Overheating boilers should be considered an emergency. As we always say, do not attempt any repairs on gas appliances unless you are Gas Safe-registered! If your boiler is overheating, turn off the water and gas supply to the appliance and arrange an emergency repair. If you have boiler cover with 247 Home Rescue, we can get an engineer to your home in less than four hours!
A boiler that won’t shut off is at a real risk of overheating, too; if your central heating will not turn off, then turn off the gas and water supply immediately and call a specialist. If you think the situation warrants it, then contact the fire brigade too.
Don’t turn off the electricity supply unless an engineer advises you to do so; water will not circulate within your boiler and will be unable to cool down efficiently if there is no power.
A boiler that is overheating will almost certainly be condemned as ‘immediately dangerous’ as it could lead to a boiler explosion and will have to be replaced.
Why do boilers overheat?
Typically, boilers overheat due to the failure of safety controls that maintain the gas and water supply, the temperature and the pressure. In some cases, this can lead to a condition called a ‘runaway boiler’, which is very dangerous to both occupants of the property and emergency service responders.
When boilers begin to overheat, the internal components of the boiler are put under immense stress and are likely to suffer from irreparable damage. In some cases, the boiler can set alight or even explode.
Boiler explosion risks
An overheating boiler can become over-pressurised when the pressure relief valve fails and any other control fails simultaneously. While historically, boilers would over-pressurise and explode with alarming regularity, modern boilers are manufactured to be able to withstand excessive pressure, and can typically handle an operating pressure of 20 PSI. When pressures increase beyond this level, the boiler can fail, which can lead to an explosion.
Gas boiler repairs can also increase the risk of a boiler explosion, especially if the repairs are performed by an inexperienced engineer. Some of the repairs that have been linked to overheating boilers include:
- Wiring errors
- Manually opening gas valves, leading to a continual flow of gas into the appliance
- Plugging up or removing pressure relief valves, such as when attempting to resolve leaking boilers, which can make it impossible for the boiler to relieve excessive pressure
If you do not turn off the water supply to your boiler when it begins overheating, then cold water will be introduced to the appliance. This boiler will immediately ‘flash’ into steam as it touches the hot components of the boiler, which causes a dramatic and immediate rise in pressure and can lead to an explosion or cause the appliance to rupture.
Do not attempt to cool down the boiler yourself for this reason; water or other liquids sprayed on to the boiler can flash into steam, and as you will be in close proximity to the appliance when this occurs, you will be unable to protect yourself from any subsequent explosion.
A constant flow of gas into the boiler will also cause the temperature and pressure to increase rapidly, which can lead to a runaway boiler.
Even if the boiler does not explode, its internal components may still melt, creating toxic smoke and vapour that can prove fatal.
In doubt? Call us straight away.
If in doubt, call someone out and never attempt to touch the boiler or its components yourself. We offer a wide range of cover plans for boiler breakdown, repair or home emergencies and are never more than a phone call away so get in touch today to see how we can best protect you.
Call us on 0345 3192 247 and we can help. Our technical team will run through some simple troubleshooting to see if your problem can be resolved on the phone or they can book one of our friendly and knowledgeable Gas Safe registered engineers to get you back up and running as soon as possible.
247 Home Rescue accepts no liability for any injuries or damages you sustain following the advice on this website. If in doubt, seek professional assistance.