Whole-house RCD - is this legal?

[Tony Eva]

I know this is not a new topic, but searching the archives hasn't revealed a post with a definitive answer.

The situation: I've just had an extension built, as part of which the old fusebox was replaced with a dual consumer unit (13 MCBs in total). The main house supply is a TT system - one phase from overhead 3-phase street cables, with local earth via an earthing rod.

Problem: The electrician has installed a 30mA 80A RCD as the main switch, i.e. the whole house is now on this single unit. There are no other RCDs or RCBOs.

I know that this is a Bad Thing (tm) for various reasons of convenience, but is it actually contrary to the current wiring regs? i.e. am I within my rights to demand that he come back and install the proper combination of 100mA whole-house RCD + individual 30mA RCDs where appropriate, at his cost? If so, can someone tell me exactly which of the regs I should say have been contravened?

TIA

[BigWallop]

It sounds correctly done to me, if it's how you describe.

[Andy Wade]

[TT system]

The IEE 'On-Site Guide' (OSG) which provides authoritative guidance on the interpretation of the wiring regulations has this to say on the subject:

"Installations are required to be divided into circuits to avoid danger and minimise inconvenience in the event of a fault and to take account of hazards that might arise from the failure of a single circuit, e.g. a lighting circuit. [Regs 314-01-01 and 314-01-02]

"Where an RCD is fitted only because the earth fault loop impedance is too high for shock protection to be provided by an overcurrent device, for example in a TT system, the rated residual operating current should not be less than 100 mA."

The OSG goes on to describe three acceptable methods of using RCDs in the consumer unit of a TT installation [Fig. 3a] - briefly the three options are:

(i) main switch feeding two RCDs in parallel; socket-outlet circuits fed via 30 mA RCD; all other circuits fed via 100 mA RCD;

(ii) 100 mA time delayed RCD acting as main switch and also feeding a 30 mA RCD; two groups of final circuits, as (i) above;

(iii) main switch feeding individual RCBO devices with 100 mA or 30 mA residual operating current as appropriate.

In my opinion the work you have had done (assuming the electrician was charged with the design as well as the execution of this installation) is not of satisfactory quality and should be rejected. Regulation

314-01-02 has not been properly applied in context of your installation. Both inconvenience and danger (loss of lighting) are likely to arise in the event of operation of the single RCD, such event being made more likely by the use of an excessively sensitive RCD to protect a large number of circuits.

HTH

[Stephen Dawson]

I agree with you Andy, the installation has been done on the cheap, I would get the customer to refer to contract as to what was asked of the electrician.

Stephen Dawson

[mrcheerful]

from the other replies it is not as recommended, but this is exactly what the electricity board did to my mums house a few years ago. it was a pain in the arse as she had an electic cooker which if not used for a few days would blow out the rcd ( I assume the element packing must absorb atmospheric water ?) I would then have to drive round and reset it at odd times. I eventually got her to do the resetting.

mrcheerful

[John Rumm]

It is a "bad thing" for reasons of safety as well. Also it does not comply with the current wiring regs.

Wheather you would be "within your rights", would very much depend on the "contract" - i.e. what you asked for, and how much you paid.

[Tim S]

On an aside, there were installations done like this in the mid

80's - my last flat (and all the others on the same estate) had this setup. Mind you, I'd prefer to have this than no RCD at all (current rented house).

Then, for many flats, the likelihood of nusiance tripping is lower - you're less likely to run running an arcwelder or garden machinery off an extension lead (wot garden?).

Timbo

[Dave Jones]

Although the insulation does not meet the required regulations, there is no legal requirement on domestic dwellings, so unless you have a contract stating in writing "to be wired to the current regulations" then not a lot you can do legally.

You could argue the point and see what he says, but he'll probably charge you extra to fit it!

[Lurch]

On Wed, 01 Dec 2004 23:26:08 +0000, Tony Eva strung together this:

What's a dual consumer unit?

Yes, RCD should be 100A really, and depending on whether you are in a bungalow or not depends on whether you need a split load.

Nope, did he say he was going to install everything as per BS7671? If he didn't say anything, and you didn't ask then you have nothing to go on. There are currently no laws stating that all electrical work hjas to comply with BS7671.

