IR testing result

[Mattyi26]

Hi all,

I have come across an issue that i know others would have.....

I done an Insulation resistance test on a lighting circuit with no selv or pelv just regular pendants circuit. Now the customer informed me they had a leak from a bathroom a few months ago and when i tested this particular circuit my first result came out at 0.4 mega ohms at 250v (method 2).

Now i know this could be down to the water damage or something in circuit electrictronic etc so i took another 3 readings at once and the readings went up by 0.2 each time so i thought id try and see if i could get to 4 mega ohms.
After about 20 tests i could achieve over 4 on L-E and over 5 on N-E on 500v method 2.
I must be drying out any damp in the cable when doing each test but leaving for half an hour the next result went down to 2.5 and 3.0 respectively.
Now customers leak has been "fixed" by plumber but the circuit must still have an issue.
How can i make sure its all ok without ripping up the floorboards and replacing the circuit cabelling affected, could i just keep doing the test like above?
Any help much appricated.

Thanks

Matt

 

[The Ghost]

I think its kinda tricky to answer this as there are so many unknowns. But it is clear a reading such as you have will require FI. Even if that means taking up floorboards. Can you get an inspection camera in there ? The reading going up is really just your battery wasting away charging up the circuit.

 

[Wilko]

Hi Matt, yes - what V said. If you want to start digging - I've seen some nasty cabling at top o pendants, partic if it's an older instal and someone has added a timer fan and then loose insulation and dirt (and then water...). So is there a pendant beneath the bathroom that might have been water affected? Remember to safe isolate

 

[HandySparks]

... and replacing the circuit cabelling ...

The fault is much more likely to be at a light or junction box than in the cable (unless it has been damaged, exposing the conductors).

 

[Richard Burns]

As handysparks says the fault is likely to be at a cable connection, because the insulation is removed at that point and water can collect.
Taking down each light fitting and ensuring you have inspected all the cable joints, remembering that it would have to be a thin film of water for this sort of result, should eliminate most of the problems, the next part would be discovering if there are junction boxes in the above ceiling space. Your inspection of the lights should have given you a clue as you would know the wiring method and the expected number of cables. If there are junction boxes then this is down to taking up floor boards.

 

[westward10]

If is has risen from 0.4 Meg to 4.0 Meg I wouldn't be looking too hard. When was the leak rectified.

 

[westward10]

Do you know the IR before the leak occurred.

 

[PEG]

With an older install,or other influences,such as water,an actual physical inspection is always a good move.

The raise in readings from a fail to a pass,does not infer confidence,as it is only a limited spread.

I have had excellent readings,far in excess of the OP's,and then a visual discovers large sections of missing insulation,on VIR,with bare conductors strung like telegraph wires...

As with all test and inspect,one set of readings or sightings,are only part of the picture.

 

[westward10]

With an older install,or other influences,such as water,an actual physical inspection is always a good move.

The raise in readings from a fail to a pass,does not infer confidence,as it is only a limited spread.

I have had excellent readings,far in excess of the OP's,and then a visual discovers large sections of missing insulation,on VIR,with bare conductors strung like telegraph wires...

As with all test and inspect,one set of readings or sightings,are only part of the picture.

We have no idea the age of the ops installation.

 

[PEG]

Hi,which is why i included an "or" in my first sentence

As with most of these conundrums,all missing history and information,makes it very hard to make accurate assessments.
I feel my last sentence is correct,even with NO information.

The crux of my witterings,was aimed at not assuming repeated testing was "curing" any issues,and to investigate what they could be.

I also,am very aware of the cost/time/inconvenience constraints,placed upon sparks,by the great british public...a restriction i have not,and would not endure

 

[westward10]

Hi,which is why i included an "or" in my first sentence

As with most of these conundrums,all missing history and information,makes it very hard to make accurate assessments.
I feel my last sentence is correct,even with NO information.

The crux of my witterings,was aimed at not assuming repeated testing was "curing" any issues,and to investigate what they could be.

I also,am very aware of the cost/time/inconvenience constraints,placed upon sparks,by the great british public...a restriction i have not,and would not endure

Am agreeing here but the op maybe chasing shadows as the IR before the leak isn't known. I would give it a few weeks then retry it.