Quantity of Mech Units on 1 circuit

[NEC User]

How many Exhaust Fans - 460/3/60 - 1 HP Each can I put on one 20A circuit?

I see it as each one is 1 HP = 746 W

I can design for 80% of a 20A breaker is 16A. At 460V 3 phase this converts to 12,748 W able to be connected to the breaker.


12,748 / 746 = 17. This means I can put 17 of them on one circuit.

Are my missing something?

Anyways, for my project there are 8 of them. Can I put all 8 on one circuit fed from a 20A 3-pole breaker?

 

[xformer]

How many Exhaust Fans - 460/3/60 - 1 HP Each can I put on one 20A circuit?

I see it as each one is 1 HP = 746 W

I can design for 80% of a 20A breaker is 16A. At 460V 3 phase this converts to 12,748 W able to be connected to the breaker.


12,748 / 746 = 17. This means I can put 17 of them on one circuit.

Are my missing something?

Anyways, for my project there are 8 of them. Can I put all 8 on one circuit fed from a 20A 3-pole breaker?

As many as you want to.... Functionality and code compliance are other issues...

Sorry, I couldn't help myself. In all seriousness, you cannot size the circuit the way you describe. I would suggest looking at article 430 and sizing the motor circuit properly. Start with 430.6 then look at 430.24... then look at 430.52 and 430.53

 

[charlie b]

One thing you are missing is that it takes more than 746 watts of electrical energy to drive a motor that is intended to deliver 1 HP of mechanical energy. This is not a simple matter of unit conversion. A quick look at one of the relevant tables that you will encounter when you follow xformer's advice tells me that our electrical load calculations need to account for the motor drawing 2.1 amps. Eight of them will therefore draw more than 16 amps. So without further review, I conclude that at least two circuits would be needed.

If you start plodding your way through article 430 and get lost, come back and tell us what you have found and what you still do not understand. Then we can provide more help.