Insulation Resistance testing

[thomo27]

Morning all

IR tests arghh im practicing at home but also trying to find a fault that keeps tripping the RCD

Up and downstairs ring , cooker , SWA to the dettached garage are the circuits on the RCD side

Ph&N - E for all circuits gives me high readings which Im happy with

N-E as above

P-N for the Cooker and Garage as above

P-N for the rings 0.00 !!!

Nothing plugged in im sure of it , when you do these connections do you put the lead on both P and the other lead on both N or do you put them in connector block and stuck your probes in ? My test leads aren't fused so ive never thought of doing it that way Ive always put the croc clips on the cable and let go then put the 500V through the system

[batty]

Hello thomo
You still have something plugged in somewhere. Nusaince tripping could be caused by cooker. Try keeping it switched off to see if Rcd trips out.
batty

[thomo27]

Hi Batty

How do you do your connections for the IR tests on a ring ?

I have triple checked nothing is plugged in ?

Perfect IR results on the cooker .

If something was plugged in would get 0 or just a lower reading , i know that all major appliances i..e wash machine , cooker etc are off.

[Mr Sworld]

Have you got any neon indicators on the circuit?

[batty]

When testing insulation resistance on a ring you take the two live conductors and the two neutral conductors and test resistance between them. I thought you said you got zero meaning that something is plugged in.
batty

[thomo27]

Hi Batty

Im adament there is nothing plugged in and no FCU's on , when I test the up and downstairs ring between P-N I get 0.00

I understand that you test between the 2 P and the 2 N conductors just wondering if you use the croc clips on the leads to connect onto the copper or whether u put the cable ends in connector block

[batty]

It makes no difference either way if you are getting zero between phase and neutral i would think something is connected somewere. you don't have a tv booster in loft do you.
batty

[Theorysparky]

Thomo

just a thought...have you done continuity tests on the ring ???

if you are sure everything is disconnected then you could be looking at a faulty socket

[seajayess]

The P-N 00.00 reading wouldn't cause the tripping as RCD monitors P-CPC faults. Have you got a socket with an inbuilt RCD, if not I recon somthing is still plugged in, because with a reading like that if it was a true P-N fault the protective device would operate when the supply was conected.:8}

[thomo27]

RCD also monitors N-E faults as when an MCB is off and the RCD trips it cant rule out that circuit as the leakage current can come from the N ;)

The protective device is the RCD which is tripping.

[thomo27]

Thomo

just a thought...have you done continuity tests on the ring ???

if you are sure everything is disconnected then you could be looking at a faulty socket

Hi

Yeah continuity was present throughout , oh bother , just wait until we start doing 17th edition installations even more circuits on an RCD unless people go down the expensive RCBO route:)

[thomo27]

The P-N 00.00 reading wouldn't cause the tripping as RCD monitors P-CPC faults. Have you got a socket with an inbuilt RCD, if not I recon somthing is still plugged in, because with a reading like that if it was a true P-N fault the protective device would operate when the supply was conected.:8}

No sockets with an RCD , Im gonna have another look next week , cheers for your suggestions/advice

[seajayess]

RCD also monitors N-E faults as when an MCB is off and the RCD trips it cant rule out that circuit as the leakage current can come from the N ;)

The protective device is the RCD which is tripping.

Yes know RCD monitors N-E faults just stating it would only detect faults to earth, and with a P-N fault the protective device RCD would not operate :D CJS

[seajayess]

What type of conection is it ie. TNCS and is the main isolator off. If TNCS and main isolator still closed could be P-E fault but conecting through N-E PEN conductor just a thought CJS

[kme]

Just a thought. Connect up to do Ins. test, but ACTUALLY do low. impedance test (i.e. continuity.) If there is a load of any size, it should read on there ( <=2K ).

Follow me??

Lets sort out this issue with the ring first, then look for the RCD problem.

[cheggers]

No sockets with an RCD , Im gonna have another look next week , cheers for your suggestions/advice

I thought you said that you were testing at home aren't you home for the week

Morning all

IR tests arghh im practicing at home but also trying to find a fault that keeps tripping the RCD

Up and downstairs ring , cooker , SWA to the dettached garage are the circuits on the RCD side

Ph&N - E for all circuits gives me high readings which Im happy with

N-E as above

P-N for the Cooker and Garage as above

P-N for the rings 0.00 !!!

