18th May 2014By Julie Curnow
Getting the Most out of Your Wood Fire: Part 2
Creosote build up
This is the second part of my “5 Tips to Getting the Most out of your Wood Fire” blog. The first part looked at the importance of choosing the right wood and storing it appropriately. The second part looks at burning the firewood efficiently.
Putting these small steps into practice can help improve the efficiency of your heater, saving you time and money.
Tip 3. Minimise Creosote Build Up
The smoke from a wood fire contains a dark brown or black substance called creosote. This is commonly found inside chimneys when wood has burned incompletely.
At temperatures below 120oC creosote will condense on the surfaces of chimney flues. When the temperature gets below 60oC the creosote deposit will be thick, sticky and similar to tar. This tends to trap carbon from smoke which dries and bakes inside pipes and flues.
- To minimise creosote you need to minimise smoke and keep your fire burning hot (refer to Part 1 and How to Build a Fire).
- Removing the creosote build up is important if you want your fire to work efficiently because it is a lot harder to establish a fire if there is a build up in the flue.
- A fire can also occur in your flue if creosote isn’t removed because this substance is very flammable.
- You can either clean it yourself or pay a chimney sweep to do it. This should be done annually in Western Australia and more often in cooler climates with a longer winter.
In addition, clean the creosote off the glass viewing pane and inside of the fire with a soft damp cloth each time your fire dies down and your fire is cool enough to touch. The creosote comes off easily, particularly if the fire is warm but not hot.
If there is a rapid build up (seen on your glass viewing pane) this is a sign that you are either using the wrong wood or are not operating your fire at a hot enough temperature (too little air).
Tip 4. Do Not Overfill the Heater
A fire needs an adequate supply of air to burn properly thereby minimising smoke and creosote and maximising heat output.
- Even in a hot combustion heater, the gas given off by the wood will not burn if it is not mixed with enough air. It is also worth noting that if the gas and air do not mix together until they reach the flue, they are too cool to ignite and all the gas escapes unburnt. It then condenses into droplets of creosote and causes a lot of smoke.
- There must be space over the top of the logs to allow the gases released from the wood to burn off.
- You will also need to leave space for the air to move down the glass and into the base of the fire (5 – 10 cm between the front of the logs and the door is usually sufficient).
- Place the logs in the firebox at least 2 cm apart to allow air to get into the hot area of the fire for better combustion.
Tip 5. Maintain your Combustion Heater
- If you have a slow combustion heater you need to check the door seal for wear or damage and replace it when necessary. This will allow you to maintain optimum efficiency of your wood fire and prevent harmful smoke leaking into your home.
- Combustion heaters rely on a good airtight seal around the door to work properly.
- Cracked glass in doors should be replaced as soon as possible.
- Slow combustion heaters have a baffle between the fire and the flue. Soot build up on this baffle reduces, and may eventually totally block, air flow to the flue. Removing soot from the baffle is an essential part of regular heater maintenance.
- When the fire is out and the ash bed and baffle have been cleaned you can inspect the firebox, baffle plate and the sides of the heater for signs of deterioration. Some rust and flaking of metal is to be expected but this should not be so great that it might lead to a hole forming.
- Most heater retailers will be able to provide spares or recommend someone who can repair your wood heater.
- With proper maintenance certified wood heaters will last for many years.