† † † Buy Cheap Sockets and DIE! † † †

[jfgw]

Three sockets in a small commercial premises were found not to have an earth present. When the tester tried to demonstrate one of the faulty sockets to the proprietor, it tested ok. These three sockets were replaced, as was a fourth socket which was giving problems. This fourth socket was spurred off of another socket so the wiring at that (fifth) socket was checked. The wiring was ok so the fifth socket was put back and tested where it was found not to have an earth even though it tested ok before. It was then noticed that wriggling the test plug produced an intermittent earth connection.

All images are mine.

An innocent-looking socket:


The same socket from the back. Manufactured a bit less than 11 years ago:


With the back cover removed, it looks like this. Those earth contacts don't look very substantial:


I did check and there were no additional spring clips on the earth contacts:


With the plug in, it doesn't look too good:


With some orange paper behind, you can see past both sides of the earth pin:


The brass clips do not seem very springy and are easily bent. The clips for the line and neutral pins are more copper-coloured and stiffer.

I am aware that some socket covers (those things mis-sold as safety devices) are poorly made and have oversized pins which can cause this type of damage to sockets. I do not believe that these have been used here, however.

A few thoughts:
When testing sockets, it seems wise to wriggle the test plug to check for any intermittent contact.
If you have sockets like these, replace them as a matter of urgency.
If you have ever used those so-called child safety covers, either test or replace any sockets that you have used them in.


Julian F. G. W.

[XFool]

The brass clips do not seem very springy and are easily bent.

Shouldn't they be phosphor bronze?

The clips for the line and neutral pins are more copper-coloured and stiffer.

Phosphor bronze?

[Lootman]

In Japan, almost all sockets and outlets have just two pins. They quite simply don't have an earth connection at all. You do sometimes see 3-pin sockets in hotels but I believe that is to placate American visitors, who use the same plug/socket format, but do require grounding.

So are Japanese appliances so good that they never short out? That's the only time an Earth or Ground connection would flow anyway, no?

[jfgw]

In Japan, almost all sockets and outlets have just two pins. They quite simply don't have an earth connection at all. You do sometimes see 3-pin sockets in hotels but I believe that is to placate American visitors, who use the same plug/socket format, but do require grounding.

So are Japanese appliances so good that they never short out? That's the only time an Earth or Ground connection would flow anyway, no?

I am not familiar with Japanese appliances. Most UK appliances such as vacuum cleaners and radios are not earthed. It would be possible to design the others so that they would not pose a significant risk. A plastic washing-machine anyone? Combination ovens with their grill and oven elements and motors (and higher working temperature) would be more of a problem to design, hence the earthed metal case.

The Japanese 100V supply is less likely to kill you than the UK 230V supply.

Julian F. G. W.

[gryffron]

Earth connections are not that common globally. Much of the world seems to do without them. It's only there for insurance after all. Likely most people never need it.

I worked in an assembly works when PAT testing was introduced. It drove us all mad and we were constantly trying to sneak electrical devices in past the quality (sorry "Quality") inspector. Then the company bought 1,000 premade sealed IEC (kettle) mains leads from China. Every one had the mains and earth wires crossed over. Worst possible fault, as it means the metal shielding of your box is live. After that we queued up outside the inspectors office to get all our new kit tested.

Gryff

[dspp]

In Japan, almost all sockets and outlets have just two pins. They quite simply don't have an earth connection at all. You do sometimes see 3-pin sockets in hotels but I believe that is to placate American visitors, who use the same plug/socket format, but do require grounding.

I am not familiar with Japanese appliances. .......The Japanese 100V supply is less likely to kill you than the UK 230V supply.

Julian F. G. W.

I gathered that There are two (or three) different power grids in Japan, depending on whether you count by voltage, by frequency, or by plug style.

https://www.japan-guide.com/e/e2225.html

Welcome the world of non-tariff barriers within the WTO. I can promise you this is only the most superficial part of the issue(s) with penetrating the Japanese electrical market.

Do you know where the errant (UK) socket was made ? Who was the CE importer ? Have you reported it to trading standards ? Or to Snorvey who has just had his kitchen done up and is missing a part P certificate ?

regards, dspp

[csearle]

Earth connections are there for class 1 appliances so that if a live conductor comes into contact with the metal enclosure then the supply to the appliance will be automatically disconnected. If this were not done then the enclosure would become live, lying in wait for a potential victim to come along and touch it.

