20A for commercial 15A residential minimum breaker size

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480sparky said:
OK, so what is a 'horizontal neutral' and 'horizontal slot'?
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You know the ability to use a true 20amp plug on 20 amp outlet that wouldn’t work if you tried to plug into a 15 amp outlet bc it’s missing the horizontal neutral....


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Aledrell said:
I have wired several retail phone stores, clothing stores, several restaurants, medical offices, and ER surgery centers, most of which 120/208 Y. Never been allowed to install a 15 amp outlet anywhere on these jobs, inspectors look for the horizontal neutral. Is most of this over zealous engineering? Perhaps but as an EC you don’t roll the dice and and rock the boat. You’re installations should be based on your experience and besides most bolt on commercial panels have a few spare breakers in them, trouble is I haven’t ever run across them as 15 amp they are always 20 amp.
I’m in a bigger city, so if your in a smaller municipality you can get away with things you can’t here.


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Pretty much mirroring 480 and Roger's response, but I don't see what there is to "roll the dice" about or "get away with". I'm not talking about changing things that are on approved plans. Most of my commercial stuff is design build and I do typically do things as if I were the one paying for it and skip much of that boiler plate crap if it serves no purpose for a given situation.
 
Electro,
But in commercial if your panel schedule says 20 amp and 3/4 the inspector doesn’t have to allow your modifications to 15 amp circuits and 1/2” Emt without a revision to said plan resubmitted through the city.
Residential you can redo the entire panel schedule and they don’t care....


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We almost always specify 20 amp for 120 volt, single phase general-purpose circuits so #12 (or #10 for VD) is what's used. For higher voltages and multi-phase, the conductors and breakers are most often dictated by the equipment or outlets that will be fed from these circuits.
 
Aledrell said:
You know the ability to use a true 20amp plug on 20 amp outlet that wouldn’t work if you tried to plug into a 15 amp outlet bc it’s missing the horizontal neutral....


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(y) I thought it had something to do with the actual neutral conductor.... or how it was terminated in the panel.
 
Aledrell said:
Electro,
But in commercial if your panel schedule says 20 amp and 3/4 the inspector doesn’t have to allow your modifications to 15 amp circuits and 1/2” Emt without a revision to said plan resubmitted through the city.
Residential you can redo the entire panel schedule and they don’t care....


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I don't get the point you are trying to make. Sure generally if you are doing a job that requires plan review then the inspector is looking that what is installed matches the approved plans. Where I work residential almost never requires plan review. What does this have to do with 15A in a commercial occupancy?
 
electrofelon said:
I don't get the point you are trying to make. Sure generally if you are doing a job that requires plan review then the inspector is looking that what is installed matches the approved plans. Where I work residential almost never requires plan review. What does this have to do with 15A in a commercial occupancy?
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I second that. The thread is about NEC requirements, not contract documents or plan review.
To expand on plan review requirements, if a contractor won a competitive bid based on engineering and then short changed the customer by using something less there's more cheating and ethics involved than just worrying about code requirements.

Roger
 
electrofelon said:
I don't get the point you are trying to make. Sure generally if you are doing a job that requires plan review then the inspector is looking that what is installed matches the approved plans. Where I work residential almost never requires plan review. What does this have to do with 15A in a commercial occupancy?
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In some jurisdictions, when the plans state ¾, AWG 12 and 20a minimum, you wouldn't be permitted to use ½. AWG 14 and 15a without a review buy the AHJ.
 
hbiss said:
He's looking for 20A receptacles with the "T"slot. We've many times established that most cases they are a waste of time and money.

-Hal
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Yes they are, just like the magical ground rod triad.

Roger
 
I did a government-supported housing project a few years ago. Only 20a circuits and 20a receptacles. Never understood it.
 
Agree that the question was about the NEC. Table 210.21b2 for cord and plug allows a 15 amp receptacle to be on a 15 or 20 amp breaker as long as the maximum load amps is less than 12 amps.


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electrofelon said:
I don't get the point you are trying to make. Sure generally if you are doing a job that requires plan review then the inspector is looking that what is installed matches the approved plans. Where I work residential almost never requires plan review. What does this have to do with 15A in a commercial occupancy?
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Even in commercial projects I have done that have engineer drawn plans, I have never had an inspector here look at plans unless we were discussing some unusual situation, they just don't do that here. They are inspecting to code, if an engineer wants to assure you followed his specifications then it is up to him or his representative to assure that has happened, not the code inspector. I won't say there has never been situation where if you do it to specifications that it might not be code compliant or at least get some questions out of the inspector on some those things you maybe don't see often.
 
electrofelon said:
IMO much of this comes from engineers who often draw up plans for commercial and do all sort of wasteful things like wire EGC's, everything 20A, no AL conductors etc. I would use 15A in commercial for certain things without even thinking twice about it. I probably in general wouldnt do general use receps on 15, but lighting sometimes is real handy to do with 14 AWG.
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No reason not to use 14, especially for lighting. But using 12 is probably a truck answer, or what I used to tell my students
4 Answers to a code question
1. Code answer
2. AHJ answer
3. Toms Answer
4. Truck answer
 
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