I had a strange problem today.
The house (mid '50s)in question has the mains coming in, after the meter, the tails go to 2 fuse boxes.
The only Earth coming into the building vanishes into the wall cavity and is covered with green only sleeving. It is tinned or aluminium as the wire is silver coloured.
The 2nd fuse box feeds only the upstairs ring and one socket in the kitchen, which I have diss'd and retreived (the kitchen socket, not the u/s ring).
There is earth bonding between the boxes.
While tidying up the wiring in had disconnected the earth between the two boxes in the first box, when I reconnected it I noticed a small spark.
So I disconnected it again and the measured with a DMM the PD between the two earths (ie the earthing block in the 1st box and the earth lead to the second) and got a reading of 150ish volts @50Hz.
I tested for L-E,E-N and L-N faults on the wiring for the second ring and got no faults.
So,
1) am I correct in assuming a T-T or PME earthing system ( this is not a rural area)?
2) Is this to be expected? (A PD between a 'real' earth and the earth of the cct?)
3) Should I measure current?
4) Do I need to take any further actions?
I DID reconnect the Earths after measuring this.
r
Paul
The house (mid '50s)in question has the mains coming in, after the meter, the tails go to 2 fuse boxes.
The only Earth coming into the building vanishes into the wall cavity and is covered with green only sleeving. It is tinned or aluminium as the wire is silver coloured.
The 2nd fuse box feeds only the upstairs ring and one socket in the kitchen, which I have diss'd and retreived (the kitchen socket, not the u/s ring).
There is earth bonding between the boxes.
While tidying up the wiring in had disconnected the earth between the two boxes in the first box, when I reconnected it I noticed a small spark.
So I disconnected it again and the measured with a DMM the PD between the two earths (ie the earthing block in the 1st box and the earth lead to the second) and got a reading of 150ish volts @50Hz.
I tested for L-E,E-N and L-N faults on the wiring for the second ring and got no faults.
So,
1) am I correct in assuming a T-T or PME earthing system ( this is not a rural area)?
2) Is this to be expected? (A PD between a 'real' earth and the earth of the cct?)
3) Should I measure current?
4) Do I need to take any further actions?
I DID reconnect the Earths after measuring this.
r
Paul
