Insulation resistance test on new circuit

[SPARTYKUS]

moddeydhoo

as I said, not high enough for me, for a new circuit. Different when reporting on an existing install. It also says just below your quoted reg

"Insulation resistance values are usually much higher than those of Table 61"


Regulations are that, regulations. In effect a guide. The values in Table 61 are the minimum. If they are that low or lower than the infinite reading on your Megger / Fluke / Robin / whatever then ... there is a reason!

the other point I was trying to make to the OP was that it is better to find the fact for the low reading rather than just hoping it will be ok! Facts are good with electrical installations. Guessing is not

 

[AndyL]

1Meg with all final circuits connected, so lots of resistors in parallel

 

[moddeydhoo]

I have been testing for years and years, 1 meg ohm, i would take a look for damp or damage on a circuit, simple to brerak down, and test, over 2 would not waste my time, stick it to 10o0v and test 99 times out of 100 the ohms will rise, damp.

 

[ferg]

I've always worked on the principle that it's better to track down the cause of unexpected readings. Even if the only thing it does is satisfy my curiosity and improve my knowledge.

If it turned out to be a crushed/damaged cable better to deal with it now than later.

Joiners have a terrible habit of trapping cables when putting up plasterboard etc.

 

[somersetsparks]

Id just be happy with 50 Million Ohms an anomaly but something you could easily waste hours to no avail on, still 50x better then the minimum!

 

[ferg]

50 million ohms is a huge number but another way of looking at it is less than 10% of the expected result.

 

[somersetsparks]

In the words of whitney houston 'its not right but its okay'

 

[Engineer54]

On any NEW installation that is having it's first or initial recorded circuit IR tests, then you should always be testing for at least a 1 minute duration. Those lower than expected values will almost certainly be due to the surrounding damp conditions. Another very good reason to take 1 minute IR readings rather than the usual few seconds....

 

[electric will]

In the words of whitney houston 'its not right but its okay'

that theory didn't work very well for her though did it?

 

[ExArmy]

i've come accross this too, and after much consideration I just put it down on the cert. last month i done one and all circuits were around 100M and rising L+N - E but it was just plastered that day so what can you expect.

 

[SPARTYKUS]

on newly installed wiring 2 meg is certainly not acceptable.
but 50 meg on newly plastered walls is pretty good and will certainly climb after a drying period.
liking the new avatar sparty.

thanks

 

[bigbaddave]

2m on a new build and your happy... Mmm ok bud me thinks not. I appreciate its a pass in the regs but in my opinion there's is a reason in which why its low and with that reading would spend a little time investigating the fault.

 

[SYKRAPS]

I have been testing for years and years, 1 meg ohm, i would take a look for damp or damage on a circuit, simple to brerak down, and test, over 2 would not waste my time, stick it to 10o0v and test 99 times out of 100 the ohms will rise, damp.

Why test at 1000v?

 

[SPARTYKUS]

Why test at 1000v?

It increases the incidence of temperatures.

 

[SYKRAPS]

It increases the incidence of temperatures.

But testing at 1000v gives poorer readings and is not required

 

[SPARTYKUS]

Sorry I was being an idiot... Agree its not required.