RCD Protection for submains

T

TJC1

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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
 
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essex said:
If the installation method of the sub-main requires RCD protection then how will fitting RCBOs on the final circuits protect the sub-mains?
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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
 
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Whilst cables above ceilings and below floors require additional protection where they pass through joists or battens. RCD protection is not an acceptable method.
 
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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.
 
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TJC1 said:
Im not sure on the depth and the cable is T&E
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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.
 
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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.
 
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FLICK said:
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.
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Yes, that’s correct.
Only started needing RCD protection when the 17th came in, as they would be used by unsupervised ordinary persons.
 
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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.
 
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FLICK said:
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.
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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.
 
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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 ?
 
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45140 said:
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 ?
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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.
 
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Date is never relevant on an EICR.
It’s tested to the current edition and a code given if deemed a safety concern ,whether it complied before to the 14th,15th,16th or 17th,is irrelevant.
Existing installations may not be unsafe in that respect but non compliance’s giving rise to danger must be recorded regardless of age.
Why this keeps coming up for debate is ridiculous.
 
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The basic issue is the sub mains are a pvc cable buried in the fabric of the building and there is no RCD protection to any of the fuse boards within the room and associated circuits or on the the sub main cable.

regardless of when it was built its a Commercial property so health and safety law will Trump over old regs rule, if there is a perceived risk then it need to be acted on.

(Personal I would c2 unless they had the original certificate with as build drawing and as wired. If you don't know where the Sub main cables are buried in the walls then there is a real danger to maintenance staff / general contractors . As it a commercial building .)

If you go for the 30 mil RCBO on the sub main you need to be careful, as a fault on a circuit in the rooms from the fuse board would trip the sub main RCBO first. which mean reg 314 (I think top of my head ) segregation of circuits would apply, and the installation would not conform to that.
you would then need to put 10mil amp RCBO in the fuse board in the room to obtain correct discrimination for the RCBO's
Or replace the sub main to an appropriate cable with mechanical protection and just put 30 mil RCBO's in on the rooms.

There is no cheap way out I'm afraid .
 
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Ian1981 said:
Date is never relevant on an EICR.
It’s tested to the current edition and a code given if deemed a safety concern ,whether it complied before to the 14th,15th,16th or 17th,is irrelevant.
Existing installations may not be unsafe in that respect but non compliance’s giving rise to danger must be recorded regardless of age.
Why this keeps coming up for debate is ridiculous.
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Yes it is ridiculous.
It’s ridiculous that people advise testing to the current edition, while at the same time advise ignoring the current edition?
I guess until people stop ignoring the current editions, this debate will continue.
 
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essex said:
The date of installation bears zero alliance with how safe it is.
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Exactly.
So why advise that older installations are unsafe?
Take for instance something mentioned today:
RCD sockets and RCD FCUs do not comply with the 18th Edition requirements for additional protection.
Does that mean any installation which has RCD sockets is now unsafe?
Does that mean any of the construction projects started last year are now unsafe if the design specified RCD sockets?
 
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spinlondon said:
Exactly.
So why advise that older installations are unsafe?
Take for instance something mentioned today:
RCD sockets and RCD FCUs do not comply with the 18th Edition requirements for additional protection.
Does that mean any installation which has RCD sockets is now unsafe?
Does that mean any of the construction projects started last year are now unsafe if the design specified RCD sockets?
Click to expand...
As long as the sub-mains were installed correctly to the previous edition of BS7671 the installation is safe. What has happened over the years is more and more layers of safety have been added. Years ago all was relied upon was a fuse then came RCD's and RCBO's for outdoor equipment then they were introduced into circuits to protect if someone is stupid enough to drill a hole in the wall above a socket.trades and maintenance staff should be aware of cable zones. The risk is that to the person using the sockets in each room.
 
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I think that there are misconceptions about what BS7671 really requires given conversations I have had with people in the Industry, such as time-served electricians trainers, trainees, etc. I am also surprised at the number of people whom I have met who either do not know about the 18th or more widely have not undertaken any training to update themselves, even to 16th or 17th Editions. Thus in some cases there is a genuine surprise at some of the latest requirements.

I then find that there is a misunderstanding about the need for compliance with changes to BS7671 with some people thinking that just because an installation now does not meet the 18th Edition that somehow it has suddenly become unsafe overnight and everything needs to be changed. Here we go back to the lack of briefing.

I think it would be foolish and quite wrong for anyone to infer that just because BS7671 now requires a specific means or method and type of equipment, that any previous arrangement is now per se unsafe. Modifying an existing installation to meet the 18th will bring about an incremental enhancement in safety but there is NO absolute requirement for this to occur until modifications are made, and then the need is only for the circuits involved to be brought up to the 18th Edition. As I understand it only certain requirements are absolute. This was my training.
 
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spinlondon said:
Exactly.
So why advise that older installations are unsafe?
Take for instance something mentioned today:
RCD sockets and RCD FCUs do not comply with the 18th Edition requirements for additional protection.
Does that mean any installation which has RCD sockets is now unsafe?
Does that mean any of the construction projects started last year are now unsafe if the design specified RCD sockets?
Click to expand...

If I come across a socket that is likely to feed portable equipment outside without an RCD installed that was installed prior to RCDs being a requirement that will be a C2. End of.

Just as if I come across a fused neutral that was installed when they were allowed.
 
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essex said:
If I come across a socket that is likely to feed portable equipment outside without an RCD installed that was installed prior to RCDs being a requirement that will be a C2. End of.
Click to expand...
Are you saying that it would be a different code, if the socket was not likely to feed portable equipment outside?
 
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TJC1

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