Earth fault Loop Impedance Question

[oldtimer]

I guess we should then, also consider that your test instruments are calibrated in a controlled environment at 20C. I wonder how many are as accurate at 30C and upwards??

We have to draw the line somewhere, and go by the information given to you in the various regulatory publications!! ...lol!!

Yep I agree I seen a national companies forms and they highlighted the max Zs then the actual Zs and some were just below the max ie 90-95% and when I queeried it I was told its in the BRB

 

[rich.250]

I guess we should then, also consider that your test instruments are calibrated in a controlled environment at 20C. I wonder how many are as accurate at 30C and upwards??

We have to draw the line somewhere, and go by the information given to you in the various regulatory publications!! ...lol!!

I'll be honest I have never even thought of the calibration temp of test equipment......
Yes we could take this too far lol.
Aren't we just verifying the design which has the temp increase allowed for.

I also don't see the need for the box on the form if it's not the value you are working too lol

 

[jdd]

80% is based @ 20c. As long as it's below this then at 70c it will be ok. (Obviously as heat increases so does resistance.)

 

[NoSparks]

And a little bit of reality:

If your close to the limit, re-connect your test meter, ie if using a plug pull the plug and re-insert, if using probes press somewhat harder. That will resolve 60% of problems. If its a double socket try the other, that will resolve another 35%. If your still close to the limit then check the voltage drop. If Zs is close to its limit then 10 to 1 on the voltage drop will be out of range, so you can forget Zs and concentrate on the real problem.

Again in my (limited) experiance if the circuit is healthy then Zs will be well be low the limit. If it's not healthy then Zs will be sky high.

What have other people found?

 

[Guitarist]

If you are having problems with a high "measured" EFLI, then try doing it with Ze+(R1+R2). This is an acceptable way of carrying out the test (the best way imo) and without the resistance of the RCD/MCB you will usually find that it is lower and probably within limits.