Glowworm 54/4 backboiler cycling

[Kenneth]

Our Glowworm backboiler serves ten radiators. Sometimes it fires up and stays on, at other times it cycles on and off in quick succession (10 - 45 secs) perhaps a dozen times before it stays on. The pump is set to max flow rate, there are 2 Honeywell motorised valves, both seem to be working okay. It's driving me mad - any help/ideas would be VERY greatly appreciated

 

[Agile]

Cycling when the system is heating is normal is usually caused by inadequate flow rate.

If your pump is working properly then I would suspect the system and perhaps pump needs bleeding.

There could also be a lot of sludge.

Tony

 

[Kenneth]

Thanks for your quick response Tony. I will try bleeding the system again (I have been doing this) before going ahead with 'sludge busting'. Over a period, I have changed a couple of ground floor radiators, and there was only a small amount of black water in the bottom. Would sludge automatically collect at these lowest points, and if so, it would not appear that I have anything worth worrying about. I have always run my central heating with protection additives.