10mm SWA into CU

[JohnW2]

It's not a matter of the size of the cores - it's the number of them. In other words, the choice is between taking two sets of SWA cores into the CU or just taking one set of cores (as T+E or singles) from a 'JB' into the CU.

Clearly the outgoing cable to the shed is a continuation of the incoming one, i.e. there's no submain from the garage CU to the shed CU.

Exactly.

So not only would I not try and make that joint inside the CU, I'd use a switch enclosure rather than a JB so that I could isolate the shed if I needed to without isolating the garage as well.

Indeed - that would be even better than a 'JB'.

Kind Regards, John

 

[SimonH2]

It's not a matter of the size of the cores - it's the number of them. In other words, the choice is between taking two sets of SWA cores into the CU or just taking one set of cores (as T+E or singles) from a 'JB' into the CU.

Ah, I'd forgotten about there being two cables.
It's arguable which is better - design wise. Taking the two sets of tails into the CU and terminating them into the existing terminals/terminal bars - or create an extra set of joints.
And 3off 30mm^2 of cable aren't trivial joints to stuff into a small adaptable box.

and nothing qualifies as a circuit if there's no upstream OPD.

But there always is one, even if it's the service fuse.

Not if the cable isn't connected to anything - that was my point.

The OP is proposing that he install some cabling and CUs, but not connect the submain to any supply. Therefore according to the definition in the BRB/BGB there is no circuit, therefore no new circuit, therefore not notifiable.

There will only be a new circuit when the qualified sparky comes along and connects that SWA into a supply. That then brings up a question as to what the sparky would be certifying when he does the notification.
If he certifying the whole downstream installation, or is he just certifying the work he's been contracted to do (connect exiting SWA into supply) ?

And of course, what of the stuff connected to the new CUs ? If there's no supply connected, do those qualify as new circuits yet ?

 

[JohnW2]

Not if the cable isn't connected to anything - that was my point. The OP is proposing that he install some cabling and CUs, but not connect the submain to any supply. Therefore according to the definition in the BRB/BGB there is no circuit, therefore no new circuit, therefore not notifiable. There will only be a new circuit when the qualified sparky comes along and connects that SWA into a supply.

Ah! ISTR we've discussed this one before. One might even try to extend a similar argument any electrical work (even in bathroom zones), by arguing that a collection of interconnected cables and accessories does not constitute an "electrical installation" (which is what Part P refers to) unless/until it is connected to a source of electricity. However, as you go on to say ...

That then brings up a question as to what the sparky would be certifying when he does the notification. If he certifying the whole downstream installation, or is he just certifying the work he's been contracted to do (connect exiting SWA into supply) ?

That's the question. That work of 'just connecting the SWA' would only be notifiable (in England) if it were regarded as 'installing a new circuit' - in which case I would imagine (at least in terms of common sense) that(s)he would have to certify the whole of that new circuit - which obviously could result in problems.

As has been discussed at length in the past, it has always been true (even pre-April, and in Wales) that one can probably do this the other way around - get the electrician to install and notify 'token new circuits' (just OPDs and a short length of cable(s) terminated in something), after which those circuits can be 'extended' without notification (provided they were not outdoors or in kitchens or bathroom zones - now, in England, only bathroom zones).

Kind Regards, John

 

[syl]

It's two sheds, not a garage and a shed (the main house CU is in the garage). In fact it may be three sheds in future (all of which are next to each other and it seems a waste to run three separate cables from the house).

I can't see a time when I would want to isolate one shed. If I wanted to work on one shed's wiring I could switch off at the CU in that particular shed. If I ever wanted to work on the CU then I would be happy to switch off the circuit to all the sheds entirely. They are just sheds. Adding another switch just prior to each CU seems to be an extravagance I can do without.

The best way seems to be to get the electrician to wire up a new circuit from the house CU to a box on the outside. I will then extend the circuit myself from there (or connect up my wiring if already installed).

I will get someone qualified round before I do any work - don't want to dig all those trenches out if there's a problem with my proposal.

