Something I don't understand - 2.5mm Cable Rating

pbar · 3 Jul 2007

I've been wondering this for a bit, as I understand, 2.5mm cable has a maximum amp load of 20 amps. And you are allowed to have a single double socket spur from an existing ring main socket. Therefore, will this not have the possibility of a potential current of 26 amps going through the spurred cable? (2 x 13 amp appliances)
What have I got wrong
(I haven't done any of this, and don't intend to do so, just don't understand and ignorance isn't bliss!)

FatGit · 3 Jul 2007

13A is the TOTAL load for the socket (i.e. between both outlets).

pbar · 3 Jul 2007

But what is to stop someone (unknowingly or otherwise) plugging in two high powered appliances and causing a potentially dangerous situation. As I understand the regs don't require an FCU for this spur either.

Chivers7 · 3 Jul 2007

refer to onsite guide pages 152 to 153

a non fused spur feeds only one single or one twin or muliptle socket outlet or one Permanently connected equipment....

If in doubt fit a fused spur.

pbar · 3 Jul 2007

Chivers7 said:
refer to onsite guide pages 152 to 153

a non fused spur feeds only one single or one twin or muliptle socket outlet or one Permanently connected equipment....

If in doubt fit a fused spur.

Hmmnn....you've basically reiterated the point I've made. There is nothing to stop someone inadvertantly plugging 2 appliances into a double socket spur (with no FCU) and overloading the cable. And it's legal. I've gotta be missing something here!

JohnD · 3 Jul 2007

What makes you think 2.5mm is 20A?

The socket will melt first.

pbar · 3 Jul 2007

JohnD said:
What makes you think 2.5mm is 20A?

The socket will melt first.

Because that's the rating it gives on this site, in the 'How To' cabling section. Is that not right.

bernardgreen · 3 Jul 2007

pbar said:
And it's legal. I've gotta be missing something here!

Lack of information to the general public. The term 13 amp should never have been used for plugs. They should be sold with no fuse or a 3 amp fuse to remove the idea that they can in any location take 13 amps.

The GPO down rated 13 amp plugs to 9 amps maximum to avoid problems with double sockets being overloaded. Also they found some cheaper plugs were "not reliable" at 13 amps.

JohnD · 3 Jul 2007

pbar said:
Because that's the rating it gives on this site, in the 'How To' cabling section. Is that not right.

It will do for a rule of thumb but the full calculation is more complicated.

As I say, the socket will melt first if you put two 13A loads on it for long periods. The best quality plastic double sockets start to fail above 20A combined and cheaper ones may not manage that much. They are only designed to carry the standard load of 13A total as specified in the British Standard.

In the past I have used some industrial metalcad sockets with ceramic mouldings inside, I imagine these would stand up to the heat better.

pbar · 3 Jul 2007

Interesting.
Thanks very much guys.
This can be a very interesting hobby.

Jeeeez, today on here I've stated that RCBO's are sexy and that electrics are an interesting hobby.
Think I'm spending far too much time on here

FatGit · 3 Jul 2007

pbar said:
But what is to stop someone (unknowingly or otherwise) plugging in two high powered appliances and causing a potentially dangerous situation. As I understand the regs don't require an FCU for this spur either.

What's to stop somone doing this on any socket?

Spark123 · 3 Jul 2007

Not a lot, how many times have we seen the washing machine and tumble drier plugged into the same double socket?
Saying that, those 2 way adaptors you can buy for about 99p don't have a fuse in either.
Some bedtime reading on the origin of the BS1361 plug and socket outlet

ricicle · 3 Jul 2007

2.5mm² T+E is rated at 27A clipped direct !!!

equitum · 3 Jul 2007

Recently speaking to 2 instructors on an NICEIC course, and when I pointed out that the two kettles in the training school kitchen were plugged into the same twin socket outlet and was therefore overloading the socket I was told I was talking boll*cks (In their opinion they were two 13A sockets on the same outlet and therefore rated at 26A) ! I did suggest that they consult BS1363..............

If experienced and timeserved electricians are blissfully unaware then what chance does Joe Public or a 5 day wonder kid like me got ?

pbar · 4 Jul 2007

FatGit said:
pbar said:

But what is to stop someone (unknowingly or otherwise) plugging in two high powered appliances and causing a potentially dangerous situation. As I understand the regs don't require an FCU for this spur either.

Click to expand...

What's to stop somone doing this on any socket?

Because 'any socket' won't always be a spur.
On a ring, the load is spread over 2 cables.

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Something I don't understand - 2.5mm Cable Rating

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