L&N-E IR Test (and we still haven't fixed the stupid 20 characters)

[hightower]

When you do a L&N-E IR test, is there anything (other than a fault) that could be left plugged in that would produce a low reading?

 

[telectrix]

surge protection?

 

[hightower]

surge protection?

I'm not asking for a particular scenario, like I'm not having issues. Just wondering if there's any predicament that could cause a L&N-E IR test to cause a low reading and stick that knowledge in the back of my head somewhere.

I guess with surge protection, it would show on a 500V test but wouldn't show (or show to the same degree) on a 250V test?

Anything else?

 

[telectrix]

IT equipment. computers are renown for having small earth leakage.typically around 3mA apiece. that's why you never put too many on a circuit with RCD protection.

 

[hightower]

IT equipment. computers are renown for having small earth leakage.typically around 3mA apiece. that's why you never put too many on a circuit with RCD protection.

See what I'm trying to understand is that the regs says it's okay to tie L&N together and test to earth when vulnerable equipment is on the circuit - so what would be the point of that if they give false results

 

[Pat H]

I had a socket outlet RCD in a RFC give me low readings. Likewise a shaver point.

 

[Octopus]

Deffo RCD's, pumps, pretty much anything....

 

[hightower]

So what's the point in doing L&N-E if you're just going to get false results still?

 

[PEG]

Always remember,that the test you describe,is a way round doing the correct,full test

 

[Octopus]

^^ otherwise known as cutting corners

 

[hightower]

Well no, it's not necessarily a way of cutting corners. The regs describe the test, but my question is what benefit does it bring if the results are still going to be influenced by equipment

 

[Octopus]

If somebody does L + N to earth and they fill out the cert as 100 m ohms I begin to doubt the test results

 

[hightower]

OK, the scenario where I'd imagine using this is not for an EIC but maybe to do a quick global IR to make sure an RCD will hold - obviously this will then have a full test but I'm thinking just a quick way to find out if it should generally be OK

 

[Bobster]

Because the results are most likely going to be worse than if you split test with all loads disconnected. Thus if it passes with results that are going to be pulled down by equipment it stands to reason that the circuit is serviceable and without loads, be in better standing.

 

[LankyWill]

Its a handy method for EICRs when you either cant disconnect everything, or are unsure of any loads that are connected without your knowledge.