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

 

[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?