Electrics tripping when turning boiler off

[bewsh]

Baxi Bermuda, gravity h/w, pumped c/h.

Whenever customer turns the boiler off on the clock the electrics trip. So I thought must be faulty switch on programmer, so fitted new programmer and tested but the same problem.

Investigated further and found 106vac on the earth connection to the room stat, no voltage on any of the earths at the programmer, and different colour wires coming in to the stat than what leave the programmer, so guessing there's a fault with a wire somewhere which a earth is touching a live or something.

But I would have thought that the voltage on the earth should trip the electrics anyway?

And sometimes when you turn the boiler off at the programmer, it only trips a certain circuit on the consumer unit (not sure which circuit as nothing labeled), but the heating circuit is still live?

Anyone got any ideas?

 

[jonnyswamp]

If it were me and there was nothing obvious, I'd strip out cables and start again checking all electrical components as you go
Has it got a 2 port and stat, or just power from clock straight to pump/boiler

 

[ShaunCorbs]

turn boiler off at fused spur and test earths if theres still voltage you need a spark

if theres no voltage need to test each component until you find it

 

[stevetheplumber]

i would dis the stat and put the switch live direct to the pump see what happens

 

[stani]

The earth wire on the stat may not be connected to earth, so it could be feedback from other cables, you need to find where all the cables connect and check them out.

 

[bewsh]

No power if fuse spur is off.

The room stat doesn't actually work either, if I take it off the wall and just leave the wiring in place, the boiler still fires up.

I think the problem is with the wiring to the stat, I think I'll try disconnect that wiring and just fit a wireless stat next to the programmer.

And no, there isn't a 2 port, just a feed straight to the boiler/pump (supposed to be through a room stat)

 

[ShaunCorbs]

No power if fuse spur is off.

The room stat doesn't actually work either, if I take it off the wall and just leave the wiring in place, the boiler still fires up.

I think the problem is with the wiring to the stat, I think I'll try disconnect that wiring and just fit a wireless stat next to the programmer.

And no, there isn't a 2 port, just a feed straight to the boiler/pump (supposed to be through a room stat)

i would say prob room stat but not unheard of boiler going to earth