What causes low IR readings?

[ppelec100]

Put it this way; if you had used a Megger 15xx, the ring circuit readings would have off the scale as it only goes up to 299M at 500v.
I've spent all day getting a circuit from 0.00M to 5M before now and gone home pretty happy!

Well when you put it like that

Thank you mate!

 

[PS Electrics]

Put it this way; if you had used a Megger 15xx, the ring circuit readings would have off the scale as it only goes up to 299M at 500v.
I've spent all day getting a circuit from 0.00M to 5M before now and gone home pretty happy!

Agree, the Dilog tester I have only goes up to 200M these readings are fine!

 

[KungFuTurkeyLeg]

Probably moisture and those are good readings. The scale of your MFT (assuming MFT) probably aren't helping your conscience. I have a couple of different Kewtech models, and sure one caps at >200 and the other >999 on the reading.

 

[DefyG]

Perfection is impossible and not worth the time investigating. 200-300Mohm on a switch cable is well within spec (according to BS7671) and I'm sure I and like many others on here would be happy with the measurement/reading.

 

[pc1966]

If you are seeing several 10Ms or more, and especially if it increases as you keep the test voltage on it, then I would not worry.

Edit: Look up "Polarisation Index" or "Dielectric Absorption Ratio" if you want some more info.

 

[timhoward]

I was at the other end of the results spectrum today.
As I was driving home I had a call from my "Mrs Richards from Fawlty Towers" lady, very deaf and not the simplest to work for. She lives alone in a large detached town house. Consumer unit is in "the cats room", I gave serious thought to bringing some 20mm conduit in to breathe through.
Anyway, right hand RCD wouldn't stay on. Quickly traced to socket circuit, 0.00M.
After shouting various questions and getting nothing very useful back I worked out which sockets were served, unplugged things one at a time, and unplugging an extension lead caused a leap to 27M. That will do for 6pm when she's made it very clear she's waiting to watch Wimbledon.
"Oh yes I was mowing the lawn when it happened". (nice of you to mention it afterwards)