Following our article on problems with wood-burning stoves, we’re now turning our attention to boiler stoves.
These are all problems that occasionally crop-up with boiler stoves. Where possible we’ll tell you how to solve them yourself. If we can’t do that, hopefully we’ll at least point you in the direction of possible causes.
So, here are some issues that might result in your boiler stove not working correctly.
Boiler not heating radiators downstairs
This usually points to a problem with the circulating pump on the heating system. Radiators upstairs can heat on gravity but downstairs radiators require a circulating pump.
Stove is going out with unburnt fuel left
Try increasing the setting on the boiler thermostat. If the problem persists it could be a faulty thermostat in need of replacement.
Also, check that a heat leak radiator (i.e. a radiator that is on all the time when the boiler stove is working) has been fitted if the appliance installation instructions say that one is needed.
If you do have a heat leak radiator, check that it is working properly. It should be fitted with two lockshield valves, which cannot be turned off.
Check the gravity circulation to your hot water tank is working properly. Boiler stoves rely on the heat leak radiator and the hot water gravity circuit to give them work to do. If these are not working and there is not enough work for the appliance, it will be shut down by the thermostat and the fire will go out.
Stove going out overnight with all fuel burnt
This could be due to the boiler thermostat being set too high. As a result, fuel topped up for an overnight burn has been spent too quickly because the stove has been producing more heat than necessary.
You just need to turn down the boiler thermostat and find a balance between burning all the fuel and the stove going out.
Boiler stoves burn more fuel when the circulating pump is on for the heating. In most circumstances, you can switch the pump off at night and set it to come on automatically using the time clock. This will extend the burn time and stop the fire going out early in the morning.
Stove is not shutting down properly
Check that all the door and glass seals are sealing properly. Also, ensure that the flap on the boiler thermostat closes properly and is not obstructed by debris, such as coal or ash.
If the water temperature of the stove is very hot and the boiler thermostat is free from debris but will not close it may need adjusted by your installer. Also there could be a fault with the thermostat. In this case the thermostat may need to be replaced.
If the water in the boiler is not hot then the thermostat will automatically be kept open while the boiler stove increases the water temperature.
Switching on the circulating pump will send cold water back from the radiators. The thermostat will react to the drop in temperature by opening the air intake flap and the stove will fire up. This is normal.
Stove not getting radiators up to temperature
Try increasing the temperature setting on the boiler thermostat. If this doesn’t work, check that the air intake flap is opening properly when the thermostat temperature is increased.
When the stove is burning well but the radiator temperature is not at the desired level, it can be because too many radiators are connected to the boiler stove. You can check this by turning off half of the radiators and seeing if the temperature increases.
If the radiators still fail to reach temperature then you could have a problem with your circulating pump. Check whether the radiators are warm at the top and cold at the bottom. This indicates circulation problems.
If the radiators do come up to temperature after turning half of them off, turn one radiator on at a time to see how many you can use before it impacts the temperature. A boiler stove with an insufficient heat output is likely to be the cause of the problem.
Water appearing in the stove
This can happen when warm, damp air in the appliance hits the cold surface of the boiler during lighting. This type of dampness should disappear shortly after lighting when the boiler reaches temperature.
If the dampness continues it might be because a pipe thermostat is either not working properly or is set too low. It should be set to allow the pump to operate above approximately 40°C.
Another possible cause is condensation from the flue. This can happen if a stove is not working hard enough. Flue gases can cool when leaving the stove and create condensation, which goes back into the stove. Turn up the boiler thermostat and avoid heating radiators when the stove is idle to resolve this.
If the problem persists, check that the heat leak radiator and gravity circulation to the hot water cylinder are working properly. If the stove does not have enough work to do it will be shut down by the thermostat and this can cause condensation to build up in the stove and the flue.
Condensation problems inside the boiler can be caused when a boiler with an output higher than that required for the heating system has been specified in error. This leads to the boiler spending to much time at a slow burning rate and this can cause condensation problems inside the boiler or flue.
If there is dampness when the fire is out and it isn’t coming from the flue or chimney, a leaking boiler in the stove could be the cause. Have this checked by an engineer.
Radiator is warm at the bottom but cold at the top
This is usually due to a build-up of air in the radiator. Use a radiator key to loosen the square plug vent at the top of the radiator and release the air.
Radiator is warm at the top and cold at the bottom
Circulation problems are the likely cause. Check the radiator valve is open fully and if this doesn’t solve it, check that the lockshield valve at the opposite end is also fully open.
The system may need balancing if all the radiators are heating but one or two are warm at the top and cold at the bottom.
Radiators closer to the circulating pump will get priority over those further away on long runs or smaller pipe work. Your heating engineer can balance the system by partially closing the lockshield valves on the radiators that are working well. This will give a bigger priority to those further away.
If you’ve got a problem that wasn’t answered in this article, please get in touch and we’ll try to write an article to help you.