Neutral and Earth wrong way round

[chrisproud]

I'm been slowly checking all the sockets in my new house (1930s). In one socket I found the neutral wires were in the earth terminal and the earth in the neutral!!! How could this work? I thought any current feeding back through earth would trip the circuit beaker. Apart from further dodgy wiring in the house, could this be an indication of a bigger problem, ie circuit breaker not working?

I'm going to keep checking and fixing the rest of the sockets in the house, not being an electrician I can only really check the wires and the correct way round and secure. Is it worth getting a qualified electrician in to run some continuity checks etc? What else could they check for?

Cheers

Chris

[David Hansen]

On Sun, 16 Mar 2008 03:31:38 -0700 (PDT) someone who may be [e-mail] 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?

[dennis]

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.

[Jim Alexander]

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

[meow2222]

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

[ChrisP]

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

[ChrisP]

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?

[meow2222]

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

[ARWadworth]

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

Adam

[Jim Alexander]

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

[meow2222]

MCBs then

NT

[David Hansen]

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.

[Peter Parry]

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

This will tell you your overall assessment is "unsatisfactory" and that your installation doesn't meet current standards (it doesn't, nor does it need to), that it needs a new consumer unit (it probably doesn't) and a rewire (it almost certainly doesn't). It will also include a few items requiring "urgent attention" (they probably don't).

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 :-

socket tester will alert you to wiring faults but not to earth fault loop impedance faults. More complex ones such as

also test earth impedance.

[John Rumm]

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.

[Peter Parry]

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.

[meow2222]

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

[ChrisP]

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.

[Andy Champ]

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

[Ed Sirett]

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.

[Andy Wade]

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.