Ir Testing Advice

[Mattyi26]

Hello all,

Hope you all enjoyed your bank holiday!
I have a question that i know someone can give me the answer to.
So to keep this short i basically have a lighting circuit with 3 street lights via a time clock.
Circuit goes >3 phase DB> 10amp C type Mcb > time clock > 1,2,3 street lights.
I am currently doing a EICR on this property which has this circuit on and when i have come to IR this circuit the readings i got where 0.08 or there abouts doing method 2 linking L/N. These street lights i believe have sodium lamps in and are too high up for a ladder to access so difficult to judge without a cost of cherry picker or the like. These 3 street lamps are approx 15 years old.
So basically is the reading due to lamps? Or is there something im missing inside the street pole that i should be linking out? Etc.
I tested at 250v not 500v.
I understand i could just put LIM in the box and move on but i want to understand the reason why im getting this result and would ideally prefer to do it correctly at 500v as i want to know the true reading of the cable/s that feed these outside street lights.

Thanks for your time.

Matt

 

[Richard Burns]

Where did you test the insulation resistance?
The time clock, if electronic, could possibly demonstrate a low IR reading, however if you tested each light's wiring after the time clock (with the time clock disconnected) then the ballast should be able to give a reasonable IR reading (L+N to E).
With a reading of 0.08Mohms it might be worth measuring the resistance at a low range to get a more accurate reading, but this is probably fruitless.

 

[westward10]

Have the columns got cutouts in them so they can be isolated from the circuit so you can isolate the fault/s. If the heads are causing this IR reading this is the result I would put on the schedule, why can't you test at 500v.

 

[Farmelectrics]

What was the outcome