Insulation resistance tests

[lyledunn]

I carried out an IR test on a single phase 250v circuit in an office building as part of a routine inspection. The tester outputs 500v dc. I thought I had been careful to ensure that the circuit was clear of any equipment vunerable to the test. Turns out that I may have damaged an expensive scene set lighting dimmer control which was hidden away in a locked cupboard. Any way, I also made sure that I had bonded phase and neutral of this circuit and tested between these two conductors bonded together and earth. Can someone shed some light on exactly how I may have caused this alleged damage? Regards,

Lyledunn

 

[sparky001]

Lyledunn,

You have by your description applied a potential of 500vdc to the dimmer which is designed to operate on a supply of 250vac.hence dimmer goes bang!!

 

[lyledunn]

Thank you Sparky, really not the answer I was looking for. I am well aware of the consequences of IR testing hence the caution in my test routine. I was hoping to engage some debate about the responsibilities manufacturers might have as well as perhaps finding out just what may have been damaged!
Thank you any way. Regards,

Lyledunn

 

[briand2]

lyledunn,

I believe you have a right to be upset!

Here in the UK (where the single phase mains voltage is a nominal 230 V), we generally test for insulation resistance at an applied potential of 500 Vdc (on IT equipment, for instance). As you have stated, we would of course tie the Line and Neutral together for the test. We do not expect equipment to fail such an insulation resistance test unless it is defective. (In general, we would not do a "Flash Test" (applied potential 1.5 to 3 kV rms) unless requested to do so by the client.)

My view is that if the piece of equipment that you tested failed under the test you described, then that is good; it is better to fail under a controlled test by competent personnel than to fail at some other time!!

Regards,

Brian