Today I have been carrying out a PIR at a branch of a well known convenience shop company.
In the switchroom I found an old 100A TP head which had clearly been too small to supply the premisis, so by the looks of things a new supply has been put into the building about 2 - 3 yeary ago.
The new supply is a 250A per phase TP supply with TN-C-S earthing.
The old supply which is still live (The fuses have been pulled but the supply is still there) was a TN-S supply
The two different earthing types have ended up connected together, and when I put my clamp meter on the earth there is a current flow of about 4 amps
This entirely dissapears when the two earth supplies are seperated, and yet no potential exists between the two supplies when seperate.
Is this something to do with parallel earth paths?
Old supply:
New supply:
In the switchroom I found an old 100A TP head which had clearly been too small to supply the premisis, so by the looks of things a new supply has been put into the building about 2 - 3 yeary ago.
The new supply is a 250A per phase TP supply with TN-C-S earthing.
The old supply which is still live (The fuses have been pulled but the supply is still there) was a TN-S supply
The two different earthing types have ended up connected together, and when I put my clamp meter on the earth there is a current flow of about 4 amps
This entirely dissapears when the two earth supplies are seperated, and yet no potential exists between the two supplies when seperate.
Is this something to do with parallel earth paths?
Old supply:
New supply: