INSULATION RESISTANCE - WHO DOES?

[TraineeSpark]

Hi All, I know I will get slated for this question, but gonna ask anyway.
The firm I work for expect 6 test and inspects (including certs) in as many hours. In an attempt to get this achieved, nobody bothers with I.R tests,myself included, though I hate signing to say its been done. The general consensus of opinion is: insulation breakdown, and either breaker or r.c.d would keep tripping. Whilst I partially go along with this train of thought, I am far from happy with working in this way. But like most of us, have to keep my crappy job, to pay the mortgage etc etc.
So question is, who out there does or does not do I.R tests? And what are the potential problems I am not seeing here? Can anyone tell me of examples when insulation may have broken down, but circuit protection does not trip/blow? Have got myself in such a 2 and 8 over this, I cant see the woods for the trees. Up until this firm I work for now, have always prided myself on doing everything by the book.
Oh, and the other little gem on this firm is to only do R1+R2 for rings. On all other circuits they guess-estimate it. Some of them dont even bother doing readings for rings.
Please help guys, we aint all cowboys at my place, and I worried bout the safety of the clients, not 2 mention being in the dock at some time in future.
TIA TS.

 

[ebee]

Why on earth are you working for this firm.
They should have their heads nailed to the floorboards.
Get out and whistleblow you might save a life.
Criminal negligence?
Don`t forget there`s one lecky in Jail already

I know of a firm who`s a bit like that (are you from my neck o` woods?)

 

[ban-all-sheds]

I'm a DIYer and I do IR and R1+R2 tests properly.

If this company is registered with NICEIC/ECA/whatever, make a complaint to someone senior there.

And don't forget there are laws to protect whistleblowers - this company is breaking the law and defrauding its customers, and they deserve a hefty slap.

If you know it's wrong, and do nothing about it you could end up in trouble..

 

[Lectrician]

R1 + R2 can be calculated on a PIR - just mesaure Zs.

Or, you can do it vise versa.

On a new build, you MUST do the R1 + R2, but may calculate the Zs if you wish.

I often only test insulation resistance from L and N to E. This will more than likely show any problems. It isn't always practicle to test L to N.

It is important to ensure ring continuity - you should also cross the rings and test at all sockets.....unless you can physically see a ring is in place by being able to see the entire cable run.

You must be as thourough as possible, and any limitations must be noted.

 

[69er]

Agree with ebee and bas - I always do ir tests.

 

[ebee]

R1 + R2 can be calculated on a PIR - just mesaure Zs


No No No No No & No

you are not allowed

Zs = Ze + R1 + R2 but Zs - Ze <> R1 + R2

 

[TeesdaleSpark]

If your doing a PIR you can do an insulation resistance test with live and neutral shorted together and then test to earth. Do this on the whole installation i.e. all together not each seperately.

Guidance Note 3 and the NICEIC testing book as well as the regs allow calculation of Zs from R1+R2.

A circuit will fail an insulation test before it trips a mcb or rcd.

What are you meant to do in 1 hour? A whole installation?

 

[ebee]

Someone once said, drive past, count windows and guess Zs`s

 

[Lectrician]

R1 + R2 can be calculated on a PIR - just mesaure Zs


No No No No No & No

you are not allowed

Zs = Ze + R1 + R2 but Zs - Ze <> R1 + R2

I had this discussion during my last NIC Inspection, and it was agreed at the time that there is no point doing the R1 + R2 once energised - the column can be filled in by calculation.

I am not saying the assessor was correct - but this is how I have been taught to do it. I know 100% that you can ommit the Ze test on a new circuit, as you will have to have done the R1+R2 dead test.

 

[sparkybird]

Sadly, doesn't suprise me. In last month I have worked for two customers who had PIR's done recently by other electricians (both by NIC Domestic Installers) and neither had done Insulation Resistance and one had obviously 'calcuated' R1+R2 by subtracting Ze from the circuit Zs. Only problem was that his maths was rubbish! The schedule of inspections was also really poorly completed.

The PIR's were pretty useless in my opinion - I mean surely one of the reasons to have one done if your wiring is getting on a bit is to check out Insulation Resistance so you can tell how long it might last? Of course the customers don't have a clue, unless it's explained to them.....

Not doing a systems IR test is just lazy - if you test between P/N and cpc as suggested it's very quick.

SB

 

[TraineeSpark]

Thanks all for the replies, much appreciated. I do already calculate Zs, as my meter dosen't have d-loc. But don't understand why you can't calculate R1+R2 in instances when Zs and Ze have been measured. I know its not allowed, but don't know why. Can someone please explain.
Also, this is the first firm where I have done P.I.R's. In past only tested new installs, and measured I.R between all conductors seperately. Stupid question I know, but if I link out N bar and E bar at board, and measure I.R for whole installation, do I remember correctly that I only need to remove lamps, and unplug sockets? What I mean is, is there no need to disconnect electronic timers etc? Can someone please re-iterate the procedure for doing it this way?
Sorry in advance for all the lame questions, but just wanna make sure I am doing everything correctly. Been kinda thrown in at deep end, and it's spun my head out a bit. Find myself doubting the way I do things all of a sudden.
Cheers, TS.

 

[TraineeSpark]

Sorry, meant to say if I link out N bar and L, in post above... Doh

 

[ebee]

The problem of calculating R1 + R2 if Ze & Zs are known is this.
In maths the Ze + R1 + R2 = Zs is OK and then it would follow that Zs - Ze = R1 + R2.
The problem is that Zs is correctly measured with power off and then bonds disconnected therefore you get the true Z external to the installation.
However you reconnect the bonds before reapplying power to safely measure Zs.
The bonds often give parallel paths which would lower that Ze if you checked it again.
Also parallel paths with R2 say from supp bonding etc lower that so the measured Zs includes all these paths.
Therefore Ze (no bonds) - Zs (with bonds) would not equal R1 + R2.
Ze + R1 + R2 would give a calculated Zs and the meassured Zs with bonds etc is often lower than the calculated one.
Sorry I waffled

 

[ban-all-sheds]

Sorry, meant to say if I link out N bar and L, in post above... Doh

That's why there's an

button...

 

[securespark]

I know many who do not do IR. It "slows them down"...

They just write "LIMS".

Bad....

But like most firms, there is pressure to complete many jobs per day, and it would be impossible to do your quota within your allotted hours unless you cut corners.

That is why I always end up getting home late from work. But then, at least I can sleep at nights.

Whatever I put my signature to is always 100%.