Expert: Master Bob - 6/4/2004

Question
Master Bob, I am hooking up a swamp cooler, I have got some good advise from you before, so here I am again. I have 3/4" emt that going through my roof, where it hooks up to the swamp cooler I had to use a 1/2" ridgid pipe. Can I run 5 #12ga through this 1/2"? Basically how many # 12ga can I run through 1/2" gal. pipe and if I need to change the whole thing to 1/2 EMT how many #12ga can I run through 1/2" EMT. Thanks Rick Baker.  

Answer
Hi Rick,

 Sorry for the delay - had to replace the cooling fan in our main office computer - kept me off line for a few hours...

 Thanks for the kind words on previous advice...( I recall your name and your comments in the ratings)..it is imperative that ONLY good advice be given for electrical work...due to the nature of electricity and the possible dangers when it is done wrong. I do the best I can and will even research answers if necessary - to assure that my answers are as correct as they can be.

 Years ago, conduit fill was simply a matter of just looking up the pipe size in the Code book.....input the wire size and type....and the chart would tell you the max amount of that wire that could go in the pipe. But - the new Code books now give internal pipe diameters, wire diameters, etc...making this more of a chore.
 
  Fortunately, Table 9 Chapter 1 still gives these values....based on pipe type and wire type. You didn't state what type of wire you were running in these pipes...THHN is the most commonly used.

 For 1/2" EMT....you can pull up to 9 #12 THHN wires...but I don't recommend that....we find 7 is pretty tight in the field. The stats stay the same for 1/2" rigid....9 (again - I recommend only a max of 7 from experience).

 5 runs of #12 shouldn't present a problem with EITHER pipe type... but that depends on what type of #12 wire you are running....the insulation is thicker on some wire types.

 Please follow-up with the wire type you are using in this 1/2" pipe...and I'll cross-reference the max pipe fills for you...(unless you are running THHN...then I've already covered it above)

Best Wishes,

Bob Osgood
Master Electrician

RKO ELECTRIC

www.rkoelectric.com