Certificating distribution circuit which is TN-C-S one end and TT the other?

[cornburn]

Having recently installed a submain, sheath to TN-C-S earth at supply end, isolated and TT'd at the far end I'm a bit unsure on the cert.

I have ticked both earthing types but am stuck on how to separate the values for each installation to put them on the same cert. Max Ze for example, should this be Ze from the meter, or Ze of the rod 100 metres away? We've done nothing whatsoever with the installation on the far side, just the distribution and provided an earth.

Common sense is telling me to write our cert just for the distribution cable up to the external board, as someone else is doing all that side and certing it separately. If they had installed the rod it would have been simple as it effectively falls on their side of the installation, but obviously we need to note the rod's Ze somewhere.

Anyone done a similar installation before and overcome this confusion? If so HELP I'M GOING CRAZY!!

Thanks

 

[malcolmsanford]

There is only 1 Ze and that is at the origin of the installation. What your saying I think is that you have TT an outbuilding. I would call the Zdb on the certs.

Is that of help

 

[cornburn]

Yes indeed TT is to an outbuilding, and I have included the details of the rod and Ra in the particulars of installation at the origin as it's the only place to put them. As that figure (whether we class it as Ze or Zdb) is already noted, I'll put the Ze using the TN-C-S earth down under supply characteristics. It says to put the higher value down if more than one supply, but doesn't mention if one supply and more than one earth. That seems to make the most sense, even though the rod is from a sub dist board and not at the origin. Cheers

 

[brucelee]

hi mate have you used two schedule of test results one for the supply which will have your origin tn-c-s Ze and the other schedule for the ccu in your outbuilding with the tt Zdb which is also the Zs for the the circuit from your distribution board supplying your ccu in outbuilding
you have 1 eic ,1 schedule of inspections and 2 schedule of test results 1 for each board