Shower install

[aes2011]

Looking for the best solution on a damage limitation rewire...

Two bedroom semi with a 10.5kw shower in bathroom upstairs wired to a 45a p.c in 10.0mm t&e. There is no way of getting to shower unless the wall is chased out in bathroom or hallway. Problem is client does not want her bathroom damaged or hallway damaged and insists on no trunking. The existing switch wire is run in 6.0mm t&e.

Any ideas?

 

[GLENNSPARK]

whats she getting round her gaff??.....half ov the local football team after the match...lol.....

 

[GLENNSPARK]

"come and get into MY SHOWER BOYS"..lol......its better than the clubhouse...lol.....

 

[Rampage]

It should be realised that the shower does not run flat out all the time only when it is heating at max.

Surely that's all the time? The resistance of the coil will very slightly after its warm. But it probably won't be noticeable.
The temperature control on the front varies water flow not current!

To control the temperature with electricity rather than water flow would double the price of showers!

 

[Guitarist]

I think people are getting a tad confused about how most showers work. You choose the high (full) setting or the economy (half) setting and then vary the temperature with the flow rate. Apart from when the incoming mains water is very warm, everyone will choose the max setting which pulls full load current. Turning the heat down a bit does not stop a shower from running at maximum power.

 

[PC Electrics]

AS a 10.5kW shower pulls 43.5A and you are using a 45A ocpd then what's the problem with using 6mm?
6mm has a ccc of 47A provided the installation method is C. If it passes through any insulation in the loft, then re-route it so it's on the woodwork in fresh air. Use 4 inch pipe to provide an air space where the cable must pass though the insulation layer.

 

[J&M Electrical]

If the cable is clipped direct then as Table 4D1A states the cable is rated at 47 amps.

Chances are though that the cable is run from the Pull switch through the loft under the insulation therefore reducing the current carrying capacity drastically. The OP could clarify this.

We have always (old company policy and what we see as good practice) run any shower >9.0KW on a 10.0mm cable or chose a different shower. Better to be safe than sorry

 

[J&M Electrical]

AS a 10.5kW shower pulls 43.5A and you are using a 45A ocpd then what's the problem with using 6mm?
6mm has a ccc of 47A provided the installation method is C. If it passes through any insulation in the loft, then re-route it so it's on the woodwork in fresh air. Use 4 inch pipe to provide an air space where the cable must pass though the insulation layer.

Beat me to it DOH!!

 

[Guitarist]

Don't forget that most showers are quite a way from the CU, so VD must be taken into account.

 

[Jdsparky]

And you need to follow manufacturers instructions which usually say they want a 10.5kw on a 50a breaker which if 6mm carries 47 amps best case is not good enough so you would need to upgrade to 10mm anyway to adhere to the instructions, and probly for warranty reasons too if anything goes wrong with it in future

 

[Guitarist]

And you need to follow manufacturers instructions which usually say they want a 10.5kw on a 50a breaker which if 6mm carries 47 amps best case is not good enough so you would need to upgrade to 10mm anyway to adhere to the instructions, and probly for warranty reasons too if anything goes wrong with it in future

You are so right. Most manufacturers' instructions are now telling you minimum cable size as well as breaker size.
Also, we keep hearing about "clipped direct" cable ratings, but tbh I have never seen a shower close to the CU AND only clipped direct. Once you apply even small rating factors it is amazing how much larger the cable must be to comply with regs.