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Topic Title: Fluke failed to run insulation resistance test
Topic Summary: R1+Rn to R2 failed at 80v
Created On: 20 March 2017 09:37 PM
Status: Read Only
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 20 March 2017 09:37 PM
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ChewPropertyServices

Posts: 10
Joined: 14 November 2016

So I was running the above test today on a final ring circuit and had joined r1rn because there were appliances I could not disconnect. Pretest ran ok to 500v but the actual test stopped at 80v and failed to report a resistance?

What was I doing wrong? I've used this successfully in the past on similar circuits.

Thanks in advance for reading and responding.

Chris
 20 March 2017 10:08 PM
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mapj1

Posts: 9348
Joined: 22 July 2004

normally this means that there is a 'pick-up' problem between the circuit you are testing and an adjacent live one - the tester will refuse to test if it detects a voltage on the circuit being measured.
Modern electronic meters have a very high input impedance, and can easily be fooled by stray voltages capacitative coupling between live cables and dead ones along side..

-------------------------
regards Mike
 20 March 2017 10:14 PM
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ChewPropertyServices

Posts: 10
Joined: 14 November 2016

Hi Mike,

Thanks for the response. The whole board was off and this was a circuit at the far end so I don't understand how it could be adjacent live circuits. Any other ideas? I turned the circuit off with a washing machine mid cycle - could that do it?

Thanks again

Chris
 21 March 2017 07:04 PM
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geov

Posts: 386
Joined: 22 February 2004

Do the circuit conductors run close to the incoming live tails? I've had a similar, but different problem with a Megger1720 when trying to do a continuity test. Main switch was off, but the incoming tails ran alongside most of the final circuits as they entered the back of the consumer unit.
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