phase and nutral to earth insulation test

[tom1]

am i right in thinking if i do insulation test with phase and nutral to earth i wont damage anything like transformers, heating clocks or anything left plugged in

 

[kme]

IF everything is correctly connected / wired, yes. UNLESS:

An item is plugged into a 13A S/O, which is switched off. As phase is isolated, you`re effectively testing that item N-E, which COULD have issues.

Best way to check if anything is still plugged in is to do an initial L-N test at 250V or lower. If you have a low reading (you may need to switch to continuity range to get a usable reading (i.e. <2K). There is a grey area in between (2K-500K), where a standard multimeter can be more useful.

Once you`ve identified and disconnected any loads shown at this point, you can up the test voltage to 500V

HTH

KME

 

[tom1]

this i what i posted last night on another thread

so best way is to test on 250v, low readings <.5 M

check everything is disconected and retest. if still low

test on 500v but phase + nutral to earth if still low then cable fails, if high >50 M then cable pass and there is prob a pendent with bulb hidden in the loft.

so this way cables are tested and any sensertive equipment including selv and fluresent control, dimmers is left undamaged???

and this is not correct becuse if a single pole socket is off it would do nutral to earth on plugged in appliance and could bugger it

 

[kme]

If still low on 250, no point testing at 500, because the reading can only get worse! You need to find any loads (another way can be to energise if this is a PIR ONLY, and check for drawn power)

You need to identify all loads, to verify that local isolation is available for that item. further, if there is a P-N leak, your test won`t find it. i.e. in a JB, or bad termination.

Dimmer switches & PIR units are the most easily damaged at 500V, other than plasma TVs (but that`s another story!). Confirm local isolation for the PIRs, and short out the dimmers, then there`ll be no issues. I always ask the householder to disconnect all their appliances, in advance. That way, if you`ve explained why, they are responsible for any damage caused by the testing, not you.

KME