Alarms when IR testing

[lilman]

When testing IR with L/N connected to earth - would an intruder alarm affect the reading? I presume so. Testing today and discovered an alarm setup with no visible isolation/FCU and didn't want to mess with alarm. Reading of 0.00.

 

[Revved Up Sparky]

Yes it definitely would affect the reading. I would declare a limitation "unable to carry out 500v IR test as load could not be disconnected"... and enter an observation regarding the lack of local isolation.

 

[Andy™]

you should get a decent reading L&N to E, just like everything else, but best test on 250

 

[lilman]

[quote name='Andy

 

[Andy™]

definately

at that reading, i would expect RCD's to trip

also, if its 0.00, you may get a better reading on continuity between L to E and N to E

 

[Lurch]

Not neccesarily a fault, could be the mains in the panel has filtering which would cause low IR readings. Unless you can isolate the alarm then I'd mark it as a limitation. Assuming you have already had the power off to the alarm with no ill effects would it be possible for you to install a spur i the existing cable so you can test up to that?

 

[Andy™]

or take the cover off the alarm and see if there is anything between live & earth?

 

[Lurch]

[quote name='Andy

 

[Andy™]

depends on the alarm - if its something like an veritas 8 and you have the engineer code, then go ahead (but i can tell you this alarm has nothing connected to earth!)

 

[Lurch]

[quote name='Andy

 

[Andy™]

Well yes, unlikely to be a problem on something like that but still, if you don;t do alarms, don;t touch it. Not by default, but a lot of alarms I have fitted do have surge suppression across the mains.

im not saying that some dont, im just saying a veritas 8 doesnt!

 

[Lurch]

[quote name='Andy

 

[Revved Up Sparky]

The purpose of an insulation resistance test (at least for a PIR or EIC) is to test the insulation of the fixed installation, not the loads connected to it - which strictly speaking, are not part of the installation. If there is no point of local isolation and you cannot open the panel to disconnect the supply then, as I said earlier, you need to declare a limitation as by measuring the IR of the supply + load you will be recording a false reading.