80 Volts at boiler L-N

[Grubbsy]

Hi all, just been back to fit an expansion vessel to a Grant 26/36 oil boiler, and was then going to rectify the lack of oil pressure at the pump, but on arrival the on/off switch is dead. Having traced the power lead back to a programmer (rather than an isolation switch - so unable to find the fuse) I got my multimeter out and discovered 80 volts at the L-N to the boiler.

Its a big house with underfloor heating downstairs/rads upstairs and a nu heat thermal store

I presume somewhere there has to be an isolation switch for the boiler/heating controls - landlord and tenant unable to help - so will go to the fuse box.
What I dont understand is why is there 80 volts at the boiler - presumed it would be zero or 230
As fairly new to the fault finding, any guidance/help would be greatly appreciated

Cheers
Grubbsy

 

[pmac10]

check between earth and live (should also be 230) and also earth neutral ( should be zero). if you have 230 earth/live then your neutral is at 150v which would suggest a loose or nearly disconnected neutral somewhere on the circuit (or the multimeters' battery needs changed😉) or a faulty isolator. ive seen oil boilers spurred directly of lighting circuits (not fused down), and the only way to isolate is to pull the fuse for the lighting circuit, not good.

 

[et0]

I'd suspect the programmer, if the switch or relay contacts have become worn / damaged then you could have a very high resistance.

 

[HoodedClaw]

If your getting 80v on L/N then check the socket its wired into. the problem is probable there, wires probably not attached securely and burnt. the coating then produces resistance.. not good.

 

[Grubbsy]

Thanks all for the help, boiler takes power fm programmer!! and traced to loose N on motorised valve, all working happily now, will look into course on getting most fm multimeter I think

 

[HoodedClaw]

Glad it work out, sometime the simplest of things.. not to find the gremlin that loosened it!