OT: UK 3-pin mains plug

[Mike Clarke]

That's odd they show up as in stock here - 6 minutes after your post.

[Andrew Gabriel]

One much talked about here, IIRC, where an electrician was installing a new oven, and took the fitted 13A plug and lead off to wire it in to an existing flex outlet. A 2 year old child was subsequently found electrocuted in his bedroom, having picked up the discarded lead, wondered into his bedroom, and plugged it in, and handled the live end.

There was another one a few years ago involving a bar heater which a child plugged in (presumably not IP2X, but older ones never were).

I looked at their website (not recently admitedly), and it was full of all sorts of possible things you could do (half of which you can do with a standard 13A plug too), but not a single case of anyone actually being so much as injured. One thing they could perhaps do is argue for improvement in quality of the socket covers, or some other design (such as developing a child-proof socket switch).

[Andrew Gabriel]

No, it's only for the lead. If the appliance requires fusing to remain safe, it must include its own fusing, and is not permitted to rely on any fuse further back.

[John Rumm]

Part of the criticism of the plug protector things seems to be that they are easy for children to remove anyway...

Also one needs to consider what is typically more readily to hand, a plug on the end of an unterminated flex, or a miscellaneous bit of conductive material that could be poked into the live hole should the child have used the plug protector to open the shutter. I would suggest the latter is more likely.

The issues of poking fine wires down the sides of the protectors are less serious I would expect. However the ease with which you can invert one and use it to open the shutters is a concern. (you can't usually do that with a proper plug other than on the end of 4/6 way trailing socket. (which for some reason seem to have escaped the dimension requirements in BS1362)

Mandatory use of 30mA RCD protection on any circuit with sockets accessible to children (which is pretty much the defacto standard now anyway) might be worth considering. Having something which is a right PITA to pull out with adult sized hands and easy for someone with toddler sized ones, does seem to be a bit of an own goal.

[Dave Plowman (News)]

Not so. Most electronics would get no protection at all from a plug fuse.

[Andrew Gabriel]

The ones in my brother's house aren't.

But that's assessing the wrong risk - the availability of a paperclip verses real evidence that anyone's died or even been injured this way? I presume if there was, it would be all over fatallyflawed's website, but they have no cases whatsoever.

OTOH, we have real cases which socket protectors would have avoided.

Saying the paperclip risk is higher than the risk of not using socket protectors simply doesn't match the evidence, which is why I suggest it's an incorrect application of risk assessment.

I'm not necessarily saying I would advocate the use of socket protectors, but running a campaign to ban them seems to be rather OCD to me.

That's an argument for a better design, not banning them (again, given no evidence of any resulting injuries).

That isn't the case with the ones I've seen.

[Andy Burns]

Depends if the child who was capable of inserting the plug with cut flex into a socket would also have been capable of removing the protector, I have to say I don't really know how cunning the rugrats are ..

[Andy Burns]

I hadn't noticed the newer Nokia chargers until recently (who buys Nokia now? Nobody evidently!)

It's a shame they don't make this one with the sliding earth pin as a version with USB socket, rather that the flying lead to a very narrow barrel connector

[Adam Funk]

A couple of years ago, I repaired a microwave oven that had suddenly completely stopped working by opening it up (keeping my fingers well clear of anything that might possibly be a capacitor) and finding an obviously blown fuse (clear glass tube kind) near the power input. I took the fuse to a local electrical shop & showed it to the man, who said "microwave oven, eh" & sold me two for less than £1. It worked for years after that.

Note 1. "No user serviceable parts" indeed. Buy a new appliance, sucker.

Note 2. The internal fuse was 10 A; the plug fuse was 13 A.

[Andrew Gabriel]

,

Well, it means it should be serviced by a service centre, and there are some reasons. However, I expect you did fix and test the door interlock switches as required before replacing a microwave's mains input fuse...

and in other countries without 13A plugs, it would have been protected by a 16A or 20A fuse or breaker, so it's not allowed to make any presumptions about having a 13A fuse. We have the

13A fuse because appliance flexs would not be well enough protected by our 30A/32A ring circuit breaker.

[Terry Casey]

How very strange ...!

I hadn't closed the tab so was able to take this snapshot ...

before hitting refresh ...

... which brought back the prices again!

[Andrew Gabriel]

Ah, a Chinese container ship probably just docked...

[ARWadsworth]

Twas a handyman not an electrician. And he did not do the basic safety job of twisting or snapping off the live pin (faster than removing the fuse and just as safe).

I don't recall that one.

But both of these assume the kids could not remove the safety covers. My 5 year old nephew removes them from the sockets when his mother needs to use one as she cannot remove them with her trotters. She keeps them as she also has a 2 year old.

A proper standard is needed.

[ARWadsworth]

Only used on some MK sockets AFAIK. It's not a requirement.

[Dave Plowman (News)]

A fire can start in electronics protected by a fuse much smaller than 13 amps. The plug fuse is *only* to protect the flex.

[Tim Watts]

Those have been around since the mid 70's!

[2BSur2Bsur]

complaint as a shaver socket.

Will a 2-pin 5A plug fit in a 3-pin 5A socket? Because a UK shaver plug won't fit in a 3-pin 5A socket (I've tried, wrong pin spacing).

[2BSur2Bsur]

Quick Q on that - the flex found on appliances in this country is typically the same flex found on appliances sold around the EU (only the plug is different).

Yet, one would normally fit a 3A or 5A fuse to the plug of an appliance with low current requirements (eg a radio).

If used in the EU, this kind of device would have no plug fuse and have a

2-pin Euro plug, plugged into a Shucko or French or whatever socket. Typically those sockets are protected by a 16A or 20A fuse or breaker. What protects the flex in this instance?

Why don't we just fit 13A fuses to everything, since surely the flex has to be suitable for use on 16A or 20A fused outlets?

[John Rumm]

That 16/20A breaker.

As you are probably aware, the "protection" required in these circumstances is fault protection, rather overload protection. So in the event of a short circuit on the flex, you need the circuit breaker to open quickly enough to stop the conductors in the cable vaporising or the whole thing bursting into flames etc rather than protecting it from a long duration overload.

(Fault currents will be way in excess of the maximum continuous current rating of the cable).

In many cases, one could - typically flexes on products designed to be sold all over the EU, need to be man enough to handle the fault currents for the longer response times of the larger protective devices.

Some appliances here may have thinner flexes, that ideally require lower rated fuses (a practice that used to be more common here prior to harmonisation with the EU), I am not sure whether the makers produce different versions for these for sale in other parts of the EU, or just "hope" that they will hack it in most circumstances, on the grounds that other countries are less anal about these things ;-)

(using the style of MCBs that we use, you need 80A of fault current to open a 16A breaker quickly, and 100A for a 20A, but only something in the range of 6 to 18A for a 3A fuse)

[Andrew Gabriel]

You are correct, at least for all appliances since harmonisation. This was done by limiting the max lead length to something like

2 or 3 metres for the thin flexs, so they will still pass enough current in the case of a short circuit to trip a 16 or 20 Amp breaker in the fault current part of its graph. In these cases, you could fit a 13A fuse in them all.

Appliances manufactured before harmonisation may have flexs that are too long for a 13A fuse, meaning the resistance of the flex (when added to the supply impedance or the earth fault loop impedance) is too high to blow a 13A fuse fast enough to prevent risk of overheating the flex.

The other grey area is extension leads. These probably wouldn't be allowed today if it wasn't for the fact they're in widespread use already. Working out the max safe fuse is not trivial - it depends on the cable rating and the cable resistance (length). They can often be found operating with unsafe protection (too large a fuse).