[Lurch]

On Thu, 02 Dec 2004 00:38:53 GMT, "BigWallop" strung together this:

Just shows how much you know about electrics then.

[dms1.go-plus.net]

[dms1.go-plus.net]

It is effectively not illegal what he has done, as it is though the installation is overprotected IE on a TT system the regulations state as you say below is required.

However you want to point out to him that he is in effect in breach of other regulations with regards to the reliability of the supply and that the system has been designed incorrectly under BS7671. Which it has. Under the requirements of BS7671 and that of TT installations.

Under BS7671 regulation 131-01-01 states that "the electrical installation shall be designed to provide for:

(ii) the proper functioning of the electrical installation for its use.

So the breach of BS7671occurs because the 30mA RCD protecting the whole property makes the designed use of the electrical installation invalid. If you get what I mean, and if he has never heard of this regulation and you have not received any test information then he is also breaking BS7671

Regards John pp

[Owain]

"Dave Jones" wrote | Although the insulation does not meet the required regulations, there | is no legal requirement on domestic dwellings,

in England and Wales (at the moment). The Wiring Regs must be followed in Scotland.

| so unless you have a contract stating in writing "to be wired to | the current regulations" then not a lot you can do legally.

There is an implied condition that work will be done to a 'reasonable' standard. An installation which is a cause of danger (increased risk of accident caused by loss of light on a power circuit trip) is, I suggest, not reasonable. I think most people (and the courts) would accept that a reasonable standard was compliance with the Wiring Regs, and that a customer was entitled to reject as Unsatisfactory work which wasn't.

As well as 314-01-01 and -02, other Regs may also apply:

130-01-01 Good workmanship and materials shall be used.

130-02-01 All equipment shall be ...installed .. so as to prevent danger as far as is reasonably practicable.

With 13 MCBs there is probably some spare space in the CU, so should not be excessive workload or cost for the contractor to swap the 30mA with a 100mA time-delayed RCD as main switch, and put in RCBOs for those circuits requiring 30mA protection, without having to replace the whole CU.

Owain

[Tony Eva]

Sorry, probably not the correct term, I meant two CUs co-located with the RCD in one and the protected supply taken to the MCBs in both CUs.

Not a bungalow - a 4-bed detached house. With a garden and garage so the likelihood of using electrical equipment outdoors is high.

I can see that, but I would expect a certain minimum standard of work, and the right to withhold payment if that standard is not met. Compliance with current regs would seem to be a reasonable expectation.

As it happens, I did not specify the work - the electrician was sub-contracting to the builder and so I was not involved at all. I have not yet made the final payment to the builder for the whole extension, so I am checking whether I would have grounds for asking the builder to get the job redone.

Thanks to everyone who has offered comments and information, it's been very helpful.

[Lurch]

On Thu, 02 Dec 2004 19:18:39 +0000, Tony Eva strung together this:

Ah, I'm with you.

Well, the usual idea is that at least the lighting circuit shouldn't be RCD protected so that in the event of a faulty appliance knocking the RCD off you aren't falling down the stairs in the dark to reset it.

Not unless you agreed to a certain standard, I can see your point but it doesn't sound like it's *too* bad. Still not quite right, but probably not bad enough to start a Watchdog article on. It all comes back to agreements and contracts, if you didn't have one then, tough!

As I said, unless he said he was going to do it to the regs then you haven't got anything on him.

In that case then, the builder is the one you had the contract with, the same advice still applies re: contracts and stated intentions etc... but if the builder never mentioned any particular compliance then you still haven't really got anything. I do agree with you though, I would like to have a proper job done to the correct regulations. FWIW in my T&Cs on all my quotations it does state that all work will comply with BS7671, if I'd have done the work then the builder would be able to get me back to do it properly or not pay if the customer complained. I'd ring the builder and sound him first before doing anything too drastic, obviously the builder will have an agreement with the electrician, either written or verbal. There is the possibility that the electrician will come back and do it so as not to lose any future works with the builder.

[BigWallop]

But we don't what exactly is connected to the thing. So. Maybes Yeah, Maybes No. It all depends.