Reverse Polarity

Hi all I’m after some advice if possible please, I have an ‘old’ immersion heather cable in the loft which has a socket in the end of it. When I switch the power on at the board and plug in my socket tester it’s showing as reverse polarity but when I look in the socket the wires are correctly positioned, as they are in the board so I’m confused why this would be? It’s a decent socket tester and when plugged in to all other sockets it reads correctly. The only thing I can think of is we’ve had an extension built and I’m wondering if the builders have gone through the cable. Would that cause a reverse polarity situation? Wanted to use it as a socket for a tv aerial booster in the loft but not sure now if it’s safe. I know it’s reverse polarity and can mark it up as that and nobody else goes up in the loft but don’t want to take any unnecessary risks.

Thanks in advance

Have you done an r1 + r2?,  have you tried your mft?

have you traced the cable back at all?

Don't use it as it is. There will be no fuse protection on the live side.

Hum .... not all socket testers can determine a missing earth, then this may then suggest reversed polarity ...

Murdoch said:

Have you done an r1 + r2?,  have you tried your mft?

have you traced the cable back at all?

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Hi I’m sorry I don’t know what r1 &r2 is sorry.

ive traced it back as far as I can before it disappears behind a new wall which is part of the new extension.

As has been said earlier, a plug-in basic socket tester has numerous limitations that cannot correctly detect all potential dangers on 13A socket outlets..

There is an industry guidance booklet discussing several types of these testers..

 https://www.electricalsafetyfirst.org.uk/media/1205/best-practice-guide-8-issue-2.pdf

With a summary on page 8 of the above PDF booklet that says...

"No socket outlet test device can be relied on alone to provide full assurance that a socket is safe to use. "

Basically they can fail to diagnose some faults.. and/or mis-diagnose others.

depending upon the earth arrangements at the supply to an installation.

You would require a more comprehensive test meter, that costs a lot more money, to fully diagnose your exact fault symptoms.

They have their uses, but you need to be aware of their limitations...

As they would never be recognised as a formal safety checking device used in a professional context.

Basic rule with anything electrical, if in any doubt seek help from a qualified and competent person..

As electricity can kill a healthy adult in less than half a second.

I would suggest you need continuity tests carried out on all of the conductors, live, neutral & earth from the fuse box to the socket.

and insulation resistance tests between the conductors.

Before you reenergise the circuit.

If you don't have access to suitable meters for doing these tests, you probably need to find a local electrician who can come and test it for you.

Where about are you?

There may be a forum member local who could help?

Guinness  

Geoff1946 said:

Don't use it as it is. There will be no fuse protection on the live side.

Click to expand...

Ok, Thankyou. 

It would be most unusual for a cable to go straight from the consumer unit up to the loft for an immersion heater.  Most likely is there will have been a switch somewhere to turn the immersion heater on and off, very often in a kitchen.

My guess is someone has removed that switch and made a mess of connecting the wires together. That adds another element of "problem" to it in that you have a hidden connection somewhere that may be connected wrong and no way to inspect it or correct it unless you can find that hidden junction.

It is probably better to abandon it and connect a new feed to a loft socket from an existing properly working circuit.

ProDave said:

It would be most unusual for a cable to go straight from the consumer unit up to the loft for an immersion heater.  Most likely is there will have been a switch somewhere to turn the immersion heater on and off, very often in a kitchen.

My guess is someone has removed that switch and made a mess of connecting the wires together. That adds another element of "problem" to it in that you have a hidden connection somewhere that may be connected wrong and no way to inspect it or correct it unless you can find that hidden junction.

It is probably better to abandon it and connect a new feed to a loft socket from an existing properly working circuit.

Click to expand...

Hi Thanks for your help. Apologies I should have made myself clear, this cable used to go to a switch inside the immersion heater cupboard then a feed into the heater itself. This cable was pulled back into the loft and a socket put on it but was never used. I’d like to use it now as it’s the only feed I can see up there but after asking this forum I have decided to take the advice given and abandon using it altogether and try and get a new feed up there. Thanks all

appreciated.

Clarky said:

Hi Thanks for your help. Apologies I should have made myself clear, this cable used to go to a switch inside the immersion heater cupboard then a feed into the heater itself. This cable was pulled back into the loft and a socket put on it but was never used. I’d like to use it now as it’s the only feed I can see up there but after asking this forum I have decided to take the advice given and abandon using it altogether and try and get a new feed up there. Thanks all

appreciated.

Click to expand...

before you start running new cables why don’t you get a local spark to do some proper tests on the cable you have?

shouldnt cost too much and you may get the existing cable up and running

as you only wish to connect a TV aerial booster, it would be far easier to tap into the lighting - no doubt there are plenty of cables running around the attic. NB there is nothing wrong with a socket on a lighting cct. 

binky said:

NB there is nothing wrong with a socket on a lighting cct. 

Click to expand...

not sure I agree with that, but there’s nothing wrong with a fused spur off the lighting circuit

Murdoch said:

not sure I agree with that, but there’s nothing wrong with a fused spur off the lighting circuit

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Why do you need a fused spur?  It will probably be on a 6A mcb.

Just a label to say "TV amp only" and job done.

You could even fit a 5A socket and put a 5A plug on the tv amp.

ProDave said:

Why do you need a fused spur?  It will probably be on a 6A mcb.

Just a label to say "TV amp only" and job done.

You could even fit a 5A socket and put a 5A plug on the tv amp.

Click to expand...

just my preference, then DP isolation can be achieved easily when the rcd starts tripping

binky said:

as you only wish to connect a TV aerial booster, it would be far easier to tap into the lighting - no doubt there are plenty of cables running around the attic. NB there is nothing wrong with a socket on a lighting cct. 

Click to expand...

Thats what I  often do  ,  just loop off a ceiling rose  or fit a JB  and wire to a  socket in  1.00mm  .      I don't see any problem  arising  .  

Evans Electric said:

Thats what I  often do  ,  just loop off a ceiling rose  or fit a JB  and wire to a  socket in  1.00mm  .      I don't see any problem  arising  .  

Click to expand...

can be nice to put a little lable on it, but no one is likely to be plugging in high wattage appliances in the attic, and saves peeing about with 5 amp plugs. The important issue is that the Circuit protective device i suitable for the cable.

I did once find a single socket in a lounge that was connected to the lighting cct, customer was complaining that every time she plugged hoover in it tripped out, not clocking it was the lighting cct that tripped. Told her to use a different socket, problem solved !

As you rightly say  Binky,     the 6A  breaker resolves the issue  .        And often saves the issue of a messy or unsightly job trying to get a 2.5  up from a  ring circuit into the loft. 

Pre lockdown job for my plumber

new baby hroom

YT2 running around hall way into loft....nice

2.5 in it

what did it feed?........bathroom Fan wired off its own breaker in the board in case it needed to be switched off????????