Alpha 240E CH problem

[CAM66]

Our 240e is 10 yrs old now and last winter I noticed that the boiler keeps firing when its reached CH temperature. As a layman it seems to me that it doesn't know it has reached the desired temp set by the boiler thermostat.

I have tried various temperature settings / pressures but it makes no difference, once the desired temp has been reached the flame goes out and it almost immediately re fires. The most re fires I have counted is 14 before I turned it off.

Does anyone know what the cause might be?

To get around this we use the on off function on the clock for 20min bursts.

I changed the CH thermistor sensor but it made no difference.

thanks

 

[45yearsagasman]

It sounds like its short cycling. Do you have a room stat? The boiler stat will allow the boiler to cycle. You need a room stat to shut the boiler down when room temp is reached.

 

[CAM66]

Thanks for the reply.
No we do not have a room stat, only the stats on the radiators.
Should we get a room stat and are they easy to fit to a 240e?
Now you mention it I do recall the commissioning engineer saying it needed a room thermostat but didn't think much of it at the time. Why don't they come with one?

thank you.

Further to this I have fitted a Drayton Combi Stat, which works well.
ebay £15 free postage.

I also serviced the diverter valve with a kit from Sabre Spares as it was leaking, it took a few hours. I took numerous pictures as I dismantled it.
Saved me about £190. I used fernox ds-3 to clean up the housing although most of the scale appeared to be on the valve heads.

And further more the ignition PCB died this week. I think that was the root cause of the problem we were having. Oh well saved on the diverter at least, £280 to have the pcb replaced.