Cable Size Help Please

[xavier]

7KW Shower, 10m cable run. Is 6mm2 OK Please? No tables here, only chairs :)

Xav

[Stefek Zaba]

Definitely maybe ;-)

7kW is 30A at 240V (well, 29.2). The OSG's Table 7.1 of Conventional Circuits gives 39m as the max length for a 6mmsq radial with a 32A Type B MCB/RCBO, for "broadly all" installation methods including "directly in a thermally insulating wall", so you look to be OK. However, 7kW units are falling out of favour, with more power-hungry 8.4kW and upwards being most widely available. Since cable cost is a small proportion of the overall job, you'll be better future-proofed running the circuit in 10mmsq, which would allow a later uprating of the MCB to 40A (45A only for the more restrictive clipped-direct, embedded-in-plaster, or in conduit/trunking - not the in-thermally-insulated wall case) allowing a future shower to be rated up to 9.6kW.

This quick OSG lookup ignores other factors - cable grouping, higher ambient temps, and so on; nor is it backed by any form of liability insurance. It's a random collection of bytes apparently written at a keyboard attached to a machine with the source IP address you'll see in the headers; if following this advice makes your house burn down or your visiting US-personal-injury-lawyer-just-using-the-shower fry, hard luck!

Stefek

[Tim (Remove NOSPAM.]

Install 10mm- you'll soon become annoyed with the pathetic output of a less than 9.5kw shower. Personnally I'd not install anything less than a 10.5kw unit.

Tim..

[xavier]

Thanks a lot. Actually it's not for me, it's for a relative and he will definitely be using 6mm because he says the small carpet tacks he's using to clip the cable directly to the wall just aren't long enough to go all the way through the 10mm stuff and still get a good fix. Now that's what I call forward planning. :)

xav

[Alan]

Cable clips *through* cable????

[Rob Morley]

***WHOOSH***