IR testing . . .

[doodarr]

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.
Thanks

 

[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

 

[trev]

A bit of slightly damp plaster on the terminals maybe?

 

[doodarr]

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)

 

[trev]

Condensation?

 

[Deleted member 19807]

is there not a boiler or heating controls connected?

 

[doodarr]

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.

 

[ezzzekiel]

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

 

[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]

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.

 

[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.

 

[ackbarthestar]

But its a brand new install that he has just put in, that's why the non maximum IR readings are puzzling.

Having reread this there is a possibility that you maybe correct However, bits of c**p across the terminals will have a similar effect.

 

[doodarr]

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

 

[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

 

[doodarr]

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.