With double insulated (class 2) appliances it is considered that the chances of any exposed metal parts becoming live are sufficiently small to obviate the need to Earth them.

So with Julian's socket if a class 1 appliance were plugged in to it, and the Earth pin wasn't making contact, and within the appliance a live wire (specifically the line as opposed to the neutral) were to come loose and dab against the enclosure then nothing would happen until some unsuspecting soul received either a tingle or an electric shock, depending upon what else they might be touching at the time.

Regards,
Chris

[Urbandreamer]

Earth connections are there for class 1 appliances so that if a live conductor comes into contact with the metal enclosure then the supply to the appliance will be automatically disconnected. If this were not done then the enclosure would become live, lying in wait for a potential victim to come along and touch it.

With double insulated (class 2) appliances it is considered that the chances of any exposed metal parts becoming live are sufficiently small to obviate the need to Earth them.

So with Julian's socket if a class 1 appliance were plugged in to it, and the Earth pin wasn't making contact, and within the appliance a live wire (specifically the line as opposed to the neutral) were to come loose and dab against the enclosure then nothing would happen until some unsuspecting soul received either a tingle or an electric shock, depending upon what else they might be touching at the time.

Regards,
Chris

There is a further design issue. In this country we see it in razor sockets. What is the voltage between earth and one of the pins. A UK razor socket (which has no earth pin) will show a voltage of 'appoximatly' 55V on the 110V socket and 115V on the 230V socket. In this case it is done by using a issolating transformer and earthing the middle of the secondary. In the UK our 3 phase neutral point is connected to earth. Domestic supply is one phase, the neutral and the earth. Other countries use a split phase system as I described in our razor socket to reduce the voltage from line to earth (through a human).

However I'm getting off topic. UK domestic plugs and sockets are designed for HIGH loads. Some think that makes them klunky. Some regard them as overspecified. All would be true, if they were not expected and required to supply 3KW per plug. Six KiloWatts (two electic fires on full) for the socket shown. In the case of a electical fault in the equipment the earth connection on the socket should more than cope with 13A and the wires on the ring with more than 26A (30A + is the normal design). I'm not sure if the silver earth strap on the pictures is the main earth connector. If it is then all the critisisem of it is entirly correct. If not then its sole purpose is to ensure that the screws and possibly backplate of the socket are connected to earth. The backplate only matters if a metal backplate rather than plastic one is used. The fact that the earth pin was not gripped by the socket though is totally inexcusable.

Personally I suspect that this socket is a counterfeit one. There was a large concern in the mid 90's of counterfeits making their way onto the UK market. Why anyone should counterfeit such devices escapes me, but evidence shows that they have and continue to do so.

Ps Bronze alloy is used because of its low friction coefficient and so that, unlike pure copper, it can act as a spring.

[jfgw]

So with Julian's socket if a class 1 appliance were plugged in to it, and the Earth pin wasn't making contact, and within the appliance a live wire (specifically the line as opposed to the neutral) were to come loose and dab against the enclosure then nothing would happen until some unsuspecting soul received either a tingle or an electric shock, depending upon what else they might be touching at the time.

I came across an example of such a fault a few days ago where a rat had decided to investigate the inside of a gas cooker. Electricity was used for ignition and a warming plate, and was supplied via a 13A plug. The leads to the warming plate had been detached and the end of one (with a big blob of solder on it) was resting on the foil surrounding the oven cavities. The stray leads and one dead rat were removed.

There are still many installations without rcd protection or with protection on downstair sockets but not upstairs so a missing earth can pose a real risk. While an rcd is not a substitute for a reliable earth, it greatly reduces the risk of death.

Julian F. G. W.

[jfgw]

There is a further design issue. In this country we see it in razor sockets. What is the voltage between earth and one of the pins. A UK razor socket (which has no earth pin) will show a voltage of 'appoximatly' 55V on the 110V socket and 115V on the 230V socket. In this case it is done by using a issolating transformer and earthing the middle of the secondary. In the UK our 3 phase neutral point is connected to earth. Domestic supply is one phase, the neutral and the earth. Other countries use a split phase system as I described in our razor socket to reduce the voltage from line to earth (through a human).

