NIEIC inspection

[tom-the-sparky]

Hello everybody

Ive got my niceic inspection soon. On my recent fuse board change and test i completed Zs tests for each circuit but only calculated R1 + R2 (apart from the ring mains) IS THIS OK? Also if anyone has had the niceic guy come out, any words of warning?

Thanks

 

[AlanWirral]

If you did the Z's why didn't you do the R1 + R2's at the same time?

 

[Sintra]

You MUST test R1 + R2 or R2 at every point on every circuit. This test can not be calculated.


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[Ponty Massive]

How did you calculate R1+R2, did you measure the Ze then measure the Zs and take one from the other?

 

[tom-the-sparky]

Yep took a direct Zs measurement on each circuit and a Ze at the board and took one away from tother!!

 

[olly w]

You MUST test R1 + R2 or R2 at every point on every circuit. This test can not be calculated.

At every point on every circuit? are you sure it's not just the furthest point on every circuit?

 

[Des 56]

At every point on every circuit? are you sure it's not just the furthest point on every circuit?

If its a board change only
No requirement for Zs throughout the circuits,a reading at the extremity of the circuits is ok
I would also do a loop test at all the sockets if possible as well as continuity of the ring

 

[waynie2010]

i usually calculate R1+R2 on existing circuits too (except on ring circuits) and only measure it if its a new circuit. I also am looking into NICEIC enrolement soon and would like to know the assessors views on this so plz post the outcome,
cheers,
wayne

 

[WayneL]

Yep took a direct Zs measurement on each circuit and a Ze at the board and took one away from tother!!

Why?

Why did you want to know what R1 + R2 was?

 

[WayneL]

i usually calculate R1+R2 on existing circuits too (except on ring circuits) and only measure it if its a new circuit. I also am looking into NICEIC enrolement soon and would like to know the assessors views on this so plz post the outcome,
cheers,
wayne

If he's any good, he'll ask you what possible use a 'calculated' R1 + R2 measurement was to anyone.

 

[IQ Electrical]

Why?

Why did you want to know what R1 + R2 was?

Because he was following the great myth that states "thou shalt have a value for R1+R2 but I'm not sure why"

 

[Spudnik]

Must admit chaps, there is no reason not to measure R1+R2 on a CU change.

This would then go towards ensuring the cpc is continuous throughout the circuit, which a Zs measurement would not.

 

[WayneL]

Must admit chaps, there is no reason not to measure R1+R2 on a CU change.

This would then go towards ensuring the cpc is continuous throughout the circuit, which a Zs measurement would not.

I agree, Jason - measure it. Your cables are already disconnected etc etc. so why not.

A calculated R1 + R2 is as much use as a chocolate teapot - what does it tell you? Nothing.

 

[Guest123]

You mention to your assessor that you calculate R1+R2 from Zs-Ze, and he'll explain why this is no good.....on your re-assessment!!

 

[telectrix]

good post Lenny, but would be ok IMO to measure R1+R2 , and calculate Zs?

 

[Smugley]

It's okay to calculate Zs based on measured Ze and measured R1+R2. But only just okay!

Measuring Zs aswell makes me feel I have completely tested the installation. Remember that Ze is measured before the CU and R1+R2 is measured after it. Measuring Zs directly at the extremities of each radial and at least one point on each ring is the only test that includes any possible poor connections, high resistance joints etc that may lurk within the board.

 

[Guest123]

It's okay to calculate Zs based on measured Ze and measured R1+R2. But only just okay!

Measuring Zs aswell makes me feel I have completely tested the installation. Remember that Ze is measured before the CU and R1+R2 is measured after it. Measuring Zs directly at the extremities of each radial and at least one point on each ring is the only test that includes any possible poor connections, high resistance joints etc that may lurk within the board.

Agreed.

It is the only real test of a full circuit and all it's components.

 

[mark scotia]

Gentlemen

The correct method which is accepted/NIC guidance is to measure your r1 + r2 and from this you would calculate your Zs with the following equation Zs= (r1+r2)x1.2 + Ze, the reason being to verify polarity and most importantly it gives an accurate reading where your direct Zs measurement incorporates parrallel paths.

Hope this clears it.

 

[IQ Electrical]

Gentlemen

The correct method which is accepted/NIC guidance is to measure your r1 + r2 and from this you would calculate your Zs with the following equation Zs= (r1+r2)x1.2 + Ze, the reason being to verify polarity and most importantly it gives an accurate reading where your direct Zs measurement incorporates parrallel paths.

