Insulation resistance - strange readings

[Neon Vagabond]

Im getting some strange reading on a new circuit(ring main) ive installed and i was wondering if anyone else had experienced the following.

insulation resistance at 500v on L-N is >500mQ (which is fine)
then insulation resistance between N-E starts at 400 then climbs to 500mQ
then insulation resistance L-E starts at 210 then slowly rises to 500mQ with the button held in.

There are no appliances connected and no sockets have been fitted at this point of testing.

Test meter is fluke 1625c (calibrated in november)

Quite bamboozled on this one
surely a damaged cable would get a bad reading and the reading wouldnt climb up to >500MQ eventually?

 

[Pete999]

Any damp present?
Did you null the the leads before retesting?
Are there any poor connections, croc clips not making contact properly?

 

[westward10]

I don't see an issue.

 

[telectrix]

those readings are way up in the sky, so why are you concerned. probably breathing on the leads.

 

[buzzlightyear]

There are no appliances connected and no sockets have been fitted at this point of testing.

how are you testing ?

 

[Neon Vagabond]

its an open new build site so you could say maybe some damp.
but its a ring test so ive connected all the points together and then i have the two ends at the boards so i dont know if damp can effect them.

nah i didnt null the leads

think the clips should be fine but i will re-check on that one.

My biggest fear is that somewhere, somehow, when ive been pulling them through joists thats ive got burning on the cables but i did try to take care, not overloading holes etc

 

[westward10]

Delete.

 

[The Ghost]

Is it the climbing reading you are worried about?

 

[westward10]

Null leads on an IR test??

 

[stevethesparks]

More than likely capacitive reactance. As long as it climbs, no worries.

 

[Octopus]

Its well over minimum readings, record reading, move on ...........

 

[buzzlightyear]

 

[Neon Vagabond]

yeah probably right, i do love to panic

 

[buzzlightyear]

yeah probably right, i do love to panic

 

[The Ghost]

Mhmm that video has his earth out of the earth bus bar on IR test.

 

[Deleted member 26818]

Readings that climb as the button is held on are generally down to damp.

 

[Risteard]

Mhmm that video has his earth out of the earth bus bar on IR test.

Well spotted. The 17th Edition prohibited insulation resistance being tested this way.

 

[Risteard]

Mhmm that video has his earth out of the earth bus bar on IR test.

Well spotted. The 17th Edition prohibited insulation resistance being tested this way.

 

[Deleted member 26818]

Well spotted. The 17th Edition prohibited insulation resistance being tested this way.

Think you’ll have to back that statement up with a Reg. No.

 

[The Ghost]

surely readings climbing are the capacitive effect of wasting batteries on charging up a cable effectively no? And in lore, maybe damp being dried out?

 

[buzzlightyear]

you swear that I made that video of I/r testing ,risteard .

 

[The Ghost]

Check Regulation 612.3.1 It used to be done with the earth disconnected but there was a change and now it is required to have the earth connected to the bus bar. Can't remember the exact reasoning behind it.

 

[Risteard]

Aside from regs you want the earth connected for the "biggest bang" scenario.
P.S. check Regulation 612.3.1 It used to be done with the earth disconnected but there was a change and now it is required to have the earth connected to the bus bar. Can't remember the exact reasoning behind it.

Because there could be a fault to Earth that isn't to the cpc.

 

[Risteard]

you swear that I made that video of I/r testing ,risteard .

I never suggested that. I voted disagree because the information in the video is incorrect.

 

[Risteard]

Think you’ll have to back that statement up with a Reg. No.

Don't have Regs book on me until Monday. If you read the section about insulation resistance testing needless to say that's where the regulation is.

 

[Deleted member 26818]

Don't have Regs book on me until Monday. If you read the section about insulation resistance testing needless to say that's where the regulation is.

It’s as Vortigern says, 612.3.1.

 

[dksanders]

Any damp present?
Did you null the the leads before retesting?
Are there any poor connections, croc clips not making contact properly?

How do you null test leads for an insulation resistance test? Continuity sure, but IR? Neither my Robin nor Kewtech MFT have such a function.