Shower circuit, is it acceptable?

[woko27]

Hello, I have a shower circuit in my house and I wish to find out if it is acceptable.

A 6mm cable on a 32 amp breaker runs from the consumer unit to the kitchen 45 amp cooker switch (with 13A socket). The cooker is gas so switch is not needed. The 6mm cable runs from the switch through the wall into a conduit outside. Up the outside wall through conduit into the attic. It then runs down from the attic into the bathroom, through a bit more conduit into the shower.

Is this ok? The cooker switch does work and isolates the shower, the shower is 9.5KW which I know will pull about 40 amps, so is the cable big enough?

Thanks in advance.

 

[lizzieg]

Hi woko

in conduit for a shower that size it needs to be 10mm on a 40 A mcb.

As to the use of the cooker switch with socket, I do not know, but I cannot see how it could be correct, but someone will be along later to confirm or put me right

Lizzie

 

[woko27]

Hello again, Thanks for the quick reply Lizzieg, I have made a mistake though. The shower is a 8.5KW, could you please advise again on the cable size please.
I have consulted an OSG and table 6E1 on page 123 states that if enclosed in conduit with 1 two core single phase then a 6mm cable will cope with 38Amps and by my calculations a 8.5KW shower will pull 36 amps, so is this ok? I don't have the confidence to say myself from looking in the OSG.

Thanks

 

[martin43]

Hi Woko

32 amp breaker

and by my calculations a 8.5KW shower will pull 36 amps

Rather answered your own question. Firstly the breaker is undersized for the load, you need a 40A one. Secondly 6mm cable will carry 38A in a conduit but only 32A enclosed in a wall, therefore you need 10mm cable. Additionally at the specified load you can have a run of 36.5m before volt drop becomes an issue, how far is your consumer unit from the shower, in cable length terms? In 10mm at that load you can have a run of 60m.
Thirdly you make no mention of local isolation of the shower, is there a pull switch in the bathroom? Lastly use of a cooker switch to isolate a shower is almost certainly a no no.

Regards
Martin

 

[martin43]

Woko

Just thought of something else. A shower has to be RCD protected, and like as not your cooker circuit won't be, have you RCD protection?

Regards
Martin

 

[woko27]

Hello,

No RCD protection, its a wylex fuse board with 4 outlets, Ring for whole house, lights, shower and alarm.

I imagine i'll need the CU changing and the shower ciruit rewired in 10mm, best call in the electricains.

Thanks for all your help.

 

[martin43]

Woko

I imagine i'll need the CU changing

Yes

shower ciruit rewired in 10mm

Yes

If it's as old as your description suggests then I'd seriously consider a complete rewire.

Regards
Martin

 

[Steve]

shower doesn't NEED RCD protection, but it is desirable for peace of mind when you're standing naked and wet, inches from a heater pulling 10,000w of electricity.

 

[securespark]

Regs don't say you need RCD, however, most manufacturers say you should use one, and that to my mind overrides the regs.