Here's one that's really doing my head in and I hope that it's lack of experience rather than a dangerous situation.
I have installed a new kitchen ring main from scratch, it has 7 double sockets and 4 spurs for wired-in appliances (cooker hood, gas hob igniter, washing machine and dishwasher)
I thought I'd test it before connecting it to the fuse box (it will be protected by a 30A fuse and RCD, these were out of the cct for testing)
The run is about 20m if that.
I had correct readings for R1+R2 (0.01 Ohm), but Live to Earth and Neutral to Earth had 8MOhms each, but not 16MOhms between L and N.
When I split the ring in the middle I could see the fault on one side, so worked toward that way, taking the faceplates off, testing the ring, then untwisting the wires and testing in both directions to isolate.
At one point, the fault vanished, however, just poking about I got 8Mohm between the 2 lives, into and out of the back box.
I put it all back together and still saw the 8MOhm L-E and N-E.
Here is where I *may* have gone wrong, I was testing with a Fluke 175 DMM which should measure up to 50MOhms, however, when I used a 'proper' Robin Megger, I saw no faults at all on 90V and 500V.
Is this a case of using an inappropriate tool for the job or do I really have a fault?
Regs say anything above about 2Mohm is ok, and when I connected the circuit, nothing happened when I rather dubiously turned it on, I tested all of the sockets with a socket tester and the all came out normal, so I guess there were no crossed L and Ns.
So I'm totally stumped.
Has anyone any clues as to whether I really have a fault and a dangerous installation?
Thanks in advance.
Paul
I have installed a new kitchen ring main from scratch, it has 7 double sockets and 4 spurs for wired-in appliances (cooker hood, gas hob igniter, washing machine and dishwasher)
I thought I'd test it before connecting it to the fuse box (it will be protected by a 30A fuse and RCD, these were out of the cct for testing)
The run is about 20m if that.
I had correct readings for R1+R2 (0.01 Ohm), but Live to Earth and Neutral to Earth had 8MOhms each, but not 16MOhms between L and N.
When I split the ring in the middle I could see the fault on one side, so worked toward that way, taking the faceplates off, testing the ring, then untwisting the wires and testing in both directions to isolate.
At one point, the fault vanished, however, just poking about I got 8Mohm between the 2 lives, into and out of the back box.
I put it all back together and still saw the 8MOhm L-E and N-E.
Here is where I *may* have gone wrong, I was testing with a Fluke 175 DMM which should measure up to 50MOhms, however, when I used a 'proper' Robin Megger, I saw no faults at all on 90V and 500V.
Is this a case of using an inappropriate tool for the job or do I really have a fault?
Regs say anything above about 2Mohm is ok, and when I connected the circuit, nothing happened when I rather dubiously turned it on, I tested all of the sockets with a socket tester and the all came out normal, so I guess there were no crossed L and Ns.
So I'm totally stumped.
Has anyone any clues as to whether I really have a fault and a dangerous installation?
Thanks in advance.
Paul
