Embarrassing to admit but...

[HappyHippyDad]

Evening all.

I have just left a customers house after doing a few preliminary checks prior to a job.

I was at the CU, had disconnected the Main Earth in preparation to check the Ze. The customer is very friendly and is talking to me continuously, asking me all about my life!! I am not good at concentrating when I am being talked to but also I dont like to be rude, so....

I took my Ze, it was 0.19Ω. (PME)

Said goodbye eventually and left. Half way home I realise (can't believe I'm admitting this) that I had measured between line and neutral. What possessed me to do that!!!! Immediately thought 'I have to go back', but then I wondered what that result actually is? Having never tested it before!

The tails are approx 1.5m as is the main earth (16mm). Have I actually tested Ze (almost), as the only difference in the Earth fault loop Impedance will be the 1.5m of neutral tail (16mm) as opposed to the Main earth which is connected to the neutral in the cutout?

:blush5:

 

[Darkwood]

She must have been very pretty

 

[Richard Burns]

I can sypmathise with the being talked at scenario, very distracting, but of course as we are professional we can do the job blindfold without thinking and get ti perfect.

Oops. Interesting error to measure to neutral after disconnecting the earth.
The problem I can see is that it is vaguely possible the the earth is not connected in the service head and this is what you have not tested, however I would think this a remote possibility and would expect the actual Ze to be within 0.03 Ω of your measured Z[SUB]LN [/SUB]and certainly within the 0.35 Ω limit. If you also have your PFC values this would tell you the variation from N to E, if any (and also confirm the earth connection).

 

[HappyHippyDad]

Thanks Richard,

I suppose it is obvious that it has to be the same figure as the Ze (almost) (I bet you've never had to write Zln before (cant work out how to make the LN look like yours!)) but it was such an odd thing to measure that my brain needed to hear it from someone else.

As for the remote possibilty that the earth may not actually be connected, that is of course vitally important but if it does come to that then I shall pass it over to the DNO rather quickly!

 

[andyb]

You've already gone above and beyond IMO by going there to do pre work checks,

But since you were distracted as you were, are you sure you reconnected the earth?

 

[Hellmooth]

You've already gone above and beyond IMO by going there to do pre work checks,

But since you were distracted as you were, are you sure you reconnected the earth?

I thought that's was HHD was going to say he had done in the first place :rolleyes4:

 

[HappyHippyDad]

You've already gone above and beyond IMO by going there to do pre work checks,

But since you were distracted as you were, are you sure you reconnected the earth?

Ha! Valid point... 'yes'.

 

[Clive P]

HHD,

As has been said on here many times before, one way to prove you have a PME connection is to check your L-N reading against your L-E reading and if they are the same or very close you have confirmed. So if your earth is connected at the cut-out then jobs a good un. As has been said, you carried out pre-checks, so all is good.

Regards.