RCD Protection for submains

[TJC1]

Evening all

We have been asked to do some redial work picked up by a testing company i a hostel. It has been picked up that is no RCD protection in the rooms

There are 5 submain circuits that feed the 20 consumer units, 4 consumers units per submain (B32) Each room have a consumer unit which has two double sockets off a 16a radial and a lighting.

They asked my advice on whether to change the submain MCB to RCBOs or whether to change the consumer units for main switch and RCBOs

They supply cables to each consumer unit are above a plasterboard ceiling but cant be sure of the installation method, does the submain need to be RCD protected? As i dont want to put RCBOs on each circuit and also on the submain also

Thanks

 

[Nigel]

If the installation method of the sub-main requires RCD protection then how will fitting RCBOs on the final circuits protect the sub-mains?

 

[TJC1]

If the installation method of the sub-main requires RCD protection then how will fitting RCBOs on the final circuits protect the sub-mains?

That's my question, do the submains need to be RCD protected? Seems ridiculous that i need to install an RCD on the submain when it protects 4 consumer unit. It would be much better to be able to install separate RCBOs on the consumer unit and leave the submain.

Does above plasterboard ceiling count as buried? Or require an RCD

 

[Deleted member 26818]

Whilst cables above ceilings and below floors require additional protection where they pass through joists or battens. RCD protection is not an acceptable method.

 

[snowhead]

Does above plasterboard ceiling count as buried? Or require an RCD

If you screwed a 50mm screw into the ceiling would it hit the Submain anywhere along it's length?

 

[TJC1]

Whilst cables above ceilings and below floors require additional protection where they pass through joists or battens. RCD protection is not an acceptable method.

How would you get over my issue?

 

[45140]

The answers you seek are in BS7671

 

[Bait Account]

What type of cable are the subs and what edition of the regs was the original work done to?

 

[Deleted member 26818]

Seems to me, that you have been asked to supply RCD protection for the rooms.
I’m assuming that’s for socket-outlets and circuits of locations containing baths or showers?
You can either install an up front RCD for each room, or swap MCBs for RCBOs.
How you do that is up to you.

 

[TJC1]

What type of cable are the subs and what edition of the regs was the original work done to?

Im not sure on the depth and the cable is T&E