13 Amp socket tolerances

[John Rumm]

Not entirely sure why dennis is prattling his usual tripe about ring circuits when the question is about travel adaptors - fused or otherwise.

Well lets say the multiway survives the sustained 20A load (the better ones might), and someone fairly clueless manages to cobble together 10kW of load all in one room at one time, and connect it into a pair of 4 way trailing leads. Then they plug them both into a double socket...

(obviously this is only ever likely to happen in dennis's house - but dear reader, for the moment, pretend its somewhere in the real world).

We will skip over the fact that there is not a double socket out there that will take 40A for long before it becomes bleeding obvious to all that something is not happy, and assume perhaps our dimwit has used a pair of sockets on the same circuit, and look at what will happen to the circuit...

The answer?

Bugger all really. If the sockets are right at one end of the ring close to the CU (which obviously they won't be because unlike dennis, competent electricians think about things like this, and use appropriate topologies for the circumstances), one cable may get a tad hotter than it ought. If kept that way[1] it will probably shorten the life of the cable. The more likely outcome is nothing exciting will happen.

Obviously that worries dennis, he would rather it all burst into flames for some reason...

(no doubt the millions of homes that have not spontaneously combusted due to non dennis circuit designs being employed, will in no way dent his belief since these numbers are obviously statistically not relevant)

[1] Obviously keeping that 10kW of load sustained is actually quite a challenge, but I am sure dennis can think of a way.

That would be a woosh...

Still apparently dennis is not going to argue with me any more (unless he was telling porkies yet again!) so we can enjoy the silence...

[dennis]

snip same old.

Still arguing that the rules keep it safe, even though the users don't even know what the rules are.

Still argues that the iee know best, even though they are constantly changing the rules as they cover up previous mistakes.. like only fitting one socket to a 2.5 mm spur when they used to allow two. Shame about the millions already out there.

Still argues that overload protection can be left to a user supplied device, one the user knows nothing about or what it does or what happens if its done incorrectly.

Still calls anyone with contrary views about safety wrong even when the recommendations are safer and don't rely on the user knowing the rules, or supplying safety devices.

You really don't have an argument, you just be a good boy and do the minimum the "regs" say, I will just exceed them as usual.

[John Rumm]

Ah, apparently he was fibbing again... really dennis!

Where does anything I said require user knowledge of rules?

Know best? possibly. Know better than you, I believe so.

I don't recall multiple sockets ever being allowed on an unfused spur. Perhaps you could say when you believe this was the case?

However as a more general point, I actually find it reassuring that the wiring regs change and evolve. It demonstrates good engineering that research is still being done, empirical data are being collected, and the guidance being revised or improved in the light of this. Patterns of use change, and technology advances. It is right and proper that the guidance moves on to accommodate these changes.

I don't believe I did argue that. In fact I think I explicitly said that the plug fuses were there for fault protection of the appliance flex, not overload protection.

Well if you make clearly erroneous and misleading statements about the absence of a plug fuse resulting in:

"Don't say that, it means a ring could be put into a dangerous state which is not prevented by the protection circuits built into the ring."

That is not a "contrary view", its simply nonsense.

The daft thing is that your idea of "exceeding" the regs comes down to reducing the functionality and flexibility of standard circuits, while increasing their expense and time to install, and yet yielding no demonstrable improvement in safety.

As with most efforts to "over engineer" a solution, it demonstrates a lack of any real engineering finesse.

[ARWadsworth]

Did you mean talent not finesse?

[dennis]

No it just means that I use a breaker that is less than the capacity of the cable.

Something you don't appear to understand.

[ARWadsworth]

What you choose to use is of no concern to anyone else.

YOU are not the person writing the IEE regs or the British Standards which have made this country's electrics one of the safest in the world.

[The Medway Handyman]

Dennis - you are a bell end.

[John Rumm]

Well both really. Any fool can keep nailing 4x2"s on until it stands up. It takes and engineer to do it with the minimum of materials, and cost, and still get it to stand up and meet all the customers requirements.

[dennis]

Hmm, it was an engineer that made the walls too weak on the Comet. It was an engineer that design Chernobyl It was an engineer that put the cooling plant for Japans reactors too low down.

