Upgraded supply for a new shower?

[Wooej]

I have a nasty suspicion that I know the answer to this, but I want to pose the question:

I have a Triton electric shower which has failed after many years of service and I want to replace it with a more powerful electric shower.

The present supply is a 6mm cable which was adequate at the time, but which will not be sufficient for the intended new 10.5kW replacement.

The question is: can I run a parallell 6mm cable from the consumers unit to give sufficient capacity? My proposal is to run both cables into a heavy duty switch box, and from there a 10mm feed to the new shower - a distance of c. 2m.

In case it is relevant, the existing cable run is 14m from cellar to first floor and is surface-laid; not conduited.

Any comments or advice appreciated!

 

[PrenticeBoyofDerry]

The cable does not run within any thermal insulation?
May I ask why would you consider running another 6mm cable rather than installing 10mm and doing away with the existing cable?

Anyway not against the regs to run cables as you have suggested, would be some concerns if the appliance was higher rated than the 6.00mm cable and one became disconnected though.

As it stands simple calculations taking in to consideration no de-rating factors for method of installation, would say 10500W/230CV=45.7 Amps
6.00mm T&E cable can carry a max current of 47A under reference method C, the voltage drop is compliant to requirements.
But you are not going to get a MCB that is suitably sized

 

[EFLImpudence]

10500 / 240 = 43.75A or

9660 / 230 = 42A.

Take your pick

 

[Wooej]

The cable does not run within any thermal insulation?
ANS: No, it is on the surface mostly, and boxed in in some places.


May I ask why would you consider running another 6mm cable rather than installing 10mm and doing away with the existing cable?
ANS: The two considerations of cost and ease of handling.


Anyway not against the regs to run cables as you have suggested, would be some concerns if the appliance was higher rated than the 6.00mm cable and one became disconnected though.
ANS: Yes, that was the reason I thought it might not be permitted.


As it stands simple calculations taking in to consideration no de-rating factors for method of installation, would say 10500W/230CV=45.7 Amps
6.00mm T&E cable can carry a max current of 47A under reference method C, the voltage drop is compliant to requirements.
ANS: So in theory I could connect to the existing cable? I thought 6mm would be inadequate.


But you are not going to get a MCB that is suitably sized

ANS: Hmmm. That's a thought. I have what used to be wired fuses which I changed over to Wylex push plug in MCBs of various powers, this one is 30Amp.
So, a secondary question arises: where do I go from here?

 

[PrenticeBoyofDerry]

.
where do I go from here?

You will get a 40A plug-in MCB but the 45A if I remember have been discontinued for the wylex boards.
You will find that the manufactures Instruction of 10.5 kW showers will state 45A.
Option would be 9.5kW, also I would be looking to have RCD protection on this circuit.
The difference in cost between 10mm and 6mm cable would be about £20.00.

 

[RF Lighting]

Virtually all plug in type wylex boards will only support a maximum out going load of 30A

 

[Wooej]

Thanks to all for various inputs.

I have decided that my best option to achieve what I want is to replace the two modified plug-in Wylex CUs with a modern Wylex 12-way Split Load RCD unit and replace the 6mm cable with a 10mm run.

It's going to be interesting replacing the CU in a windowless cellar room. I just hope it can be done quickly enough to keep 'her indoors' happy and not let the freezer defrost! Better wait until this cold snap is over, though, with dependence on central heating.

 

[PrenticeBoyofDerry]

I have decided that my best option to achieve what I want is to replace the two modified plug-in Wylex CUs with a modern Wylex 12-way Split Load RCD unit and replace the 6mm cable with a 10mm run.

It's going to be interesting replacing the CU in a windowless cellar room. I just hope it can be done quickly enough to keep 'her indoors' happy and not let the freezer defrost! Better wait until this cold snap is over, though, with dependence on central heating.

It's not difficult to knock up a temporary supply for lighting in cellar and C/H
I doubt the time the power is off will affect the frozen food.

 

[RF Lighting]

I normally have power off for 4 hours when changing a CU. This won't be a problem for the freezer as long as you don't open the door.

I have a 75W HID torch which is ideal for lighting a whole room while the powers off.