EICR thoroughness.

[dlt27]

I have been doing An EICR report today with another electrician from my workplace. He has tested double the amount of circuits I have. Now I follow testing to the book however he basically said that he:
1 calculates R1+R2 and just measures zs as he says as long as it is ok what does it matter if there are parallel paths. After all zs test is as it is when the circuit is live. Also says half the time can't disconnect parallel paths anyway.
2 Doesn't megger test between n-e as he says worst that can happen is circuit will trip when there is a low reading if on an rcbo. Says there isn't a danger if there is a low reading between n-e. Sometimes doesn't do l-e either as he says worse case scenario is it will just trip anyway.
Just wondered if somebody could give me some hard factual stuff I could throw back at him for not carrying out these tests.. Also truthfully how far does everybody else go when testing.
My NAPIT inspector even said to me he does end to ends at socket and doesn't do insulation resistance test because I said how does he do insulation resistance test without disconnecting the neutral at db.
Thanks for any reasons for carrying out testing properly.

 

[HappyHippyDad]

I would always undertake Insulation resistance tests. I think if you need to give a reason you could ask your colleague if he thinks the standard of the insulation around the conductors is important? he's probably right, the RCD probably will work but I just think thats an excuse for bad practise and will start leading to further poor habits just to save time.

Also the EICR asks for IR test results, thats some pretty good amunition to throw at him.. It simply is part of the EICR, unless he always writes it down as a limitation (discussed with homeowner) then it should be undertaken.

Also, you could show him the Best practice Guide number 4 (http://www.electricalsafetyfirst.org.uk/mediafile/100126678/best-Practice-Guide-4.pdf) which states the following as a C2:

Insulation resistance of less than 1 M​

Ω​

between live conductors connected togetherand Earth, when measured at the consumer​

unit with all final circuits connected


The only 'short cut' I would take with regards IR testing is that I would not always test L-N on an EICR, however I would still test L-N if I got poor (<2Mohms) on a L-E.

 

[Octopus]

I think the "thoroughness" of an EICR comes down to the age of the installation and access to prior reports.

Old installation, no report - VERY thorough EICR, none of this L&N to CPC testing - allow a day

Newish installation - previous report by me - redo tests - allow 1/2 day


If the client doesn't like my quote, I don't do the work.

 

[Pete999]

Can't see how your mate gets his R1+R2 measurements if he doesn't disconnect the neutrals from the DB.

 

[Guest77]

Can't see how your mate gets his R1+R2 measurements if he doesn't disconnect the neutrals from the DB.

Easy, think of a number and write it down, lets say 0.73, that will do, next circuit

 

[urbanmonkey]

Can't see how your mate gets his R1+R2 measurements if he doesn't disconnect the neutrals from the DB.

Zs=Ze+(R1+R2)....

Council lot I worked for instructed us to only ever calculate R1+R2. Takes too long to disconnect stuff and measure things apparently!

 

[ImpededLoop]

Can't see how your mate gets his R1+R2 measurements if he doesn't disconnect the neutrals from the DB.

I think the OP meant that his colleague does the good old favourite: R1+R2=Zs-Ze.

For any trainees reading this, you shouldn't calculate R1+R2 like this as the R2 value may be reduced by parallel earth paths such as bonding or multiple circuits in multigang switches etc.

 

[trev]

Zs=Ze+(R1+R2)....

Council lot I worked for instructed us to only ever calculate R1+R2. Takes too long to disconnect stuff and measure things apparently!

But Zs - Ze doesn't necessarily = (R1+R2)
I've seen installs where that figure would have been a negative number because of parallel paths. I'm sure we all have. as Murdoch says though. A lot depends on the circumstances in the lead up to the EICR.

 

[urbanmonkey]

Couldn't agree more! I always measure things properly, actually got a -------ing on one EICR because the guy in charge of certification had done the calculations from my figures and my measured R1+R2 couldn't possibly be right according to him! I lasted 2 months of it before I quit.