A centre-tapped transformer is used for the 110V supply used on building sites so the voltage to earth is only 55V. A shaver socket of the type used in a bathroom, however, is isolated (there is no connection to earth). If you touch only one side of it, you will not receive any shock at all (unless there is a fault). If you touch both sides, it might kill you and, as there is no flow of current to earth, your rcd (if you have one) will not trip.

Split-phase supplies have been used in remote areas in the UK and, due to the cost of upgrading to three-phase, I suspect still are. I have come across a 480V single-phase motor of several kW that was used on a remote farm.

Julian F. G. W.

[dspp]

Split phase is all over the UK, not just in the normal rural locations. You will find it in many of the old DC areas such as south London and Bournemouth for example.

[csearle]

A UK razor socket (which has no earth pin) will show a voltage of 'appoximatly' 55V on the 110V socket and 115V on the 230V socket. In this case it is done by using a issolating transformer and earthing the middle of the secondary.

This is not my understanding. As far as I've been taught (never actually dismantled one) the shaver points in this country offer safety precisely by not Earthing the centre point of the secondary winding*. In this way if either of the 55V end points of the secondary were to come into contact with a wet occupant then there would be no actual circuit to Earth (for example through the occupant's body and, say, a water pipe) and so no current would flow.

However I'm getting off topic. UK domestic plugs and sockets are designed for HIGH loads. Some think that makes them klunky. Some regard them as overspecified. All would be true, if they were not expected and required to supply 3KW per plug. Six KiloWatts (two electic fires on full) for the socket shown.

A double socket outlet, as shown, is only rated at 13A, that is why e.g. washing machines and dishwashers should not be plugged into the same double socket as it would become overloaded were they both to be heating water at the same time. I find it almost scandalous that double socket outlets are not rated at 26A.

In the case of a electical fault in the equipment the earth connection on the socket should more than cope with 13A and the wires on the ring with more than 26A (30A + is the normal design). I'm not sure if the silver earth strap on the pictures is the main earth connector. If it is then all the critisisem of it is entirly correct. If not then its sole purpose is to ensure that the screws and possibly backplate of the socket are connected to earth. The backplate only matters if a metal backplate rather than plastic one is used. The fact that the earth pin was not gripped by the socket though is totally inexcusable.

On some sockets there are Earth terminals at both ends, so in those cases the Earth conductor could use the metal busbars as part of their circuit; on others there is only one so it is as you say mainly there to Earth the plate screws (which are accessible to occupants) and any metal back-box. On Julian's socket there appears to be only one Earth terminal.

Regards,
Chris

PS The Earth connection could well be subjected to 1kA or much more in the event of a line short-circuit to Earth. In fact this huge current is desirable in order for the mini-circuit breaker to disconnect the supply within the specified 400ms.

* Safety Extra Low Voltage (SELV) system

[Urbandreamer]

Sorry for misleading people. I too am shocked to find that a unfused double socket is not rated to cope with a full draw from both plugs. MK (a respected manufacturer) rate their double sockets at 19.5A, but they are not required to do so.

Here is a discussion on the subject at IET (IET was IEEE who wrote the regulations).
https://www.theiet.org/forums/forum/mes ... adid=33787

I believe that those who pointed out that I was wrong in the specific case of razer sockets were also right to correct me and that it is a isolating transformer, though split phase is used elsewhere.

[dspp]

Sorry for misleading people. I too am shocked to find that a unfused double socket is not rated to cope with a full draw from both plugs. MK (a respected manufacturer) rate their double sockets at 19.5A, but they are not required to do so.

Here is a discussion on the subject at IET (IET was IEEE who wrote the regulations).
https://www.theiet.org/forums/forum/mes ... adid=33787

I believe that those who pointed out that I was wrong in the specific case of razer sockets were also right to correct me and that it is a isolating transformer, though split phase is used elsewhere.

I fully agree - MK are an excellent brand and highly recommended.

Actually IET is/was IEE, not IEEE. The IEEE are the far more important US institution. It is worth joining the IEEE for the content, whereas the only reason to pay IEE subs is as part of the CEng process.

regards, dspp

[bungeejumper]

Having once had an electric convection heater that literally welded itself into a mid-range 13 amp socket, I now never use anything but MK. The socket in question was one of twenty that had been fitted in our kitchen by a fully certified electrician - I suppose it's possible that the fault may have lay with the plug, though?

Either way, it scares the life out of me that you can buy a flimsy double power point in our local pricecutter for £1.99 - or for £1.77 on Ebay if you don't mind not having a switch. Mind you, they'll probably last you for the rest of your life....

