Reverse Polarity Mains Sockets

[Chris M]

Hi

A friend of mine recently had seven white plastic double mains sockets repl aced with metal looking sockets. After about a month of this being done the RCD that covers these sockets started to trip soon after switching on the TV. I checked the sockets with a tester and it identified that in three of the sockets the neutral had been connected to live and live connected to ne utral. The TV was connected to a correctly wired socket. I rectified this w iring error in the three sockets and the problem appears to have gone away. As I understand it, this wiring error should not have tripped the RCD and for a month this was the case, but yesterday the RCD dedcided to trip out s everal times within minutes of switching the TV on. This would point to the TV being at fault, but since the wiring correction in the sockets all is w ell again (so far anyway). Any views welcome.

[dr.s.lartius]

You and your friend should immediately report this to whoever is responsibl e for whoever did the wiring - manager, director, wife, father, etc. - with a view towards that person not being allowed to do that sort of work ever again.

From days of yore, but post-war, I have heard a tale, which I firmly believ e, about a lecturer, JLW. Mrs JLW had an electric sewing machine, with a m etal body; all seemed well with it. One day, JLW brought the machine into a lecture, plugged it in to one of the fairly new 13A sockets on the fairly old lecturing bench, and put his hand on it. He thereby received 230 volt s AC, with the usual short-term effects but no permanent harm. Investigati on soon showed that (IIRC) Neutral and Earth were transposed in the machine 's plug, and (2) Live and Neutral were transposed in all of the sockets on the bench.

[tabbypurr]

placed with metal looking sockets. After about a month of this being done t he RCD that covers these sockets started to trip soon after switching on th e TV. I checked the sockets with a tester and it identified that in three o f the sockets the neutral had been connected to live and live connected to neutral. The TV was connected to a correctly wired socket. I rectified this wiring error in the three sockets and the problem appears to have gone awa y. As I understand it, this wiring error should not have tripped the RCD an d for a month this was the case, but yesterday the RCD dedcided to trip out several times within minutes of switching the TV on. This would point to t he TV being at fault, but since the wiring correction in the sockets all is well again (so far anyway). Any views welcome.

Insulation test your appliances. Otherwise you're just guessing. If you don 't want to buy a megger, a multimeter sometimes picks up the problem.

NT

[Bob Minchin]

It is not unusual for the filters fitted to appliances with switch mode power supplies to increase the leakage current on a circuit enough to trip an RCD. This does not make the TV faulty but there are possibly a number of such devices with filters in and just maybe a further "genuine" leaky device on the same circuit.

[harry]

placed with metal looking sockets. After about a month of this being done t he RCD that covers these sockets started to trip soon after switching on th e TV. I checked the sockets with a tester and it identified that in three o f the sockets the neutral had been connected to live and live connected to neutral. The TV was connected to a correctly wired socket. I rectified this wiring error in the three sockets and the problem appears to have gone awa y. As I understand it, this wiring error should not have tripped the RCD an d for a month this was the case, but yesterday the RCD dedcided to trip out several times within minutes of switching the TV on. This would point to t he TV being at fault, but since the wiring correction in the sockets all is well again (so far anyway). Any views welcome.

Unrelated problem. Your RCD simply determines if there is any difference between incoming and out going current. So the trip is caused by a (potentially dangerous)leakage to earth somewher e. Or the trip is faulty. You need to find out which. Get them back in. You shouldn't have fiddled with it, they will blame you.

It might be an appliance. But only ones with earth wires can cause this fault. Does your TV ave an earth wire? If so, an insulation test is called far (on the TV)as first possible remedy .

Some of these faults can be hard to locate, especially if intermittent. And nuisance trips can be caused by electrical disturbances called "transie nts". (Heavy loads being switched/lightning strikes etc.)

[charles]

There will be an "earth" or screen on the aerial socket. Could this be getting grounded somehow?

>

[tabbypurr]

class 2 appliance plugged into something earthed can too. Or sitting on something earthed. But class 1 more likely to trip an RCD.

NT

[Peter Parry]

A very common (and often very difficult to find) cause of RCD's randomly tripping is a neutral to earth fault. The trip can often be caused by equipment totally unrelated to the fault and perfectly serviceable. Your TV has a noise filter which may (perfectly normally) have a small leakage current. Somewhere else in the house will be a neutral/earth fault which is pre-sensitising the RCD. Plugging the TV in (it doesn't even have to be on in some cases) causes the RCD to trip. Change the TV and the problem goes away

The other common cause of odd tripping is moisture in the insulation of oven heating elements or immersion heaters.

[DerbyBorn]

If the aerial is a flush accessory won't it earth to the socket box?

[Peter Parry]

Should have added - only to come back a week later!

[AnthonyL]

Many years ago I worked on an off-shore pipe laying barge of French construction/operation. All it's electrics had been wired live as neutral, and vice versa. The start of the project was delayed until the issue was rectified.

[Brian-Gaff]

Well, it kind of makes you wonder what other c*ck ups are hidden in the installation. Brian

[David]

Not much use to you, but RCD tripping on Earth/Neutral faults was one reason I had RCBOs fitted when the house was rewired.

Cheers

Dave R

[Robert]

+1 pre-sensitising An extension blocks with surge protection caused me a lot of problems at work as did a fluorescent batten with a dodgy ballast. RCD would be tripped intermittently by switching on a whole range of other appliances.

[Andrew Gabriel]

Well, the French don't have polarised sockets. Indeed, on double socket outlets, the two sockets are always (AFAIK) hard-wired the opposite way around.

[Adam Funk]

Weird, why?!?

[Andrew Gabriel]

I guess it makes them easier to manufacture, but I don't know if that's the only reason.

[Ash Burton]

A certain well known French manufaturer of electical accessories used to make DSSO's with switches at each side end of the DSSO plate, as opposed to being together in the centre, as is usual with UK brand items.

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[Fredxxx]

I'm assuming all is now well with the wiring?

I have had RCDs trip where a capacitive load is connected to live and neutral. I presume the RCD had sufficient imbalance in its measurement to cause a trip.

In the past I have also disconnected the earth leg of a mains filter to stop tripping, to ensure there is insufficient live/earth current through the filter.

I presume the TV is double insulated?

What about items connected to it, through signal/aerial cabling?

Strange to go off after a few minutes.

[Chris M]

Thanks for all the answers and advice for this problem. The problem has rec urred and it has happened with nothing plugged in to the sockets that the R CD covers. We have had another electrician look at it and he cannot find an y fault. However, since he switched the RCD back on it has not tripped and that was on Monday, but sometimes it can go days without tripping.