Earthing Conductor to dual tariff CUs

[Andrewr3]

Hi all

I am looking for ideas for best practice for Earthing Conductors to a dual tariff CU. Should two 16mm Earthing Conductors from the MET be installed, one to each earthing busbar? Or one earthing conductor to one of the earthing busbars and a link of 16mm to the 2nd earthing busbar? Assume for now that 16mm in total will be an adequate size anyway (I'll be checking the regs/calc on that later tonight anyway). I have a job with a 20 year dual tariff single CU install that may need a few changes.

Thanks

 

[Engineer54]

If the original CU will need some changes being made, it would make far more sense to renew the CU, if as you say it's already 20+ years old.

If a CU has dual supplies (2 set's of tails to two DP isolators) to it then you'll need separate main earthing conductors from the MET to the separate earth bars within the dual enclosure...

 

[goodview]

yes i agree with engineer54, but can the earthing conductors be linked to create a better earth or would this pose a problem with RCD's? should any faults arise on either side of the CU?

 

[Engineer54]

yes i agree with engineer54, but can the earthing conductors be linked to create a better earth or would this pose a problem with RCD's? should any faults arise on either side of the CU?

If that was the case, you'd have problems with the typical dual RCD CU's wouldn't you??

 

[GLENNSPARK]

If the original CU will need some changes being made, it would make far more sense to renew the CU, if as you say it's already 20+ years old.

If a CU has dual supplies (2 set's of tails to two DP isolators) to it then you'll need separate main earthing conductors from the MET to the separate earth bars within the dual enclosure...

effectively an `earth marshalling block`...which then splits off to the points it serves.....
in this case the 2 dis-boards

 

[goodview]

hi guys, point taken just thinking out loud

 

[Andrewr3]

If that was the case, you'd have problems with the typical dual RCD CU's wouldn't you??

As it happens there is only one RCD in this one on a few power circuits. But even if separate RCDs on off peak and normal tariff, then yes I have the same question, please why could it cause a problem?

 

[Engineer54]

As it happens there is only one RCD in this one on a few power circuits. But even if separate RCDs on off peak and normal tariff, then yes I have the same question, please why could it cause a problem?

It WON'T!! lol!!