Dunkirk boiler series PSB-5D

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PB1
PB1 Posts: 2
in THE MAIN WALL
Hi, I have a Dunkirk boiler series PSB-5D. It’s about 20 yrs old. When our home thermostat calls for heat it heats up ok but will not shut off when the set temperature is reached. I have to switch it off manually. We have changed our home thermostat and the same thing happens so it must be a problem with the boiler. Any ideas?

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  • JUGHNE
    JUGHNE Posts: 11,644
    How do you switch it off manually.....power switch or gas valve?
  • PB1
    PB1 Posts: 2
    It’s just a switch. Looks like a light switch.
  • JUGHNE
    JUGHNE Posts: 11,644
    If power disconnect shuts it down and tstat is satisfied and off, then perhaps there is a sticking relay for the boiler.
    You could disconnect the tstat wires at the boiler to see if it still stays on.
    If you see the relay, there is also a high tech method to see if it is sticking....sometimes. ;)
    I take a rubber handle screwdriver and "thump" the body of the relay with the handle. If boiler shuts down that is it.

    Pictures might help.

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