It an engineer that thinks 32 Amp breakers are OK for 22 Amp cable. To justify this he states:

well the user will never have enough appliances to overload it.. oops wrong. you can stop overloads because there is a 13A fuse in the plug which blows at 20A.. oops you can get faulty and/or fake ones that don't. the user will never do anything stupid to the plug.. well we all know how stupid that idea is. need anyone go on?

Just design the damn circuits so they are properly protected at the consumer unit without the user having to provide additional protection. Anything that requires user cooperation is inherently less safe. Even the IET can manage it as can be seen with the modern radials they want electricians to use. You know the ones that actually specify a breaker that protects the cable even if the user puts a nail in place of the plug fuse.

[Mike Humphrey]

From

:

Unfused spurs from a ring wired in the same cable as the ring are allowed to run one single or double socket or one fused connection unit (FCU). The use of two singles was previously allowed, but was banned because people replaced them with doubles.

Mike

[Old Codger]

A double socket was certainly acceptable on an unfused spur with 7/.029 cable and I am pretty certain continued to be acceptable long after the changeover to 2.5 sqmm. Didn't know it had changed but not being an electrician I only look at BS 7671 when I actually need to know.

[Old Codger]

Ah, the days before ring mains when we had 5A 10A and 15A sockets, all radially wired with their own (wire) fuses. What a waste of cable when most folk had only one electric fire of one or possibly two Kw, possibly a 1Kw electric kettle and the rest were standard or table lamps (not many of them either) and a wireless.

[John Williamson]

The walls had a problem with the stress raising sharp corners on the rectangular windows, which caused cracks to start and propagate. Nobody knew anything about metal fatigue in aluminium at the time. They know now, and that fault will never happen again. New problems are appearing with the composites that are now being used in aircraft. They are being solved as they appear.

It was a team of operators that operated it outside its design specs, and bypassed all the safety gear.

It was a combination of an unprecedented earthquake and tsunami that wrecked it. And even after that, it was losing the diesel tanks for the standby generators that finally did for it. Some things you just can't plan for. The emergency battery standby systems lasted longer than predicted.

If the cable will just about carry 22A, then you're right. IME, most,if not all, cable used in fixed installations will carry at least twice its rated current for long enough for a circuit breaker to operate.

+1 on that point. And *never* underestimate the ingenuity of fools when designing a foolproof system.

[dennis]

Modern radials allow lots of 13 A sockets on a 2.5 mm cable all protected by a 20A breaker.

[John Rumm]

One double socket or one single socket it fine - always has been and still is. (double sockets are actually treated as 20A peak loads)

Dennis seems to be suggesting multiple sockets were permitted.

[John Rumm]

Yup I have seen it there, but can't as yet find a reliable reference for when it was supposed to be so. (note also this is subtly different from "multiple" sockets). You can still have one double socket on a spur.

[ARWadsworth]

You usually do until the nurse gives you your tablets.

[dennis]

Bullshit, I have never suggested any such thing.

[ARWadsworth]

dennis, you said bullshit. Is there someone naughty in your ward teaching you new words?

[John Rumm]

No one is perfect - there are plenty of other examples where things have broken in unexpected ways as well. Fortunately some areas of engineering are open to far more scrutiny and peer checking than others.

Actually the situation in Japan reflects quite well on the engineers who designed it. Given that it performed remarkably well when faced with circumstances well in excess of what it was apparently designed to cope with. Each of the backup systems did what they were supposed to as well. It was unfortunate that the magnitude of the quake and wave were so far in excess of those believed possible, that it caused cascaded failures of multiple redundant systems.

Correction dennis; 2 x 22A cable - and that is being rather pessimistic.

2 x 27A cable in many cases. And note that is 27A continuous duty without any cable life degradation.

You will also note a regulatory requirement to select and implement circuits such that they are not subjected to long term low level overloads (as would be permitted by a typical MCB)

Its actually surprisingly difficult to do. However since overload protection is designed into the circuit, that is not a problem.

That would be a woosh then...

No... the plug fuse is not going to stop an overload; not its job.

No, you only seem to be subtracting from your argument.

They already are. There is no onus on the user to provide any additional protection.

The circuit protection does not require user cooperation.

You yet again demonstrate a failure to understand the differences between circuit protection and appliance flex protection, and overload protection and fault protection.

A user replacing a plug fuse with a nail has no impact on the circuit protection at all - fault or overload. It may however compromise the fault protection of the appliance flex (again it has no impact on the overload protection for the flex - if it is required - since that should be implemented in the appliance.