Glow-worm Hideaway FF: on, off, on, off, on......

[State of Flux]

Scenario:

- pumped CH in 22mm, Gravity HW in 28mm
- stat and two channel programmer working fine
- pump spinning (whole house gets heat within a few minutes)

All as you would expect from a 2005 installation and the house gets heat and HW.

Question:
- how frequently should the boiler be cycling on and off? (I'm no expert on this boiler)

When the rads are cold and the cylinder needs reheating it only runs for about 10 minutes then shuts down. 5 minutes later, up it comes again. Everything shouts OVERHEAT STAT in boiler but it does it so quickly.

I'm minded to change the (10 year old) pump as it's noisy but don't expect this to stop the cycling as the issue is there in HW only. Might it simply be a faulty overheat stat that needs replacing?

Appreciate your insights...........

 

[Simon F]

you will get limited response but,
what is the temperature of flow and return?
what setting is the thermostat on?

 

[State of Flux]

Simon, thanks. I've tried low, med and high on the stat with no change. I'll measure temps when next there to see if it is simply failing to lose enough heat but I'd be surprised given that the rads and water get piping hot. Wondering whether the overheat stat is simply too sensitive in its old age.

 

[IDCHAPPY]

Man, gravity HW?? have i went back in time 40 years?

 

[Mike Jackson]

It's not the overheat stat. Sounds like normal operation for a boiler with gravity hot water.

 

[State of Flux]

Cheers for the inputs. Owner looking to extend property and replace at some point - will advise to live with its foibles and save up for something better