Requirements for RCD protection ?

[SimonH2]

As I understand it, all sockets need to be RCD protected now, but unless there are buried cables, light and storage heaters don't.
So in an (office) installation where the wiring is in metal trunking & conduit, only socket circuits would need RCDs ?
Is there any reason that the RCD for a socket circuit cannot be external to the DB ? In our offices, we have "old" Bill DBs, and a DIN rain box mounted above them with contactor(s) for the night storage heating. I'm thinking that a quick way to upgrade to current standards would be to throw an RCD or two in this box and move the tails.

This is the only photo I have at the moment. Ignore the soot marks - the contactor has been replaced at some time in the past !

I figure the answer changes for those units where the switch drops are buried in plaster with galv capping.

There are several reasons for me asking. Partly it's to check that I'm understanding the regs properly.
Partly it's having been told that "they must be replaced as obsolete".
And partly, as part of some shifting around in our own unit (all metal trunking & conduit) I expect some wiring changes will be needed and if they use the same sparky as in the line above, I expect he'll be insisting that everything be RCD protected - I'm not keen on the server room sharing an RCD with circuits that could make it trip.

Interestingly, while helping out the centre manager*, in conversation it turns out that they asked the aformentioned sparky to leave the breakers from the boards he's taken out to use as spares. Apparently they "must have ended up on the van by mistake" I said "yeah right", apparently I wasn't the only one to have said that.

* They have a unit where part of it was once a meeting room and is on the landlords supply, and part was a self contain unit with it's own supply. Part of a wall was removed a long time ago so it's one unit now. She was asking me how big a job it was to sort it out, and whether it needed a new supply - on the basis that she knows "very little" about electrics and wanted a bit of knowledge so as to be able to tell if someone was "talking up the job".
I was able to confirm that there are two supplies (what appear to be original circuits in the old meeting room part stayed live when the main switch was off in the other part), but it's also clear that there's been "additions and changes". I did say that it needs a sparky who is reasonably good at working out what's been done and what goes where, but it shouldn't be a big job to sort out. But once anyone starts working on circuits, any circuits they work on will need to meet current standards - hence the need to add RCD to some circuits.

 

[SimonH2]

Just to add ...
Yes I am trying to stay out of it, but equally I don't like standing by and watch people being taken for a ride. There's also an element of increased costs for the landlord mean increased costs for us.

 

[ericmark]

My first concern would be lack of blanks or original MCB's even if not connected to fill the gaping hole. It does not seem to be a locked cover. Yes the RCD can be after the MCB so you could have a panel full or RCD's after the distribution unit but cost of a double pole RCD v RCBO and boxes etc. Likely not a viable option.

Two supplies to a room is something which has come up before and never really answered. One is allowed to have a three phase or split phase supply to a room, but convention is that one room if single phase comes off the same phase. It is more about health and safety than electrical regulations. If one expect a switch to isolate and it does not there is danger.

As to server the answer is simple. If there is a problem with power loss it will have UPS, if no UPS fitted then clearly the owners are not worried about power cuts. Simple yes!

 

[Simon35]

Whether the drops have galv capping or not is irrelevant to RCD protection, a bit of capping won't stop a nail or drill, so doesn't count as mechanical protection.

There is no requirement to bring the existing up to the latest requirements, only any changes and additions.

It might be argued that an employer should always be looking to improve the safety of the working environment, and providing RCD protection on circuits might be one way to do that,

 

[EFLImpudence]

As I understand it, all sockets need to be RCD protected now,

New sockets yes, obviously a good idea to incorporate the existing ones as well.

but unless there are buried cables, light and storage heaters don't.

No appliances or lights require RCD protection; it is the (new) concealed unprotected cables which do.

So in an (office) installation where the wiring is in metal trunking & conduit, only socket circuits would need RCDs ?

Yes, as above.

Is there any reason that the RCD for a socket circuit cannot be external to the DB ?

No.

 

[SimonH2]

My first concern would be lack of blanks or original MCB's even if not connected to fill the gaping hole.

It has been noted, but there's no busbar in there, just a din rail for the contactor - and you'd have to be really trying to reach any of it's terminals.

Yes the RCD can be after the MCB so you could have a panel full or RCD's after the distribution unit but cost of a double pole RCD v RCBO and boxes etc. Likely not a viable option.

In most units there is just one socket circuit - so it's the cost of one (or for the larger units, two) RCDs vs a whole new board and fitting. I don't know how, but the guy seems to need two days to replace one.

Two supplies to a room is something which has come up before and never really answered.

It's not a "problem" in terms of safety, it's just that they have a unit where not all the supplies are on the tenants meter - so the landlord is providing them with unmetered lecky which he doesn't like There is the secondary issue that the tenant has some lighting and sockets on circuits where if it goes off, then they have no access to the distribution board to reset a breaker. Apart from these historical oddities, there only the submain fuse the tenants don't have access to without getting a key to the meter room from the centre manager. Given that the fuses are 63A cartridge fuses, I think someone would have to be trying in order to blow that - I don't think even we could with our server room maxed out charging batteries after a power outage and all the heating on full.

Whether the drops have galv capping or not is irrelevant to RCD protection, a bit of capping won't stop a nail or drill, so doesn't count as mechanical protection.

Even if it's earthed ? Though I don't know how easy it would be. One bit I saw lifting a ceiling tile had a fair bit of exposed capping sticking up past the top of the plaster. In any case, it only means a second RCS for the lighting circuit.

