Have I got this right?

[Tucosweep]

Hello guys,
I am wiring a shower and need to know if I have got this right?

It is a 8.5kw shower with a 15m cable run in mini trunking.

I have selected a 40A mcb, 6mm cable with a current capacity of 38A, and the volt drop is just inside.

BUT, after looking in the electricians guide to the wiring regs it says I must have 10mm cable for a shower rated between 7.5-9.5kw,

can I proceed with the 6mm cable?

kind regards
Grant

 

[telectrix]

your CCC at 38A would require a 32A MCB ( In < Iz ). a 32A MCB ain't gonna trip on 8.5kW for the length of time the shower is on. calc. current is 36A but i bet a clamp meter will show a bit less.

 

[Octopus]

Hello guys,
I am wiring a shower and need to know if I have got this right?

It is a 8.5kw shower with a 15m cable run in mini trunking.

I have selected a 40A mcb, 6mm cable with a current capacity of 38A, and the volt drop is just inside.

BUT, after looking in the electricians guide to the wiring regs it says I must have 10mm cable for a shower rated between 7.5-9.5kw,

can I proceed with the 6mm cable?

kind regards
Grant

Grant, surely you know that the MCB is to protect the cable so if the cable rating is 38A and the MCB is 40A which is going to fail first?

 

[Ducksy]

Has I understand it (8.5kw @ 240) that's (7.8kw @ 230) is says that on the box.......now 7800/230 = 34 amps which mean you need a 40amp mcb.....as for cable you need higher then 40 because that's the fuse size. now cable 6mm clipped direct method C is 46a which is fine but in trunking method B (your way) is 38a just not enough so 10mm is required.........as for the guide its always suggested 10mm because people will swap the unit from 8.5kw to 10.5kw when it comes to replacing it. So 10mm covers all angles

 

[Tucosweep]

Hi,
Yes, I have been a bit slow on this one.
i have stupidly bought 6mm cable, is there a way round it?
can I strip the cores into singles to give me a CCC of 41A then sleeve the earth?
kind regards
Grant

 

[Tucosweep]

Thanks Dusky

 

[telectrix]

strangely enough there is no reference method B quoted for flat T/E cable. IMO.6mm T/E will happily run all day long at 40+A in mini trunking, so I'd
go with a 40A MCB up to 9KW. tin hat on boys.

 

[Octopus]

If you are running a new cable I'd go with 10mm. tin hat on!

 

[Guitarist]

Grant, are you actually an electrician? Also, this work is notifiable under part P (either before you commence work if not registered, or after completion if you are).
I only bring up these points due to the fact that you bought the 6mm cable without being sure, and stated that you were considering running cable you rated at 38A with 40A protection.

 

[dan86]

If you are running a new cable I'd go with 10mm. tin hat on!

+1....

 

[telectrix]

if you use 10mm then those nice men in the disposable white overalls can come and smother it in 12" of itchy-poo crap wthout it overheating and setting the attic on fire. one day they might even manufacture pull switches that can accomodate 10mm cable and still get the outer sheath inside the box.

 

[Octopus]

if you use 10mm then those nice men in the disposable white overalls can come and smother it in 12" of itchy-poo crap wthout it overheating and setting the attic on fire. one day they might even manufacture pull switches that can accomodate 10mm cable and still get the outer sheath inside the box.

Crabtree 50A pull switch?

 

[telectrix]

fitted one of them for my mate. had to replace it when it failed. only been in 15 years!.

 

[Rockingit]

one day they might even manufacture pull switches that can accomodate 10mm cable and still get the outer sheath inside the box.

You not used the Crabtree (or much cheaper Scolmore identi-copy) 50A pull switches, then? 10mm no trouble at all with a bit of sheath inside.

 

[Rockingit]

You not used the Crabtree (or much cheaper Scolmore identi-copy) 50A pull switches, then? 10mm no trouble at all with a bit of sheath inside.

Sunday = slow typing