Commercial EICR - Your opinion?

[HomeCert ltd]

Hi All,

Being doing a commercial EICR over night (7-7) for the past week, still got a good few nights to go.

The installation is most likely 40-50 years old, was originally done well. About 5 years ago they had another contractor redo a lot of the electrics to accommodate the current owner. The previous electricains work is unreal, he has completely ruined the installation.

I'm not 100% sure how to approach this. There's a lot a minor things which need doing which I will report back, but the lighting in some of the areas is unreal. The previous contractor had used SY cable everywhere, not correctly terminated at any point, which I found out is carrying a healthy 157v on the braiding. Basically every earth has been cut out throughout the lighting, mainly class 2 fittings, but due to the fact a lot of he circuits are new and all the existing work has an earth, would that be a C2. As it should comply with when he installed it.

Also getting 287v back down a neutral when not connected via a circuit fed by a Seperate DB on the other side. Earths used as feeds in some cases, some lighting circuits supplied via 2/3 circuits, all with no CPC and low IR. Due to the fact it's suspended ceilings everywhere etc... I was thinking it might just be easy to just redo a lot of the lighting instead of trying to break it down and see what's salvageable.

What would any of you do?

 

[ipf]

Rarely do a global IR as I generally work large commercial or industrial sites and from past experience it rarely pans out unless it is a few rudimentary circuits.

Exactly. Same here.

 

[Ian1981]

Most of the time if you do a global IR test on a 3 phase db then it’s gonna be less than 1Mohm so it’s pointless in my eyes.

 

[Ian1981]

Always good to know how others carry out their work, when doing an EICR would you simply test the IR on a DB as a whole. Did a 48 way board the other night, low IR with a 3 pole main switch, so went through one by one to identify one circuit which was low. But I remember when I was taught the guy who taught be said not to do that, record low IR for the board as a whole and then call for further investigation to identify any specific circuits.

I suppose if your IR reading for the whole board was 1Mohm or higher then it is acceptable but I would note it in the comments section

 

[Risteard]

Most of the time if you do a global IR test on a 3 phase db then it’s gonna be less than 1Mohm so it’s pointless in my eyes.

That problem won't disappear if you test them individually though as the requirement is for the insulation of the whole installation or DB to be above the values and not simply each circuit.

 

[Ian1981]

That problem won't disappear if you test them individually though as the requirement is for the insulation of the whole installation or DB to be above the values and not simply each circuit.

Just pointing out it’s in my opinion to test the circuits individually as the bigger the installation and circuit numbers then the lower the resistance in terms of going a global test

 

[Risteard]

Just pointing out it’s in my opinion to test the circuits individually as the bigger the installation and circuit numbers then the lower the resistance in terms of going a global test

The whole point is that it's lower though. BS7671 requires the installation/distribution circuit with final circuits connected to exceed the minimum values rather than individual circuits. Strictly speaking the quoted values are for initial verification though. No particular value for periodic insulation testing is mentioned.

 

[ipf]

That problem won't disappear if you test them individually though as the requirement is for the insulation of the whole installation or DB to be above the values and not simply each circuit.

A quick way of doing IR testing on a 48 way 3 phase board?....Global test below 1Mohm, C2, installation fail.
May get pay for an extra day or two on remedial work...on top of the initial quote, I suppose.
No wonder I get undercut.....

 

[Ian1981]

A quick way of doing IR testing on a 48 way 3 phase board?....Global test below 1Mohm, C2, installation fail.
May get pay for an extra day or two on remedial work...on top of the initial quote, I suppose.
No wonder I get undercut.....

Exactly!

 

[Ian1981]

The whole point is that it's lower though. BS7671 requires the installation/distribution circuit with final circuits connected to exceed the minimum values rather than individual circuits. Strictly speaking the quoted values are for initial verification though. No particular value for periodic insulation testing is mentioned.

I stick with 1 Mohm personally.
If the overall value is lower than this then I code it

 

[The Ghost]

I agree, I wouldn't stop the inspection

I meant halting the inspection.

It is a legal requirement EAWR and H&S. That is to make safe where dangerous conditions are found, with the agreement of the person ordering the work. Common sense should tell anyone if you find a dangerous situation such as a possibility of electrocution due to touch voltage being present at a hazardous level you would (?) rectify it??? or not. I certainly would out of consideration of the safety of others, hang the legal implications it is just horse sense.

 

[Risteard]

A quick way of doing IR testing on a 48 way 3 phase board?....Global test below 1Mohm, C2, installation fail.
May get pay for an extra day or two on remedial work...on top of the initial quote, I suppose.
No wonder I get undercut.....

Lets say that you measure 20 circuits at 10 Megohms each. The fact is these resistances are in parallel so would you wrongly consider that to be OK in spite of the fact that the requirement in BS7671 is for an installation/distribution circuit with all final circuits connected and not for any one circuit?

 

[Ian1981]

Lets say that you measure 20 circuits at 10 Megohms each. The fact is these resistances are in parallel so would you wrongly consider that to be OK in spite of the fact that the requirement in BS7671 is for an installation/distribution circuit with all final circuits connected and not for any one circuit?

That’s why we are tought the 1/Rt method of calculating the total resistance in parallel.
Scientific calculator at the ready

 

[Wilko]

I am puzzled. 157v on braiding? Is that not a real and immediate risk of electric shock? If so would it not warrant a C1. In which case the person ordering the work should be informed in writing and the inspection halted until that situation has been dealt with???

Hopefully this will be an induced voltage (if braid left floating say). Perhaps the 2 pole voltage tester will be helpful?

 

[The Ghost]

induced voltage

Indeed, I use a drummond with the two buttons that to check that out. I guess the OP has taken this into account?

 

[davesparks]

BS7671 requires the installation/distribution circuit with final circuits connected to exceed the minimum values rather than individual circuits.

Then why do the model forms provide individual boxes to record IR for each circuit? If they had intended us to measure and record global tests then surely the model forms would reflect this?