Electrical problem

[--s-p-o-n-i-x--]

16th ed regs say that not all circuits must go through a sinle RCD. Presumably it's so that if you have a major electical failure or fire the lights stay on..

sponix

[Bob Watkinson]

Don't think it does. Which reg says that then?

[Andy Wade]

No, not explicitly, but...

... 314-01-01 & 314-01-02 when read in conjunction with the guidance to their interpretation given in the On-Site Guide.

[John Rumm]

Might be worth adding that you will need RCD protection for *all* circuits if you have TT earthing.

[Lurch]

On or around Sat, 12 Nov 2005 21:10:45 +0000, John Rumm mused:

But I stil wouldn't fit a front end RCD board for a TT. I see what you're getting at though.

[John Rumm]

I get the impression that a time delay RCD in the incomer position and a standard RCD mid way down is a pretty standard layout in these cases.

[Alex]

Why would using a battery and bulb be a better tester than a proper instrument?

alex

[Bob Watkinson]

314-01-01 states that 'Every installation shall be divided into circuits as necessary to 1) avoid danger in the event of a fault, and 2)facilitate safe operation, inspection, testing and maintenance.

The On Site Guide does not give specific reference to RCD's and this reg either and indeed the subject has regularly come up for debate on other forums. What you have to consider is each installation and what is needed to comply with the regs. For example in a large multifloor Victorian house there would be considerable risk of a person falling down the stairs if because of a fault on another circuit the RCD tripped. On the other hand in a small ground floor office it is difficult to imagine how danger could be caused by an RCD trip. In any case if emergency lighting were used the problem again disappears. In short, the use in itself of a single RCD does not necessarily breach 314-01-01. My view is that 314-01-01 is primarily aimed at considerations for overcurrent protection

314-01-02 requires that other circuits remain energised when a circuit is faulty. Again, I interpret this as for overcurrent protection. If you interpret it as being for earth faults then you would not even be able to use a split board, unless there were a separate rcd for each protected circuit

[Andy Wade]

Section 3.6.2 gives advice on the application of RCDs and cites

314-01-01 & -02. That seems to me to be fairly "specific."

True, but it does not necessarily comply either.

It doesn't actually say that, though.

"Circuit" doesn't necessarily mean "final circuit" (see definitions). The arrangements feeding the supply to (say) the two halves of a split-load CU are "circuits" so far as this reg. is concerned. The key words in 314-01-02 are in the final sentence "... and due account shall be taken of the consequences of operation of any single protective device."

[Bob Watkinson]

erm, no I've just re read 3.6.2 and it doesn't mention 314-01-01 or 02. Although I accept your version may be newer

correct. It all depends on the application

correct again. Though it is stio my view or interpretation if you like.

A sentance which like this whole issue is open to interpretation

[Andy Wade]

I suspect yours is ancient. I have every edition back to the original red one (1992). Mention of 314-01-01 first appeared in the green edition (1995) and of 314-01-02 in the blue one (2002) - the latter being the one that introduced us to the term the term "shower cubical" (sic)! We are now on the brown (2004) edition which still has cubical showers.

I agree with everything else you say.

[Bob Watkinson]

Yep mines the red one. Shows what an old fart I am doesn't it ;-) I really ought to go out and get a new one.

[Andy Wade]

Ah...