9.5 kw shower on 6mm ?

[jonthesparks]

just been to a job , saw that the shower 9.5 kw is on 6mm t&e the cable goes in the wall and under floor boards ,No insulation, to the board (A cable run of no more than 10 m) . I said downgrade the shower to 8.5 max. Is it really necessary ? never quite sure , its borderline to me .

 

[Dave 85]

That's going to look great on open forum isn't it
People have enough trouble trusting tradesmen without nonsense like that being in public view

Come on Trev, you know I'm only messing about. Just annoys me people advising clients to fix things that arn't broken.

 

[trev]

Dave you may well be messing about but put yourself in a potential customer's position. A lot of people are nervous enough about tradesmen ripping them off and we get plenty coming on here looking for advice.

 

[trev]

I agree that there's an over reaction to fixing things that aint broken but you can't tell people's inflection from what they type mate.

 

[Guest123]

Lets not get silly now chaps, remember, potential customers could also be reading this thread........:wink5:

 

[telectrix]

agreed . after all, we're electricians, not plumbers.

 

[somersetsparks]

Just to add my tuppence worth,
I have seen many, many 8kw and above showers wired in 2.5mm flex from the isolator to the actual shower unit in my time testing, none of which showed any signs of damage, poor terminals and terminations cause many more,
I think in an ideal world there should be a 'domestic shower diversity' added to the regs, it irritates be to give a code 6mm supplying showers in houses, in fact I often give it a code 3 rather then 2 if there is no heat damage.

 

[Guest55]

Just to add my tuppence worth,
I have seen many, many 8kw and above showers wired in 2.5mm flex from the isolator to the actual shower unit in my time testing, none of which showed any signs of damage, poor terminals and terminations cause many more,
I think in an ideal world there should be a 'domestic shower diversity' added to the regs, it irritates be to give a code 6mm supplying showers in houses, in fact I often give it a code 3 rather then 2 if there is no heat damage.

Dont understand why you would code it at all ?
On what grounds ? for what rating of shower is 6mm unacceptable ?

 

[sedgy34]

Thread closed!!!!!!

 

[somersetsparks]

Thread closed!!!!!!

Nearly fooled me!
Biff55, I meant when they are on 40MCB's with referencve method 101 or A (or the dreaded 103... arhh!)

 

[Paul P]

Agree with robd , as a fixed load , 9.5kw @ 230v pulls 41.3A
i wouldnt replace cable for an extra 1A for a few mins.

As a shower is a fixed restance i think you will find it rated at 9.5kw @ 240v so only 39.58A

At 230v it would be a 8.7KW shower so only 37.9A

 

[steveberry11]

If you design your circuits correctly you must be aware that.
As a 9.5KW shower draws 41.3A you are unable to use a 40A MCB You need to use the next size up. This would be a 45A
it is correct that the tabulated current carrying capacity of a 6mm T&E cable is 46A this is the value prior to any correction factors being taken to account. I would suggest that the there are multiple cables exiting the DB at the same place so the grouping factor will reduce the cable rating below 41.3A without taking into account any other factors.
It is not acceptable to assume that no harm will be caused to the cable as the shower will only be on for a short while or the loading is only 1A over the 40A MCB rating.
When the electrical installation certificate is issued you are sating that the installation complys with BS 7671 and is a legal document in the event of future problems.
I would suggest if this size shower is to be installed a 10mm cable minimum cable should be used. Pay now or pay later.

 

[Djlelectrical]

Just make sure the MCB is sufficiant for the cable, Either that or upgrade to 10mm cable

 

[sedgy34]

If you design your circuits correctly you must be aware that.
As a 9.5KW shower draws 41.3A you are unable to use a 40A MCB You need to use the next size up. This would be a 45A
it is correct that the tabulated current carrying capacity of a 6mm T&E cable is 46A this is the value prior to any correction factors being taken to account. I would suggest that the there are multiple cables exiting the DB at the same place so the grouping factor will reduce the cable rating below 41.3A without taking into account any other factors.
It is not acceptable to assume that no harm will be caused to the cable as the shower will only be on for a short while or the loading is only 1A over the 40A MCB rating.
When the electrical installation certificate is issued you are sating that the installation complys with BS 7671 and is a legal document in the event of future problems.
I would suggest if this size shower is to be installed a 10mm cable minimum cable should be used. Pay now or pay later.

Welcome steve
what scam do you work for

 

[steveberry11]

How do you know the calculated cable capacity and suitable MCB rating without calculations, you also need to take into account loop values prior to changing MCB's

 

[Old School1]

Good Stuff