Saturday, 17 January 2015

Stove Problems.

It your boat stove causing problems - There are no default answers to a boat stove problem. Each situation is different. The fire in the stove is a controlled conflagration - the more air it gets the faster and hotter it will burn.

Restricting the air supply damps down the rate of burning and cuts back on the amount of available heat. But there is a point where the rate of burning is insufficient to keep the fire in. The fire needs a certain amount of internal heat to maintain combustion. Starve the fire of air and it will go out.

There are lots of issues to understand. The first is with the type of fuel being used. The second is the construction of the stove. The third is how you control the heat and how much heat you want. The fourth is how the heat is used.

I will stress one point - you must get a good pair of smoke and CO detectors fitted at each end of the boat. Test them on the first day of the month.

1) Different fuels need different amounts of air to burn efficiently. Mixing different types of fuel can create additional problems. The efficiency of the fire can be judged by the flame colour. The more yellow and floppy the flame, the more air is required for complete combustion. Adjustment of the air flow below the grate should be done in tiny amounts.

2) Some stoves only take air from below the grate and others have an airwash which allows air to enter the fire above the grate. This is useful as the air will not pass through the coals, but will help to burn all the part burnt gasses entering the flue. Additional air fed to the flames improves the combustion efficiency and reduces internal sooting. 
READ the Stove operating manual so you know what controls are available - where they are located and how to adjust them. If you don't have a manual - download one from the internet.

3) There are other controls such as a damper which maybe a fixed item and located in the top of the fire. The damper maybe in the flue pipe and adjustable. Hot air rises and heat is given off by the body of the stove as well as the flue pipe. As the air/gasses in the flue cools it becomes heavier. You can get a situation where the top of the flue is quite cold. A double skinned chimney can help in such situations especially if the air gap is filled with a fireproof insulation material.

3a) Down drafts can create unpredictable situations within the fire. A chimney cowl especially one that turns in the wind can help to reduce such situations. As soot and other products of combustion build up inside the flue they also act as a constrictor and as an insulator making the flue pipe less efficient at passing heat from the hot flue gasses into the boat. Clean the flue every couple of months and clean above the damper once a week. The damper is a restriction which can block well before other parts of the flue.

3b) Under and over ventilation. To much ventilation will take away heat. Not enough ventilation can cause condensation problems. The spread of heat in open plan boats will perform differently to boats with internal walls. Err on the side of safety and never block the bats ventilation system.

3c) The roof area will always be warmer than the floor area. When you are sitting down the majority of warm air is above your head. You might want to consider a small low speed fan to circulate the air more. Check the difference with a thermometer - you might just get a surprise at the temperature gradient.

4) If you have a back boiler, the temperature inside the fire box can be even more difficult to control. Especially when there are thermostats controlling part of the flow of water. Our bedroom bathroom radiators have thermostats which we use to provide comfortable heat in the different areas of the boat. Always have one radiator without any restrictions as a safeguard. Our calorifier is also unrestricted. Fans on top of fires do work - however, you may not notice the movement of air. To prove the point, get a joss stick and light it, next to the fire then go to the far end of the boat. You will be surprised how soon the scent arrives.

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