Main Earth regs

**LC2** · 27th March 2009, 08:53 PM

Hi all, got a job with two consumer units stacked on top of each other, main one and a secondary for economy 7 (storage heaters and immersion heater on the secondary) anyway the main consumer unit has a main earth 16mm to it and the secondary is earthed via the main one (10mm just dropped down to it. Does this meet 17th regs or does the economy 7 consumer unit need its own main earth ???

**Polmenna-Martin** · 1st April 2009, 05:54 PM

I don't think it would need a separate Main Earth. Although separate boards they are all still the same installation and fed from same supply just via 2 meters.

**blackie** · 21st May 2009, 05:07 AM

All installations should really have their own independent means of protection.This helps later on with fault finding etc-and if a problem should occur on any of the two boards,by having an independent earth on either one can stop this problem spreading to the other.always think ahead when planning an install-if its you thats got to come back later to add on or fault find-make future life easy for yourself.

**akaboosi** · 5th June 2009, 09:03 PM

I think it depends on the size of the tails feeding the consumer unit for the economy 7 heating.

Check out table 54.8 on page 134 of bs7671.

**amooramin** · 9th June 2009, 01:20 PM

yes, AKABOOSI is right.

**Matt the Spark** · 15th June 2009, 11:48 PM

Hi LC2, if PME System (TNCS) will be 16mm CSA min.

You've prob sorted it by now anyway.

**lickthebusbar** · 19th June 2009, 08:29 PM

16mm the ****er and u cant go wrong

**davron11** · 24th June 2009, 08:06 PM

it should be ok as usually these boards are supplied by 16mm so the earth can be a 10mm some boards have the white meter on the same board as the domestic and although 2 supplies are there there is only one 16mm earth for the full board