, greatly increasing the risk of chimney fire and the requirement for sweeping.
  • Carbon requires lots of oxygen and heat for the particles to combust. When the oxygen supply is limited, dangerous sized carbon particles are released. Many of these particles make it to the outside air as fine dust pollutants , polluting the environment and causing health problems such as respiratory and lung diseases.
  • Heat or the lack of. In order for a fuel to release its stored heat, it must react with oxygen, it being the catalyst for a combustion reaction.
  • Cost. Slumbering will shorten the life of stainless steel liners, increase the need for servicing, sweeping and maintenance. It will reduce the heat value that you should get from the fuel, making it less cost effective too.

In conclusion

Ideally you would only burn dry wood logs in an environment that has adequate air/O2 for moderate flaming combustion to take place. This is achieved by adjusting the air supply so that flames are not sucking up the chimney but not limited too much. Smoke should not be visible in the firebox, only in the fire.
Also by adding only as much fuel as is needed to fill the fire box with flames, because burning too much or too little fuel at a given time is another mistake to be avoided.

Your chimney sweep should give tips on fuels and how to achieve adequate flaming combustion, fuel storage, types, sweeping frequencies and many other important factors surrounding good use practices.

Fake News and wood burning stoves

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Wood burning stoves have been unfairly targeted by blogs, the press … just about everyone lately and are being painted in a very negative light. The reality, which in my view is very different to that portrayed in the press of late. So i will attempt to address the matter somewhat here in this post.

Firstly, wood is one of the only truly renewable fuels but yet is often compared to diesel due to some of the particles that are emitted when burned. Diesel is a fossil fuel derived from crude oil and although some particles are emitted during burning wood (in a bad way & in old appliances) I’m pretty sure that diesel does not produce a major percentage of the worlds oxygen like trees do.

With the massive deforestation that has takes place in recent history, ethical log suppliers are now rapidly planting trees which will help safeguard our future generations. Those same planted trees will store the carbon released from today’s log burning making the cycle neutral.

Statistics can be a funny thing and are often taken on an annual basis. As we know, the wood burning season in the U.K. is relatively short beginning late September through to the end of March/April. During the rest of the year any measured pollution does not come from wood stoves. Ironically it is the summer months when the dangerous carbon dust particles are often at their highest levels.

As far as i am aware, there are no statistics specific to wood-stoves published in the U.K. with regards to air quality or pollution. Instead statistics are based on all domestic burning of wood and its’ derivatives and includes open fires, camp fires, pizza ovens, BBQ s and bonfires. The last two in the list are some of the very worst pollutants and yet somehow only wood burning stoves are being attacked.

I understand that there is a genuine problem with the use of some wood burning stoves. There are four main issues that chimney sweeps must advise on; in regards to wood burning in order for clean combustion.

1. Moisture content and quality of wood logs.
During the combustion process it is necessary for there to be high enough temperatures within the firebox in order to burn the majority of the carbon particles. When excess water is present, the energy which would normally ignite these particles is instead utilised to evaporate the water contained in the log. This causes much of the fuel contained within the wood to not burn and is instead emitted as smoke.

**I personally always suggest you only burn sustainably sourced (preferably hardwood) logs with less than 20% moisture content. Using wood-sure logs will help as the checks have already been done but you can always invest in a moisture meter and check for yourself.

2. The way the end user burns their stove: specifically the dangers of slumbering, over-fueling or under-fueling.

As is often with many ‘old school’ things, some strange ‘old wives’ tales have developed about how stoves should be used. It has unfortunately become a ‘normal’ practice for many to fill the stove with wood and then reduce the air supply in order to make it last through the night. The process is referred to as slumbering and it is very bad indeed with regards to air quality and pollution. Not to mention the safety and functioning of your stove +/ liner.

To use layman’s terms; if you remember the Bunsen burners in school science labs. When the air hole on the side is open the flame is sharp, blue and clean. But limit the oxygen by closing that hole and the result is a flame that becomes lazy, yellow and soots up whatever it touches.

This yellow, colder flame in also inherently more dangerous because the levels of carbon monoxide are very much higher in a reduced oxygen environment (combustion is incomplete). Limiting the oxygen results in a much lower combustion temperature meaning many volatile components do not burn when slumbering, therefore it is far more polluting.

Like all hydro carbon based fuels wood needs oxygen in abundance for all of the gasses emitted within the fire box to combust completely and cleanly. Limiting the air does not limit the gas released by the logs it only limits how much of the gas will burn.

***Users are advised to always burn the quantity of wood that the stove was designed to use and with primary & secondary air controls open enough to provide moderate flaming combustion. [This is when the entire window is filled with rolling fire and no smoke is seen but not so much that the flames can be seen sucking up the chimney.]

3. The third problem relates to the age and efficiency of the stove. It is a fact that older stoves are very much more polluting than newer, more modern appliances. ****Consumers should be advised that new appliances will save on fuel, give more heat and allow much better quality air that we breathe.

4. Finally, servicing and maintenance.
It is understood that regular sweeping of chimneys, cleaning flue-ways and servicing appliances are all essential for continued efficient combustion. Chimney sweeps should ideally ensure that stove servicing and education is a part of their repertoire in order to bring this essential service to their customers.
*****Indeed, my own advice is always to burn clean dry logs (<20%). Do NOT slumber and use the correct amount of fuel in each fill. For what it’s worth i also try to suggest clients update outdated appliances where necessary and should get our sweep service up-to two times per year.

It is the general opinion of the profession that further debates or articles should be fairly measured against all sources of pollution and not unfairly target wood burners alone. The minutiae of the fixes for wood burning stoves are simple and the industry has made great progress in these areas already.

Surely, the issue of particulate emissions rests firmly in the hands of other industries; which now need to be ethical as we have always been, engage in debate and effect change.

For example; one wonders what is being done to educate the consumer with regards to, BBQ s Chimeneas, patio heaters and pizza ovens? Thousands of these are sold each year in the UK and yet such heavy polluters never make fair target for the press? As previously mentioned they are often used in the summer when pollution is at its highest. Also consideration too, should be given to bonfires and the burning of urban dung fires which produce extreme amounts of pollution.

In conclusion, the discussion on clean wood burning needs to be addressed holistically and not simplistically target any one tiny segment of the overall market.