Ohm readings on THHN

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CIECO

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Quick question, what is an acceptable ohm reading on 500 MCM (KCMIL saw that post) in conduit. And does the length have any affect.
 
First of all I guess I have bin a a DIY for the past 30 years but the sign on the door does say electrical contractor. Sorry I can not keep up with the typing or spelling. The real question was about insulation resistance to ground
 
CIECO is the door with the sign labeled Electrical Contractor Located in Maumelle, or on your front door in Vilonia?

ive been told one Meg-ohm per volt applied if you are referring to meg-ohm insulation testing
 
you want about 100 megaohms at least to energize. 500 megaohms is a lot better. on new THHN you will probably get fullscale depending on the range of your megger. im talking about a megger with about 2000 megaohm range. even the fluke 1507 might show full scale at 10 gigaohms

if you have 100 megaohms on new wire i would question the installation.
 
I just tried out my new megga on a 225' run of 6 AWG THHN in EMT. I got 2.2 Gigga Ohms each phase, does this make sense at 1000 VDC?
 
Thank you for the answers, But I was looking for maybe UL spec or something. If I megg a run I would like to see infinity But that is not always the case, and on a new install there should be a spec or an accepted standard to go by. PS what or where the heck are Maumelle or Vilonia?
 
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izak said:
CIECO is the door with the sign labeled Electrical Contractor Located in Maumelle, or on your front door in Vilonia?

ive been told one Meg-ohm per volt applied if you are referring to meg-ohm insulation testing
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As a general rule, the One-Megohm Rule (1MΩ per 1000 volts) is the widely-accepted absolute minimum insulation resistance value for normal electrical equipment.

Chris
 
In my book 1M is pretty darn low, not saying I would not energize it. But on a new run, must have plenty of yellow 77 in there. Plus in the long run it costs in energy use. I will wind a motor if can't get it above 4-500M.
 
CIECO said:
In my book 1M is pretty darn low, not saying I would not energize it. But on a new run, must have plenty of yellow 77 in there. Plus in the long run it costs in energy use. I will wind a motor if can't get it above 4-500M.
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1 meg PER VOLT. For your 460-3-60 motor, that would be about 500 megohms
 
CIECO said:
Thank you for the answers, But I was looking for maybe UL spec or something. If I megg a run I would like to see infinity But that is not always the case, and on a new install there should be a spec or an accepted standard to go by. PS what or where the heck are Maumelle or Vilonia?
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You won't find a UL spec or any other "spec" on this matter, it's more of a rule of thumb. Now, on another note, you WILL find inspection regulations that call for certain results varying on different applications. IR testing is not regulated across any board. I speak for LV only.
 
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