Neutral and Earth wrong way round

On Sun, 16 Mar 2008 03:31:38 -0700 (PDT) someone who may be snipped-for-privacy@hotmail.co.uk wrote this:-

There are several types of circuit breaker. They work in different ways to detect certain types of fault. Without more information on what sort of circuit breaker you are talking about it is impossible to say whether it should have detected that particular fault.

What sort of things are written on it?

A circuit breaker in a household fuse box only trips if the current is exceeded. You have to have a RCD type device to trip on earth current which you probably don't have.

If its an old house new to you and you are only able to check sockets - yes. Ask for a Periodic Inspection Report. Was nothing said about the state of the electrics during the house purchase? If so definately get the PIR and revisit your legal advice. If not put that down to experience and get the report anyway.

Jim A

MCBs are like fuses, they only trip when excess current flows, so no they don't care about live or earth. It does mean you've got no working RCD, which probably isnt a problem, but can be in a minority of cases. Are you in country or town? Do you have something marked as an RCD or ELCB?

E/N swap is only a tiny risk. It means that like most oldish installs, things haven't been checked in a while.

NT

They are BS3871, 32A for the socket ring mains.

Thanks Jim, nothing was mentioned on the survey when I purchased the house (I used the banks full survey option, cost me =A31500 and they were rubbish!). Think it will have to go down to experience!

Any idea what I can expect to pay for a PIR in Greater London?

MCBs trip on overcurrent, so they won't care. It means you have no working RCD or ELCB supplying the sockets, which is usually not a problem, but if you're out in the country on a TT install that would be a big problem.

The risk caused by a N/E swap is tiny. It means your electrics havent been checked in a while, which is usual for non-new installs.

NT

Also a RCD will not trip with a NE reversal at a socket unless that socket is used.

Adam

Thanks Jim, nothing was mentioned on the survey when I purchased the house (I used the banks full survey option, cost me £1500 and they were rubbish!). Think it will have to go down to experience!

Any idea what I can expect to pay for a PIR in Greater London?

Can't help with the actual costs because it's impossible to quantify except to say the remediation costs are likely to exceed the cost of the Report which is a report and not a fix. I've sat in on NICEIC PIR seminars at trade shows and the open endedness of the process is a little worrying. The tester is supposed to discuss with you what you want (how much?). Unfortunately the background, 70 years or so of inadequate electrics, years of possible botching, recent change of ownership and already identified faults are actually what the process is designed to address.

Not endorsing NICEIC, there are other bodies too, but research their website and Google generally about PIRs first.

Jim A

MCBs then

NT

On Sun, 16 Mar 2008 05:16:12 -0700 (PDT) someone who may be ChrisP wrote this:-

Then it is an MCB and it would not operate for this sort of fault.

Probably about £150-300. For this you will get about 2-4 hours of work (so don't expect any amount of detailed inspection) and a tick the box report such as the examples at

In fact many of the items on those example documents will appear on yours, they may as well be pre-printed. A Periodic Inspection Report is an important sales opportunity for any ambitious electrician.

For checking the wiring in your sockets you can either visually inspect them after removing them or use a socket tester such as :-

I would agree with most points, but:

Much depends on the state of the cables. A '30s place could well still have rubber insulated wiring and urgently need rewiring.

It could, but as it already has MCB's that is very unlikely. Even if it was rubber it might well not even be picked up in a Periodic Inspection Report unless its somewhere it can be seen without lifting boards etc. PIRs are far more of a customer paid for sales opportunity for electricians than anything useful.

I'm wondering how practical it is to suggest the OP could do the main points with a bit of reading or explaining. Its not particularly hard.

NT

The house has been rewired, I'm just not sure when.

The offending socket has been used fine, including a vaccum cleaner which i think consume a fair number of watts.

I've checked a few more sockets and found loose wires where spurs (sometimes more than one!) have been added. Just looks like a bad DIY by the previous owners I can rectify myself.

Thanks everyone, your comments are very helpful.

I don't see the relevance of the age. Neutral-Earth swap is just wrong, whenever it was installed.

Or do you have in mind the interesting image you've given me - that if you don't keep an eye on them, the wires will move about? :P

Andy

As others have said this will not cause a circuit breaker to trip. Given that this particula fault is rather rare (it is plausible to misplace Line and Neutral bit much less the Earth with a Conductor). It brings a serious question mark over the whole installation.

If the cabling is pre-1984 2.5 mm^2 T&E - quite possible in view of the older BS 3871 type MCB mentioned - then the earth conductors acting as neutral will only be 1 mm^2 and could be liable to serious overheating under overload, not protected by the MCB. With later 2.5 T&E the problem won't be quite so bad.