Was the outbuilding CU change necessary?

[ChrisB1966]

Due to faults / issues found on house CU (bypassed RCD and radial / ring-main circuits (all in 2.5mm2) on one 32A MCB for example) the CU has been changed to a high integrity metal Wylex with a mixture of RCD and RCBO protected circuits

One of the RCD protected MCBs feeds (via SWA cable) to an outbuilding (approx 35m)

In the outbuilding was a two way CU (lights and power) but no RCD protection.

I was advised that for the outbuilding to conform to 18th edition all circuits had to be RCD protected, so a new CU was installed at a cost of £500+VAT

But as the MCB in the house, from which this outbuilding CU is fed, is already RCD protected was this necessary?

Regards

Chris

 

[conny]

Not sure if it was necessary, (doesn't appear to have been but I am not an electrician), and to charge £500 to supply and fit a replacement 2 way with RCD seems to be a massive rip off to me.
How long did it take them to change it out for the new one? I would imagine 2 hours maximum and that would include testing for that that particular section.

 

[JohnW2]

... One of the RCD protected MCBs feeds (via SWA cable) to an outbuilding (approx 35m) .... In the outbuilding was a two way CU (lights and power) but no RCD protection. .... I was advised that for the outbuilding to conform to 18th edition all circuits had to be RCD protected, so a new CU was installed at a cost of £500+VAT. But as the MCB in the house, from which this outbuilding CU is fed, is already RCD protected was this necessary?

Definitely not. As you say, all of the circuits in the outbuilding are RCD protected (by the RCD in the house), which is all that the regulations require. Furthermore, it's very probable that you don't actually need a CU at all in the outbuilding, let alone a £500 one.

I'm afraid that you have definitely 'been had'.

Kind Regards, John

 

[winston1]

In fact you don’t want another RCD in the outbuilding. If there is a fault either or both will trip.

 

[oldbutnotdead]

Yep, you've been had over there.If the supply to outbuilding can be moved to a non-rcd protected mcb in the main building you'll at least get some benefit (damp outhouse won't trip house)

 

[dannyboi2003]

Really need more info and some pictures before we can say if you've been 'had' or not in my opinion. Can you post a picture of your consumer unit in the house along with the incoming supply/meter, and a picture of the shed consumer unit? We need to determine the earthing type at the supply origin and perhaps they converted the shed to it's own TT system if the earth supplied via the armoured cable was inadequate, also need to confirm if the shed supply is actually RCD protected at the house end or not. Need a better idea of the shed size too, are we talking just a single socket/light or multiple and does the shed feed any power out to things in the garden (water feature, lights etc.)?

 

[JohnW2]

Really need more info and some pictures before we can say if you've been 'had' or not in my opinion.

I don't really see why. As I understand it, all that has been done (for £500 + VAT) is to replace the outbuilding's CU, because "18th edition [require that] all circuits have to be RCD protected", despite our being told that everything in the outbuilding is already protected by an RCD in the house. If what we have been told is correct then, regardless of anything else, that surely constitutes "being had", doesn't it?

Can you post a picture of your consumer unit in the house along with the incoming supply/meter, and a picture of the shed consumer unit? We need to determine the earthing type at the supply origin and perhaps they converted the shed to it's own TT system if the earth supplied via the armoured cable was inadequate, also need to confirm if the shed supply is actually RCD protected at the house end or not. Need a better idea of the shed size too, are we talking just a single socket/light or multiple and does the shed feed any power out to things in the garden (water feature, lights etc.)?

Whilst everything you mention is relevant to the electrics in an outbuilding, I can't see that any but the RCD protection (highlighted above) could detract from the fact that he has "been had" as regards the (unnecessary) CU replacement. As for the RCD protection, as you are aware, the OP had told us ...

... One of the RCD protected MCBs feeds (via SWA cable) to an outbuilding (approx 35m) ...

... but if you feel that we cannot necessarily believe him, I suppose that some 'confirmatory evidence' would be worth seeing.

Kind Regards, John

 

[BS3036]

Probably another 'electrician' who thinks that the RCD in the house is too far away to work properly. Wouldn't be the first time.

 

[JohnW2]

Probably another 'electrician' who thinks that the RCD in the house is too far away to work properly. Wouldn't be the first time.

Ah, you must have heard my story about the 'electrician' I sacked a good few years ago

Kind Regards, John

 

[sparkwright]

Out of interest, do both 'RCDs' protecting the garage have 30mA (or 0.03A) written on them? (I think they will.)