TravisR100
Cast Iron
- Joined
- Aug 7, 2006
- Location
- Houston, TX
As much reading and researching as I've done I believe I've only managed to confuse myself rather than arrive at any conclusions. I've got a new shop and I'm about to put a couple of machines in. I currently have a manual lathe with a 5 hp motor, a band saw with a 1.5 hp motor, and I hope to add a mill at some point with a 3 hp motor. This is a home shop and I can't see any situation where any of the 3 phase loads will be running concurrently. All are 240 volts.
I'm first trying to figure out which AR phase converter to buy. It would seem like the AR model would be fine however American Rotary tech is telling me to go with the ADX. Their web site isn't very clear what the technical differences in the models are. Can anyone offer any input on this? I do believe, and they concur, that a 10 hp phase converter would be adequately sized.
My next question is about the circuits. From everything I've read it seems that I would be complying with NEC code by running all three loads off of a single circuit breaker for over current and short circuit protection as long as each load has its own overload protection. If this is true, then I figured the following:
Conductor size is based on FLC. The 5 hp motor has an FLC of 15.2. The 3 HP motor has an FLC of 9.6. The 1.5 hp motor has an FLC of 5.2. Conductor should be sized for (15.2 * 125%) + 9.6 + 5.2 = 33.8 amps. Rounding up to 35 amps this would require 10 gauge wire on the 3 phase load side.
Circuit breaker is based on FLC. With the FLC numbers above, circuit breaker should be sized for (15.2 * 250%) + 9.6 + 5.2 = 52. Rounding down, 50 amp breaker.
Fuse rating is based on FLA. FLA = 2.5 amps per HP. Fuses should be no more than 115% to 125% of the FLA for each motor.
My question is, is this all correct? Or is it against code to run multiple 3 phase motors of the listed sizes off a single branch circuit? I'd like to avoid having to buy a 3 phase load center and circuit breakers for each load unless I need to in order to be safe and code compliant.
And what about the wire size and breaker size on the single phase side going to the converter? If there was just the single 5 hp motor on the 3 phase side I figure the breaker on the single phase side would be the 15.2 FLC of the 5 hp motor * 1.73 * 1.25 = 32.87. So rounding down I'd need a 30 amp breaker.
I'm first trying to figure out which AR phase converter to buy. It would seem like the AR model would be fine however American Rotary tech is telling me to go with the ADX. Their web site isn't very clear what the technical differences in the models are. Can anyone offer any input on this? I do believe, and they concur, that a 10 hp phase converter would be adequately sized.
My next question is about the circuits. From everything I've read it seems that I would be complying with NEC code by running all three loads off of a single circuit breaker for over current and short circuit protection as long as each load has its own overload protection. If this is true, then I figured the following:
Conductor size is based on FLC. The 5 hp motor has an FLC of 15.2. The 3 HP motor has an FLC of 9.6. The 1.5 hp motor has an FLC of 5.2. Conductor should be sized for (15.2 * 125%) + 9.6 + 5.2 = 33.8 amps. Rounding up to 35 amps this would require 10 gauge wire on the 3 phase load side.
Circuit breaker is based on FLC. With the FLC numbers above, circuit breaker should be sized for (15.2 * 250%) + 9.6 + 5.2 = 52. Rounding down, 50 amp breaker.
Fuse rating is based on FLA. FLA = 2.5 amps per HP. Fuses should be no more than 115% to 125% of the FLA for each motor.
My question is, is this all correct? Or is it against code to run multiple 3 phase motors of the listed sizes off a single branch circuit? I'd like to avoid having to buy a 3 phase load center and circuit breakers for each load unless I need to in order to be safe and code compliant.
And what about the wire size and breaker size on the single phase side going to the converter? If there was just the single 5 hp motor on the 3 phase side I figure the breaker on the single phase side would be the 15.2 FLC of the 5 hp motor * 1.73 * 1.25 = 32.87. So rounding down I'd need a 30 amp breaker.
