Unsafe Insulation Resistance testing?

[wizards-sleeve]

In what circumstances is IR testing phase to earth, neutral to earth unsafe?
To avoid any possible damage to any circuits should I only test to earth with phase and neutral connected together
Any help would be appreciated on this

 

[DESL]

Schedule of tests requires P-N & P-E IR test however where vulnerable equipment is connected then PN-E is done and note on form.

ELV lighting, CH programmers, aerial amps, dimmers to name a few vulnerable bits of kit.

 

[wizards-sleeve]

So where vulnerable equipment is present N-E, P-E is not safe?
Is it better practice (safer) to conduct PN together to E
Can IR testing P-E, N-E cause damage, is it unsafe?
I was always under the impression it was perfectly safe

 

[Albert]

I know that the requirements are to test with 500V, but when I do IR I start with 250V, if this is ok (on my meter a 200Mohm) I will test with 500V as not every circuit has sensitive accessories. If the result is too low, I will test L+N to earth and make a note in the cert.

 

[wizards-sleeve]

I do the same test at 250V and then 500V if all clear. However I am still uncertain how IR N-E, P-E can cause damage?

 

[Albert]

I do the same test at 250V and then 500V if all clear. However I am still uncertain how IR N-E, P-E can cause damage?

I think that the L-N can cause damage, as far as I understand L or N to E should not cause damage...

 

[bernardgreen]

Can IR testing P-E, N-E cause damage, is it unsafe?
I was always under the impression it was perfectly safe

Cases of equipment and filtered sockets left connected and the input filters ( surge suppressors phase to ground and neutral to ground ) being damaged by the 500 volt test. They will absorb the small amount of energy from a transient spike much greater greater that 400 volts ( or there abouts ) but cannot absorb the prolonged energy at 500 volts supplied by the test instrument. They burn out, appear normal but cannot absorb spikes later and the equipment they are intended to protect is no longer protected.

 

[Adam_151]

Schedule of tests requires P-N & P-E IR test

Its not just phase you have to test to earth...

Remember neutral is a live conductor and teh schedule says live/live and live/earth