Replacing a CU switch for an RCD

[mntmouse]

Hi,

I have checked the previous posts and could not find this question, please direct me to it if i have missed it.

I am currently in the process of replacing an existing electric shower with a Triton 100i 9.5kW. I notice in the instructions that an RCD is required between the shower and the CU.

Having been to B&Q to see if a stand alone RCD was available (only for use on the shower circuit) and found nothing suitable, however i have returned home with an 100A, 30mA RCD. Can this be directly replaced with the existing standard switch on my CU? (all components are Wylex and the CU is rated at 100A)

Thanks for your help

MNT

 

[plugwash]

yes and no

if the wylex board is an older NN unit then i don't think you can

if the wylex board is an NS unit then the swapout could be done but

1: putting the whole house on rcd while not explicitly prohibited in the wiring regs is considered very bad practice nowadays
2: you would either have to pull the service fuse or do it live neither is reccomended for diyers

 

[comms]

Not a good practice if the rcd trips all circuits are lost, hard work if its dark.

 

[ryanj]

You could buy a seperate enclosure, 2 or 4 way.

And then mount the RCD in there, between the cable from the MCB to the shower. Simple.

 

[mntmouse]

Thanks for the advise so far. I actually purchased a second 2 slot CU at the same time. How would this connect to the incomer though?

Is it connected with a second set of tails from the main incomer or is it connected with tails coupled to the incomer to the first board?

My incomer has an off switch before the meter that is all part of the Yorkshire Electricity equipment (there is no 'do not break this seal' sticker over it and i have switched it in the past to make double sure the supply is not getting through when inspecting the CU)

 

[breezer]

This way is correct,

Is it connected with a second set of tails from the main incomer

but you must use the same size of tails that you have already, and connect it to the henly blocks

 

[mntmouse]

Thanks for all the advice, I have however found this product:

http://www.toolstation.com/?code=96020

(the GE shower unit) which i will use instead (unless someone recomends against it).

I have not seen the wiring diagram for it yet but i assume that it is wired: output from MCB -> into shower RCD unit incomer terminals -> through the unit -> to the shower.

 

[plugwash]

you could wire it that way but if the main incomer on your existing CU is only rated at 63A its probablly better to henly the tails from the meter to the CU (especailly as you already have an isolator in place before the meter)

 

[kai]

For adding RCD protection to an existing setup, why not fit one of these, it's a 3 way din-rail box, with a DP RCD and an appropriate MCB in one.

Mine is set up to protect the 32A ring circuit service the Kitchen and Living Room, (or downstairs ring), so that RCD protection covers the at risk sockets with 30MA rcd protection.

I bought a 40amp RCD from Newlec, same price as the 32amp, but I felt it was safer to have a 40amp one instead. The MCB feeding it is a B32.

 

[Damocles]

Don't fancy one of those in the corner of every room

 

[Lectrician]

Why an MCB as well, if you are leaving one in the main CU??

 

[kai]

Actually the MCB is unused, the facility just came with the Unit - it's marked "Spare" and not wired, as main CU still has the B32 MCB in it.