off peak Ze

[17thman]

Hello

I am installing a consumer unit, circuits and storage heaters on friday for an off peak supply. A dual tariff metre and tails will be there.

The size, length and material of the tails will be the same as the existing cu give or take a few cm's. So in order not to have to do the Ze and pfc at an unsociable hour, would it be reasonable and correct to take the Ze and pfc reading from the existing cu and use that as a Ze for the new cu figure. I can obviously add my R1 + R2 to get ZS. Luckily the new circuits will be run in such a method that RCD protection is not required.

Regards

 

[RF Lighting]

Yes that's fine. Take a Ze reading from the peak supply and then verify continuity from the MET to the OP CU.

 

[PrenticeBoyofDerry]

Why would it be a problem taking the Ze when new CU is installed?
and why are you calculating Zs and not measuring it?

 

[EFLImpudence]

I think it would be reasonable to assume (never assume) that the Ze should be the same.

However, you should do the test to determine that it actually is the same.
I.e. the conductors, especially earthing conductor, are connected satisfactorily.

 

[17thman]

Regards Gentlemen.

To PBoD, I understand your questions but I do not want to be waiting around or returning a midnight waiting for the off peak to energise.

 

[securespark]

I can't see a problem with using the Peak tails to provide power and connecting your croc clip to the OP earthing conductor.

 

[Lectrician]

With two CU's next to each other, I would pickup the live from the peak supply and the earth from your new board. If the tails are visible and short, there is no issue here at all.

On new installs, the prefered method is to measure the R1+R2 of the final circuits, calculating the Zs. You do not have to test both the R1+R2 and the Zs, but both columns need filling in on the paperwork. As you MUST carry out the R1+R2 (as it is a required dead test before energising), there is no point in then carrying out a Zs too.

When doing a periodic, you can do a Zs if you find it easier than an R1+R2 as the circuit is already energised.