Insulation resistance help

[schoe]

Hi all, just a quick question when doing an insulation resistance test on a 2 way lighting circuit do both switches have to be open at the same time to get a <500 m result, because when they are both open and both closed I get this result, but when one switch is open and the other is closed I get a Lower reading?

Also if I leave a fluorescent light connected but remove the bulb would this still affect the insulation resistance result?

Thanks very much Chris

 

[Des 56]

Are you following the set procedure for doing an insulation resistance test ?

Loads will affect the readings unless they are dis connected
With 2 way switching,they are not open or closed,they make on both poles

Welcome schoe to the forum
Just noticed you have been here for ages,but welcome anyway

 

[telectrix]

with 2 way switches you should test with each switch in either position. leaving the florrie connected will influence the reading, esp L/N.

 

[Guest123]

The IR test should be conducted with switches operated in both positions so as to include your strappers aswell.

 

[schoe]

Will it also affect N-E and L-E? Any suggestions as to why the 2 way switching results are lower when one switch is open and the other is closed?

 

[schoe]

I have been on the forum for a while but only no how to post a comment as a new member, I recognise all your names as you have offered me advice in the past, thank you. How do you post a comment without it saying I'm a new member every time? Thanks chris

 

[Guest123]

How do you post a comment without it saying I'm a new member every time? Thanks chris

Can you not start threads in any other forum section then???

P.S, I'll move this one.:coolgleamA:

 

[telectrix]

I have been on the forum for a while but only no how to post a comment as a new member, I recognise all your names as you have offered me advice in the past, thank you. How do you post a comment without it saying I'm a new member every time? Thanks chris

go to the approprate forum e.g. theories and regs. or testing etc. and post new thread.

 

[schoe]

Thank you just realised where you need to go to post a new thread. So back to the insulation resistance test, Will a insulation resistance also affect a florriebetween N-E and L-E if it isn't disconnected? Any suggestions as to why the 2 way switching results are lower when one switch is open and the other is closed?

 

[Deleted member 9648]

I'ts only really necessary to disconnect loads if you are testing L-N as clearly you will get a reading through the resistance of the load,not only will that give a misleading result it may damage the equipment.
The reading may vary on the two way because of a difference in IR when a load is switched in and out.....or because of a difference in IR when the strappers are switched in and out....what readings are you getting?

Edit...just noticed in the OP you seem to think a reading of >500 mohms is required.....in fact a reading >2mohms complies with the regs for a final circuit.

 

[schoe]

The readings I'm getting are 425 mega ohms rather than the 500 mega ohms on the fluke meter. Thanks

 

[nickblake]

The readings I'm getting are 425 mega ohms rather than the 500 mega ohms on the fluke meter. Thanks

In that case nothing to worry about tests can fluctuate picking up a neon etc as for the flourie short the L and N together and test to earth and mark on cert also if you are in doubt that there is a light etc connected test at 250 volts first a simple thing to to but could save the agro of damaging equipment , wire pullers post is top notch mate , nice to see you on here again

 

[MarkieSparkie]

Hi, welcome back to the forum Schoe.

 

[wade88]

My megger only goes as far as >299 Mohms. But rememember greater than 1 Mohm at 500v is a pass and 0.5Mohms at 250V SELV and PELV. Skin of its teeth pass mind you so advisable to investigate all the same, as there is obviously deteration somewhere.