Is your boiler’s thermostat on the blink again?

A faulty thermostat (or thermostat controls that connect to your boiler) can be incredibly frustrating, and as an experienced heating engineer, I often get calls from concerned customers about these issues.

Below, I’m going to share with you five of the most common thermostat problems in this troubleshooting faulty boilers blog, and how to fix them.

Problem 1: The room overheats

This happens when your boiler’s thermostat can’t tell when to cut off the heat, so the room just gets hotter and hotter. This one is particularly annoying, as you’re normally left with two options: turn the heating off, or have the heating at full blast.

Problem 2: Water is far too hot

If your hot water is coming out of the tap scorching hot, this may be due to an old gravity fed system where the temperature of the water is controlled by the boiler thermostat.

Problem 3: Tank in the attic ‘kettling’

This means that the tank in your attic is basically making noises that sound like a kettle boiling (known as ‘kettling’).

This may be due to the heating thermostat turning off the motorised valve. A faulty boiler thermostat will cause the water in the expansion tank to boil.

Problem 4: Your overflow dripping warm water

If this happens, it could also be down to your expansion tank. If your expansion tank is boiling, the level of water tends to rise and as a safety measure, it will overflow to the outside.

Problem 5: An unresponsive room thermostat

If your room is overheating, but the boiler goes off when you turn down the boiler thermostat, it could be your room thermostat that’s the problem.

If your boiler is unresponsive when you use the room thermostat’s controls to turn down the heating, then you’ll have your answer.

I was recently called to a job where the client couldn’t get their heating to come on. Originally, I  thought it was the motorised valve as this was not opening to allow heat through.

However, upon testing with a volt meter, this was found to be sound. The actual problem was a blown room thermostat which was not sending a signal to the valve, which would have allowed the radiators to heat.

Do you have any of the above problems? Then follow my advice, below:

How to fix it

First, turn the boiler’s thermostat to minimum and see if the boiler switches off. If not, turn off the boiler’s time clock and check again.

For any of the issues above, you should either call in a Gas Safe registered engineer, or if you have electrical experience and feel confident enough, try changing the boiler thermostat as detailed in the owner’s manual. Hopefully this should solve any problems.

Remember, please call in a professional if you have no knowledge of electrical circuits. You could cause more expensive damage and short circuit the boiler.

Conclusion

If your boiler’s thermostat is playing up, it can be very frustrating. Above, I’ve listed five common problems you can experience with your thermostat, and how to fix them.

These problems include:

• The room overheats

• Water is too hot

• Tank in the attic ‘kettling’

• Your overflow dripping warm water

• An unresponsive room thermostat

This could either be down to your boiler’s thermostat or your room thermostat controls that connect to your boiler.

To fix it, call in a Gas Safe registered engineer. If you have some electrical experience and feel confident enough, you could try replacing the thermostat yourself by following the instructions detailed in the owner’s manual.

Good luck!