Central Heating Not Working

I was asked to have a look at a central heating system that was not working correctly. The initial complaint was that a few times the central heating had not been coming on. To get the heating to come on the lady was resetting the boiler, a Glowworm Micron, and the central heating would come on.

At the time of the faults the timer was set to be on as they leave it on 24 hours a day, the room thermostat was turned up, but there was no lights on at the boiler and no noise coming from the boiler. Initially I suspected that it was either the thermistor or PCB causing the fault. I had a PCB but suspected it was more likely to be the thermistor so would return with one in a few days.

On my return the customer told me that the heating had come on at the weekend, and would not go off. The usual cause off this problem is the motorised valve getting stuck, fully or partially, in the central heating position whilst the hot water is calling for heat. Therefore, I replaced the motorised valve on the assumption that this was causing both problems. I may be wrong and it may be the room thermostat that is the problem.

I still cannot explain why the customer was able to get the central heating going by resetting the boiler. The boiler had the newer PCB on it which has a diagnostic sequence built into the two display lights, which should show a fault if resetting is required. If anything changes I shall update you.

Disclaimer: The works described in this blog are a record of work undertaken and should not be taken as guaranteed to solve your problem. Work should only be carried out by persons qualified and competent to do so.