diebog
Member
- Location
- California
- Occupation
- Electrician
Hi all, my name is Jeremy. I have some questions about what is considered a fail when it comes to insulation testing. Our company was asked to do some testing on the insulation of the feeders that supply a privately owned eye surgery center O.R. room. We have the Fluke 1587 FC (which I highly recommend its such an awesome meter), so we tested the feeders 1 minute @1,050v phase to phase, phase to ground and phase to neutral on 5 separate sub panels ( 3 phase 208) and all feeders on these 5 panels shot up to 2.2GΩ within seconds, so all passed with flying colors. We go to test the main 400 amp feeders that route from the generator backup transfer switch (in the P.G.E utility room) to the main distribution panel (at other end of the building) During our testing, phase to ground, Phase A comes in at 2.2GΩ, Phase C at 2.2GΩ, but here is the kicker, phase B starts very low and after a minute the reading only goes up to 127MΩ. Now this test was phase to ground, but when testing Phase B to the other phases and Phase B to neutral the reading is normal and quickly goes up to 2.2GΩ. The issue is only Phase B to ground.
The feeder in question is 500mcm copper, about 150ft long (rough guess). This wire is rated at 600v and we are testing for 1 minute @ 1,050v. From what I understand a min reading is 100MΩ for 600v rated wire. So just barely up at 127MΩ, is that a Pass or Fail? Ive never seen a reading on feeders so different from one another. Because Phase B is so much lower, I was thinking maybe there is a small nick in the insulation somewhere to cause the irregular reading. But is the reading low enough to warrant replacement? From what I understand this facility has never had the wire insulation test done and its been there sense the 2000's.
I appreciate all your help. Thanks
Jeremy
The feeder in question is 500mcm copper, about 150ft long (rough guess). This wire is rated at 600v and we are testing for 1 minute @ 1,050v. From what I understand a min reading is 100MΩ for 600v rated wire. So just barely up at 127MΩ, is that a Pass or Fail? Ive never seen a reading on feeders so different from one another. Because Phase B is so much lower, I was thinking maybe there is a small nick in the insulation somewhere to cause the irregular reading. But is the reading low enough to warrant replacement? From what I understand this facility has never had the wire insulation test done and its been there sense the 2000's.
I appreciate all your help. Thanks
Jeremy
