Insulation Resistance testing

[johnnyjb]

I know your meant to disconnect electronic devices from circuit when performing an insulation resistance test. But if you only do a L+N to earth test will this not damage any electronics in the circuit. I am thinking that there is no potential across the live neutral so there will not be damage. If so would the test voltage matter.

Thanks

 

[RF Lighting]

There is still a risk of damage to things like computers due to some filters in their power supplies which are connected to earth. (this is what produces the high CPC currents, and why high integrity earthing is required for computer supplies)

I can't think of a time when you would need to / want to IR test a circuit with computers still connected. I certainly wouldn't want to risk it.

 

[johnnyjb]

Thanks ,I know what your saying i would plug out any obvious appliances that are visible. Im not asking out of laziness but im worried about electronics that are not known to be connected or that have no isolation or its impractical to disconnect. Aside from the computers you mentioned would there be a problem RF

 

[JACKC]

PIR's, dimmer switches and burglar alarms etc contain electronic components and do not like 500v up em, many use the earth as a reference voltage, that is why you disconnect. The test voltage is important as its in the regs and thats that I'm afraid. You can always leave connected and turn the controlling switch off, marking your test sheet as "tested to local isolaton point". It depends on how easy it is to disconnect.

 

[lazygit]

im worried about electronics that are not known to be connected

Always a good idea to test at 250 first, just to show up any loads.
If your tester doesnt have a 250V setting then do a continuity test between conductors to confirm there are no loads present.
Regards

 

[dingodeano]

If you test from the meter tails at an installation will 500v kill rcds too?

 

[Spark123]

It can kill electronic RCDs, the type often found in RCBOs and SRCDs (sockets with RCD built in), RCD FCUs etc etc. These are normally supplied with a label to attach to the consumer unit warning they should be disconnected before doing IR test.
The bog standard old type RCD which does not have any electronics isn't a problem.