Reverse polarity

[STI]

I went to a rented property today for a PAT test. Plugged in the tester and low and behold the machine showed a reverse polarity on the socket outlet. Took the socket outlet off the wall and the conductors are wired "correctly" but it is a spur. Did a visual check at the CU and it was wired correctly. So fair assumption that the other end of the spur where its taken off the ring has been wired in reverse.

The problem is this was in a kitchen and i think the spur was put in first then the kitchen because i cannot trace the spur connection back to any of the accessable sockets.
No junction boxes under the kick boards and no cut outs in the back of the cabinets.

So it really isnt practical to rip out the cabinets, what would you do. My first thought is to sleeve the wires at the socket outlet so the sleeves represent the correct colours for the conductors, and reverse them around so that thay are in fact correct polarity.

I know this is not the ideal solution but in a real world scenario is it what you would do.

 

[skenk]

You did try the tester in other sockets?

 

[STI]

Yes and no problem. I also got the socket n see showed the same ( reverse polarity) on this socket the other 3 i tested in this way all ok.

 

[sparkwright]

It has been known for consumer units to have been manufactured wrong so the whole installation has reversed polarity. Hager, I think that was.

 

[STI]

Hi Sparkwright. No I tested 3 other sockets 2 in the kitchen and 1 in the lounge directly behind the faulty socket, all these showed correct polarity. Only two ring finals on the CU 1 for upstairs and one for down.

 

[sparkwright]

I would say it's hard to wire one cable the wrong way round when connecting to others.

However, it's quite easy to wire something like a fused connection unit wrong, if that helps at all.

 

[STI]

Yes i see what you mean and i didnt look for a FCU although definitely there wasnt one within a meter of it, I looked at everything withinin that distance, trying to track where the ring was tapped in to unless its behind one of the cabinets.

 

[pjcomp]

And how long can you afford to spend looking for something like that when you're only there for a PAT test anyway.

Did a PIR on a property once and found a reverse polarity on a bedroom socket. When I opened it up the L and N were reverssed, but it was obvious from the state of decoration round the socke that this was the first time the socket had been opened since the house was built, which had to have been 30 years before. This was a bedside socket, so probably never had anything more than a light or a clock radio plugged in.

PJ

 

[kfelec]

is the socket wired on the socket circuit?

have you checked the cooker socket?

 

[Electrifying]

Am I missing something - what the hell are you doing PAT testing fixed wiring?

The name itself is a giveaway - Portable Appliance Test - so I don't understand what you were doing.

 

[timbim]

My reading of it is that he plugged in the PAT machine in order to test portable appliances, it then complained about reverse polarity on the socket, which he then went on to investigate.

Tim

 

[Electrifying]

Gotcha

 

[riveralt]

My reading of it is that he plugged in the PAT machine in order to test portable appliances, it then complained about reverse polarity on the socket, which he then went on to investigate.

Tim

So we have move from a PAT to a PIR then.

 

[TicklyT]

Have you proved CPC continuity to the offending socket?
A floating CPC can totally confuse some equipment, particularly if the equipment designer hadn't even considered that possibility.

The tester may expect to see the Live conductor at a significantly different potential to Neutral and Earth, and expect only a small difference N - E

If the CPC is floating, it may appear to the tester to be nearer the potential of the live conductor than the Neutral, and erroneously indicate L & N are reversed.

 

[STI]

Sorry been away and not noticed the new replies.

Thanks to those who answered the Fixed wiring enquiry, spot on

No ii havent checked for a floating CPC other than doing a visual check i havent tested for anything to do with the fixed wiring.
As was stated I was there just for the PAT and couldnt spend too much time on the RP. However i was interested in whether the sleeving option was acceptable given the potential upheaval to trace the point of the RP. A lot of other tests need to be done before then but if the worse came to the worse and it is a RP situation and the point of the reversal is behind some fixed cabinet is sleeving the wires an acceptable way round it.