High ze and circuit zs ????

[sidekick]

Urgent advice please.

I have done a consumer unit change where the main earth is 10mm and meter tails are 16mm.
I have connected new 25mm tails on consumer side of isolator switch and 16mm main earth to single pole block onto DNO 10mm earth.

Problem I have is a Ze of 0.54 and PSCC of 10KA. Is this something I can correct or is it a DNO problem?

Zs on all circuits is within limit except oven circuit which is 1.52 against max permitted 1.44.
Obviously will come down if Ze does.

 

[sidekick]

So your R1+R2 on a cooker circuit is nearly a whole ohm?!

What CSA is the cable, and how long is the run?

Yep 0.98
6mm t/e and only about 5 or 6m to the cooker switch which is within 2m to cooker outlet.

Possible poor connection but switch tiled in many moons ago and cooker not been moved for years either. Will need to pull both out to check.

 

[Guest123]

6M of 6.0/2.5T+E, should have an R1+R2 of 0.062ohms.....you have something very wrong there methinks.

Is your test equipment working properly???

 

[sidekick]

6M of 6.0/2.5T+E, should have an R1+R2 of 0.062ohms.....you have something very wrong there methinks.

Is your test equipment working properly???

Fluke tester just back from calibration 2 days before.
Tested circuit 2 or 3 times and got same reading.

Will check all connections on circuit and leads on tester and test again I think.

 

[pevvers]

If the R1+R2 and Zs are correlating, then I would think that it's not a problem with the meter, but more the fact that you have a relatively high resistance joint somewhere in the cable run.

Putting an RCD would allow it to trip out in the required time in the event of an earth fault, but this would be just covering up a much more serious fault that appears to be a dodgy joint could possibly cause a fire through arcing.

 

[Spudnik]

...... but this would be just covering up a much more serious fault that appears to be a dodgy joint could possibly cause a fire through arcing.

I would have thought that if it was going to catch fire through a bad joint, then it would have by now.

But of course, thats not to say that it never will, so i would tend to agree.