Routing SWA &/or T&E

[ParttimeDIYer]

Got a nice little challenge.

As crow flies distance CU in house to new Garden Office 17.4m
However route cable needs to take around obstacles etc if stay outside/buried c20-22m. But mean cutting through concrete slab and patio... not welcome.

Got an option to make it much easier for self (and not wreck expensive patio etc). By going via the garage. Distance house CU to garage 5m. Garage to shed 8m. They form a nice 90 with the garage at the apex. Would have to transit inside the garage at ceiling height.

Cannot use the circuits in garage as already in use got it's own connection to the House CU.

House CU will 'probably' use a 40A MCB
SWA is 2.5mm 3 core (I have remains of a 100m reel already)
Garden Office will have a 'garage unit' 3 way 1x10A, 1x16A and 6A. (Spilt A/C, Socket and lighting)

The question is this:

Do I use one continuous run of SWA from House CU to shed irrespective of through garage or not (would fix to wall about 100mm AGL) or do I break it and go house to garage then garage to shed with T&E inside garage between lengths of SWA? SWA cable isn't expensive that said I have some metal enclosure 60A joints as well. Having to redo the patio will be Obviously will have to be aware of the bend radius of the cable.

Sparky will connect it all up and test to be certified but I doing the physical work (trench, holes and cable pull).

Please be gentle



Read more: https://www.diynot.com/diy/threads/routing-swa-and-or-t-e.552965/#ixzz6YDoANgMW

 

[ParttimeDIYer]

House CU has all metal enclosure and is is at current regs, there is space for SWA compression gland and pushout exist and the extra circuit can be accommodated ... that already checked out.

 

[AndyPRK]

well 40A with 2.5mm is not correct. 16 or 20 A MCB

if you can get SWA to the CU without much bother, then its easier to just have one length of cable. (also it means it doesn't require RCD protection at the house CU which is a big bonus)

Is A/C air con ? or across

 

[ParttimeDIYer]

A/C Aircon, one of those heat pump things, heats in winter cools in summer. Not on all the time, unless get weeks like recent ones.

The SWA in one length is a faff but possible, trying not to have to go through the patio as that would be a nightmare. There is a border around it that could be used instead why the extra length. Inside or outside garage, inside obviously have to drill entry and exit holes and route cable, got to fix either way. It doesn't matter which way?

40A MCB are what the previous spark fitted, so I never questioned it TBH. So the House CU could be down rated for this or should I obtain some 4mm SWA instead? Garage (4 double 13 sockets and lights) is using 40A MCB at both ends. RCD protected at garage end. The house CU is one of those split load types with separate trips on both.

 

[AndyPRK]

Yeah I would be going for 4
Or 6 mm really cus is the air con.

Or add up the wattage of everything you will use at once.

Not sure what you mean about existing 40a. Do you mean rcd? Pictures help

 

[Taylortwocities]

should I obtain some 4mm SWA instead?

40A is still too large, even for 4mm². 32A is your limit for that.

40A MCB are what the previous spark fitted, so I never questioned it TBH.

But not for 2.5mm²? If you have 40A MCB on a 2.5mm² circuit it need serious attention.

 

[ParttimeDIYer]

Yeah I would be going for 4
Or 6 mm really cus is the air con.

Or add up the wattage of everything you will use at once.

Not sure what you mean about existing 40a. Do you mean rcd? Pictures help

It is not 2.5mm, it is 6mm so no problems with the cable. Don't have camera but I pulled off one end to check. The AC is rated 8.5amp 240vac peak btw.

 

[ParttimeDIYer]

40A is still too large, even for 4mm². 32A is your limit for that.

But not for 2.5mm²? If you have 40A MCB on a 2.5mm² circuit it need serious attention.

My bad but not a sparks so know my limits, the cable is a lot thicker. 2.5mm is the normal stuff, this is way thicker overall with heavy strands.

 

[Taylortwocities]

The size of SWA is usually embossed on the sheath. It may say something like 3x6. What’s on yours?

 

[ParttimeDIYer]

The size of SWA is usually embossed on the sheath. It may say something like 3x6. What’s on yours?

Thanks, not read it, dark now. I know the wooden reel isn't marked, label fell off ages ago. Cable outer is thickness of your thumb at least. Will check in morning.

 

[ParttimeDIYer]

Thanks, not read it, dark now. I know the wooden reel isn't marked, label fell off ages ago. Cable outer is thickness of your thumb at least. Will check in morning.

Says
Electric Cable 600/1000V BS5467 Made in UK
No mention of 3*??

 

[ParttimeDIYer]

I will measure the nominal outer diameter, 16.6mm for 6mm and 19.5mm for 10mm, might be 10mm certainly thick enough cable for that. Either way I assume spark had made sure was correct cable capable of 40A MCB everything else was fine. Sadly he has retired would otherwise have asked him.

 

[ParttimeDIYer]

I recall I needed 20mm drill bit to make hole for cable.

 

[Taylortwocities]

ither way I assume spark had made sure was correct cable capable of 40A

The size will be on the Electrical Installation Certificate that he gave you.

Have I missed something here. The 40A MCB. Is this on an existing circuit? What has this to do with the new circuit that we are discussing here?