Noisy Combi

[52classic]

The pump on our Combi is getting noisy and therefore due for replacement, Temperature stability is a bit erratic so I thought a new thermistor would be a good idea as well. All within the scope of what I would call servicing.

However, the noisy pump has caused me to notice that when the hot water is used then turned off the boiler will restart after about 5 seconds for just a second or two and will perhaps do that a couple of times.

Not enough for the burner to fire up and with a new pump you wouldn't notice it.

Is this normal and why does it happen?

[52classic]

Hope you don't mind a bump on this but someone must know!

[Ferg]

Is it the boiler dumping the heat from the heat exchanger down the heating circuit?? They normally do that.

[52classic]

If you mean does the heating circuit warm up when the domestic circuit is operating then no. Had a new diaragm fitted about 6 months ago.

Boiler is upstairs, above the kitchen and it just seems strange to hear the pump start up again after the call for water has stopped. Haven't noticed it happening with other peoples boilers but then their pumps are not knackered!

[Ferg]

I suspect that's what it's doing, but there's negligible heat to dump.

[52classic]

Thanks Ferg.

Does that mean a diverter valve fault? If so, valve, pump, thermistor, Looks increasingly like a new boiler would be cheapest option.

Probably run it for a couple of months as it it then replace.

Phoned for parts, thinking we fitted it about 6 years ago and the supplier says Saulnier 30 has been out of production for 8 years! Time passes so quick when you're enjoying yourself.