Low Insulation Resistance Readings

[danielspencer]

Hi there,

I have a customer that wants some lights fitted to an existing circuit.

When doing some preliminary testing on the insulation resistance for the circuit, I was getting strange readings. Line/Earth & Neutral/Earth were well over 500Mohms. When testing Line/Neutral, I was getting only 0.5Mohms. Line/Neutral connected together and tested to Earth are also well over 500Mohms.

Some of the lamps are really awkward to get to, and the customer would prefer it if I try not to remove them. I decided to carry out the test with all the local switches in the OFF position.

As far as I can make out all the light fittings are BC with no low energy or SELV fittings in sight.

I know I don't strictly have to carry out and record this test, but if anyone has any ideas why the Line/Neutral reading is so low, I would appreciate the input.

Many thanks

 

[Spudnik]

If L/N is low then there is possibly a PIR sensor or something else, un-isolated on the circuit somewhere.

Thats why your L/N - E readings are clear.

 

[kkc35348]

Could it be a neon indicator in a switch somewhere? - often found in the double pole switch controlling outside lights.