Domestic IR testing . . .

Discuss IR testing . . . in the Electrical Forum area at ElectriciansForums.net

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doodarr

DIY
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36
Hi Guy's totally new to website.

Quick question. Doing a new install and the IR for N-E is 87.6 M ohms for first half of the split board. L-E & N-L are both >500 and the complete second half of the board is >500 for all results.
Could it possibly be how close the wires are in the CU giving a lower reading. I'm not worried and know all results pass regs but its just for my own satisfaction. :eek:
Thanks
 
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E

ezzzekiel

new install meaning just new board?
are you sure all items of equipment were unplugged, often something left in will pull n/e readings down slightly
 
OP
D

doodarr

DIY
Messages
36
Hi guy's.
No complete re-wire. Nothing at all plugged in as the CU doesn't have power yet. No damp plaster as all wires are surface mounted in trunking at the request of the customer..... (except in the loft where it is very neatly clipped)
 
OP
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doodarr

DIY
Messages
36
No condensation I can see or think where it could build up.
CU is not connected to power supply and wont be until week end so boiler and lights are still connected to old CU till then.
Just tested the 5 20A radials I put in with 2.5mm. All separate for each room so less than 20m run's each. The 3 on the second N bar are all >500 plus it's just the 2 on the first N bar which are lower......
Only thing I could think is how close the wires are in the CU (single insulation) and due to the nature of the board N & E wires on the first N bar are close when they pass but separate directions on the second N bar.
 
E

ezzzekiel

have you disconnected and tested seperately to see which circuit is pulling it down
 
J

JamesBrownLive

Only thing I could think is how close the wires are in the CU (single insulation) and due to the nature of the board N & E wires on the first N bar are close when they pass but separate directions on the second N bar.
I don't think how close they are is what is giving you the strange readings. If you look at T&E end on you will see the cpc is touching both L &N without anything inbetween anyway. If anything you could say that when the CPC from the circuit is terminated in the CU it has the additional protection (insulation) of sleeving.

What readings are you getting individually on the 2 dodgy neutrals in the first N bar?
 

ackbarthestar

Forum Mentor
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A lower IR than >whatever the maximum instrument range is, is quite common for older/installed circuits. It maybe that you have a filter fitted on a load, such as a PIR, somewhere and/or plaster and grit/spiders and the like have got in across the terminals of the switches. This will lower the IR.

Another test you could try is if you switched on all the lighting circuits, the loads connected and then measure the IR and continuity between the N-PE. and then the N-N between the two neutral bars.
 
J

JamesBrownLive

A lower IR than >whatever the maximum instrument range is, is quite common for older/installed circuits.
But its a brand new install that he has just put in, that's why the non maximum IR readings are puzzling.
 
OP
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doodarr

DIY
Messages
36
No havn't retested individual cuircuits as I didn't have time and it was just a quick check of the IR for 20A Radials and continuity test. Will check each individual one when I get back there. I know it's all above reg limits but was curious to why it wasn't perfect ha ha
 
B

BluSparx

No havn't retested individual cuircuits as I didn't have time and it was just a quick check of the IR for 20A Radials and continuity test. Will check each individual one when I get back there. I know it's all above reg limits but was curious to why it wasn't perfect ha ha
When you say you didn't have time ALL circuits should be checked before energising not just cutting corners to save time, otherwise how do you fill in your circuit test results FOR ALL CIRCUITS on your SCHEDULED OF TESTS. or do you just divide your overall reading by number of circuits to give you a rough idea.

If your not sure how to do IR results correctly and in full you should not be installing and testing
 
OP
D

doodarr

DIY
Messages
36
BluSparx,

The lights and bolier are not yet connected therefore I could only test the 20A Radials which were fully installed. They will be re-tested again at the weekend along with the rest of the tests for a full re-wire before energised and after lights and boiler have been connected to new CU.
I know how to test IR which is how I got the results . . my question was any idea's why the N-E IR was lower on the 1st bar than the 2nd when tested.
I also said I hadn't retested - as in disconnected everything on bar 1 and earth to check which MCB was dragging the IR down as was suggested on here.
Trying to get the results perfect and improve my knowledge thats all.
This was all explained in the previous posts.
 
B

BluSparx

BluSparx,

The lights and bolier are not yet connected therefore I could only test the 20A Radials which were fully installed. They will be re-tested again at the weekend along with the rest of the tests for a full re-wire before energised and after lights and boiler have been connected to new CU.
I know how to test IR which is how I got the results . . my question was any idea's why the N-E IR was lower on the 1st bar than the 2nd when tested.
I also said I hadn't retested - as in disconnected everything on bar 1 and earth to check which MCB was dragging the IR down as was suggested on here.
Trying to get the results perfect and improve my knowledge thats all.
This was all explained in the previous posts.
TBF I understand what your asking but as I said unless you test individually you would not be able to complete your test cert correctly. I get sick of seeing made up results on test certs that are so obvious it beggers belief.

If you had tested individually first your circuit dragging the readings down would have given you a clearer indication of where the problem lies, if all the circuits where fine then it could be a problem with a loose connection, the bar screws etc.

Also the questions that are asked on the forum from "sparks" sometimes makes me wonder how people managed to complete there courses and qualifications.

I aint having a pop at you but IR testing and identifying the cause for low readings should be pretty straight forward
 
OP
D

doodarr

DIY
Messages
36
It is straight forward. One ofthe easiest tests there is. I never make up results which is why I was annoyed that my results weren't >500.
just after some original ideas for any reasons why that could be before I go back. 2 heads is better than one etc.
That's what I thought the forum was for ****ing ideas about. I'm new so sorry if it isnt.
 

Richard

Electrician's Arms
Messages
558
Have you split the circuit?

I would test individually to Identify which circuit it is pulling down your value and check terminations. I'v had it before where insulated cables crushed in the backbox have brought down readings.

Rich
 

wirepuller

Forum Mentor
Messages
5,536
Location
south uk
TBF I understand what your asking but as I said unless you test individually you would not be able to complete your test cert correctly. I get sick of seeing made up results on test certs that are so obvious it beggers belief.

If you had tested individually first your circuit dragging the readings down would have given you a clearer indication of where the problem lies, if all the circuits where fine then it could be a problem with a loose connection, the bar screws etc.

Also the questions that are asked on the forum from "sparks" sometimes makes me wonder how people managed to complete there courses and qualifications.

I aint having a pop at you but IR testing and identifying the cause for low readings should be pretty straight forward
A tad harsh I feel...as far as I can see the OP knows how to carry out IR tests and knows what results to expect...he has not claimed to be an expert and is clearly trying to improve his testing knowledge...nothing wrong with that as far as I can see.
 

telectrix

Scouser and Proud.
Respected Member
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Location
cheshire/staffordshire
agree there , wp, OP is part way through his testing, if i read his posts correctly and has come across a lower than expected reading. this could be ,as previously suggested, a squashed cable , or even a socket face that has been exposed to moisture prior to fitting.
 
E

ezzzekiel

its a pass but if you really need to know then you will need to test circuits seperately until you find the low circuit and trace it from there.
 
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