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

 

[Nigel]

I have just re-read the op.

The EICR that was done has highlighted a lack of RCD protection on final circuits on all CUs.

The client is trying to cut costs by asking if fitting ‘up front’ RCDs on the sub-mains instead of the CUs therfore installing five RCBOs rather than 40.

This is not an option due to selectivity so I would say no to that.

 

[Deleted member 26818]

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

If the cables are just laid on plasterboard, there’s no requirement for a minimum depth.
The drill through the plasterboard, the drill will push the cable away.
Where cables run through joists or battens, the drill can’t push the cable away, so additional protection is required.
1.Depth between cable and the surface of the floor or ceiling has to be greater than 50mm.
2.Earthed sheath, conduit or trunking.
3.Steel plate between the ceiling/floor and the joist/batten.
Unlike for cables concealed in walls, RCD protection is not an option.

 

[Bait Account]

My take on this is that if it was installed to the 16th edition or before then the sockets don’t require the additional protection unless they could be reasonably expected to be used for outdoor equipment.

 

[Deleted member 26818]

My take on this is that if it was installed to the 16th edition or before then the sockets don’t require the additional protection unless they could be reasonably expected to be used for outdoor equipment.

Yes, that’s correct.
Only started needing RCD protection when the 17th came in, as they would be used by unsupervised ordinary persons.

 

[Bait Account]

The thing is we don’t know when it was installed. We also don’t know if the guy who issued the report is aware of the changes between the 16th and 17th. My point is that I’d like to know these facts before banging in RCD’s.

 

[Deleted member 26818]

The thing is we don’t know when it was installed. We also don’t know if the guy who issued the report is aware of the changes between the 16th and 17th. My point is that I’d like to know these facts before banging in RCD’s.

Personally, If I’m asked to provide RCD protection, the age of the installation doesn’t matter.
I’ve done some work for a customer who owns a Cafe.
Installed a split load board a few years back, installed a new circuit for his dishwasher, installed some 600mm X 600mm LED lights, and a few other things.
Not all at the same time, but over a period of years.
The latest was to swap out the innards of the split load board and replace with RCBOs.

 

[45140]

The client may well have done a risk assessment and the remediation is the provision of RCDs given it is a hostel, so surely the basis upon which it was wired is hardly relevant ?

The correct solution would be an RCD for each room for obvious reasons and is surely the right answer ?

 

[Bait Account]

The client may well have done a risk assessment and the remediation is the provision of RCDs given it is a hostel, so surely the basis upon which it was wired is hardly relevant ?

The correct solution would be an RCD for each room for obvious reasons and is surely the right answer ?

We don’t know that bud but it is possible. It’s also possible that the person that carried out the report wasn’t aware of the requirements of additional protection in the previous editions of the regs. Anyway we can speculate all night as I doubt we’ll ever know the full facts.

 

[Toneyz]

The answers you seek are in BS7671

In that case my preference would be RCBO's to each circuit.

 

[westward10]

When I do EICRs I am not overly interested when it was installed with regard to additional protection it is a statement of fact it is not provided.