Shower Cable Confusion

I know this question has been asked a thousand times before (for which I appologise) but once more can't hurt can it?

I want to replace an electric shower in my bathroom.
The current unit is an Aqualisa Aquastyle I but it gives no clue as to the power rating.

The house is of modern construction, though is now about 10 years old and I'm guessing the shower is that old.

Before purchasing the new unit I've been up in the loft and found the pull switch for the existing shower. There's 6mm cable coming up the breeze block wall from the consumer unit (presumably) to the switch and then 6mm cable going from the switch back to the unit. Except the cable lengths from the wall to the switch and back the cable is between the breeze block wall and plasterboard.

So reading the back of the boxes in Homebase (and the other posts on this site) it suggests that 6mm cable is only good for showers upto 7.2kw - and I don't seem to be able to buy one of those.

Nearly all the showers I see (online and in shops) are 8.5/9.5/10.5kw.
I've chosen the shower I'd like, which is 8.5kw - but I'm not going through the hassle of upgrading the main feed from the consumer unit to 10mm cable. (I forgot to say the shower circuit is on it's own breaker in the unit).

So,
Q1, Have the regs changed with regards to this, or have showers just increased their power consumption over the last ten years?
Q2, Are there any circumstances under which I can run a 8.5kw shower on my existing 6mm circuit?
Q3, Can you still buy a shower with a 7.2kw (or less) power rating, where from and is it worth it?

Many thanks, much appreciated.


C.

http://www.tlc-direct.co.uk/Product...7.2kw shower&gclid=COC53qv94pMCFQpPQgodGGOvzA That anwsers 3 but I wouldn't rely on it being good in winter on a cold and frosty morning.

Your questions are mostly irrelevant.

6mm² cable can carry a maximum of 47 amps at its optimum installation up to a certain length.

This means that along its whole length it is able to dissipate heat to the surroundings. At 47 amps, it will get warm. Its not recommended.

Anyhow, 47 amps is 10.8kw.

But if we take into account that your cable is probably not run in free space and is unable to dissipate heat along its whole length (loft insulation?) then I'd say fit a maximum of 8.5kw shower.

You cant fit a shower over 9.5kw anyway, since you'd be unable to protect the cable adequately (you'd need a 50A MCB with a 10.5 or 10.8)

What rating of MCB currently protects the shower circuit?

I'd recommend you check the cable does not run in insulation, and isn't a stupid length, then fit an 8.5kw shower on a 40A MCB.

DIYC said:

I've chosen the shower I'd like, which is 8.5kw - but I'm not going through the hassle of upgrading the main feed

Click to expand...

You seem to agree with the "shops" that 6mm² is not suitable for more than 7.2kW, yet you want to use a 6mm² cable to run an 8.5kW shower from.