Thoughts on nuisance trip - Caused from another supply !!

**ssizen** · 29-01-2011

Hi
New to the forum so would appreciate any help that can be given, have a problem that has puzzled 2 electricians I have spoken to so I thought throw it into the wider web!!
Ok we have 2 supplies from EDF into our farm, one does the shop / butchers and one the house. Totally sperate meters and even accounts. So here is the issue. On a frequent basis, even turning a light on in the shop trips our main RCD in the house. Happens a lot. Nothing is connnected between the two, distance wise about 100m.

Any ideas? The house trip is very sensitive and does nuisance trip an awful lot but soon we are re-doing the house so will rewire to latest regs from scratch but am concerned the issue will still occur. Both have bonded earths (no earth rods).

Cheers all
Shaun

**telectrix** · 29-01-2011

i would first suspect the RCD that is tripping. either some cumulative leakage on the house installation or a tired RCD. ramp test of the RCD and IR testing on the house would be the ideal start

**solo2771** · 29-01-2011

is the farm haunted? lol

**malcolmsanford** · 29-01-2011

What earthing supply do you actually have. This fault can be typically found on a TT installation where a Neutral fault say on that lighting circuit can be picked up onto a neighbouring systems via the mass of earth and insuficient bonding. As your house RCD may be more sensative than the protection device at the shop/butchers/farm.

Whatever the fault is you will have to engage the services of an electrician who will test both your installations for you and track a fault down.

This is all theory as obviously without testing it is impossible to say what is causing the RCD to trip, it could be something totally different. IMO you need to get someone competant in to help you.

**ssizen** · 29-01-2011

Hi all
As far as I know the only spirits here are gin and vodka but when the mother in law comes rounds that can be blooming scary

Thanks for the tips, I know basics and would claim to know no more than that, just nice to get some shared input having had 2 qualified electricians round who were a bit stumped on this one. As far as I can ascertain no earth rods are used, the earth appears to come from the main 100A fuse so would think its off the shielding of the incoming SWA feed.

It is though 100% for sure any actions on the other supply that trips ours, we know when the staff arrive for work as our power goes off!! Not great though when on holiday, it is an old system so no split load or anything. Old crabtree stuuf so can no longer get parts but we did swap with another second hand (e-Bay) RCD and that made no differance, maybe just have to wait for a full rewire and test this year...

Cheers
Shaun

**solo2771** · 29-01-2011

I don't agree with malcoms theory but I do think someone needs to take a good look at the entire istallation ie both properties including the supply.
Paul

**SimpleSimon** · 29-01-2011

Sorry to suck eggs but you sure there is nothing between the two? Have u been in the property since it was all installed? Do either of the properties supply outbuildings? If so Malcolm's theory could stand....

**ssizen** · 29-01-2011

No worries, being the son of a chicken farmer, egg sucking was me specilality

Almost 100%, the farm shop was rewired by an electrician about 2 years ago, we laid new wires into everything. Aside from equipment in the shop, the only supply is to a pool and a barn and both those were all new cables back to that consumer unit, which is in turn only fed from the incoming supply.

Could it be that the RCD in the house is almost at its trip limit and any small spike up the effectivly shared neutral could push it to trip? Or would it make matters worse if both were on the same phase, I thought I heard once they alternate the 3 phases for each property as they go up a road but shoot me down if thats witchcraft talk

Thanks for all the input to a a non qualified, to be honest I find it all quite interesting, always loved electrics, found it quite logical (hence I restore old pinballs and older jukeboxes), mind not sure I have much logic with this issue !!

**Pat Tester** · 29-01-2011

I agree with the others that you should get someone to look at it, who has some experience. However one thing that may work is to change the rcd for a time delay one, if the problem is caused by an spike from the other supply due to dodgy switch
or such the time delay rcd will ignore this spike, but will still trip when faced with
a normal fault ! (if you see what i mean) good luck and let us know how it goes.

**ssizen** · 29-01-2011

Good point on someone to look at as others have suggested. I guess and hope when its all redone this year to regs it will go away, could try the time delay but its such an old Crabtree system that you cannot get parts for it any more, I suppose I could get a new consumer unit installed but its a shame as in 6 months we hope to change the whole lot and rewire the place from scratch, I have a new electrician I have used on a few other jobs so I'll pull him in and if he finds out I'll post back, just in case anyone ever gets a call where they start "I have 2 supplies into my farm...."