Glowworm Ultimate Cutting Out After Five Minutes

I was asked to look at a Glowworm Ultimate that was not working correctly. The customer was complaining that the boiler only seemed to come on for five minutes before cutting out and that the heating was not getting hot.

When I arrived I put the hot water on and that appeared to be running correctly, they had a tank full of hot water and the system sounded as if it was circulating correctly. I put the heating on and there was no reaction from the system and I checked that the room thermostat was turned up, which it was. I then checked in the junction box for the heating system to find that there was power on both the white and grey wires to the motorised valve after turning the hot water off.

I replaced the head on the Drayton MA/1 three-port motorised valve, and retested the system which was no operating correctly. It would appear that the heating may have been coming on when the valve was in the mid position but not moving over fully to supply heating only.

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.