Common Boiler Faults

Common Boiler Faults

Noisy boiler? Leaking boiler? Boiler switching itself on/off?

We have compiled a list of the most common faults our engineers are faced with. In some instances, common faults may be rectified without needing to call in an engineer, however others will require the services of an experienced professional. Remember, if in doubt, always seek help from a Gas Safe Registered engineer.

Noisy boiler or central heating system – A strange rumbling noise coming from the boiler is often caused by a buildup of lime scale in the heat exchanger, this is referred to as ‘Kettling’. Banging, rumbling or whistling pipes can also be caused by air being in the system.

What you can do – By bleeding your radiator or power flushing your pipes, you can remove any air and lime scale build ups.  Strange banging noises, particularly in older systems, could indicate imminent pump failure.  If the noise continues, you should book a service with a qualified engineer.

Pilot light keeps going out – The most common reason for this is a faulty thermocouple which is stopping the gas supply. It can also be caused by damaged seals causing a draught to blow the pilot light out, or a deposit build up in the pilot light.

What you can do – In this instance it is best to leave it to a gas safe engineer to investigate the fault.

Boiler losing pressure – A water leak is the most common reason for loss of pressure. It could also mean that the pressure relief valve needs replacing, or there is a problem with the expansion vessel.

What you can do – First thing to do is check your boiler pressure. If your boiler has a built in pressure gauge you can easily check whether there is low pressure, ideally a good pressure is around 1 bar, your boiler manual may instruct you on how to re-pressurize your boiler but if you are unsure it is best to call a gas safe engineer.

Radiators are not getting hot – This may be due to a buildup of air, rust or sludge in the radiators preventing a free flow of hot water to them. It could also be an issue with the pump – where the hot water is not being circulated as it should be.

What you can do – Firstly you should bleed your radiators to remove the trapped air in the system. If this doesn’t improve the issue, you may require a power flush which will chemically clean/flush the system, removing the deposits.

Boiler switching itself off – This can be caused for a number of reasons. These could include low water pressure, air in the system, a faulty pump not circulating the water properly, a frozen condensate pipe or thermostat issues.

What you can do – You can try bleeding your radiators which will remove any air in the system. This can affect the boiler pressure so the next thing to do would be checking this. If your boiler have a built in pressure gauge you can easily check whether there is low pressure, ideally a good pressure is around 1 bar, your boiler manual may instruct you on how to re-pressurize your boiler but if you are unsure it is best to call a gas safe engineer.

If your thermostat is old or broken, this may be causing the boiler to switch itself off, therefore replacing or fixing it will resolve the issue.

If your boiler isn’t receiving enough water to heat, then this could cause the boiler to turn off. A blocked or frozen water pipe will stop the flow of water to your boiler and can cause it to turn off. If it is cold outside and your condensate pipe is frozen it may need thawing. This should ideally be done by an engineer.

If your pump is playing up then it will cause the boiler to switch off. The pump is used to move water around the central heating system, therefore if it’s not working properly the water will stay in the boiler and not circulate around the system, triggering your boiler to cut out. Regular boiler services is the simplest way to avoid problems like these occurring as they will be discovered early enough to be prevented or fixed.

No heat or hot water – Again this could be a number of different causes. This include failure of valves, broken diaphragms, airlocks, thermostat issues and low pressure levels.

What you can do – Checking the power supply. As silly as it sounds, maybe it’s a fuse or the main circuit breaker board has tripped and just needs resetting. Most boilers have built in safety devices, so if this has tripped you may need to reset your whole system. You will find how to do this in your boiler manual.

You can try bleeding your radiators which will remove any air in the system. This can affect the boiler pressure so the next thing to do would be checking this. If your boiler have a built in pressure gauge you can easily check whether there is low pressure, ideally a good pressure is around 1 bar, your boiler manual may instruct you on how to re-pressurize your boiler but if you are unsure it is best to call a gas safe engineer.

If your thermostat is old or broken, this may be causing the boiler to switch itself off, therefore replacing or fixing it will resolve the issue.

Boiler is leaking or dripping – A variety of issues may cause your boiler to leak, from loose connections inside the boiler, to broken parts. It will depend on where the water is leaking from to determine the cause.

What you can do – In this instance it is best to leave it to a gas safe engineer to investigate the fault.

Thermostat not working correctly – If your heating is turning on/off when it’s not supposed to or if is losing accuracy then it is probably time to invest in a newer one. Older thermostats do tend to deteriorate over time.

What you can do – Firstly, make sure that the power supply is switched on and working. Check your thermostat clock and timer settings after a power cut. Remember to adjust your settings on your thermostat, when the clocks go forward/backwards. If these points don’t apply, then call a gas safe engineer who can advise you on a replacement thermostat.

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