Blank IR Test etc

[Traineeboy]

I’m just wanting to Clarify something. 
 

am I correct is thinking to do a blanket Insulation resistance test at 250v would help identify any possible issues before a board change is done. 
 

i.e if you link the neutral bar to the busbar then put one probe on neutral bar and one probe on earth bar. Testing L-N to Earth @ 250v this would  would give an indication if there could be issues. 
 

I assume that is you were to do the same but do a continuity test it would also show if there was continuity between L+N to E thus indicating if any earth wire is touching live conductors. This would be particularly useful if it is a non RCD board. 
 

Hope that makes sense and I am right in my thinking. Your thoughts. Please I don’t want direct answers and be spoon fed but just pointers or clarification. I am keen to learn. 
 

In all honesty my current placement isn’t great and will be looking to move but give the current situation it’s hard. 
 

thanks 

 

[boltonsparky]

Have a think about your test voltage. Also using this method can sometimes make the whole installation look like low IR because of how adding resistances work so splitting the installation is required if that's the case, it's that formula you may or may not have come across yet  1/RT= 1/R1 + 1/R2 + 1/R3 and so on. 

Guidance note 3 has all of this stuff in it so it's a worthwhile purchase. There's also an old book I have from around the time of the 16th edition that is very useful, yes things move on but the fundamentals of testing pretty much stay the same. ISBN 2-9524138-3-5

 

[Murdoch]

If an older style installation has an rcd fcu or a rcd socket these can give extremely low IR results so a quick IR doesn’t always tell you much.

a

 

[Phoenix]

If an older style installation has an rcd fcu or a rcd socket these can give extremely low IR results so a quick IR doesn’t always tell you much.

a

Yeah can be a right pain in the *** if you don't know its there (I have a big bugbear with folk, who in commericial put them in 'hidden' places--- yeah someone is totally going to unscrew this chipboard fascia and press test button every 6 months....)

if you know its there and press the trip button before turning the supply off, then most of the time it won't drag reading down