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Mend Myson Boiler Fires Cycle

Myson Apollo Fanfare Boiler?

My boiler fires up okay but at the end on its cycle the is a loud banging and water streams out of the overflow pipe from the expansion tank. It is worse if the thermostat switch on the boiler is on the high setting - it happens every cycle. On the low setting it only happens after it has been running for about an hour. Is there a thermostat inside the boiler?

David Dowbiggin
September 2007
radiators hot, hot water warm only?

Kevin
February 2011
Yes there is. There is a temperature switch, which is supposed to stop the cycle when the water reaches the high temperature, as selected by the High switch on the boiler. If this is faulty then the boiler keeps going until the water is much too hot, hence causes all the banging and flow into the expansion tank. There is a second (safety) over temperature switch which eventually stops the cycle. I changed this High thermostat on mine many years ago and that fixed the problem. That was after CORGI heating engineer changed the water / heating motorised valve at great expense and to no effect. Note that there is a similar Low thermostat inside the boiler, which is selected by the Low setting on your boiler. It is unlikely that both will be faulty so you can leave it on low. My experience is that it is fine for the summer warmer months, but in winter it is insufficient. You will also find that it will take a lot longer to heat up a full tank of water when set on low. I have found I have to set my tank thermostat down from about 65 to about 60, to give it a fighting chance of reaching its goal.

Mike
August 2009
no theres not but i would check your cyl stat if i were you sounds like the water in your cyl is getting too hot going out of your expansion pipe over filling your feed and expansion tank

dw
November 2007

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