Electrician installed a whole installation RCD

Hi,

In a small commercial office that was covered by a 12 way Wylex fuse consumer unit (that had been "upgraded" with MCB's), an electrician installed a whole installation 30mA RCD recently.

This installation covers about 10 rooms, which includes a total of 8 PC's and associated IT kit.

We are getting this RCD tripping randomly, he came out today, and I asked if he could firt an 100mA RCD for now, but as he didn't have one with him, and we need people to be able to work, he is going to replace the RCD with an isolator "At our request"

My question is, is it against the regs to install this whole installation RCD in this situation in the first place?

He said it was done because he fond one of the lighting circuits upstairs didn't have any earth, and this was the easiest way to protect this.

I basically want to know if we should use him to replace the CU with a new 17th edition one, probably with RCBO's, or we need to find another electrician.

Thanks!

Reply to
Toby
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Its certainly a deprecated way of designing things, and probably not really meeting the requirement to maintain discrimination (i.e. limiting the effects of a fault in one part of an installation on other unrelated circuits)

Easiest for him perhaps...

Assuming his quality of workmanship is ok, then he ought to be able to do an all RCBO install since there is not much in the way of decision making ;-)

Reply to
John Rumm

I think a single RCD protection is ok as long as you have emergency lighting.

Given your setup and the potential loss of data etc when a trip occurs, I wouldn't have any hesitation to have a full RCBO setup.

In theory he should be able to test insulation of your boiler, and a PAT check on your other items if need be.

I have known PC PSUs to cause nuisance trips. In reality after investigating and ruling out the obvious boiler, it could be anything!

Reply to
Fredxxx

He could have put a RCD FCU on the supply to the lighting circuit if that w as all he was worried about.

And I think the fire alarm panel (if it's a commercial panel system) MUST N OT be on an RCD circuit but should be on a protected cable like MICC or Fir eproof which does not need RCD protection, connected as close as possible t o the origin of the installation.

If he's taken your fire alarm installation out of its BS compliance then th ere may be costs to correct this at the next annual inspection, and insuran ce implications meantime.

Anyone putting a single RCD on an installation with 12 circuits these days needs their understanding of the Regs questioned.

Owain

Reply to
spuorgelgoog

You can determine the cause by leaving items turned off one by one until the problem stops. Start with stuff that only runs intermittently.

All your portable equipment should be PAT tested anyway.

Reply to
harry

However, a PAT test won't necesarily show up a fault which is either intermittent or takes time to develop.

Reply to
charles

Thanks for the link. Under the first 100mA entry in the table, page 4, it says: "For an installation forming part of a TT system, a 100mA RCD is generally installed at the origin. A time-delayed or 100mA ?S-type? (or selective) device is often used to permit discrimination with a downstream 100mA device". Reg. nos. 413-02-19, 531-02-09, 314-01-02

So as you say, appropriate for a TT system.

The diagram on page 3 "Discrimination achieved" is pretty much what I have, although of course differing in exact detail.

Reply to
Chris Hogg

That's what all the PAT testers tell you.

PAT testing is a con.

Reply to
ARW

PAT testing - because one year is up since the last test IS a con. PAT testing on a proper risk assessed basis can show up faults - but most are seen on the visual bit for which you don't need a meter. I have some RED stickers and I have used them. Once on a piece of brand new kit.

Reply to
charles

Fine if you have an unlimited budget, as so many of these places seem to. IMHO, totally unnecessary for a small office.

Reply to
Dave Plowman (News)

What on earth are you on about?

The sum total of RCD sockets in my place is a few % at most of all sockets.

I did say: certain common/accessible areas. I did not say every office, lecture room, corridor.

It's certainly cheaper to do what they did than upgrade the circuit (bearing in mind then they'd have to test the circuit possibly with dozens of sockets, and these are commercial breaker panels so I expect RCBOs will cost a little more than domestic ones).

Reply to
Tim Watts

Then you must have many with no RCD protection. To give the same degree of protection, they'd all have to be RCD outlets. And have you looked at the cost of them? At least four times that of a non RCD outlet.

It would be a very brave person who would guarantee there was never a need for RCD protection on some sockets, while accepting it was needed on others. In any form of public building.

Reply to
Dave Plowman (News)

If you read back, my point was that universities DON'T tend to have RCD protection on all sockets - very few IME out of a small sample set.

There'd seem to be a lot of brave people then... Remember, it's not a domestic environment, nor one deemed to have vulnerable people.

Reply to
Tim Watts

Our local authority, in the case of village halls says "sockets on stage" must be RCD protected.

Reply to
charles

Nothing should fault at even 2 milliamps. If something is tripping a 100 ma RCD, then an appliance or some household wiring has a major defect. Find and fix that serious human safety issue. Never cure symptoms - ie blame an RCD. Find and fix a human safety defect.

Reply to
westom

What do you mean by local authority?

Reply to
ARW

work out what the leakage current of 30 PC RFI units with 15nF caps from live and neutral to earth is.

Well over 30 mA IIRC

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Reply to
The Natural Philosopher

Maximum that any should leak is 100 microamps. PCs typically leak 60 microamps or less. That is 1.8 milliamps maximum. In other venues, an RCDs trips on 5 ma

- because no appliances all grouped together should never leak even 5 milliamps.

That 100 milliamp RCD has detected a potentially serious human safety problem.

Reply to
westom

Borough Council who are responsible for issuing licences to such premises.

Reply to
charles

But surely in good nick those present a balanced load to both line and neutral?

Reply to
Dave Plowman (News)

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