Todays fault finding

[sellers]

Ooh I did have a little fun this afternoon, just over an hour of fault finding.

This may seem plain as day to you as I explain it, but it did stump me for a little while, might be of use to some of you in the future?

Plumber calls me up explaining he's had a belt off some pipework in someones garage (outbuilding) I get there and theres the incomming to the garage stop cock with the outgoing pipework in the building disconnected. 0v on incomming, 120v on garage pipework. After finding out the circuit being the kitchen ring which spurs out to the garage to 2 lights and 1 socket. I do an IR test which produces dead short live conductors to earth. I unplug the washer in the garage and fault clears,

Ah faulty washer me things, test at plug and get 2.8meg between live conductors and earth, so it must be on its way out, but still not a dead short. But still when I plug it back in I get a dead short on the ring. My heads starting to think about too many things here, and to keep it simple I think lets do a loop on the socket. Loop tester goes through sequence but shows >2.99kohm, right there must be something loose, or wrong behind this socket.

Tada, there it is, after carefully taking off the socket due to VIR cables we have earth and neutral crossed around and an old bond from the neutral to the water pipe. So the pipe was being used as the neutral!! And obviously when disconnected one end becomes live. Also the earth that was in with the bond was disconnected at a local JB. Swapped round, re-connected earth in JB. Issued danger notice for cables spured of spurs and no bond on the incomming water to the garage, job done.

Its always nice when you get there in the end. Allthough still whats left of the installation isn't ideal but at least I'd covered myself. Just to note, I got 0.05 at water stop tap in the garage even though it had no bond, does this mean it doesn't need a bond??

Hope this makes sense, and may help some people someday

 

[spinlondon]

You got 0.05ohms at the stop tap to where?

 

[sellers]

You got 0.05ohms at the stop tap to where?

MET in the house!

Sorry forgot to add I got 240v on the pipe from a cleaner contact.

 

[spinlondon]

No point in bonding back to the MET then.

 

[matt.leung]

today i also got 230v in the cpc of a ceiling rose, looked in various ceiling rose points, inside switches and can not find where the N & E are crossed over...

 

[spinlondon]

Check out some other circuits.

 

[sparkytim]

If this is the Main stop tap for the rest of the building then YES this is where the Main Bond should be. Your low ohm continuity from this position MAY be due to several things, Is the pipe Bonded further into the building maybe nearer to the MET? or perhaps a Water heater is providing a link from its CPC to the pipework.

 

[Larnacaman]

Bonding is required no matter how low a reading you get on a service pipe. Bonding is required to bring all services to an equal potential condition throughout the premises.

ie.... Equal Potential Zone

 

[spinlondon]

Fellas, it's a pipe into the garage from the house.

 

[sparkytim]

Thats not how it read to me, but maybe Sellers can confirm the set up.

 

[Larnacaman]

Sorry, ....misunderstood, thought it was the main incoming water supply to the house. Wet Fish

 

[sellers]

Its a lead pipe in garage with a stop tap, I can't confirm if it comes from house or mains??

 

[sparkytim]

Then YES it needs Bonding, its likely to be a split fed main coming up in two or more points

 

[sellers]

I thought it might! I did tell the customer is needed it and issued a danger notice! I gave him a price for garage re-wiring and new and he seemed keen for new year but who knows??

 

[Larnacaman]

If it's Lead, it's more likely to be an incoming mains water supply, than a just link from the house. So as S Tim stated, be it a single or dual fed main, it requires bonding!!!