Is there such a thing as

[STI]

A 43A RCD FCU. Or anything above a 13A one. Yep sorry back to the shower and bathroom again. Currently have a 100ma S-type RCD in place. Rather than replace this i thought perhaps i could put a 30ma RCD between the CU and the electric shower (9kW). I can find 13A RCD FCU but nothing above this rating. Do they exist. Also am i correct in thinking that because the 100MA RCD in place is an S type that this is a time delayed RCD.
Thanks

 

[Steve]

You just need a 45 amp RCD full stop. An FCU is for connecting a permenant appliance to a ring final.

 

[JohnD]

No, FCUs are for putting on ring or radial circuits, and the max fuse is 13A.

Yes, an "S" type RCD is time delayed. Thsi is unsuitable for shower protection. A 100mA RCD is unsuitable for shower protection

If your shower is fed from a 45A radial then it presumably hasa 45A fuse or MCB protecting the circuit already so should not need a second fuse

The MCB could possibly be cahnged for an RCBO depending on brand, model and age.

It is notifiable work, not a DIY job.

 

[STI]

Thanks for the replies. Just to clarify a little the CU is full. The 100ma RCD is already in place and although i know this doesnt meet 17th edition requirments for a shower circuit (or sockets for that matter) i believe it met the requirements when it was wired up about 9 years ago. It protects the shower circuit and a couple of Ring circuits for the sockets all of which have their own MCB's. I was trying to see if there was a way of adding the additional protection to the Shower circuit without having to replace anything in the CU. It sounds as though there isnt.

 

[JohnD]

an RCD could go in the cable between the CU and the shower.

Preferably in a labelled enclosure adjacent to the CU.

 

[ColJack]

try swapping the 45A breaker for a 45A RCBO in the board.. or rather get a sparky to do it for you.. saves on the Part-P cost..

 

[STI]

Great thanks for the help and suggestions.
I hadnt realised that RCBO's fit in the same size gap as a MCB?

 

[ColJack]

the do, but it depends on your CU if you can get RCBO's to fit..

post a picture of your CU and a close up of the breakers so we can see what they are adn advise if RCBO's are available to fit..

 

[STI]

View media item 15943 [/img]

Hopefully you can see the image. The MCB is the 40a right next to the RCD.

Before anyone shouts, i know it should be turned off before opening the CU but its in an understairs cupboard and my telephone doesnt have a flash so i needed the light on.

The end breaker 32a is not currently being used but i may split the sockets so i have two circuits rather than 1 as it currently stands.

 

[JohnD]

that appears to be the late model Crabtree Starbreaker with the spike busbar connector (not a screw as you see).

You can get single module RCBOs to fit (you don't want a double-module one), part no beginning with 61

However everything to the right of the RCD is protected by that RCD. the busbar has fixed positions on it. So you can't put an RCBO on the right.

It is poss to get a new busbar, but it would be easier to put the RCBO to the left of the RCD.

This is notifiable work.

 

[Spark123]

What is the purpose of the 100mA RCD?

 

[STI]

Hi Johnd. Is the spiked connection you refer to the black tabs at the bottom of each of the MCB's that connect to the line busbar. Does this mean everything to the right of the busbar is in effect a single unit ie you cant replace any individual MCB. If these are as you say fixed how can i move them down to allow me to create space to the left of the RCD. Or do you mean remove one of the MCBs to the left of the RCD and rewire the shower to that. I would then have a unused 40a MCB.

Apologies if i misunderstood what you meant.

 

[STI]

SPARK123, I guess it was put in to add some additional protection or as this is a rural location it may have been when it was wired in this way, it was a TT system. It is now a TN-C-S . I am afraid it was done before my time so i cant be sure why.

 

[JohnD]

I mean remove one of the MCBs to the left of the RCD and rewire the shower to that

each MCB has a prong out of the back that goes into a slot in the busbar. It is pushed into place. The busbar is made with n non-RCD slots and n RCD slots. You can't change the slot layout without changing the busbar.

The busbars in other brands of CU work differently.

You do understand what notifiable work means, don't you?

 

[STI]

Hi Johnd Yes i do understand notifiable work thanks.

Regarding the push in of the MCBs i dont think these do. They are attached to the holding rail in the CU I have tried to remove the unused 32A MCB at the end and i have to admit it beat me. I pulled as hard as i dared and it didnt give any sign of coming out. So i stopped!!

Everything was switched off at the board and i stayed well clear of the incoming supply to the main breaker before doing this.