CPC for shower!

[bluesky]

Hi guys, i just changed a 8.5kw electrical shower for a friend, the live is 6mm2 and i believe it is fine, the only thing is the cpc, looks like 1.0mm, at most 1.5mm, i checked codes, but still not sure about it, is this cpc ok?

cheers

 

[Hawk81]

was the cable a 6mm twin and earth? If so it has a 2.5mm earth. Which is fine.

 

[pennywise]

6mm should have a 2.5 cpc, sure you haven't got 4mm.

 

[bluesky]

it is very old cable, yes it is twin and earth, but looks so slim, dont look like 2.5...

 

[Hawk81]

are you sure its 6mm. If so it will be a 2.5mm cpc.

 

[All Sorts]

Hi guys, i just changed a 8.5kw electrical shower for a friend, the live is 6mm2 and i believe it is fine, the only thing is the cpc, looks like 1.0mm, at most 1.5mm, i checked codes, but still not sure about it, is this cpc ok?

cheers

First response to a post for me. Assuming both protective and line conductors are copper, then according to table 54.7 in regs (pg 130 in mine), suggests csa of protective conductor should be (at least) same as line conductor?

Thats the way I'm reading it anyway, but have to admit I've never seen a 6mm cable with a 6mm earth? Having said that, if you can imagine nearly 40amps running down your skimpy cpc in a fault condition then it doesn't sound ideal to me!

Pat

 

[Risteard]

First response to a post for me. Assuming both protective and line conductors are copper, then according to table 54.7 in regs (pg 130 in mine), suggests csa of protective conductor should be (at least) same as line conductor?

Use the adiabatic equation.

 

[Hawk81]

Use the adiabatic equation.

you beat me to it

 

[Sav]

Hi,
Whats the length of the cable and how is it run ( under floorboards, clipped direct etc ).

You said its old cable, is it the old colours Red, Black ??

You also mentioned 8.5kw shower, so that equates to 36.95 amps ( ib ), so depending on your fuseboard, you need at least a 40amp mcb.

So work out your current -carrying capacities, volt drop and adiabatic to get correct cable selection. You should really know what size cable you have selected, as this can have a big effect when the shower is on ( over heating the cable etc ).

Hope this helps,
Sav

 

[bluesky]

Hi,
Whats the length of the cable and how is it run ( under floorboards, clipped direct etc ).

You said its old cable, is it the old colours Red, Black ??

You also mentioned 8.5kw shower, so that equates to 36.95 amps ( ib ), so depending on your fuseboard, you need at least a 40amp mcb.

So work out your current -carrying capacities, volt drop and adiabatic to get correct cable selection. You should really know what size cable you have selected, as this can have a big effect when the shower is on ( over heating the cable etc ).

Hope this helps,
Sav

i only changed the shower and did not touch anything else. the colors are old: read and black. 6mm.

i could find easily the minimum size of main bonding conductor is 10mm, but just cannot find minimum requirement for cpc in the bs7671, is 1.5mm really ok?

 

[Sav]

i have not done the adiabatic equation, but guessing as some of the results i got previously from using that equation, they maybe , yes .

BUT, you must make sure you do it properly i.e supply protective device etc.....

Sav