boiler switches off before room thermostat reaches temperatu

[kevandalice]

i have a glow worm 50ff boiler that supplies the heating and hot water. I noticed earlier that the boiler had switched off before the room temperature was high enough to trip the room thermostat.
Then after a while the boiler switched on for a few seconds and then off again.

If i turn the stat down past the click and then up again, the boiler will switch on, then switch off about 5 mimutes later.

The pump in the airing cupboard runs constantly during all of this, unless i turn the stat right down.

The boiler seems to work normally for the hot water, although i notice the pump and motorised valve and running/staying open for a few minuted after boiler switches off

Can anyone suggest where my problem may be?

Thanks in advance

kevin

 

[swbjackson]

Sounds like the problem may be in looking for one that isn't there. The boiler is controlled by a separate thermostat and when it reaches temperature it will shut off regardless of what the external controls are doing. The pump will continue running all of the time the external controls are calling for heat and when the boiler cools a bit it will fire again. The boiler may have a pump over run circuit that keeps the pump running for a short while after the call for heat has finished to dissipate excess heat.

If this has started doing this to a greater extent recently it may be that the system is partially sludged and the heat isn't getting away from the boiler as quickly as it used to.

 

[Agile]

Basically the boiler is operating correctly and providing heating water at the set temperature.

The rads are not producing enough heat to warm the room enough. Either the flow rate is too low or they are undersized.

The boiler near maximum temp will be about 80 C and at this flow temp you should be unable to keep your hand on a rad for more than about one second!

Do you even get the boiler serviced?

Tony