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VOELCB


Cislug

Question

I Completed a Periodic on Tuesday at a house which had a TT system protected by an old VOELCB does anyone happen to know what value I should enter in on the Schedule of Circuit Details in the Max.Zs column?

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I'm aware of all the options, it's deciding which one is the most relevant in this case, bearing in mind there is an additional protective device it just does not work in the same way as an RCD.

It may seem i'm being pedantic but the paperwork might as well make sense you never know who might see it, plus myself and someone else may learn something.

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I understand that you want the paperwork to make sense, my view would be that it can make perfect sense without a max. Zs value.

Standard IET forms don't have max. Zs column. (I think!! Pray)

Does the Zs affect the operation of an VOELCB?

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Hi Riggy, I've been on the IET forum Questions & Answers too and I think the general consensus is to enter LIM with an explanatory note which I can put under the Summary of the Inspection - General Condition of the Installation.

Thanks for your input and may the week ahead be richly rewarding for us all! ( I wish!? )

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I Completed a Periodic on Tuesday at a house which had a TT system protected by an old VOELCB does anyone happen to know what value I should enter in on the Schedule of Circuit Details in the Max.Zs column?

Hello Cislug,

IMHO as you are inspecting & testing in relation to CURRENT regs...

Not the regs it was installed under..

The Max Zs value is a LIM or N/A as current regs do not recognise VOELCB as a satisfactory means of protection due to the risk of failure if parallel paths present....

I would just note down guidance from top corner of page26, "Approved Doc P" which basically says these are an OBSOLETE item!!!!

and has NOT been recognised since 1981! (28 years ago:()

Also NICEIC guidance on inspection and testing which recomends these are a code 4 (assuming it still operates!!!)

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does it trip when you press the test button?

No: code 1

Yes: code 2

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VOELCB's should be changed, hence the code 1 or 2.

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It would appear to work unfortunately I d'ont have a 750VA test transformer, the place used to be a Guest House it's had a number of structural alterations in the past and the electrical work would appear to have been DIY. The present owner say's it's tripped off a couple of times, the main earth is connected to the water main which is a code 1 now but was common practice back in the 50/60's it's impressively low at 26.8ohm's though I dowt if I'l get it as low with an electrode even an 8 footer. Anyway I just need to complete the Schedule so if anyone has a copy of the 14th Ed (I think thats the one) it may have some info re: Max Zs value for circuits part of a TT system protected by one of these dinosaurs, not to be confused with the max electrode resistance of 200ohms.

Cheers

200ohms for the electrode

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The main purpose of Inspection was to evaluate the defects prior to fitting a new High Integrity Consumer unit, main earth conductor, electrode, main bonding etc.

The new electrode earth bonding etc. would not be connected until the new board is fitted, I would'nt want to create any parallel paths!

Guiness Drink

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then why be so worried about trying to find the details for something your going to replace?

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I don't know the 14th edition (the 15th came in during my apprenticeship) but if the max electrode resistance was 200ohms we should assume that max Zs was 200ohms+. Your electrode resistance is 29ohms - you'd need some fairly dire R1+R2 readings to exceed max Zs.

Unless of course I've missed the point again.

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