Commercial work. 20a minimum requirement

[Hot Tuna]

Is it a NEC or local jurisdiction/Engineer requirement that 12awg/20amp is the smallest wire/circuit size allowed on commercial work?

 

[roger]

It is not an NEC rule, it may be job specifications or a local code.

Roger

 

[Hot Tuna]

That's what I thought, Thanks

 

[tom baker]

I agree with 12 AWG min for receptacle circuits but I see no need for 20 A Tslot devices

 

[kwired]

I agree with 12 AWG min for receptacle circuits but I see no need for 20 A Tslot devices

You agree that it is your design minimum? NEC allows us to run 14 AWG/15 amp circuits for most general use lighting and receptacles. Most of the 20 amp minimum requirements are in dwellings for the small appliance circuits, bathroom circuits, the laundry circuit, now in the garage.

 

[petersonra]

It's common in industrial specifications but except for a few cases it's not code requirement.

I think it's because a lot of people hook up devices that take pretty close to 15 amps by themselves now and then like electric heaters and the thinking is that somebody turns on their electric heater and somebody else has another 10 or 15 amps on the same circuit it's less likely to blow on a 20 amp circuit. I don't know if it's really true or not but I suspect that's why it's done. You also see a few 20 amp plugs on devices in industrial settings like for big floor fans that you rarely see in commercial or residential service. That may be part of the reason it might be a common spec in industrial settings.

 

[JFletcher]

I see 20 amp receptacles in a ton of commercial places where they will never ever be needed. they probably have dedicated neutrals to them as well, just to waste more money.

 

[rbauerff]

Thoughts on 20 amp breakers and #12 awg wire as minimums.

Thoughts on 20 amp breakers and #12 awg wire as minimums.

20 amp minimum circuit breaker size is the common specified minimun, however be careful when wiring to small motors, if a 15 amp breaker is the correct size for the motor load, the code does not allow the circuit breaker to be upsized to 20 amps.

#12 awg wire is the common minimum wire size. If you do have 15 amp circuits I would be very careful using #14awg wire. Voltage drop can be a problem with # 14 wire.

I don't have a problem with using 15 amp circuit breakers if this is the right size breaker for the application, but I never use #14 wire because of voltage drop.

 

[kwired]

20 amp minimum circuit breaker size is the common specified minimun, however be careful when wiring to small motors, if a 15 amp breaker is the correct size for the motor load, the code does not allow the circuit breaker to be upsized to 20 amps.

#12 awg wire is the common minimum wire size. If you do have 15 amp circuits I would be very careful using #14awg wire. Voltage drop can be a problem with # 14 wire.

I don't have a problem with using 15 amp circuit breakers if this is the right size breaker for the application, but I never use #14 wire because of voltage drop.

Voltage drop is dependent on the load as well. If you only have a ~3 amp fixed load, you can run quite a long circuit and 14 AWG is still not giving much VD issues, especially if supply is 480 volts.

 

[peter d]

Voltage drop is dependent on the load as well. If you only have a ~3 amp fixed load, you can run quite a long circuit and 14 AWG is still not giving much VD issues, especially if supply is 480 volts.

Agreed, wire should be sized according to the load, not some "one size fits all" approach.

 

[LarryFine]

Voltage drop is dependent on the load as well. If you only have a ~3 amp fixed load, you can run quite a long circuit and 14 AWG is still not giving much VD issues, especially if supply is 480 volts.

You do realize that, unless you're talking about percentage, the voltage is not relevant to voltage drop for a given current, don't you? For a given wattage, yes.

 

[kwired]

You do realize that, unless you're talking about percentage, the voltage is not relevant to voltage drop for a given current, don't you? For a given wattage, yes.

We never use watts in VD calculations, always current.

My point when I mentioned 480 volts supply was that a 3 volt drop on a circuit at that voltage is less percentage compared to a 3 volt drop on a 208 or 240 volt circuit, and even bigger percentage difference then it is for a 120 volt circuit.