How many 2.5mm T&E into a 13A socket?

[Roger Mills]

I have a dual 13A socket under my kitchen sink - powering the dishwasher and waste disposal device. I need power for an additional appliance and would prefer to install an additional socket rather than use a 2-way adapter.

The current socket has 3 x 2.5mm T&E cables connected to it - which I assume to be two for the ring main plus a spur. The cables all disappear behind the cabinets (I didn't install them!) and there's no easy way of knowing which is the spur - other than separating the 3 and finding out what doesn't then work, etc.

If there were only two, it would be easy to wire the new socket into the ring by diverting one of the two to it and then having another short cable between the two sockets.

If I randomly pick one of the three to divert, I may well achieve the same thing. But I may instead end up with two daisy-chained spurs. [This probably wouldn't matter in practice, even though it's not in accordance with the regs].

However, if I could get FOUR wires into the existing socket, I would have a ring plus two separate spurs - which would presumably be ok? I wouldn't then need to worry about which one is the spur.

Is this likely to be possible? Any other relevant comments (ignoring Part P, of course!)?

[Tim Watts]

On Monday 01 April 2013 12:56 Roger Mills wrote in uk.d-i-y:

That might be worth doing - at least when you do the wiring - just to verify it is sane.

It would not be compliant - either with the regs or (I believe) with the terminal capacity of a standard accessory.

The correct way to do this would be to try to cut out a new flush box next to the existing socket *around* one of the ring cables (not the spur).

Then incorporate into the ring.

If your additional appliance is not power hungry, and given one load is tiny and the other is heavy but very intermittent (dishwasher - only heavy for the short time the heater runs) could you use one of the triple faceplates over the old double backbox?

I would not like to have 2 or 3 heavy power users in those, but for your scenario it seems reasonable - and better than an adaptor. But not as good as a new socket.

Cheers,

Tim

[ARW]

No multimeter?

[Bill]

I asked a colleague of mine the other day if he had a DVM and he said "A what?" and he reckons that he is a qualified electrician......

In the OP's case it would be simple to find which pair are the ring, separate all 3 T&E and then check which 2 were live, the dead one would be the feed to the spur. At least that is what I would hope to find......

Unless it was wired by a plumber of course, then a Ouija board maybe of more help.

>

[Mike Tomlinson]

En el artículo , Roger Mills escribió:

Given that you would have to take the existing socket off to add another anyway, testing is easy. Power off, take existing socket off, separate wires, power on, test (carefully!) with a meter to see which two are live - that'll be the ring. Power off, bit of tape round them to identify them. The dead wire will be the spur. You can then add the extra socket into the ring.

Bad idea. While you might be able to manage it, the terminals aren't designed for it, and you'll have fun trying to stuff everything back into the box, especially as you'll be working under the sink.

[ARW]

I was thinking power off and a continuity test!

[Roger Mills]

Yes, obvious isn't it! I don't why I didn't think of that. My brain must be addled because of the date, or something.

No, it was was wired by an electrician (and Part P certified) when the kitchen was re-done a couple of years ago. Although I photographed the first fix electrical installation prior to plastering, none of photos show quite what I need to know!

[Roger Mills]

Yes, several! I was thinking in terms of having to disconnect the circuit at the consumer unit in order to trace it - but it's now obvious that I don't need to do that.

[Dave Plowman (News)]

Easiest way is just to disconnect the earth wires, then find out which one is connected to the spur socket, by probing a fixing screw on that. If you can see which TW&E it belongs to, you have your answer. But you do need to measure a dead short on your DVM, rather than just any old reading.

[Roger Mills]

The new appliance (boiling water tap) has a 3kW heater but is intermittent - only coming on to top up the temperature of its reservoir. The dishwasher is a heavy user - but only when running. The food waste disposer only runs for a few seconds at a time when we want to get rid of some solid food waste.

The existing double outlet is surface mounted on the side of the cabinet, just inside the door - with the wiring coming from the back in a conduit. So the accessibility isn't too much of a problem. I could potentially convert it to a triple with (say) a Screwfix 17315 - but that has a 13A fuse, which would probably blow if the water heater and dishwasher both operated at the same time. Also, a triple would extend further into the cabinet (unless mounted vertically) and wouldn't clear the body of the waste disposer.

So I still think that the best bet is to install an additional single or double surface mounted socket in close proximity to the existing one. Each appliance can then draw up to 13A with impunity whenever it wants to.

[Roger Mills]

The only problem is that I don't know where the spur goes! I don't know whether it powers a socket or something like the cooker hood, or heated drawer.

But, as others have said, if I power down, disconnect all 3, power up again and check which 2 wires are live, I will know which is the spur - regardless of what it does.

[Roger Mills]

Good point!

. . or when nothing is connected to anything, if the ring has a discontinuity! Hopefully not, since I have reasonable faith in the bloke who did - and Part P certified - the electrical installation - although he did do the second fix without noticing that the plasterers had plastered over a double socket box until I pointed it out!

[harry]

Turn off power, remove socket and separate out the wires. Turn power on, check out which wires are live, they are the ring the other (dead one) is the spur.

[harry]

If it's a 3Kw appliance, it would be better on a separate circuit wired back to the CU rather than on the ring.

[ARW]

So only Dave Liquorice and myself wants to do the job properly and work on a dead supply:-)?

Easy and safer to do than a live test.

[newshound]

The other "tool" which can be handy is the socket tester thingy which looks like a 13A plug but has three lights in it. I've butchered one of these to terminate in three leads with croc clips on. Particularly useful on lighting roses but also useful here as it will reveal things like missing live or missing neutral on one half of the ring-main.

If you don't want to butcher one you could temporarily connect each T&E in turn to a spare single socket for testing.

[Dave Liquorice]

Well you can but I quite like the power down, disconnect all three and then use a meter to see which lives are still connected to each other. No second trip back to the CU, no live working. The two still connected to each other are the ring, the isolated one the spur. The fun starts when they are still all connected to each other via dead shorts...

[newshound]

Don't always agree with Harry; OP may not have a tone generator but probably has a volt stick, meter, or neon screwdriver.

If done with a bit of care, the check described above is pretty quick, safe, and reliable.

[ARW]

So is euthanasia -;)

[Tim Watts]

On Monday 01 April 2013 15:51 Roger Mills wrote in uk.d-i-y:

OK - I'm against the triple. I would not really want those on a double plate. The disposal unit takes bugger all and runs for seconds - but the water heater is likely to pull for some minutes and the dishwasher similarly.

A double socket is rated at 20A max total - and although the loads will be highly intermittent, I would do the extra work and stick a second seperate socket in.

An option involving no wall bashing would be to blank off the old socket box, and use it to hold a joint for the ring and the spur - so two cables emerge from the box at surface level and you run these around a couple of surface mounted sockets.