2" Emt fill

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Flex

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Im trying to figure out If I can put 13 ckts in a 2" emt. The conduit is around 5 ft long. Im not sure how to derate.


They would all be 20 amp ckts. #12 thhn no shared neutrals.
 
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What is the ampacity of the circuits? How many CCC will you have? Are there any MWBC's?
 
You changed the OP while I was typing. :rolleyes:

#10 THHN, 40 amps @ 90 degrees, 26 CCC's = 45% derating, 18 amps adjusted ampacity.
 
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Flex said:
Can you explain how that formula works. Also did you mean to type #10?
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Sorry the phone was ringing.

Start with your #12 THHN
Look up the ampacity (THHN 90 degree insulation) in 310.16 = 30 amp
Find total CCC's 13, 2-wire circuits = 26 CCC's. Look at table 310.15(B)(2)(a), find 26 CCC's = 45% adjustment
Multiply 30 amps * 45%= 13.5 amps, No good for your 20 amp circuits.

Try #10 THHN
40 * 45% = 18 amps, Ok to round up if your loads are not feeding multi-receptacle circuit or

Try #8 THHN
55 amps * 45% = 24.75 amps adjusted ampacity. Good to go!
 
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Try #8 THHN
55 amps * 45% = 24.75 amps adjusted ampacity. Good to go and 26 fit in 2" EMT with a #8 green.

If #10 THHN
40 amps * 45% = 18 amps adjusted ampacity. A little low!:smile:
 
Volta said:
Try #8 THHN
55 amps * 45% = 24.75 amps adjusted ampacity. Good to go and 26 fit in 2" EMT with a #8 green.

If #10 THHN
40 amps * 45% = 18 amps adjusted ampacity. A little low!:smile:
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Yet if he wires as mwbc's, the ccc's could be from 14 to 20, assuming 3? and all linear loads. He then could use #10 thhn with 50% derating.
 
Volta said:
Try #8 THHN
55 amps * 45% = 24.75 amps adjusted ampacity. Good to go and 26 fit in 2" EMT with a #8 green.

If #10 THHN
40 amps * 45% = 18 amps adjusted ampacity. A little low!:smile:
Click to expand...

Your right! I used the wrong percentage and have made the corrections. Sorry for the confusion.
 
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quogueelectric said:
Now when you leave the 2" emt and you branch off into 3/4 " emt do you cut back to 12 thhn or do you need to run 10 thhn the entire way??
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Subject to the condiitions of each section of raceway, you do not have to run #10 all the way. You can use whatever the smallest size is that has an ampacity of 20A or greater after ambient and derating adjustments are applied.
 
Smart $ said:
Subject to the condiitions of each section of raceway, you do not have to run #10 all the way. You can use whatever the smallest size is that has an ampacity of 20A or greater after ambient and derating adjustments are applied.
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Never even took that into consideration. Most engineers note #10 by me for any feeders more than 75 feet from the panel. The trend is to put more and smaller holes/pipes/raceways in for all practical purposes.
 
quogueelectric said:
Never even took that into consideration. Most engineers note #10 by me for any feeders more than 75 feet from the panel. The trend is to put more and smaller holes/pipes/raceways in for all practical purposes.
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That's most likely for voltage drop.
 
Smart $ said:
That's most likely for voltage drop.
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The reality of it has some contractors pulling and I remember that some electricians have no idea about derating and have seen and been instructed to pull 72 #10s plus a ground into a #2 pipe. I had to use the hydraulic lift to complete my mission and trashed a nice rope. When I am working for another foreman in the same shop I try to give him the respect of following his direction to the best of my ability. Right or wronng it is his responsibility for the outcome of the job. If something is an IMMEDIATE DANGER I will get involved in the losing battle to protect the unknowing. It is the contractors responsibility to hire competent supervision and when they dont I take a hands off position. It is not my problem. This is the problem with not having Statewide licencing. Noone could fault you from not going along with a gross negligence situation but here the contractor wants to just finish the job asap and let the insurance carrier cover any mistakes.
 
quogueelectric said:
The reality of it has some contractors pulling and I remember that some electricians have no idea about derating and have seen and been instructed to pull 72 #10s plus a ground into a #2 pipe. I had to use the hydraulic lift to complete my mission and trashed a nice rope. When I am working for another foreman in the same shop I try to give him the respect of following his direction to the best of my ability. Right or wronng it is his responsibility for the outcome of the job. If something is an IMMEDIATE DANGER I will get involved in the losing battle to protect the unknowing. It is the contractors responsibility to hire competent supervision and when they dont I take a hands off position. It is not my problem. This is the problem with not having Statewide licencing. Noone could fault you from not going along with a gross negligence situation but here the contractor wants to just finish the job asap and let the insurance carrier cover any mistakes.
Click to expand...

Sounds like you had need to vent a little :cool:
 
quogueelectric said:
If something is an IMMEDIATE DANGER I will get involved in the losing battle to protect the unknowing. It is the contractors responsibility to hire competent supervision and when they dont I take a hands off position.
Click to expand...

Yes, a very common dilemma. But taking the hands off position and keeping your mouth shut can be SO hard to do. I generally voice an objection and note it in my daily journal, this way I have documentation in case it comes back on me for doing it wrong. But protecting the unknowing, haha, it certainly is a losing battle.
 
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