Potterton Promax Combi 28 HE Plus Boiler

[Dauvit]

Problem with boiler now cutting out on over temp. then recycling causing shower problems . Have changed the NTC sensor without success. Also the divertor valve changed as a lot of gunk coming from the heat exchanger was evident. The 22mm CH feed pipe is as hot as the 15mm DHW feed even on DHW only. Before considering replacing the PCB urgent advice required
Thanks
Dauvit

 

[twgas]

sounds like your system needs a good clean before the fouled parts are replaced or fail completely. the plate h/ex is top of the list - how long ago was the div-valve changed?

 

[Baxmax]

Isolate electric supply to boiler, Isolate ch flow and return, isolate cold main to boiler release primary water from boiler via drain cock white knob just by pump,remove plate heat exchanger and clean all the ****e out of it and replace in reverse order from above

 

[Dauvit]

Thanks. I have cleaned out the HE and refitted. The new diverter valve has been recently fitted and the original dismantled and the internal valve faces and galleries cleaned. Still very concerned on the lack of temperature control and would like advice before committing to purchase new PCB. My simple mind says that the NT sender must activate something on the PCB? Yes? Or is there another peice of equipment which may cause this malfunction?
Very grateful
Dauvit
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[twgas]

how did you clean the /ex?

 

[Dauvit]

how did you clean the /ex?

Hi Mike

The HE was removed and washed out by mains water pressure from a hose and also by air from a compressor. This appeared to be sucessful as it dislodged a lot of black gunk which I presume was left from manufacture and perhaps an carelesss installer. I rather thought that this detreious had previously been lodged in the valve seats of the divertor valve allowing the CH feed to be hot when drawing off DHW although this heat is not evident in the first radiator
Regards
Dauvit