Cable size required?

jlparsons · Feb 13, 2018

Am running cable to my garage to provide power for a car charger. The run will be threaded through holes drilled in the center of the joists under the upstairs floor such that the cable is suspended in the air between plasterboard and floorboards. There is no insulation in there.

Would this fall under reference method C, clipped direct? It's uninsulated but still enclosed so I'm not sure?

Murdoch · Feb 13, 2018

Whats the design load?

jlparsons · Feb 13, 2018

Murdoch said:
Whats the design load?

50A over 40 meters, single phase.

Murdoch · Feb 13, 2018

Ouch ..... that's going to cost.

You must have a big house if its 40m from the fuseboard to the garage!

Are you a spark?

jlparsons · Feb 13, 2018

Murdoch said:
Ouch ..... that's going to cost.

You must have a big house if its 40m from the fuseboard to the garage!

Are you a spark?

Very long house, garage is also at the bottom of the garden so it's half T&E under floor boards and half SWA clipped to exterior brick wall. I'm not a sparky myself but I'm laying the cable run before the charger installation company sends their sparky to do the rest.

Murdoch · Feb 13, 2018

In which case best you consult the company providing the spark to test ......

steptoe · Feb 13, 2018

it's gonna be bigger than 2.5mm

jlparsons · Feb 13, 2018

steptoe said:
it's gonna be bigger than 2.5mm

Oh I dunno... We could just call it underfloor heating?

steptoe · Feb 13, 2018

you could call it a Fire Brigade call out to be a bit more precise,,,,,,,,

jlparsons · Feb 13, 2018

Murdoch said:
In which case best you consult the company providing the spark to test ......

They are not prepared to do the cable run and seem non-plussed over which reference method this represents.

steptoe · Feb 13, 2018

have you done any calcs re VD.?

that would be a bit more important that a ref method tbh

jlparsons · Feb 13, 2018

steptoe said:
have you done any calcs re VD.?

that would be a bit more important that a ref method tbh

Yup, VD fine at 10mm.

steptoe · Feb 13, 2018

jlparsons said:
Yup, VD fine at 10mm.

VD fine on a 10mm at 40m for 50A,,,,,,,,,,,,,,, glad you've been able to work that out without knowing the ref method,

try your Zs on that 4mm cpc

jlparsons · Feb 14, 2018

steptoe said:
VD fine on a 10mm at 40m for 50A,,,,,,,,,,,,,,, glad you've been able to work that out without knowing the ref method,

try your Zs on that 4mm cpc

It's fine on both reference methods b and c, one of which must be the case here.

All I'm looking for is anyone who knows which reference case should be used for cable mounted between holed joists in an uninsulated void between ceiling and floor. From the descriptions in the literature it could be argued to fall into either.

Doc Hudson · Feb 14, 2018

So who is signing the design and installation aspects, of the Electrical installation certificate, that needs to be issued once the work is complete? The signed declaration box on the certificate does carry a reasonable amount of legal liability should things go pear shaped at a later date. Their lack of interest ref installation method could be because volt drop calculations may overshadow any cable capacity (and installation method adjustments) related to the design of this new circuit. You don't say where about you are? There could be some Part-P compliance issues as well for whoever is signing the declaration boxes on the certificates. Does this garage have any lights in it as well? or just a car charger and nothing else at all?

Doc H

jlparsons · Feb 14, 2018

Doc Hudson said:
So who is signing the design and installation aspects, of the Electrical installation certificate, that needs to be issued once the work is complete? The signed declaration box on the certificate does carry a reasonable amount of legal liability should things go pear shaped at a later date. Their lack of interest ref installation method could be because volt drop calculations may overshadow any cable capacity (and installation method adjustments) related to the design of this new circuit. You don't say where about you are? There could be some Part-P compliance issues as well for whoever is signing the declaration boxes on the certificates. Does this garage have any lights in it as well? or just a car charger and nothing else at all?

Doc H

All I'm looking for is anyone who knows which reference case should be used for cable mounted between holed joists in an uninsulated void between ceiling and floor. From the descriptions in the literature it could be argued to fall into either B, C or E. I'd argue B but interested in opinions!

Sharpend · Feb 14, 2018

Cable aside what earthing arrangement are we looking at?

Evans Electric · Feb 14, 2018

You did open your post up with "Cable size required JL

I've known Sparkys who know less than you do JL .

If you just want opinions on the Install Reference I'd say its either Ref: C or Ref; 100 .

Ref B is surface conduit and Ref E is Tray miraculously floating in mid air .

jlparsons · Feb 14, 2018

Evans Electric said:
You did open your post up with "Cable size required JL

I've known Sparkys who know less than you do JL .

If you just want opinions on the Install Reference I'd say its either Ref: C or Ref; 100 .

Ref B is surface conduit and Ref E is Tray miraculously floating in mid air .

Cracking, thanks mate. I've now managed to get the installation company to commit to that too, so I know I'm good to crack on with 10mm on a 50A MCB.

Thanks all!

Evans Electric · Feb 14, 2018

Type C ???

Cable size required?

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