insulation resistance problem

[Havvy]

hello everyone,
i was testing today at a fairly new house built in the last 10years and i had a problem with the insulation resistance test on both up and down stairs lighting circuits. everyother test was fine on the circuits.
on the down stairs lighting circuit L/E and N/E wouldnt each greater then >299. hovering around the 150 mark.testing between L/N the tester read 0.00.
and on the upstairs circuit clear on L/E and N/E but 0.00 on the L/N
a little puzzled any help wanted.
thank you
craig

 

[Deleted member 26818]

What was still plugged in?

 

[Guest123]

Up and downstairs what????

 

[telectrix]

got to be measuring a load . either that or lenny's supermarket trolley

 

[Havvy]

lighting circuits my bad

 

[telectrix]

have you removed all the lamps? and what about dimmers?

 

[Havvy]

no dimmers in the house and removed every lamp

 

[Hawk81]

Sounds like you have left the lamps in. To do an ir test on a lighting circuit you need to remove all lamps. Or if there are flouresants you will get low readings even if the lamps are out. I am not sure what you mean about your live to neutral tests tho.

 

[nickblake]

As telectrix has said with the addition of fans and make sure youve disconnected the neutral from the bus bar to and be care full if your testing at 500 volts and some thing is still connected ie PIR or fans with timers you may well blow them up

 

[telectrix]

if there is any sensitive equipment that cannot be easily disconnected, then i would not IR test between L and N, but short L/N at CU and test to E.

 

[Havvy]

the test between live and neutral test the tester read a reading of 0.00 basically no reading. no wasnt testing at 500v start on the lowest 250v. all the lamps were removed. going back tomorrow so will have the fittinf down they were metal b and q fitting. would a smoke head mess with the results??

 

[telectrix]

yes. it has a finite resistance L/N

 

[Havvy]

cheers telectrix i will try that tomoorow thank you

 

[Havvy]

yes. it has a finite resistance L/N

i have a megger multi tester and normally on ir the reading on the screen always go round to >99.9/>299/>999

 

[telectrix]

anything left in across L/N, smokes, lamps, neons, dead rats,will give you naff results.

 

[tony mc]

Any fans or outside lights.

As everyone is saying you have something that is not disconnected,maybe loft light or hidden cupboard light with the lamps in.

 

[SimpleSimon]

Neon indicators is another. And like Tel said, if you can't disconnect short together L/N at the CU and test to E.

 

[malcolmsanford]

SELV Transformers

 

[telectrix]

Any fans or outside lights.

As everyone is saying you have something that is not disconnected,maybe loft light or hidden cupboard light with the lamps in.

loft light is a favorite. never think about it till head scratching time. also vanity lights, under cupboard lights, shaver points, all can f up your readings

 

[nickblake]

Out side PIR lights they always get me at the back of the house