Checking wire insulation?

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dduffee260

dduffee260

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Texas
If you want to check a set of feeder wires before termination. Would a megger be the best instrument. I have often heard of this but honestly have never used a megger. Do you simply hook up to the wire and the megger gauge shows a fault like a normal resistance meter would? Also if we have to purchase a megger which one is the best for the money?
 
Yes, the megger would be the tool. The particular model recommendation would depend wholly on the normal operating voltage of the conductors in question, and whether the results need to have a printed record and whether the instrument needs to be NIST traceable.
 
Marc, basically what we are doing is checking a set of existing copper 600 volt feeders on a 120/208 volt system. I don't think we need a recorder, just something to verify that when we terminate the wires, they will not go to fault after being energized for a period of time.
 
Testing wires after a fire

Testing wires after a fire

Hello David,
I am interested in buying a megger meter to test the insulation value of conductors after a house fire. Let me know what you come up with as I will be interested in gaining more information before I buy one. A recorded would be nice.
Whould be nice to be able to attach a printout of all circuits and there condition to the bill.
Thanks,
Fran
 
Hi Fran, how is the weather up there? I will let you know what I come up with.
As of right now I am hobbling around with a broken leg I did 4 weeks ago. One more month on crutches and I get a walking cast, maybe. Why didn't I go to a 4 wheeler riding forum and learn not to put my foot out when the 4 wheeler goes on it's side?
 
We use meggers in our day to day operation, I can not imagine turning on any feeders, busway, switchboard or any distribution equipment without meggering it first.

As far as purchasing a megger, the price range varies from a couple hundred dollars to a couple thousand dollars. Obviously, the more features, the more dollars.

At a minimum a digital display, with a analog scale, 250-1000 VDC ranges, it is nice and safer to start with a low voltage to avoid damaging equipment.
 
While the use of meggers is very common, it is very possible to have bare copper showing as the result of intallation damage and the megger show the cable as good. Just look out when that raceway gets water in it.
Don
 
Don;

While it is true that testing can under certain circumstances "MISS" somethings, IMO it beats not testing.

I know if I megger a swbd it is safe for me to energize. Busway, meggering sure beats the alternative.
 
Brian,
I'm not saying not to meg, and I agree that if you have a good meg reading that it is safe to energize the system at that time. I just don't like the blanket assumption that if it passes a megger test it is all ok. There is not really a test that I know of that will find bare wire that is not in contact with a conductive surface.
Don
 
dduffee260 said:
If you want to check a set of feeder wires before termination. Would a megger be the best instrument. I have often heard of this but honestly have never used a megger. Do you simply hook up to the wire and the megger gauge shows a fault like a normal resistance meter would? Also if we have to purchase a megger which one is the best for the money?
Click to expand...
FYI: I just bought a megger about 2 weeks ago for a fire job. It tests up to 1000 volts, with a digital display. No recording feature. It cost me $460 + tax.
 
I guess if you want a good toolbox megger, the Supco M-500 or the Extech 403360 are good beaters that are only around 100 bucks. I wouldn't have any problem certifying a 120/240 fire or water damage job with either of these.

supcomegger.jpg


EXTECHFRONT.jpg
 
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