Discuss Tragic IR fail on EICR in the Electrical Forum area at ElectriciansForums.net

Welcome to ElectriciansForums.net - The American Electrical Advice Forum
Head straight to the main forums to chat by click here:   American Electrical Advice Forum

P

putalightuponce

Hello all,
I could use some help here:
I was recently asked to do an EICR at a small warehouse/office unit.
The installation was, to put it mildly, less than satisfactory; with multiple C1 and C2 conditions. However, of greatest concern to me were the insulation resistance readings I was getting. I left the job, trying to explain the severity of the condition to the client, but still feel under the circumstances, he is unlikely to take any further action, despite his report been top to bottom in 'further investigation's.
Whereas I'm sure everybody on here has had this at some point (if not daily), it is the specifically the IR fails I am still scratching my head over.
2xsockets in floor boxes, 3xsockets in dado trunking, 3xlighting circuits, and 2xhand dryer spurs were all returning 0Mohms IR L-E, yet none of the associated breakers were tripping or had been problematic in any way. Breakers and board were old (maybe late 70s early 80s), no markings on breakers except obvious ratings, but I'm assuming wiring can't have been of same period unless floor boxes and dado trunking wre popular back then?? The decor and fittings were certainly more recent.
I was pleasently suprised to find a single A4 schedule of circuits reinforced with several layers of tipex and the board had a Ze and PFC reading written in it from 2002, but that was it for records.

Any thoughts???
 
Did you test IR at 250v and 500v or 500v only?
if so we're the both 0Mohms?
if not it could be the insulation breaking down, water ingress somewhere, an appliance hidden somewhere
 
If you are getting a 0Mohm reading, then you then need to do a Low Ohm reading to find out exactly what the resistance is between the conductors.
With some experience, you can then take an educated guess as to what the link is between the 2 conductors - a neon, a PIR switch, a lamp etc.
If it is 0 ohms, then it will be a dead short, but you are getting a reading of less than a million ohms, so could be pretty much anything connected, or maybe nothing between the conductors (insulation breakdown).
Depending on your meters accuracy, the reading could be as high as 999,999 ohms, so further testing is required to find , or indicate, the true reading and cause.
 
It's not going to be 0 mohm L-E in reality,because if it was the OCPD would operate assuming it is of the correct rating. More likely it is N-E and you are getting the reading through connected loads.
Did you test the circuits with both L and N of each circuit disconnected from the DB? If so are you certain the correct N was disconnected with the associated live?
It's very common for neutrals to be almost impossible to ID for each circuit if they are not in the correct order in a crammed DB without major disturbance,a mistake in identifying the correct N for a circuit will result in low IR readings if the correct N is not disconnected. Another common complication is more than one N for a circuit in different terminals,with the same result.
If it is apparent that neutrals cant easily be ID'd for disconnection an option to verify satisfactory IR is a global test with the incoming N isolated from the DB. Some frown on this method but they tend to be people who sit at keyboards passing judgement having never actually carried out an EICR in a real working environment.
 
It's not going to be 0 mohm L-E in reality,because if it was the OCPD would operate assuming it is of the correct rating. More likely it is N-E and you are getting the reading through connected loads.
Did you test the circuits with both L and N of each circuit disconnected from the DB? If so are you certain the correct N was disconnected with the associated live?
It's very common for neutrals to be almost impossible to ID for each circuit if they are not in the correct order in a crammed DB without major disturbance,a mistake in identifying the correct N for a circuit will result in low IR readings if the correct N is not disconnected. Another common complication is more than one N for a circuit in different terminals,with the same result.
If it is apparent that neutrals cant easily be ID'd for disconnection an option to verify satisfactory IR is a global test with the incoming N isolated from the DB. Some frown on this method but they tend to be people who sit at keyboards passing judgement having never actually carried out an EICR in a real working environment.

This sounds like quality advice to me. Thanks wirepuller, I think you're on to it!
 
most interesting point is finding out that they have electrickery in chester. lol.
 
If you are getting a 0Mohm reading, then you then need to do a Low Ohm reading to find out exactly what the resistance is between the conductors.
With some experience, you can then take an educated guess as to what the link is between the 2 conductors - a neon, a PIR switch, a lamp etc.
If it is 0 ohms, then it will be a dead short, but you are getting a reading of less than a million ohms, so could be pretty much anything connected, or maybe nothing between the conductors (insulation breakdown).
Depending on your meters accuracy, the reading could be as high as 999,999 ohms, so further testing is required to find , or indicate, the true reading and cause.

may not be on an insulation test its a low insulation reading , if it was a dead short as has been said the Protective device would have operated , the problem is more likely to be a light thats not been disconnected or even water in a light fitting
 
As per usual, no actual figures.

I was under the impression that if a reading was <1MΩ the meter gave a reading in KΩ. I must be mistaken.

What I find annoying is the OP seems willing to condemn a system when he clearly hasn’t tested correctly.
 
As per usual, no actual figures.

I was under the impression that if a reading was <1MΩ the meter gave a reading in KΩ. I must be mistaken.

What I find annoying is the OP seems willing to condemn a system when he clearly hasn’t tested correctly.

Depends on the meter, on the 1720's we use if it's <1Mohm it shows 0.00 then you have to change the setting to continuity to measure the resistance

Loads of "sparks" are the same now though tony they just record whatever the meter tells them and move on, get the report out and condem an install which is still most likely in a serviceable condition
 
Depends on the meter, on the 1720's we use if it's


not me i passed

Tragic IR fail on EICR {filename} | ElectriciansForums.net
 
Last edited:
Loads of "sparks" are the same now though tony they just record whatever the meter tells them and move on, get the report out and condem an install which is still most likely in a serviceable condition

What are the chances of them knowing how to calculate the minimum IR value?
 
1MΩ is a convenient figure dreamed up by the IET. It’s not the calculated value.

I’ll give you a scenario:
If you were to test a 50 year old 75HP 433V 3Ph motor, what would you accept for the supply cable minimum IR for L→L and L→E?
 

Reply to Tragic IR fail on EICR in the Electrical Forum area at ElectriciansForums.net

OFFICIAL SPONSORS

Electrical Goods - Electrical Tools - Brand Names Electrician Courses Green Electrical Goods PCB Way Electrical Goods - Electrical Tools - Brand Names Pushfit Wire Connectors Electric Underfloor Heating Electrician Courses
These Official Forum Sponsors May Provide Discounts to Regular Forum Members - If you would like to sponsor us then CLICK HERE and post a thread with who you are, and we'll send you some stats etc

Electrical Forum

Welcome to the Electrical Forum at ElectriciansForums.net. The friendliest electrical forum online. General electrical questions and answers can be found in the electrical forum.
This website was designed, optimised and is hosted by Untold Media. Operating under the name Untold Media since 2001.
Back
Top
AdBlock Detected

We get it, advertisements are annoying!

Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website. For the best site experience please disable your AdBlocker.

I've Disabled AdBlock