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Posted By Topic: Insulation resistance test - existing mains

Apr 11 2018 19:40

Hey guys,

Usually complete new homes and therefore complete all my test before anything is hooked up to any gear.

Got a question, existing home, im upgrading the switchboard, remove MEN links that i can find, insulation resistance test each seperate conductor P-N N-E P-E, result is coming back that they are all connected somewhere

Is this due to the transformer / sub station upline that affects the result?

All i have done is remove MEN links and main fuse.

Spent about two hours looking for something that i had missed but now im stumpped.

Thanks for the help.

Apr 11 2018 20:06

You have taking the tails out of the revenue meter eh?

Apr 11 2018 20:11

Just what I was thinking

load meter

Apr 11 2018 20:37

Ah. I was thinking that!

Cutting the tails and then lugging back together (dont have to open up meter and lines company have a meltdown).

Didnt seem right, thought if there was this massive fault, y the fuse didnt trip.

Double guessing yourself is a b*$!h

Apr 11 2018 20:51

Have you remembered to takr out all the light bulbs and disconnected all fixed wired equipment (use adjacent control switch is usually OK).

Protective Earths may connected to earth via matallic water pipes.

Apr 11 2018 21:17

Yehp i unplug all appliances, light bulbs microwave etc before testing.

Although... i have seen a diagram( proabably in testing parts of wiring rules(will read up again tonight)) that you bypass rcds, and test between neutral+phase and earth and you can leave things pluged in?

This is of course, testing on the load side of the board

Has anyone ever fried something?