Shower Installation / CU Query

[sausage1]

Hi Guys...

My mate wants to install an En - suite shower and also to utilise his loft space for use as a study / bedroom (1 x Ring Main + Lighting)....the work has been notified to the LBA and work has commenced on the Central Heating for the study / bedroom....

He has asked me to have a look and advise as to the shower size....however...on inspection, I have noted...

Mains - 100A Split Load 9 way Consumer Unit fed via 25mm Tails from 100a Fuse on suppply...

Non RCD side - feeds the cooker (32A MCB) + Immersion (16A MCB) + 2 x 6A MCBs for lighting...+ 1 x spare way....

RCD Side - 63A 30mA - feeds 2 x downstairs ring mains (Kitchen / front room) via 32A MCBs + 2 x Spare ways

I obviously need to check and confirm that designated circuits are what they say they are !!....and potentially change if reqd...(Immersion etc)

Regarding the Shower unit and ring main and lights....specifically noting the 63A limitation on the RCD - and looking to keep any shower feed to 10mm - what do you advise re the circuits in the CU ....would 63A RCD be sufficient to allow for another ring main (study) + Shower ? if so, would it also need be limited to less than 10kW ? (10mm)

Advice appreciated...TA very much...[/b]

 

[jamie.aston]

New to this but couldn't you just use RCBO's on non RCD side, this would provide MCB & RCD protection.

Jambo

 

[davy_owen_88]

10mm² twin and earth is good for 64A when clipped direct and not subject to any derating factors. If you give more info on the cable run we will be able to tell you the maximum current it can safely carry.

Regarding the RCD issue, you could go down the RCBO route for the shower as mentioned by Jambo or you could install a new RCD with a larger capacity.

 

[sausage1]

Hi Guys...thanks to davy owen / jambo....what a splendid idea....RCBO in the spare place on the non RCD side ?....never even thought of that !!!..thank you both so much...

This would free up the spare RCD protected way for the new Ring Main !!

the shower cable (10mm) would be run from the CU under floorboards (thru joists) and up the false wall in trunking / conduit...to 45A DP pull sw...about 12 metres

Methinks 45A RCBO fitted to non RCD side of the CU to feed 10mm cable and 9.5kW shower ?....would this need to be a Double Pole RCBO ?

Thanks again guys.......ATB>........

 

[davy_owen_88]

the shower cable (10mm) would be run from the CU under floorboards (thru joists) and up the false wall in trunking / conduit...to 45A DP pull sw...about 12 metres

Methinks 45A RCBO fitted to non RCD side of the CU to feed 10mm cable and 9.5kW shower ?....would this need to be a Double Pole RCBO ?

Is the false wall insulated? If not then the 45A RCBO is fine. No need for a double pole RCBO. Are you aware that electrical work in the bathroom is notifiable?

 

[sausage1]

hi _davy_owen_88

Thanks....yes....my mate has notified the Local Building Authority...

Re the false wall insulation....and the DP upgrade on the RCBO, would this be due to the 10mm cable being classed as enclosed ?

Much Obliged....for this and previous answers...

 

[davy_owen_88]

When cables are run within conduit/insulation or both it reduces the maximum current that cable can safely carry. Running 10mm² cable in conduit within a wall reduces the CCC to 52A, whereas if the wall was insulated it is reduced to 43A.