Question I'm stumped on some electrical wiring

[Dogman]

The shop is being rebuilt to handle the new work. I have to run wires from a breaker box thats about a 120' away from the motors plus run 3 sets of T-8 lights on the same line. The motors run on 120 volts and pull 6.5 amps at start up and I have a 20 amp breaker. What size wire would be best to run the 120 feet.

Thanks

 

[DaveBen]

12 awg is good for 20 amps, period. What you are doing is considered short distance. Going bigger does nothing if you are not overloading the line.

Dave

 

[BJS]

I would upgrade to 10 gauge wire to help counter the voltage drop. Here's a calculator that I like your circuit is from the breaker panel out and back so your 120' is the whole circuit.

This will help with providing the starting amp draw of the motors. I can run my well pump on a 100' 16 gauge wire based on amp draw but you can hear it start off slowly because it can't get the higher amps it needs to start.

I can say that for wiring my house (replacing all the old aluminum wire) I'm running 10 to the first junction box then 12 for the rest of the circuit.

 

[DaveBen]

The shop is being rebuilt to handle the new work. I have to run wires from a breaker box thats about a 120' away from the motors plus run 3 sets of T-8 lights on the same line. The motors run on 120 amps and pull 6.5 amps at start up and I have a 20 amp breaker. What size wire would be best to run the 120 feet.

Thanks

I think Dogman miss-quoted something here. In line 2 he states that the motors run 120 amps and pull 6.5 amps at start up. I think he means 120 volts and 6.5 amps. That current does not need the extra capacity ($$$) of 10 awg for 6.5 amps.

Dave

 

[Dogman]

I think Dogman miss-quoted something here. In line 2 he states that the motors run 120 amps and pull 6.5 amps at start up. I think he means 120 volts and 6.5 amps. That current does not need the extra capacity ($$$) of 10 awg for 6.5 amps.

Dave

you are right volts. sorry just to much going on at the shop

 

[DaveBen]

No problem Dogman!!

Dave

 

[BJS]

I read what he posted as it was intended. I would suggest measuring the starting amperage draw on the motors. If the motors can be plugged in with an extension cord then compare how they sound when starting on that load and measure the voltage available to the motor during startup.

I will say that if your power company is pushing higher voltage then it helps with motor starts on long runs of wire.