110.14

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tonyou812

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North New Jersey
My boss seems to beileve that all condutors under 100 amps have to be sized at 60 degrees. Am I reading 110.14c.1 wrong? IMO he oversizes alot of stuff. This week i wired a 3Ph 480v 20a ac with #4 thhn.
 

Dennis Alwon

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tonyou812 said:
My boss seems to beileve that all condutors under 100 amps have to be sized at 60 degrees. Am I reading 110.14c.1 wrong? IMO he oversizes alot of stuff. This week i wired a 3Ph 480v 20a ac with #4 thhn.

If the terminals you are connected to don't have a temp. rating then you must use the 60C rating, however most terminals today are rated 75C so you can use the 75C rating.
 

tonyou812

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Location
North New Jersey
25 feet with listed temp ratings he still was not convinced. oh i forgot to add that the wire was that beautifull simpull "no lube"wire. pulled it in with one arm. great stuff.
 
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tonyou812

Senior Member
Location
North New Jersey
i plan on showing it to him again and explain myself better . I think he pays to much for wire. Maybe hes only saving a few hundred bucks but its worth it in my opinion.
 

bcorbin

Senior Member
My boss has me do the exact same thing, from the design side. There are some 60C devices floating around out there, and I guess he considers it safer in the long run to be conservative, rather than micro-design every branch circuit in a 200,000 sq. ft. building.

I agree that for the AC you speak of, you are probably right. Your boss might value sleeping a bit more peacefully every night well worth a few hundred bucks though. ;)
 

barbeer

Senior Member
Although the up-sizing may be excessive and his interpretations may be flawed, remember that the NEC is a minimum code, and there are as many pros as cons from using larger than needed conductors. JMHO of course.
 
Your right about the article 110.14(c). If every thing is rated at 75 C or higher you can use 75 C colum but down here in montana its slitly different. Montana is known as a "Mini/Maxi" code state in that the adopted code is considered the minimum necessary for a safe installation, but that same code is also the maximum level of enforcement that may be imposed. National Electrical Code 2005 is the minimum. It's not illegal to install a larger size of wire. If you install a larger size of wire than there will be some room for futer expansion.
 

spsnyder

Senior Member
I'm all for providing for future expansion and sizing conservatively, but No. 4 for a 20 amp circuit is a little excessive. Are there plans in the works to replace the AC unit with a much larger unit after build-out or something? Doing a job now where a chilled water unit is being replaced with a chiller water/DX combo. Wish I had a conduit and No. 4 installed previously:).
 

steve66

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Location
Illinois
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Engineer
Sounds to me like he is sizing the wire based on the breaker size - which I think is pretty common.

But that's not always the way it has to be done. For example, for HVAC loads, the breaker should be sized per the "Maximum overcurrent protection" (MOCP) rating of the unit, and the wire should be sized by the "Minimum Circuit Ampacity" MCA.

So if a unit has a 40A MOCP, and a 20A MCA, it is possible to use #12 wire on a 40A breaker.

Steve
 

infinity

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steve66 said:
Sounds to me like he is sizing the wire based on the breaker size - which I think is pretty common.

But that's not always the way it has to be done. For example, for HVAC loads, the breaker should be sized per the "Maximum overcurrent protection" (MOCP) rating of the unit, and the wire should be sized by the "Minimum Circuit Ampacity" MCA.

So if a unit has a 40A MOCP, and a 20A MCA, it is possible to use #12 wire on a 40A breaker.

Steve

And for THHN you could use #14 on the same circuit.
 

nakulak

Senior Member
if I used #4 on that unit my boss would have a heart attack, or possibly even fire me for being incompetent (not to mention a tirade about how I'm supposed to make him money)
 

tonyou812

Senior Member
Location
North New Jersey
nakulak said:
if I used #4 on that unit my boss would have a heart attack, or possibly even fire me for being incompetent (not to mention a tirade about how I'm supposed to make him money)
thank you, at least somebody gets it
 

augie47

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Location
Tennessee
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State Electrical Inspector (Retired)
careful

careful

tonyou812,
Before you get to high on your soap box, be sure to take 344.13 into account.
It will have a bearing on the 60 deg. termination also.
 

infinity

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Location
New Jersey
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augie47 said:
tonyou812,
Before you get to high on your soap box, be sure to take 344.13 into account.
It will have a bearing on the 60 deg. termination also.


There is no 344.13.:-?
 

augie47

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Tennessee
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State Electrical Inspector (Retired)
opps

opps

sorry, had a really old code book on desk doing research...
let's try '2002 334.80
 
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