Distance Between Supplies

sean7112 · Apr 15, 2015

I wonder if someone can answer a question for me . We have to install a new dis-board in a property that already has a landlords distribution equipment installed . The landlords distribution equipment has its own service head and earthing arrangement . We wish to install a new supply taken from the tenets LV system which has its own service head and earthing arrangement some 45m away . The two systems will be sitting side by side . Do we need to ensure a distance because of the two different earthing arrangements ?

telectrix · Apr 15, 2015

what eartring system is it?

mechelec · Apr 15, 2015

Speak to the DNO it is for them to specify. Most do not like secondary supplies to the same room. There is a danger that if the supplies are from separate transformers you could get circulating current through the neutrals/earths especially with PME supplies. Another danger is if there is any interconnection between the systems and one transformer is off supply due to a HV fault it would cause a back feed through the interconnection (for a short time anyway)
What you are suggesting is generally a very poor design anyway and trying to do the job on the cheap when you should be getting the correct supply installed.