Baxi combi 80E

[eldiablo]

Hi
I have a baxi combi 80e, when running a bath with hot water everything is ok but when the tap is turned off there is a gurgling / bubbling noise coming from the boiler and if the hot tap is turned on again whilst this is on going, there is no hot water and it doesn't fire up. If I wait untill this stops (around 10 mins ) and then turn hot water on then its fine again.
I have good pressure and it does not drop, there are no obvious leaks and a year or so ago I had an issue where the pressure went up when using heating and after reading an article on here I checked the expansion chamber on the top and topped it up using a pump and this cured the problem, the boiler has never overpressurised since.
Any suggestions would be appreciated as it probably will get worse.


Thanks

 

[Agile]

Sounds as if the DHW demand switch is jamming on after a demand and causing the boiler to continue firing and overheat.

Tony

 

[eldiablo]

Thanks for your reply

I have monitored the boiler when running a hot tap, this only happens when the hot tap has been on for a long time (IE : running a bath) the boiler is running and producing hot water and as soon as the tap is turned off the boiler shuts down as it should but after 30 seconds or so you can hear gurgling almost like it is drawing in air and bubbling up through the water in the system, these gurgles are not a continuous noise they are like gurgle for two seconds, no noise for 4 seconds gurgle again and this continues for up to ten minutes. If you turn the hot tap on whilst this is happening then the boiler clicks and you hear it begining its process to fire up but it does not get to the firing up stage I suspect the valve to give the comand for gas and ignition does not happen and the water runs through the heat exchanger and os cold, once the gurgling stops and the tap is turned on it fires up and heats the water. Does this sound like the switch you mentioned ?

Cheers Chris