There is no requirement to bring the existing up to the latest requirements, only any changes and additions.

It might be argued that an employer should always be looking to improve the safety of the working environment, and providing RCD protection on circuits might be one way to do that,

Indeed. But excluding sockets, provided everything is in reasonable condition it's arguable whether adding RCD to an installation in metal trunking and conduit does actually add much if anything.

 

[Spark123]

I don't think the capping is to one of the British Standards as specified in BS7671 for the RCDs to be omitted hence earthed or not earthed it doesn't meet the standard.

 

[PBC_1966]

Partly it's having been told that "they must be replaced as obsolete".

Translation: "I can make more money out of replacing the whole lot unnecessarily so I'll use the 'Has to be done, it's the rules' lie on them."

 

[SimonH2]

I wasn't sure whether to think that, or think that he simply "doesn't understand" anything other than "bung a new split board in". When I (very briefly) observed him working in a unit a couple of doors along from us, he had a load of T&E ends sticking out, and it sounded very much like he was struggling to identify the circuits. I can tell you, it was quite hard keeping my thoughts to myself when I heard that

 

[Adam_151]

he simply "doesn't understand" anything other than "bung a new split board in".

If we are talking about '17th edition' domestic boards, then sounds like a domestic chap trying to do commercial. Such boards have no place in commercial installations.

As S123 said, capping does not meet the requirements to avoid rcd protection to concealed cables. But most of the rest of your thoughts are on the right track. You only need to add RCDprotection if you add anything which requires them, eg adding/moving general purpose socket outlets, concealing new cablong etc. Though there are benifiets to providing it to the socket circuits regardless.

RCDs can easily be added to the enclosures at the top.

That doesn't look like a suitable contactor to be mounted where the front is open to me, looks ike the terminals could be 'probed' without removing any covers?. The black mark is more likely a dust mark rather than a soot mark. I am not sure on what the exact cause is, but you often see them above contactors, I am guessing its to do with airflow caused by the warmth of the contactor.

Those are Bill tailsman boards, circa early to mid 1990s, they are equivelent to MEMshield 1. And going by what we had to pay for some of those blanks (and corrdosonding red tab for the busbar) recently from a place that specialises in obsolete switchgear , I'd be watchful what happens to the breakers!

 

[ericmark]

I think we have all seen the electrician who is out of his depth. There are so many variations to the trade it has to happen. But BS 7671 covers the lot, and there are some things which have surprised me. The steel braided cable is not in the list of cables which can be buried. One would think same as ali-tube stick a nail through it and the protective device should open. But Ali-tube is in the list SS is not. The same problem for trunking with earthed steel trunking we know anyone who puts a nail through it will connect line to earth so open protective device but it's not in the list.

Old systems can be a pain, trying to locate replacements is hard, clearly the guy at least knows that so he held onto the MCB's. I remember trying to keep a close eye on contractors and being told by boss to back off. It would seem we had one obsolete PLC and this guy had the only software and connecting leads in the area and I was not to upset him. Seems we gave him little jobs to keep him sweet.

There is a lot of this, employing him because his dad works for a firm who buys a lot of our products. As electrical engineer I was normally in the loop, I knew who I could get upset with and who I had to grin and bear it with. If it's not your job you don't need to know. Be wary of what you say to whom.

 

[333rocky333]

them old bill breakers evolved into memsheild One, mem still churn out new ones to order but apparently your looking at about 70 pound each and triple pole are in excess of hundreds of pounds as for rcbos who knows, I have only seen them in 2 module width.
Merlin gerin and most standard blanks will fit them boards instead of the single brown ones

 

[SimonH2]

If we are talking about '17th edition' domestic boards ...

The one I saw looked like it. But it was alright, it was metal cased

That doesn't look like a suitable contactor to be mounted where the front is open to me, looks ike the terminals could be 'probed' without removing any covers?

I think you'd have to be trying hard. But if you were determined to do so, then I suppose you could with a piece of thin rod (wire, knitting needle, etc).

Those are Bill tailsman boards, circa early to mid 1990s, they are equivelent to MEMshield 1. And going by what we had to pay for some of those blanks (and corrdosonding red tab for the busbar) recently from a place that specialises in obsolete switchgear , I'd be watchful what happens to the breakers!

As I say, they'd apparently specifically asked to keep the breakers but they "accidentally" left with the sparky.
I know I had to buy a new one a few years ago for a supply for the UPS and it was "a tad pricey"

 

[SimonH2]

Some more pics.

Our DB with the cover open - yes I've been at it with the labeller

And I popped into one of the other units and got a couple of pics (I see he's used a decent brand of CU )

And while I was cropping that, I see there is a circuit called "RING MAIN"

And then I lookup the meter, from RDL. I see they really pushed the boat out on a reconditioned one - I believe they are supposed to be returning to replace them with dual-rate ones.

 

[Anteaus]

"I'm not keen on the server room sharing an RCD with circuits that could make it trip."

Depends very much on the size of the IT installation. If just a single server and a broadband router, then a decent-sized UPS will take care of it. For larger corporate installations it wouldn't be considered acceptable to have the supply on a shared RCD though, from a data integrity POV.

As for the missing breakers, main issue is if there is a busbar lurking beneath the edge to give a nasty surprise to any poking fingers. Also, taking a customer's property without consent is stealing. I always ask if the customer wants old computers etc taken away. Even though they are mostly of no resale value.