Electricity in the woods.....

Well, in the country anyways.....

This talk of RCDs etc has gotten me thinking......

A friend has a small holding which for many years had a 100A servicehead which then fed a c core buried cable (100 metres or so) which then fed a small old wylex board (one of the ones which can have plug in MCB where wired fuses used to sit)

At some time over the past few years somebody (supply Co?) has fitted a 100mA RCD near the service head (Wylex board remains unchanged). I don't know if this a time delayed type, but perhaps there would be no point in time delayed if (as at present) there is no RCDs downstream, or if it is time delayed, but it just doesn't show as there is no RCDs downstream (actually, that's not always true, I have used a plug in RCD downstream, and found both RCDs go off).

Still with me??

This resulted in a lot of tripping, such that he A, Got a new "cooker (Oven and two sealed rings) cooker, and also removed his electric shower altogether. He still gets nuicance trips and as the facilities are occasionally used for things like parties in marquees when he is not on the premises he quite often has to talk peoople through finding where the RCD is and resetting it, etc.

Would there be any benefit (in terms of reducing the number of whole installation nuisance trips) in replacing the Wylex with a 17th edition board, or is it likely the RCD at the service head would also still trip as well as one or more of the 30mA jobbies in the Wylex replacement?

Is it likely that the 100mA jobbie could be upped to say 300mA and would that have an effect?

I wouldn't consider doing this work myself, but would like to offer him an informed opinion.

TIA

Chris

Reply to
Chris Holmes
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Forgot to say, I couldn't spot any earth rod(s), so I presume the earth is supplied by the supply co.

Reply to
Chris Holmes

then its not time delayed

Certainly, a trip would only take out one circuit, if each has its own RCBO, and the 100mA trip is changed.

Yes, in some cases. No, in some cases.

You'd want a 300mA delayed type, that plus the 17th edn CU would resolve it. Another optoin is to fix the fault(s), if practical.

For the unattended parties he might like to fit a backup light by the CU, if possible with a notice saying to turn power back on press this.

NT

Reply to
meow2222

I suspect that you are stuck with the RCD at the head end. However there is nothing stopping you making the CU end a separate TT supply with it's own earth rod so that faults on any of the CU circuits will only trip the RCDs on the CU and only a fault on the supply cable will take out the head end RCD.

Have a look at

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Reply to
ARW

Unfortunately thats not how it works, it won't get you any discrimination.

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and

Reply to
meow2222

It will with a time delayed unit at the head end.

Reply to
ARW

Time delayed will get you discrimination, regardless of what earth connection one uses

NT

Reply to
meow2222

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