Temporary circuit - max amps to faceplate?

[Elecpleb]

I have set up a sub main supply to my shed as follows:
32A MCB on main fuse board
6mm T&E
Sub-mains board (B&G with RCD (40A 30mA))
32A MCB
4mm T&E @ 3m
Terminating at X2 double sockets

I have been told the sockets could melt as they will only be rated for 13A plugs, not a 32A radial in 4mm T&E. Is this true?

ps this is only a temporary set up for power tools, while I renovate the shed. I plan long term 2.5mm ring off a 20A.

 

[Lucien Nunes]

There seems to be a lot of random nonsense in this thread, not all of it intentional, but clouding the issue of the original question.

Protecting double BS1363 socket outlets using 32A MCBs is normal and standard and 100% compliant.

There are lots of other things to say but that is the important one and I can't be bothered to haggle at the moment.

 

[Elecpleb]

The good thing about tools is that usually you can't use more than one at a time so no fear of overload there. The sockets could melt and sometimes do but that is usually putting 6kw on the socket and loose connections. The MCB is there to protect the cable actually, more than the accessory. You are just at the top end of 4mm on a 32a MCB so I would not worry about it. Depends a bit on how you installed it such as through insulation and in the sunshine wont help it will derate the cable. Mind you tools up to 4.2kw could be a problem for the socket. 18a is at the top end of the socket rating, per socket now that could make them melt.

The max usage would be two tools, a 2000W router and 2200W extractor so used simultaneously. The cable is surface mounted as its temporary.

Are you sure you understand what you are doing? How do you intend on drawing 32a through a socket outlet? They are generally rated at 20a so not even suitable for 2x13a plugs. RCDs in series is a bad idea also. No need for the second one if already protected at origin, however a bad design.

Not intending on drawing 32A through it, the consumer unit came with the MCBs and RCD supplied, and I already had 4mm T&E. My question was this suitable as a temporary solution, out of convenience, not design.

There seems to be a lot of random nonsense in this thread, not all of it intentional, but clouding the issue of the original question.

Protecting double BS1363 socket outlets using 32A MCBs is normal and standard and 100% compliant.

There are lots of other things to say but that is the important one and I can't be bothered to haggle at the moment.

Thanks, that was the gist of it

 

[Dave OCD]

To the OP , please correct me if I'm wrong but your initial post gave me the impression that you think a 32 amp MCB will somehow push that amount of current through its connected sockets. That is utter nonsense .

 

[littlespark]

Split that 4200W likely max load across two different double sockets.

As others have said, the faceplate may only be tested to 20A across both outlets.

Also what others have mentioned, the most likely cause of melting would be a loose connection or low quality materials.

 

[Elecpleb]

To the OP , please correct me if I'm wrong but your initial post gave me the impression that you think a 32 amp MCB will somehow push that amount of current through its connected sockets. That is utter nonsense .

No, I was questioning what had been impressed upon me, which was that a current up to 32A at the rear of the faceplate could cause issue.

Split that 4200W likely max load across two different double sockets.

As others have said, the faceplate may only be tested to 20A across both outlets.

Also what others have mentioned, the most likely cause of melting would be a loose connection or low quality materials.

Yes that’s the plan, got two double sockets so good to go for now. Triple check connections.

Thanks all, think we’ve ticked the box here

 

[Midwest]

The fact that MK have recently chosen to exceed the statutory minimum requirements on their logic plus series is great, and their outlets will be safe on the 32A supply.

Others don't and, therefore, won't. It doesn't affect my opinion on the standard itself.

Just out of interest, @Elecpleb , what brand and model faceplate have you used?

So going on from that, the maths doesn't compute, for those 20A models; like those yourself given that information, how do you advise the way forward with lessor standards. do you know better than a 20A product manufacturer?

 

[Lucien Nunes]

Split that 4200W likely max load across two different double sockets.As others have said, the faceplate may only be tested to 20A across both outlets.

Why? The router and dust extractor won't realisrltically

 

[Lucien Nunes]

Oops ^^, sat on my phone, which then ran out of battery.
Obviously there's no harm in splitting the load across two sockets, but it really ought to be OK on one double and one should not have to fret too much about these details in normal use.

The router won't realistically take its maximum nameplate load for more than a small fraction of the time. It will spend some time at part load, some time running light and some time switched off, within the thermal time constant of the socket parts. The socket heating depends on the time average of the square of the current, not the square of the average, and the current will exceed the rating during starts, so I'm going to take a guess at 1250W equivalent continous load. Let's assume the extractor runs continuously at full load. 1250+2200=3750W. We also have to guess the power factor. A mix of fully-loaded induction and part-loaded universal, not too bad, shall we say 0.85? 3750/0.85=4410VA. Total current on double socket 4410/230=19.2A which is within spec for any compliant BS1363 product, continuously for the expected life of the socket. I think the OP will expire from router-fatigue before the socket expires from total-combined-current-induced-heat-accelerated-deterioration!

 

[littlespark]

And @Lucien Nunes wins again!

 

[pc1966]

No, I was questioning what had been impressed upon me, which was that a current up to 32A at the rear of the faceplate could cause issue.

No, due to the plug's fuses (13A or less).

Cooker outlets often have 40-50A supplies and a single 13A socket for a kettle.

That is the advantage of the UK system: you can have a lot of sockets on a high current supply (ring or radial, depending on your religious persuasion) and it is perfectly safe.

The only issue discussed above is that a 2*13A socket is often rated only at 20A combined, hence it is better in kitchens with a couple of high power appliances to have a few more single outlets than doubles.

But none of that has any bearing on the supply rating (so long as it is not under long-term overload due to being too small).

 

[Spoon]

And @Lucien Nunes wins again!

Doesn't he always.. He's a hero...

 

[Lucien Nunes]

Credit for any useful answers I give is usually due to the people who worked out the laws of physics in the first place. I just bring them along to the conversation (the laws of physics, not the old guys.)

 

[goasis]

No, I was questioning what had been impressed upon me, which was that a current up to 32A at the rear of the faceplate could cause issue.

Your only going to get 32a at the socket if you put a load on it that draws 32a. Anything plugged into that socket will be "protected" by a plug top fuse of 13A or less. Same as many circuits in many houses.