Boiler function question

Harrietshaw

My boiler (Worchester Bosch) fires up when the thermastat calls for heat and runs for around 45mins or so with a plume coming out of a flue and the green ignition light lit. Then the plum stops and the green light goes out (this happens before the thermastat is turned off or temp reached) but you can still here the pump working and then it fires up again after a while and plume and light is back. Is this normal?

Gerry1

Yes. The boiler has its own thermostat; when the water reaches the relevant temperature it will shut down but the pump will continue to keep the radiators supplied. When the water has cooled a few degrees the boiler will fire up again.

Harrietshaw

Thank you. How often should it fire? How do I know when its condensing?

matelodave

It's condensing when the plume of steam comes out of the flue

Gerry1

I don't have any experience of this particular boiler, but just as the radiators need to be capable of delivering more heat than the room needs under most conditions, the boiler should also be similarly dimensioned so that it's not always running flat out. If this were not the case, the room would take far too long to warm up, and it would never reach a comfortable temperature if there were a cold snap. It's just like an electric iron, it takes a little while to reach the set temperature and then it will cycle on and off to maintain that temperature.

Harrietshaw

Thanks. Last night it had been on for 2 hours or so and then started cycling on and off a few times for about half a hour. How long should it take for the water to cool and heat again? Are my rads heating too quick or too slow?