 

[syl]

Electrician has been. Suggests plastic CU and adaptable box. I'm going to lay it all out and he will connect up/test. Will take a while yet to do the trenches (plus still waiting on one of the sheds to be erected).

What's the best (neatest) way of connecting 2x 10mm 3 core SWA and 10mm singles inside an adaptable box? The electrician suggests putting some Henley blocks inside (presumably plus an earth bar for the third core/armour). Would Pratley end connectors, or a DIN rail solution, allow a smaller box? Or any other connector?

 

[JohnW2]

What's the best (neatest) way of connecting 2x 10mm 3 core SWA and 10mm singles inside an adaptable box? The electrician suggests putting some Henley blocks inside (presumably plus an earth bar for the third core/armour). Would Pratley end connectors, or a DIN rail solution, allow a smaller box? Or any other connector?

Henleys (probably just one DP one), plus something for the CPCs/earths, would certainly be one way to do it, but wouldn't a simple 60A connector strip be adequate?

Kind Regards, John

 

[bernardgreen]

This is how I connected SWA into a CU. The cores from the SWA going directly to the main switch in the CU

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• bernardgreen
• 8 Mar 2009
• 10

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• bernardgreen
• 10 May 2009
• 17

A grommet should have been fitted to the hole where the cores leave the box.

 

[syl]

That looks neat, but I have two to get in to a smallish (MK garage type) CU which has knockouts on the side, so a connection in the adaptable box will probably be easier.

 

[mfarrow]

Yup, really can't understand the need to create a joint in the adaptable box. Also can't see how adaptablle box plus fitting/alignment time would be cheaper including labour than just buying a metalclad CU.

 

[JohnW2]

Yup, really can't understand the need to create a joint in the adaptable box.

We discussed that before. There clearly isn't an absolute 'need', but dealing with the two sets of 10mm² conductors in a 'small garage-type CU' might not be the easiest of exercises.

Also can't see how adaptablle box plus fitting/alignment time would be cheaper including labour than just buying a metalclad CU.

I agree that it might not be much cheaper, but if it's a small ('garage type') CU the OP wants, even if metal, there might be difficulties in terminating two SWAs into it - and, again, you'd have the two sets of conductors to deal with.

However, I agree that,in concept, there is much to be said for both of your points.

Kind Regards, John

 

[syl]

Henleys (probably just one DP one), plus something for the CPCs/earths, would certainly be one way to do it, but wouldn't a simple 60A connector strip be adequate?

It looks like 3x10mm2 cables will fit 60a choc block ok, but they don't look as substantial and one screw will clamp two cores. Are they just left loose inside the box and wrapped in insulating tape?

 

[JohnW2]

Henleys (probably just one DP one), plus something for the CPCs/earths, would certainly be one way to do it, but wouldn't a simple 60A connector strip be adequate?

It looks like 3x10mm2 cables will fit 60a choc block ok, but they don't look as substantial and one screw will clamp two cores.

True, and I'd probably be inclined to use a small Henley for that reason. However, 3 x 10mm² will go into a 60A connector strip:

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• JohnW2
• 24 Sep 2013
• 1

Are they just left loose inside the box and wrapped in insulating tape?

You don't even really need the tape.

Kind Regards, John

 

[ban-all-sheds]

I agree that it might not be much cheaper, but if it's a small ('garage type') CU the OP wants, even if metal, there might be difficulties in terminating two SWAs into it - and, again, you'd have the two sets of conductors to deal with.

Then get a larger one.

More space for the glands, and room inside to use DIN-rail mount distribution blocks to join cables.

 

[JohnW2]

Then get a larger one.

Sure, that would be one solution. There are umpteen ways of skinning this particular cat, many of which are not 'wrong'.

More space for the glands, and room inside to use DIN-rail mount distribution blocks to join cables.

If both SWAs were glanded into the CU, there would be no need to join any cables with blocks - the L/N of both SWAs would simply go to the supply side of the incomer.

Kind Regards, John

 

[ban-all-sheds]

True.