showers and cable size

[mickles]

hi everyone, an aquaintence with very little money has bought a 9.8 kw shower to replace his failed unit and asked me to fit it. house has a 6mm t/e shower cable. normally i would insist on 10mm cable, however, 9.8 kw at 230 volts works out at 42 amps. actual voltage measures at 245 which means real load is 40 amp. cable is 16metres clipped direct and is clear of insulation in the loft giving a volt drop of 4 volts ish. max tabled current capacity for cable is 46 amps and even at a current draw of 42 amps, it is unlikely the c/b would lift. in other words, it is right on the margin.
change it to 10mm or leave it? what do you think. (if he had lots of money

 

[Guitarist]

Just tell him to take it back and buy a smaller unit. If he's that poor he won't want to run such an expensive shower anyway.
Funny how people want to buy their own gear to save a few quid, then ask us to sort out how to install it.
What size MCB is protecting the cable at the moment?

 

[mickles]

currently on a 32

 

[Ducksy]

Ib<In<Iz
42<32<47

Fuse 32a is underrated should be 45a aside from that is boarder line and not ideal but totally within regs

IMO as long as the cable is clipped direct for the whole run and nothing to required adding cable correction factors its fine...like I said not ideal but fine.

Remember this work will require a EIC

Oh just to add a 8.5kw on a 40a fuse would be better.

 

[telectrix]

ideally, a 10mm cable, but in this case, i'd leave the 6mm and swap the MCB for a 40A.

 

[Guitarist]

What I don't understand is why he's bought a larger unit to replace the failed one, without consulting you first. He should really just swap it for a 7.5kw and there's no issue then. Even an 8.5kw would most likely run happily on a 32A MCB.

 

[Fast&Rough]

2x2.5mm t+e in parallel shoved down the cavity is the way forward

 

[DPG]

2x2.5mm t+e in parallel shoved down the cavity is the way forward

Why? and... Which cavity? DPG

 

[mickles]

bought shower new/secondhand cheap so no way to take it back. i was a bit unclear before, i intend to change the mcb to 40 and the shower isolator switch to 50 amp, just the cable size in question as it was on the margin, but you have confirmed that it just squezes inside the regs.
thanks to all

 

[ayrshirespark]

just fit it

6mm has been used for plenty of years and no probs now everyone screams 10mm, a rule of thumb is if less than 20 metre run its fine, 5 years ago you never saw 10mmtwin anywhere in a home

 

[Ducksy]

6mm has been used for plenty of years and no probs now everyone screams 10mm, a rule of thumb is if less than 20 metre run its fine, 5 years ago you never saw 10mmtwin anywhere in a home

I saw 16mm the other day with strands cut off so it could fit in the t-block :s

Defeats the point, whoever run the cable must have had it left over would be a nightmare to run.