Frequently Asked Questions

Basically, it is the process by which volatile gases that would normally be emitted up your chimney are re-ignited inside the stove creating more heat and better efficiency and cleaner emissions from the same piece of fuel. Secondary indicates that a second ignition takes place, tertiary indicates that a third ignition takes place.

However, do not be ‘blinded by science’ when you examine and compare your stove manufacturers. A fair comparison can be based on Kilowatt Rating (KW) and Efficiency rating.

Question 3

Sorry but we have to get a bit ‘heavy’ here so bear with us!

1 Kilowatt is equivalent to approximately 3,600 BTU (British Thermal Units). A BTU is equivalent to 1,055 ‘joules’ which is now the internationally recognized measurement for this type of energy.

The reason we mention BTUs is because a BTU was traditionally used as a measurement for the thermal energy required to heat 1 pound (453 grams) of water by 1 degree Fahrenheit (approx. 1.8°C).

So, a Kilowatt in terms of thermal measurement is considered to be 3,600 times more than the thermal energy required in this simple experiment heating water.

Ok so far?

Well, the Kilowatt rating on your stove is not simply the thermal energy being output by your stove. The stove itself does not produce any thermal energy in it’s own right – it is just a metal box.

Really, the KW rating on your stove is more like a measure of the ‘ideal’ thermal output that your stove can maintain during the burning process inside it whilst maintaining a certain level of efficiency as well as not prematurely damaging the stove body or internal components.

Warning! Stove manufacturers will choose what data suits the market they are targeting and publish accordingly.

For example, a stove rated as 12KW and 75% efficiency during the test process may comfortably be able to kick out 16KW without too much trouble. However, the efficiency at 16 KW may be reduced to 70% which does not suit the manufacturer’s target market so they publish the results based on the 12KW figures.

Question 4

Flues are currently not regulated here in SA so you can even find ‘galvanized’ or low grade stainless steel products on the market. Be cautious of these as you will get issues with leaks, corrosion and smoke which will dampen your fireside experience. Speak to your Charnwood distributor who will offer a full detailed quote for supply and installation.

As a basic, we recommend an ‘entry level’ grade 304 product (the non-magnetic type if you want to do a quick check with other available products).

Question 5

It is our goal to develop a network of Charnwood approved installers for our products nationwide. So far, we have some excellent partners dotted around the country who will assist. Contacts us for a distributor near you.

Question 6

Well, you did ask!

This is supposed to be the measure of how much of a fuel’s latent energy is given to your room during the burning process. EG – If I converted every single part of a log in to heat that radiated in to my room from my stove, then I would achieve 100% efficiency. This is impossible. The best wood-burners can achieve 80% (some ours 85%) but most decent wood-burners are around 75-80%. 

How do they measure this?

Crudely speaking, the ‘scientists’ set a measure for the amount of fuel to be used (weight etc) and how often the refueling will take place. They will test the emitted flue gases in the flue pipe (chimney) for temperature and carbon content (and other emissions) during the burning process allowing them to calculate how much energy contained in a given fuel has not been radiated from the stove to the room compared to how much has been lost up the chimney or left in the ash-pan. The difference gives you a percentage rating for how efficient the stove is. E.g a stove with 75% efficiency rating is effectively transferring 75% of the energy stored in the fuel consumed to heating the room.

This is useful in principle. The problem is that each manufacturer may use their own test conditions to measure the efficiency which makes it very subjective! Even within regulated countries, they can choose what fuel, how much fuel, refueling times and oxygen intake they want to use under the test conditions, provided they publish this information.

This makes it close to impossible to measure exactly ‘like for like’ as you do not know what the test conditions set by the manufacturer are.

However, the good manufacturers (like Charnwood) will publish their test conditions and refueling times which means that you have a much more genuine result and can make a better comparison with others (provided they also publish their test conditions). In addition, all Charnwood stoves comply with EN13240 or EN13229 which set down some basic principles of efficiency as a minimum. In addition, all Charnwood stoves are leading the way in terms of compliance with  ‘Eco-Design 2022‘ which raises the bar for clean solid-fuel burning standards to its cleanest in Europe ever. 

Question 7

All Charnwood stoves are tested to meet the latest EU and UK regulations. They also produce stoves that meet EPA (USA) regulations along with a host of other countries.

This is extremely reassuring as you can be assured that your Charnwood stove will meet your expectations!

Some manufacturing areas of the world (such as developing economies and cheap producers) may readily sight high efficiency ratings and KW outputs but one should be cautious when presented with impressive statistics from relatively cheap products. Like most things in life – you get what you pay for with a stove.

Question 8

We are advocates of wood. Plentiful in supply, sustainable and affordable. BUT IT MUST BE DRY (read this article to find out why). You can burn many other fuels on your Charnwood stove but wood is our preferred fuel. Your average tree will consume more carbon dioxide during it’s lifetime that it will produce when burnt in an efficient closed combustion fire place. Our fireplaces work exceptionally well with semi-hard, well seasoned non-resinous woods such as eucalyptus (blue gum).

Question 9

To start with, you will wear through your fire grate and throat (baffle) plate prematurely which could be a costly and unnecessary replacement.

In addition, evidence of ‘over firing‘ will likely invalidate your warranty in the event of damage to the body of the stove. This is the case with any stove manufacturer.

‘Over-firing’ is a common mistake made by new-stove enthusiasts. Generally, the new user believes that he should have a raging inferno at all times, when in fact, the burning process should be ‘slow and steady’ not ‘hard and fast’.

An easy way to avoid this common misunderstanding is to use a stove pipe thermometer until you get used to regulating the heat from your stove. We supply them and they work on any stove.

If used and maintained correctly, your stove body will last you a lifetime. Internal components will normally require replacement over a 5-10 year cycle.