Insulation Resistance testing method

[Bobby34]

Good afternoon, apologies if this has been covered before i've not long joined so gradually finding my way around.

I have my Part P assessment coming up on a new installation and would like to hear some opinions on how people carry out their IR tests.

In guidance note 3 it gives an example of testing the whole installation in one go (having removed sensitive equipment) using the line at the main switch (repeating the process for 2 way lighting)

My question is what are peoples thoughts on the MCB's and RCD's because unless i'm missing something glaringly obvious don't they need to be up so the voltage then passes through the MCB's and RCD's into the circuits? and if so would doing it like that potentially damage them?

I'm thinking to use the Line at the top of each mcb in turn for the assessment but not sure if thats being over cautious?

Any opinions/thoughts/experience would be much appreciated.

 

[Harry_P]

Thanks for the reply, that makes sense, a bit of both, glad you mentioned the assessor was happy thats what I want to make sure really that I don't do something thats out and out wrong

If you get into the habit of following GN3 to the letter you won't do anything wrong. Take the book on site if you can't remember the procedure in GN3 but just get into the habit of doing it exactly as it says

 

[DPG]

If you get into the habit of following GN3 to the letter you won't do anything wrong. Take the book on site if you can't remember the procedure in GN3 but just get into the habit of doing it exactly as it says

But also ensure you understand why you are doing it like that.

 

[Bobby34]

If you get into the habit of following GN3 to the letter you won't do anything wrong. Take the book on site if you can't remember the procedure in GN3 but just get into the habit of doing it exactly as it says

Yea I don't plan to guess anything for a while so anything i'm not 100% sure on I like to try and clarify, like this thread, it seems that either is ok to do but yes il ceetainly be a book worm for a while haha

 

[Harry_P]

Thanks for the reply, that makes sense, a bit of both, glad you mentioned the assessor was happy thats what I want to make sure really that I don't do something thats out and out wrong

If you get into the habit of following GN3 to the letter you won't do anything wrong. Take the book on site if you can't remember the procedure in GN3 but just get into the habit of doing it exactly as it says

Thanks, so testing globally doesn't dame the mcbs etc?

live and neutral connected together tested to earth will make sure you don't damage electronics etc,Also test at 250 v first so if there is a problem you can investigate before you give it the full 500 v

 

[Harry_P]

Yea I don't plan to guess anything for a while so anything i'm not 100% sure on I like to try and clarify, like this thread, it seems that either is ok to do but yes il ceetainly be a book worm for a while haha

I would recommend you build yourself a test unit , get a bit of plywood, get an old consumer unit and wire up at least 2 circuits in it,maybe a socket and a light but do not connect it to a live supply because you will only be doing dead testing.
It will help you to get your head round insulaion resistance testing and especially the difference between global and individual testing,that is the way to get it to sink into your head how it works