Testing Ze At Main DB Using a Kewtech KT42

[haggis31]

Hi Gents

I have just completed my 2391 corse and am practacing on my house electrics for the practical exam next week. On the course i was using a metrel multifunction tester which was great but my work have a set of individual kewtech instruments which i'm currently using.

I can't for the life of me manage to measure the external earth fault loop impedance from my consumer unit. Every time i connect the instrument i keep getting the P-N "Wiring incorrect when lit" warning light when i connect the leads.

Heres my method for measuring the external ze.

1) Isolate the main breaker in the DB.

2) Remove the earthing conductor from the cpc terminal in the db.

3) Connect the earth crocodile clip from the instrument leads to the earthing conductor.

4) Connect the red lead to line (at the live side of the mains breaker)

5) Connet the black lead to the neutral (at the live side of the mains breaker)

Could i genuley have a wiring fault???

The earthing arangement is PME

I have attached a picture of my consumer unit.

Many Thanks

 

[Zeespark]

You may need to run a polarity (I hope you did all of your dead tests before doing your live ones?) test on each circuit to find the problem. From there you would have to look at the wiring inside each accessory on the affected circuit until you have found your P-N fault. You haven't tested incorrectly, its just that your MFT has found a wiring issue somewhere on your installation.

AndyGuinness

---------- Post Auto-Merged at 13:20 ---------- Previous post was made at 13:12 ----------

One other possibility Haggis, is that your incoming mains tails have been incorrectly terminated by the DNO, which is not unheard of, to sort this phone your local DNO.

AndyGuinness

 

[kme]

Doesn`t fit, Andy - If he`s doing a Ze; the only possible fault would be polarity - and if THAT was wrong on a PME, you`d soon know.

Besides, polarity is right - we can see that from the pics. It HAS to be a tester / testing issue.

Haggis:

OK - I`ve just looked at the online manual.

Have you plugged the green "wander lead" into the back of the tester? If you have, THAT will cause the problem.

If not.....

You should just be using the "breakout" lead, with the IEC plug for the tester on one end; and the three separate leads at the other.

Set it up the way you described. Is the red light on now?

No? - proceed with test.

Yes? Take the earth clip, and connect in to the neutral (with the neutral clip). Has the light gone out now?

Yes? You have a fault with the earth connection in the property.

No? You either have a fault with the continuity of the earth lead in the breakout cable; or your meter has an internal fault. Try doing a Zs test at a socket with the other lead to prove which is faulty.

Let us know the results please.

KME

 

[Zeespark]

I apologise Haggis and to you KME, I have had a read of the KT instructions a while back, I should have re-read them fully before posting My response, again My apologies.

AndyGuinness

 

[haggis31]

Thanks Andy

This is slightly worrying as my house is a new build (only 1.5 years old) and has an inspection sticker on the front of it!

 

[Zeespark]

Follow KME's advice, in all the years I have know Him on here, He hasn't posted a bad/inaccurate reply from what I can remember.

AndyGuinness

 

[haggis31]

Hi KME

Top man, your spot on!

Just tried a zs using other lead on mains socket which was fine. Then checked fuses in live and neutral leads which were ok, then checked continuity of leads all were ok apart from the neutral lead which looks to be faulty as has no continuity.

Thanks very much for your help!

 

[Zeespark]

Again, My apologies for giving out duff info on My part Haggis, I hope it hasn't caused you a lot of inconvenience.

AndyGuinness

 

[steptoe]

PME :slap

Have you lost the neutral? :C

Follow KMEs instructions and let us know how you get on,

One other thing, do you have a single probe voltage detector, even a neon would suffice, but NOT a volt stick, try and check if there is a voltage on the N or earth.

 

[Zeespark]

Haggis has sorted the problem Steps

AndyGuinness

 

[haggis31]

Andy / Steps

Andy - No worries, thanks for guiding me to a possible problem.

Steps - just checked there is no voltage on either the neutral or earth.

 

[kme]

Andy - no apologies necessary mate - your advice was correct; but the possibility was precluded by the photos.

Haggis - glad you got it sorted. Scoob button is in the bottom left

 

[steptoe]

Haggis has sorted the problem Steps AndyGuinness

so I noticed, bloody stoopid slow phone,

 

[batty]

What a strange way to wire an REC2 isolator.

 

[steptoe]

get a load round here like that too batty,

its NOT an isolator if its wired like that!