halstead best boiler problem

[kb248]

need help with unusual boiler problem boiler wont turn off even with programme removed ! it's an old system with gravity hot water & pumped heating no zone valve . sounds electrical had external wiring checked ,changed ignition pcb & aquastat pcb not a lot left to change any ideas welcomed

 

[diamondgas]

Have you checked the mi's? Looks like this boiler may incorporate some kind of pump overrun? If you've replaced the aquastat pcb the 'jumper' needs to be in the right place for gravity hot water

 

[kb248]

thanks diamondgas, yes boiler does have a pump over run the jumper as you say is in the right place for gravity hot water . gone through the mi's all the fault flow charts are for the boiler not working even phoned there tech help line for 30 mins all they could tell me is this cant happen ! I have been plumbing for 30 yrs & never had a boiler i coundn't fix but this one has me stumped !

 

[diamondgas]

Does sound a strange one ... Is the polarity the right? I'd be removing all/any external switch lives and see if the boiler fires up. I've had fused o'heat stats on different boilers override any programmers and keep burners running. You could try disconnecting the live to permanent live to the boiler and see if that stops it firing? A couple of ways to at leas eliminate the source yeh?