Hope this clears it.

The correct method?

Please post a reference for this 'correct method' I'm intrigued!

 

[Guest123]

Gentlemen

The correct method which is accepted/NIC guidance is to measure your r1 + r2 and from this you would calculate your Zs with the following equation Zs= (r1+r2)x1.2 + Ze, the reason being to verify polarity and most importantly it gives an accurate reading where your direct Zs measurement incorporates parrallel paths.

Hope this clears it.

The correct values are R1+R2 not r1+r2, these are two very different beings.

Also a measured Zs under normal service conditions will be a more accurate reflection of the situation as the parallell paths that exist will be included as they are in normal service conditions anyway. You will also gain a truer reflection of prospective earth fault currents.



This is why for those that do it, you CANNOT calculate R1+R2 from a measured Zs reading.

 

[spud1]

Gentlemen

The correct method which is accepted/NIC guidance is to measure your r1 + r2 and from this you would calculate your Zs with the following equation Zs= (r1+r2)x1.2 + Ze, the reason being to verify polarity and most importantly it gives an accurate reading where your direct Zs measurement incorporates parrallel paths.

Hope this clears it.

Im with Lenny.

 

[IQ Electrical]

I should hope so after reading that!

 

[WayneL]

Gentlemen

The correct method which is accepted/NIC guidance is to measure your r1 + r2 and from this you would calculate your Zs with the following equation Zs= (r1+r2)x1.2 + Ze, the reason being to verify polarity and most importantly it gives an accurate reading where your direct Zs measurement incorporates parrallel paths.

Hope this clears it.

Oh dear!

The NICEIC are going to take over the world - or so they'd have you believe.

Mark, contrary to what they might lead you to believe, the NICEIC do not make the rules.

A PIR is supposed to be non-intrusive.......in other words, you don't really want to start pulling circuits out of CUs to measure R1 + R2.
You could create more problems within the installation than were there in the first place.

The (proper) guidance is :
R2 wander lead at all exposed conductive parts and center pins of socket outlets.
Zs at extremity of all radials and every socket outlet.

Remember, you are proving continuity of protective conductors - no need to measure R1 + R2, although you can use 'Method 1' to confirm continuity and polarity.
Zs is obviously required to confirm disconnection times.

The only time I would actually 'measure' R1 + R2 is if, after risk assessment, I decided it was too dangerous to 'measure' Zs, and then I would use the calculated value.

 

[Guest123]

This isn't a PIR Wayne, it's an EIC after a CU upgrade.

 

[WayneL]

This isn't a PIR Wayne, it's an EIC after a CU upgrade.

Table 3.3, Pg 73,GN3, Len - pretty much word for word.

Protective Conductor Continuity:

Between the earth terminal of distribution boards to the following exposed conductive parts-
Socket outlet earth connections
Accessible exposed-conductive parts of current using equipment and accesories.

Zs at the following positions:

Origin of installation
Distribution boards
Accessible socket outlets
Extremity of radial circuits

You are right, though, it is also the procedure after a CU upgrade.

 

[Guest123]

I meant the OP was asking about an EIC not a PIR as you mentioned.

 

[nickblake]

Agreed.

It is the only real test of a full circuit and all it's components.

i often do calc on circuits that are not powered at the time of the test IE storage heater supplies , it makes me feel that the job is unfinished and not right , especially as you can find faults doing the Zs test
oh thats not the R1 R2 test im on abut always do them as they should be done

 

[WayneL]

I meant the OP was asking about an EIC not a PIR as you mentioned.

With you, Len - Sorry - it's easy to get distracted as these posts go on.

You are pretty much doing a PIR on the existing circuits, though, as you haven't installed them.

ESC Best Practise:

10.2. In addition, as a minimum, the following tests
should be carried out to the existing circuits
connected to the replacement consumer unit.​

• A continuity test of the protective conductor of
each circuit, to the point or accessory electrically
furthest from the consumer unit and to each
accessible exposed-conductive-part.​

• A test of the polarity and a test to establish the​

earth fault loop impedance (Zs), at each
accessible socket-outlet and at least one point or
accessory in every other circuit, preferably the

point or accessory electrically furthest from the​

consumer unit.

​

 

[Guest123]

Not disputing any of your input mate, just making sure we all sing from the same hymn sheet.

 

[WayneL]

Got a bit carried away with the old PIR thing there - but still applicable.

