Garage tripping house

HoolyNI

Hello all.

For no apparent reason my electric tripped last night and would not reset, so by pulling each individual fuse I was able to establish it was related to my garage, which also has a separate fuse box. Replaced two 30 amp fuses and a 5 amp and still kept tripping. Turned off and unplugged everything in the garage and still kept doing it.

Perplexed.

Robin9

Then the fault is between the main consumer unit and the garage fuse box.

HoolyNI

What is that likely to entail? 

HoolyNI

Robin9 said:

Then the fault is between the main consumer unit and the garage fuse box.

Does that mean the fault might not be in the garage at all? Would it be worth my while unplugging everything in the house to see if I can find a faulty appliance before calling a spark?

Jeepers_Creepers

If you completely turn off the CU in the garage by its main switch, and the RCD still keeps tripping when you reset the garage's MCB in the house's CU, then it points to a fault in the cable between the house and the garage. Or, more precisiely, between the house's CU and the garage's CU.

Is it overhead or underground? If the former, go over it with a fine toothed comb - with the power off in the house. If the latter, you'll likely need a sparky to carry out a leakage test.

It is the main 'RCD' - 'earth leakage' - switch that trips in the house?

Robin9

Switch off the small fuseboard in the garage.  Replace the fuse in the main consumer unit. If it blows then the circuit to the garage is faulty. Is this grey PVC attached to a catenary ?

TELLIT01

Are you in one of the areas which had the severe storms recently?  If so, maybe water has got into the garage or the conduit between house and garage.

HoolyNI

Thanks all for replies, have checked every 30 amp fuse I have (6) and none of them have blown it's just throwing the trip....with garage off completely house still trips when I push in the garage fuse in house and wiring is underground so nice and handy

HoolyNI

Am sure it's not unrelated but have discovered a loose wire in light switch for garage, can't tighten it yet as screw that tightens wire into switch is actually missing which means it been like that since house was built in '95....will get a replacement later and fit it. But even with switch taken off wall and leads kept apart house still trips which would indicate problem lies elsewhere.

coffeehound

That would presumably trip your garage CU rather than the house one if it was the fault

HoolyNI

There is just a mains switch and two fuse sockets on the garage CU the trip switch is on the house CU.


Had checked the light switch for water damage a few years back but never noticed any loose wiring until this morning. Had long suspected the fluorescent lighting in the garage of causing previous intermittent trips but normally just hit reset and forget about it.