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Central Heating

Pressure drop, cold patches in radiators

Hi can anyone tell me why the pressure drops intermittently on the boiler, causing the heating system to cut out? Can this be fixed, and what type of tradesperson would fix this problem? At present we regularly have to check the pressure and manually help it to raise by turning two taps underneath the boiler but it would be great if there was a permanent solution.

The other problem is that we have located cold patches in some of the radiators, even when the system is working at a high temperature. Do you know what causes this, or how we can prevent it from happening? Could it be related to the 'low pressure' problem in the boiler?

Many thanks for taking the time to read these questions and if you can answer any of them....that would be much appreciated!

2 Answers from MyBuilder Heating Engineers

Hi, if the pressure is dropping within your heating system then there are two possibilities. The first being the obvious reason, there's a leak somewhere. This could be under the ground floor so you may not have any visible water marks. The second reason, and the most probable, is that the heating vessel has lost pressure. Every time the heating comes on the pipework expands and the pressure is reaching 3bar and being released from the safety valve within the boiler. Re-pressurising the vessel will solve this and will need to be undertaken by a gas engineer.


Answered 14th Mar 2015

I agree with the first reply, but would also add, that cold spots on the radiators are usually caused by sediment build up or air locks, are the radiators recent or original system? Have you tried bleeding all the radiators of air?


Answered 23rd Mar 2015

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