Nothing plugged in im sure of it , when you do these connections do you put the lead on both P and the other lead on both N or do you put them in connector block and stuck your probes in ? My test leads aren't fused so ive never thought of doing it that way Ive always put the croc clips on the cable and let go then put the 500V through the system

[kme]

Sorry mate - don`t understand your post there???

[thomo27]

[QUOTE=cheggers;13573]I thought you said that you were testing at home aren't you home for the week

I work 4 days on 4 days off 8-8 so my post was on my last day off

[kme]

To return to the original question (and my comment on it..........):

Have you taken a purely resistive reading, to ascertain the ACTUAL resistance?

If so, what was the result??

[thomo27]

Hi KME when you ask 'Have you taken a purely resistive reading, to ascertain the ACTUAL resistance?

If so, what was the result??

Am I right in saying you are refering to continuity results ?

If so Yes I have done continuity tests and the results were between 0.1-0.2 I cant remember the exact figure though but they didn't alarm me.

Im not going to be able to test for another weeks or so now , however I will give it another go and come back to the thread.


KME you also asked 'Just a thought. Connect up to do Ins. test, but ACTUALLY do low. impedance test (i.e. continuity.) If there is a load of any size, it should read on there ( <=2K ).

Follow me??'

Is this in the same way as you would link an outgoing p/n to an incoming p/n and then take a reading from the remaining p/n 's

[SPECIAL LOCATION]

Hello Thomo27...

I am just going to add my observations onto this thread a bit as-well..
Just been reading through... one or two bits still need confirming bit to open ended and as KME quite rightly said earlier..
for the moment ignore the RCD ("problem")

Verify the ring circuit readings are all acceptable first..
or you will be doin a wee-wee in the wind (as they say!!)

You question the difference between Ins Res on Rings / Radials.
Fundamentally there is no difference, other than that the far end of the circuit comes back to the CU.

When you have done you're tests are ALL of the conductors disconnected from the CU?

i.e. you have two T&E cables loose at the CU, six conductors,
2 x live
2 x neutral
2 x earth.

Personally I would step back and re-test all your readings again..
with cables open as above

1/
verify continuity, L-L, N-N, & E-E.

2/
check there are no parallel paths back to the CU bus-bars.
Switch whole installation OFF (main switch),

with Low Resistance meter
go through and test each of your L, N, E cable ends
for any direct continuity back to the CU L, N & E bus-bars?

do the same again with Ins Res to verify No high res path.


3/
With one end of your ring cable all open circuit, (not touching anything),
with meter still on low resistance scale.. and using other end of ring cable
check for any direct path between, L-E, N-E & L-N.

Then check the above again with Insulation res tester..

EVERY SINGLE ONE OF THE ABOVE TEST READINGS SHOULD BE HIGH OR OFF THE SCALE!!!

Note any low readings and tell us what you got??

[kme]

Hi KME when you ask 'Have you taken a purely resistive reading, to ascertain the ACTUAL resistance?

If so, what was the result??

Am I right in saying you are refering to continuity results ?

If so Yes I have done continuity tests and the results were between 0.1-0.2 I cant remember the exact figure though but they didn't alarm me.

Im not going to be able to test for another weeks or so now , however I will give it another go and come back to the thread.


KME you also asked 'Just a thought. Connect up to do Ins. test, but ACTUALLY do low. impedance test (i.e. continuity.) If there is a load of any size, it should read on there ( <=2K ).

Follow me??'

Is this in the same way as you would link an outgoing p/n to an incoming p/n and then take a reading from the remaining p/n 's


No, it isn`t mate. Basically, I was asking the same question both times.........

disconnect the ring from the C.U, and seperate all the ends (2 of each P/N/E.)
From your post, I understand your insulation readings P/N are 0.00.

Which, as your meter is looking at Megohms, means "less than 10K ohms". It DOESN`T mean 0.00 ohms. So, do an "insulation test" with a low resistance meter (0-2000 ohms). You`ll either get a reading of the EXACT resistance on the circuit; or an over-range indication. If its over range, use a multimeter, which will bridge the "gap" in resistance measurement, from 2K-10K. Again, you`re taking a resitance between P & N, at ONE end of the ring, while the other end is completely "open-circuit".


NOW do you know what I mean???:|