12 gauge minimum wire size for commercial work.
- Thread starter dhsvcs
- Start date
- Status
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
There isn't a NEC rule on it but it is a standard that architects or engineers will require on commercial work. Other than that you can use 15 amp circuits but it would be contrary to the norm.
Correct, not a code requirement. When I was a plant engineer responsible for the electrical systems of a factory/office complex, we just considered it common sense to always run 20A circuits for general purpose receptacles. The only cost difference was the wire - pennys per foot. Raceway, devices and labor were almost always identical.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
I think that is more of an electrical myth (that it's required by code) than a standard. I've heard it many times over the years that it's "code" for #12 in commercial installations.
And it is a widespread myth from sea to sea.
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
The first few years I was in the trade, I was told 14 is for residential only. I often use 14 for commercial lighting these days (depending on a variety of factors of course).
Best practice is always use minimum of # 12 copper in all industrial & commercial sites. At the large what they called themselves a progressive hospital that I retired from required #10 copper to first pull box then it could be reduced to a #12 copper wire for general loads such as the thousands of 20 amp 120 volt receptacles. If wire run was over 100 feet were not allowed to reduce wire size till last pull box ( junction box ) . Also required a separate grounded conductor ( yea neutral ) for every normal & emergency power circuit. Even though every device had an engraved wall plate it made it a lot easier if plate got lost and you had to use a tracer to id circuit. Read some where that they are thinking about allowing #16 copper for all LED luminaire load and placed on a 10 amp circuit breaker. Think that's a bad ideal. Can just see johnnie homeowner going to a big box store and purchasing #16 copper Romex and installing it to receptacles feed from a 15 amp breaker.
packersparky
Senior Member
- Location
- Wisconsin
- Occupation
- Inspector
It is just as easy for Johnnie Homeowner to change a 15 amp breaker to a 20 amp breaker, or use 12 awg wire on on 30 amp circuit. What somebody might do is not a good argument for a code requirement.
goldstar
Senior Member
- Location
- New Jersey
- Occupation
- Electrical Contractor
AND, I can always tell when a "commercial" electrician comes in and does residential work. It's # 12 solid for both receptacle and lighting circuits. It's so much fun jamming all those # 12's into a 4-gang plastic switch box, especially if you have dimmers.
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
I cannot agree with that. Sounds like an overly broad generalization and potentially a waste of money in some situations to me.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
In NYC the minimum conductor size for branch circuits is #12 . Many guys pull all #10's for 20 amp.circuits.
but i thought its not compliant to mix wire sizes - starting with a large wire for voltage drop and then slimming down toward the load. I know fixture wires are smaller but they are listed. You could have a long run of 12 to a nearby junction and spider 14 for the lighting loads in that zone then.
do they even sell 20 switches and outlet devices that accept #10 wire?
abandoning the general use of 120 vac wiring throughout residences
https://www.domatic.io/post/domatic-was-founded-to-answer-this-question i had been thinking that electricity use is much different since i was a kid and I Love Lucy when ricky bought her a washing machine. I believe that power is really only needed at special locations such as LAU SA1&2, and...
forums.mikeholt.com
- Location
- New Jersey
- Occupation
- Journeyman Electrician
You can start with #12 switch to #10 and go back to #12 if on a 20 amp circuit. There is no requirement to keep consistent or diminishing wire sizes.
maybe its a local sf code or an inspector thing. thanks for the insight!
i was on a standards committee that specified no wire less than #12 for 50v+ and that
it had to all be SOLID not stranded.
Contractor grumbled for one year and more!
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
It is not a code thing. More of a spec thing.
#14 is more likely to be damaged in pulling then #12.
It is also handy to have 20 Amp receptacles sometimes.
And commercial/industrial runs tend to be longer than residential runs so it kind of automatically takes care of voltage drop issues, at least for the most part.
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
Why wouldn't you let the installing electrical contractor decide on stranded versus solid? that kind of stuff really annoys me.
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
For the same reason they spec all 20 Amp circuits. Someone wants it done that way for some reason.
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
Well, IMO, there is more likely to be a practical reason to spec 20 amp circuits for receptacles (I would leave lighting up to the installer). Making a stranded vs solid decision for the the person who is going to be installing it seems ridiculous to me.
what is really the advantage in all solid? i seen alot of the 1950's institutional installs as all solid, they didn't have stranded??
- Status