Boilermate 2 constantly running pump

[DiscoKid]

You could have replaced the board and had it all sorted ages ago

Its not the board.

I made the mistake of trying to look for symptons to fit the 'its usually the PCB' fault. When I checked the 'call for heat' S/L I checked for 240v and when there is a 'call for heat' and voltage drop off when no 'call for heat'. This lead me to believe the fault must be on the PCB.

It turns out that the fault is an additional isolation switch, next to the boiler, with a very unlikely failure mode. Its a standard 240v isolation switch with an illuminating neon. Permanent Live and Switched Live have been routed through the Live and Neutral isolation terminals with the neutral 'scotch-blocked' inline, and tucked away. A voltage (42v on-load and 115v off-load) is migrating from the Permanent Live to the Switched Live, presumably via the neon indicator that is intended to be bridged across Live and Neutral.

I'm not convinced this is the correct use for this paticular isolation switch.

The temporary solution has been to remove the Switch Live from the isolation switch in the same manner as the Neutral line, as the Switched Live can be isolated from the Boilermate 2 isolation switch.

I know my heating system much better as a result of this investigation and have only had to put up with the pump running for a while. My thanks for those who have help with constructive comments.

Dave

 

[nickso]

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The temporary solution has been to remove the Switch Live from the isolation switch in the same manner as the Neutral line, as the Switched Live can be isolated from the Boilermate 2 isolation switch.

please make sure whatever the final solution is that you make anyone working on the system or boiler aware of the dual isolation. some of our lazier colleagues are likely to kill themselves with the scenario you have described.

 

[DiscoKid]

.
The temporary solution has been to remove the Switch Live from the isolation switch in the same manner as the Neutral line, as the Switched Live can be isolated from the Boilermate 2 isolation switch.

please make sure whatever the final solution is that you make anyone working on the system or boiler aware of the dual isolation. some of our lazier colleagues are likely to kill themselves with the scenario you have described.

Don't worry. It'll be sorted properly but I don't think that is the right isolation switch as there will be ocassions that there is no Potential Difference between the Live and Switched Live.

Is this the usual method that heating system installers use to isolate the system?

Dave

 

[nickso]

housebuilders are likely to use anything lying around.

 

[DiscoKid]

housebuilders are likely to use anything lying around.

I thought as much

And that temporary solution WILL be sorted out properly at the weekend.

Cheers,
Dave