BJ

[jfgw]

Either way, it scares the life out of me that you can buy a flimsy double power point in our local pricecutter for £1.99 - or for £1.77 on Ebay if you don't mind not having a switch. Mind you, they'll probably last you for the rest of your life....

£1.31 for a switched double socket from Screwfix. At least the switch is single pole so it is less likely to fail in the neutral while leaving the line connected.

Seriously, how many percent does using MK or some other good brand add to a job?

Julian F. G. W.

[jfgw]

A double socket outlet, as shown, is only rated at 13A, that is why e.g. washing machines and dishwashers should not be plugged into the same double socket as it would become overloaded were they both to be heating water at the same time. I find it almost scandalous that double socket outlets are not rated at 26A.

I have seen an oven and hob plugged into the same double socket. It was a single oven for which a 13A fuse is correct. The hob was 5.7kW and the fuse hadn't blown, which was surprising. The fault was with the socket. The owner reckoned that no more than three plates had been used at once which probably explains the intact fuse. It still would have been more than 13A though.

Julian F. G. W.

[csearle]

A double socket outlet, as shown, is only rated at 13A, that is why e.g. washing machines and dishwashers should not be plugged into the same double socket as it would become overloaded were they both to be heating water at the same time. I find it almost scandalous that double socket outlets are not rated at 26A.

I have seen an oven and hob plugged into the same double socket. It was a single oven for which a 13A fuse is correct. The hob was 5.7kW and the fuse hadn't blown, which was surprising. The fault was with the socket. The owner reckoned that no more than three plates had been used at once which probably explains the intact fuse. It still would have been more than 13A though.

I've come across many that have overheated so much that the white material has turned brown. Some I've seen had cracked right down the front and one, which I discovered after dismantling had become so hot that a spot-weld in a busbar had disconnected. An electrician colleague of mine saw one at the moment it caught fire whilst being overloaded.

Mind you the majority that I've found with two heavy duty machines plugged in have suffered no visible consequences. I imagine they were simply well made.

Regards,
Chris

[ten0rman]

Surely the problem with overloading twin-gang sockets of the type shown is that they were introduced at a time when circuit loadings were much less than they are now, and a twin-gang socket was for convenience to avoid people using a multi-way adaptor, for example for a tv and a reading lamp.

I came across this problem some years ago when in the other place I stated that a twin-gang socket could take 26A. I was quickly put right on that situation, and had a BS quoted to me, BS 1363 could it be? However, the fact remains that if someone like me, with a background in telecoms and hence having a certain amount of electrical knowledge, was unaware of this limitation, then how can you expect Joe Public to know about it. Lets face it, to most people electricity is a black art. As has been shown in the posts above, people simply do not understand and will load up willy-nilly. I find it very interesting that triple and quad gang sockets are all fitted with a 13A fuse thus reducing the problem of overloading, yet twin gang sockets are not. And yes, I am aware that an extra 13A fuse may be thought to be somewhat over the top, but what price the fire risk?

In my opinion, overloading of twin gang sockets will continue until such time as the manufacturers start fitting 13A fuses into the sockets.

Regards,

ten0rman

[bungeejumper]

.I've come across many that have overheated so much that the white material has turned brown. Some I've seen had cracked right down the front and one, which I discovered after dismantling had become so hot that a spot-weld in a busbar had disconnected.

Some of our flat tenants are not the sharpest pencils in the box, and it scares me to think of all the times I've gone in and found a washing machine and a kettle (plus, on one occasion, a toaster) plugged into a double power point. I doubt that many people have any awareness of how much power a w/machine can draw. (They might be a little more clued up about tumble dryers, though, because they've all read about them catching fire, so they've already made the heat connection.)

We check every socket for scorch marks and for radial cracks around the pins, and we go round with a socket tester (http://www.screwfix.com/p/kewtech-kewch ... ster/45558) between tenants or when we're having the annual gas check done. But it's surprising how many tenants really aren't happy about the intrusion!

Mind you, they have their reasons. One lady had covered the power point on her skirting board with a two-foot-high pile of dirty, stinky clothes. She explained that she found it easier to go out and buy a new jumper from the charity shop than to wash the clothes she'd already got, and she hadn't got round to chucking out the smelly cast-offs. But hey ho, there I go off on a judgemental tangent again. Other people's lives, eh?

BJ