UK Odd PME test result...

[Initforthemoney]

Morning guys!

Went to look at a consumer unit change today with a PME supply.

Now, right next to this was an old BS3036 60A fused mem cutout that then sent a pair of 16mm tails to the consumer unit up into the loft, across about 3m and then down the wall in surface trunking down to an old Crabtree CU, with a separate 16mm main earth along side.

Did a Z test at the CU and had a 0.45ohm result, but then the PME cutout had a Ze of 0.47?

I will call the DNO to make them aware, but from what i can see, a BS3036 fuse has an ELI max of 1.07ohms so as this is all well within the limits of the installation, so surely this is ok?

I have no plans to remove the MEM unit and replace with a new one as it is in excellent condition.

 

[westward10]

Probably just a parallel path interfering at the CU but that small difference could be could be the test leads or the meter "seeing it" differently.
Your Ze is theoretically too high for a PME system.
16.0 conductors contained in trunking are undersized for protection by way of a BS3036, 60A fuse.

 

[Initforthemoney]

Probably just a parallel path interfering at the CU but that small difference could be could be the test leads or the meter "seeing it" differently.
Your Ze is theoretically too high for a PME system.
16.0 conductors contained in trunking are undersized for protection by way of a BS3036, 60A fuse.

Thanks.

I guess i might need to swap the 3036 for a 50A MCB & enclosure
as there is currently no way to replace the tails that easily!