 

[Pete999]

I think the OP meant that his colleague does the good old favourite: R1+R2=Zs-Ze.

For any trainees reading this, you shouldn't calculate R1+R2 like this as the R2 value may be reduced by parallel earth paths such as bonding or multiple circuits in multigang switches etc.

Don't think he had a reading foe ZE did he?????

 

[ImpededLoop]

Don't think he had a reading foe ZE did he?????

True, there's no mention in the first post. I just assumed that he must have it, but who knows!

 

[dlt27]

I agree with all.
However why is low insulation resistance reading a code 2. What are the dangers associated with a low reading, or what can it cause apart from nuisance tripping?
Thanks for replies. Oh and yes he takes ze from zs for r1+r2.

 

[DPG]

I would have thought someone carrying out EICRs ought to know what the implications of low IR are. Daz

 

[dlt27]

Enlighten me! As I'm obviously incompetent.

 

[Guest55]

i'm extremely thorough with my drive-by inspections......

i even slow down to 20mph when the satnav bleeps. B-)

 

[DPG]

Apologies if that post came across the wrong way.
Well, low IR means failed/failing/damaged insulation. Now I would say the insulation is a fairly critical part of a cable. Daz

 

[dlt27]

I understand that but are you saying the implications are risk of electric shock and arcing. Because won't the protective device just trip eventually.
I have always carried out testing to the book as I always think knowing my luck I'll be the 1 in a million standing up in front of the judge. Thanks for reply.

 

[ImpededLoop]

Probably best to imagine the rcd/rcbo has failed and then consider the various combinations of insulation faults and their consequences.

 

[Deleted member 26818]

A low IR reading can also be an indication of damp, but that's beside the point.
I really don't think that a report where IR tests have not been conducted would be worth the effort of reading.

 

[Pete999]

I agree with all.
However why is low insulation resistance reading a code 2. What are the dangers associated with a low reading, or what can it cause apart from nuisance tripping?
Thanks for replies. Oh and yes he takes ze from zs for r1+r2.

Not sure I understand your reply, could you explain a little bit more please

 

[HappyHippyDad]

I agree with all.
However why is low insulation resistance reading a code 2. What are the dangers associated with a low reading, or what can it cause apart from nuisance tripping?
Thanks for replies. Oh and yes he takes ze from zs for r1+r2.

I think you're looking for a very exact 'this is what will happen due to a inadequate IR'. I'm not sure if thats possible. It's a bit like saying 'what will happen if I get out of my vehicle on a safari'? Maybe nothing, maybe you get eaten.

A pretty poor example but all I can think of.

Put simply the standard of the insulation is obviously very important. If we are just going to rely on the RCD then we may as well not bother with any IR checks at all and just wrap it in plastic bags!

A poor IR test shows that the insulation may be failing, again if we just say that doesn't really matter as there is an RCD then I think we are missing an important point, and one that I dont think I can explain clearly in words as it should just be generic.

 

[Lucien Nunes]

There are two aspects to a low IR.

One is that it can present an immediate hazard of electric shock, if something is live that shouldn't be, or fire if the failed insulation has started to char and go into runaway heating.

The other is that it is a tell-tale for all sorts of problems. Investigating the cause of low IR sometimes leads you to something nasty that you hadn't otherwise spotted - a joint box full of water, a cable with half its insulation chewed off by mice, an overheated motor...

But I agree with the sentiment above, it's so fundamental I find it interesting that one would challenge the importance of insulation. It's like a gasfitter saying it doesn't matter if you have leaky gas pipes so long as there's nothing nearby to create a spark.

 

[Engineer54]

One of the main reasons to record IR values from initial installation is to monitor them over periods of time, and why ongoing periodic inspection and testing of installations are a worthwhile exercise. They can, when and if regularly tested, clearly identify the deterioration of a circuits insulation before any catastrophic breakdown occurs.....