What I'd like to know now - especially if what 'Mark Scotia' said is true about the NICEIC guidance being to calculate Zs - is this:

If I had an assessor round and he asked me how I'd established my Zs values and I said I measured them, would he contradict me and say that was wrong?

Could I fail my assessment on this issue, even though I could back-up 'measuring' Zs with GN3 and the 2391?

 

[IQ Electrical]

If I had an assessor round and he asked me how I'd established my Zs values and I said I measured them, would he contradict me and say that was wrong?

Could I fail my assessment on this issue, even though I could back-up 'measuring' Zs with GN3 and the 2391?

Yes, if you told him you'd measured Zs on your lighting circuits from the top of a pair of 12-tread steps with a 3-lead instrument.

They're concerned about safety, if you follow the usual guidelines and use test gear in good condition to GS38 then they can have no complaints, as you already quite rightly said, the NICEIC or A.N. Other do not write the reg's or Guidance Notes.

I can just imagine my assessors comments if I told him I gave up measuring Zs values on the grounds of safety!

 

[Des 56]

Niceic regulations are emerging once again

Shall we pen them a few words,(tactfully) because they are sensitive souls,that contrary to their belief,others are responsible for the regs and they are just followers

 

[brucelee]

hi all
On all the courses I have just done including 2391 they say to calculate all except radial and ring final circuits with a suitable plug in lead. I even was told to do it this way for practical assessment and then compare to rule of thumb max measured tabulated 80% values In GN3 , they just say for safety reasons and whats reasonable not to put yourself in danger with regard to Elecy at work regs e.g. They state not to work live unless in all circumstances its unreasonable to work dead and in all circumstances its reasonable to work live and safety precautions are taken to prevent injury by using suitable PPE which is a statutory document and supersedes non stat and codes of practice and also with regards to Health and safety regarding working at heights as IQ electrical said e.g 12 tread step ladders , but at same time we had questions asking how to conduct an earth fault loop impedence on a lighting circuit in a commercial or industrial premises and also says in all the non statutory documents either way is acceptable .It Seems there is lots of contradictory info regarding different methods. too much confusion? As wayne has said this is how gn3 says to carry our Zs on a pir . The tutor also said Zs is the most important test as it not only proves there is a continuity in the loop, but also confirmes ,polarity and voltage and to ensure the Zs is low enough for a sufficiently high enough fault current to ensure the protective device will actually operate in the required time to meet max disconnection times, but again tutor still said to calculate as this is the true value where possible, measuring not accurate as it includes parallel earth paths from the main protective bonding conductors etc etc ?????????????? confused or what please dont shoot me this is only what ive been taught by my betters
I am with lenny and you guys, but if asked i am with calculating lol so do i or dont i measure that is the question?????????

 

[IQ Electrical]

We have different scenarios for City & Guilds, scheme providers and the real world!

Personally, I measure everything and I've never been corrected in this regard during the many annual assessments that I've endured as QS.

 

[Sintra]

We have different scenarios for City & Guilds, scheme providers and the real world!

Personally, I measure everything and I've never been corrected in this regard during the many annual assessments that I've endured as QS.

Same here and never once has it been questioned.

 

[olly w]

I'll get shot for this but in my opinion earth fault loop impedance is the most important test of all.

All the conditions are real with this test.

The voltage being used by the test instrument to calculate it, is the actual voltage that is at the test point.

26 amps is put down the earth to prove all connections are sound.

Polarity is proven.

And as said earlier it proves the over current protective device will actually operate in time.

By the way on a new install I think all tests should definately be carried out.

 

[Des 56]

By the way on a new install I think all tests should definately be carried out.
Yes indeed
The only weakness in full reliance on Zs tests, is the scenariowhere there are metal services, and later conversion of those services to non conducting materials, it could expose the user to potential danger if there was no cpc continuity

 

[olly w]

Yes indeed
The only weakness in full reliance on Zs tests, is the scenariowhere there are metal services, and later conversion of those services to non conducting materials, it could expose the user to potential danger if there was no cpc continuity

Whoever removes those services should be informing the user of the potential danger and advising the user to have the relevent checks carried out.

Don't forget that once upon a time it was standard practice to use the main water supply as the earth electrode!

 

[martysparky]

And Nic accept just Zs if stated on cert Zs only.

 

[brucelee]

when we did the practical for 2391 when calculated the radials we had to write Zs calc in the remarks on the schedule of test results for the appropriate final circuit