Chimney and flue installation of Fabbri wood burning space heater with flue fan
When burning wood, it produces products of combustion which need to be expelled outside of the building to which it is installed. This is via the flue (the connection from the Fabbri to the chimney), then the chimney to the outside world.
In a natural draught chimney environment, the hot air rises the chimney which allows the cold air to enter the Fabbri which allows combustion to take place. For this to occur the flue and chimney must be kept warm in cold weather conditions or this heat will be lost from the flue gasses and the air for combustion will not arrive to the fire. This is why insulated flue is always used outside a building.
Hot likes to rise vertically not travel sideways. So, any horizontal direction will slow the flue gasses or sometimes preventing them rising. This results in smoke emitting from the Fabbri heater.
The higher the chimney the faster the hot air will rise. So, a short chimney IE less that 4 metres may have issues in creating enough draught (negative pressure) to allow the Fabbri to operate properly.
Some Fabbri models can have be supplied with a flue fan option IE F55 and F85 which will assist in creating the negative pressure in the Fabbri.. The F28 is only available as a natural draught model while the F120, F240 and the F350 are only available with flue fan.
The installation of a fabbri with a chimney is straight forward but a few general rules should be followed.
- Where possible the flue and chimney should rise vertically.
- Where a bend is used aim to use 45deg changes of direction except directly off the back of the Fabbri wood burning heater where a 90 deg is acceptable.
- Always include a debris trap in the installation at the bottom of the chimney design to collect any falling soot and debris. This will help prevent a blocking of the chimney.
- Include access for cleaning the vertical section and any appliance connection.
- Use suitable support brackets such as wall bands and roof support to secure chimney.
- Use suitable designed flashing to prevent water ingress
- A storm collar is recommended as this will prevent heavy water fall coming down the chimney on to the flashing seal in storm conditions.
- Ensure the termination of the chimney is outside the down draught zone due to roof or building design.
- Rain caps can be used but they tend to slow the chimneys performance. An open top chimney using a tapered terminal is recommended. Rain which will fall down the chimney when not in use should be collected in a suitable collection system from the drain point at the bottom of the connecting tee cap.
This example uses single wall flue internal to the building and twin wall insulated externally.