Take it or leave it

[telectrix]

If you look up ref method c it makes mention of masonary brickwork concrete & plaster!

so if ref. method c it could be supplied on a 40A MCB then.

 

[Deleted member 26818]

It's not really a problem I have to deal with very often.
Usually when I tell my customers what is required, they accept it and that's that.
Occasionally I get a difficult one, and then I just do it as they request, as long as it's safe.
Then if there's any problems. I just say 'I told you so'.
In your situation, I would explain that the cable and the MCB require uprating, as the shower has a higher rating
I would then explain that if I don't replace the cable, I cannot uprate the MCB, and there is a possibility that the MCB will trip if the shower is used for too long.
Note the departure on the MWC, job done.
In a couple of months time, there will be a very good possibillity that they will be on the blower begging for you to come and replace the cable and the MCB.
More work, more money.

 

[PC Electrics]

I was taught that cable buried directly into standard masonary and plaster is method C. However I've just looked at table 4A2 and it makes mention of cables buried in a thermally insulating wall, but not the more common occurance of cables buried in plaster. As this method is extremely common isn't it odd that 7671 doesn't cover it?

Assuming I was taught correctly and the 6mm cable is clipped direct or buried in plaster or behind normal tiles, then its ccc is 47A and so a 9.5kW shower is fine on this cable with a 40A mcb.

If the cable passes through a loft and you have methods 100 or 101, then that is different. In this instance I would look to re-route this section of cable above the insulation layer and use a 4 inch pipe to maintain an air gap around the cable where it must pass through the insulation.

 

[telectrix]

bearing in mind the safety factors biult in to the rated ccc in BS7671, i would have no hesitation in rating 6mm in a nmasonry wall at 40 - 45A. and protect with a 40A type B MCB.

 

[Bubblecraft]

Thanks for all your thoughts on this guys


Sent from my iPad using Tapatalk - Couple a' Tools

 

[lauriehurman]

Electrician's Guide to the Building Regs says;

Method C; clipped direct or embedded in plaster.
Method B; run in conduit or trunking installed on, or in, plaster, masonry or the like.

Laurie