High Zs On All Circuits.. Advice Please

[TLREI]

Hello.

I have recently attended the Electrical Domestic Installers course and have my 17th Edition. I have good knowledge of Rewires and the domestic area.

today using my fluke 1562 MFT I recorded my Zs value on my house ring main.

between L-N I get what I would expect to get on sockets ... 0.45 ohms. however, when I test between L and PE which is obviously what the Zs test is I get a reading of 560 ohms. yes that it right.

Any ideas what's causing this issue? I have a TNCS supply.

cheers

 

[Hawk81]

What is your Ze?

 

[SPECIAL LOCATION]

Yes....

lots of ideas as to the cause.

the answer is very obvious and basic IMHO...

But if I say any more I shall get told off for bing rude for telling the truth!

:coat

 

[TLREI]

please say I can take it buddy

 

[TLREI]

Hi Hawk 81,

Again the Ze comes in right at 0.19ohms between the L-N setting. L- PE it doesn't test and the meter states Error4. Am I missing something simple here?

 

[NozSpark]

What other tests have you carried out???

and you need to get your terminology correct....

Ze is the external earth loop impedance, with the installation isolated and all earthing and bonding disconnected

Zn would be a better term for a L-N test

 

[kerching]

Hi Hawk 81,

Again the Ze comes in right at 0.19ohms between the L-N setting. L- PE it doesn't test and the meter states Error4. Am I missing something simple here?

I am at a loss, but i probably know less than most on the subject......

You say Ze is 0.19 between L-N................Ze used to be L-E

What does the book say Error 4 means...this may or may not help

Curses....beaten by a bloke in a bath again

 

[NozSpark]

It's sounding like you don't have a TNCS supply,,,, more like a TT without a rod!

I am at a loss, but i probably know less than most on the subject......

You say Ze is 0.19 between L-N................Ze used to be L-E


What does the book say Error 4 means...this may or may not help
Curses....beaten by a bloke in a bath again

I've left the tap running

 

[kerching]

What makes you "think" you have a TNC-S supply?

 

[Hawk81]

Hi Hawk 81,

Again the Ze comes in right at 0.19ohms between the L-N setting. L- PE it doesn't test and the meter states Error4. Am I missing something simple here?

What tester are you using?

 

[TLREI]

fluke 1652

 

[Blue Duck]

What are pefc and psc?

Err 4 is voltage on the earth possible N >E fault

 

[pewter]

GN3

 

[Andy™]

please say I can take it buddy

go get your money back from the course and us that to pay a competent electrician to do the work?

 

[SPECIAL LOCATION]

Hello.

I have recently attended the Electrical Domestic Installers course and have my 17th Edition. I have good knowledge of Rewires and the domestic area.

today using my fluke 1562 MFT I recorded my Zs value on my house ring main.

between L-N I get what I would expect to get on sockets ... 0.45 ohms. however, when I test between L and PE which is obviously what the Zs test is I get a reading of 560 ohms. yes that it right.

Any ideas what's causing this issue? I have a TNCS supply.

cheers

please say I can take it buddy

I will try to explain it like this, to be a semi reasonable electrician You need a basic understanding of:-

• How to design a circuit for the load(s) it has to supply (including all relevant calculations)
• How to select correct cable capacities taking into account installation environment, external influences, length, volt drop etc..
• How to select correct protective devices for the cable(s) used.
• How to use appropriate methods and materials to install the circuit you have designed.
• The different suppliers earthing  arrangements and how they affect the above design/installation aspects.
• Know what dead tests need to be done and what expected results should be.
• Know what dead test equipment should be used and how to use it.
• Know what live tests need to be done and what expected results should be.
• Know what live test equipment should be used and how to use it.
• Knowledge of current statutory and non-statutory regulations and guidance applicable to your alteration / addition, (and/or where to find that guidance to reference any areas that are not immediately familiar).
• Know what paperwork needs to be issued and how to correctly complete all aspects of that paperwork.
• A underpinning knowledge of Maths, Physics, Electrical science and how to evaluate unexpected meter readings to logically interpret and isolate any hazards, dangers or fault symptoms on a circuit.  
• Previous wiring regulations and how circuits designed to earlier standards may be electrically safe whilst not appearing to comply with current wiring regulations.
• The ability to evaluate inspect and test older installations, installed by others so as to establish if it is safe to extend or modify an existing circuit.
• The ability to evaluate inspect and test older installations, installed by others to diagnose and rectify fault symptoms when an installation fails to operate how it was originally design to operate.
• Health and safety aspect of your work that can affect your, your customers, any third parties all at the location you are working at.
• etc... etc..  etc..

(the older you are the more experience you gain and understanding in all aspects of the work increases...

BUT you must start with the basics in all areas IMHO)

The bit in red is what most people get from doing a short "17 edition" or "Part-P" electrical couse...

They have are taught a limited knowledge of some wiring regulations so as to pass an exam...

The other 90%+ skills and knowledge needed to work safely and efficiently within the electrical industry are NOT taught on these short courses!!

You have a basic fault finding exercise to do...

the only tips I will say are:-

If in doubt.. go back kill the power..  do the dead tests first....

Prove exactly what you have or haven't got

DO NOT ASSUME ANYTHING!!

Any "apparent faulty reading" has one of three possible causes...

1/ A physical fault or problem on the installation.

2/ A technical fault or problem with the test equipment or its test leads.

3/ A knowledge fault or problem when the person undertaking the testing doesn't understand the test equipment / the readings / or what the installation readings should be.

A logical approach to evaluation and elimination should soon show you where any problem lies.

Guinness

 

[TLREI]

Thanks.

 

[binky]

done any R1+R2s ?

 

[TLREI]

Hi Binky.

yeah I've just done the kitchen ring main and getting between 0.31 and 0.35 at different sockets.

I have also confirmed polarity

 

[ProDave]

I will try to explain it like this, to be a semi reasonable electrician You need a basic understanding of:-

• .........

I would say there's a far more basic fundamental requirement, and that is to UNDERSTAND electrical circuits.  Then you would understand what your readings meant, and what you might need to do to make them read correctly, and where to look for a particular fault.

Without that, you can know every regulation in the book to the letter, but you won't be an electrician.

 

[binky]

1/ ok so why haven't you R1+R2 the rest of the circuits, do so pronto.

2/ have you nulled your test leads / checked your plug-in test plug or whatever you are using.

3/ go home and practice on your own house get your test gear sussed before returning to site - it's a lot less embarrasing

4/ don't go testing again for a while, you don't have the skills yet - it comes with experience and understanding exactly what your test gear does, and how. It is very easy to get in a twist when you don't really understand. Stick to the offical test routines and methods and you should be able to sort yourself out, do not depart from the official routines unless you want to end up completely baffled like I did many years ago.