20A for commercial 15A residential minimum breaker size

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hhsting

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Glen bunie, md, us
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Junior plan reviewer
I have the following in commercial restaurant:

1. Duct heater 208V three phase 4.32kva full load amps of 12A

2. Exhaust fan on light circuit 120V single phase, 0.8kva total fan and light full load amps of 8.3A

3. Make Air Unit (MAU) 120V single phase 0.47 kva full loads 3.91A

4. Recirculating pump 120V single phase 0.4 kva full load amps of 3.5A.

All four items above the branch circuit breaker size provided is 20A. When asked even if you do 125% for heater or 225% for motor amps come out be equal to or less than 15A. Next standard rating would be 15A not 20A. However was told that commercial don’t use 15A breaker only in residential application.
I don’t see this in code.

Questions:


1. Should items branch breaker size be 15A or 20A?

2. Is their anywhere in code commercial application 20A is minimum breaker size and 15A is minimum breaker size for residential dwelling units?
 
Questions:


1. Should items branch breaker size be 15A or 20A?

2. Is their anywhere in code commercial application 20A is minimum breaker size and 15A is minimum breaker size for residential dwelling units?[/QUOTE]


So not sure what turnip truck you fell off of....but that’s way it’s always been. You typically won’t ever see 1/2 inch EMT used either it’s always 3/4. It’s just trade standard and typically architect spec’d these days to be that way.
Commercial electrical is designed for expansion and the 20 amp minimum allows for less service calls regarding overloading. If you’d like to protect the equipment and a lower amperage install a fuses disconnect.
It may be a local or fire building code. I’m not able to quote quote scripture regarding the NEC like some of these guys but I’m sure they’ll let you know if it’s in there.


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Aledrell said:
Questions:

So not sure what turnip truck you fell off of....but that’s way it’s always been. You typically won’t ever see 1/2 inch EMT used either it’s always 3/4. It’s just trade standard and typically architect spec’d these days to be that way.
Commercial electrical is designed for expansion and the 20 amp minimum allows for less service calls regarding overloading. If you’d like to protect the equipment and a lower amperage install a fuses disconnect.
It may be a local or fire building code. I’m not able to quote quote scripture regarding the NEC like some of these guys but I’m sure they’ll let you know if it’s in there.
Click to expand...


Their is no local code here stating as such. Designer don’t want to install fuse disco. It all depends on for all items what code says and as far as I know next standard size is 15A not sure. However anyone can charm in question post #1
 
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Item #1 is 3 Phase. So - not compatable with the other 3 loads.

Item #3 is part of an AC system? - dedicated circuit.

That just leaves 2 and 4 - 1 circuit - go for it brother.
 
hhsting said:
Their is no local code here stating as such. Designer don’t want to install fuse disco. It all depends on for all items what code says and as far as I know next standard size is 15A not sure. However anyone can charm in question post #1
Click to expand...

We’ve all been on a job where we’ve needed some help, that’s what the forum is for. But if you’re trying to install a 15amp circuit and 14 awg in a newer commercial building expect to catch a little bs for biting off more then you can chew bc you haven’t put in the bender and lift time to be taking on such contracts, member since 2018....still a pup.
Next week you’ll be back in here asking about ANSUL systems and shunt trip breakers.
 
There is no minimum cb size. As a practical matter many panel boards are only available with 15 amp breakers. There's at least one square d line that has a 10 amp breaker. In residential there are some circuits like laundry circuits or small appliance circuits that are required to be 20 amp. I don't believe there's any such requirement for commercial or industrial applications. There are some minimum ratings for overcurrent protection devices found in I think it's article 210 for branch circuits. I don't recall if there's any minimum rating for feeder circuits but I think there is somewhere. Realistically the code does not require ever using a break or smaller than 15 amps rating so why ever use it?
 
augie47 said:
1. Likely not a problem. see 430.53
2. No
Click to expand...

auguie47 450.53 would cover exhaust fan and light I suppose both are on one circuit breaker.

However what about for duct heater 208V three phase that has dedicated breaker, Make Up Air Unit (MAU) that has separate dedicated breaker feeding and Recirculation Pump that has separate dedicated breaker?
 
Aledrell said:
We’ve all been on a job where we’ve needed some help, that’s what the forum is for. But if you’re trying to install a 15amp circuit and 14 awg in a newer commercial building expect to catch a little bs for biting off more then you can chew bc you haven’t put in the bender and lift time to be taking on such contracts, member since 2018....still a pup.
Next week you’ll be back in here asking about ANSUL systems and shunt trip breakers.
Click to expand...

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.
 
Here's some code for you.
If the breaker size meets the load requirement (MOCP) and protects the wire, all is good in electron land.
That's a direct quote from the NEC - lol

You will find single phase and three phase 15 amp breakers all over the place in industrial or commercial electrical applications.
You will see them at 120V, 208V, 240V, 277V and 480V.....and possibly some other voltages as well.
 
powerpete69 said:
Here's some code for you.
If the breaker size meets the load requirement (MOCP) and protects the wire, all is good in electron land.
That's a direct quote from the NEC - lol

You will find single phase and three phase 15 amp breakers all over the place in industrial or commercial electrical applications.
You will see them at 120V, 208V, 240V, 277V and 480V.....and possibly some other voltages as well.
Click to expand...
You can even find them in 10 amp!
 
hhsting said:
auguie47 450.53 would cover exhaust fan and light I suppose both are on one circuit breaker.

However what about for duct heater 208V three phase that has dedicated breaker, Make Up Air Unit (MAU) that has separate dedicated breaker feeding and Recirculation Pump that has separate dedicated breaker?
Click to expand...
Duct heater that can be on a 15 amp circuit @ 208 volts is not a very big duct heater at all and would seldom to never be seen around here. But if it were nothing prohibits supplying it with 15 amp circuit and 14 AWG conductor.

Jump to 480 volts three phase and about maxed out 15 amp circuit is at lower end of what you might see for VA rating of a duct heater
 
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.
Click to expand...

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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If the job specs ¾EMT and 20amp minimum, you bid that and install it. If the job specs state you must wear a pink tutu, cowboy boots and a yellow foam banana hat when installing it, then you wear a pink tutu, cowboy boots and a yellow foam banana hat during installation.

It's not like you price the job with ½" and 14AWG then suddenly find out you can't use it. You price ¾ and 12.
 
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.


Sent from my iPhone using Tapatalk
Click to expand...
An inspector looking for a horizontal slot is making up his own rules and should be called on it. My career was large commercial projects in larger municipalities and the code is the same as it is in smaller areas. If the design does not call for a specific item and an inspector is calling for something that will cost the EC or owner additional money I would definitely rock the boat.

Roger
 
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