Fan circuit

[Atm]

At the top of a peanut warehousing dome are 4- 115V 1/2 HP fastened in place fans. FLC 9.8 A


A single phase 120/240V panel supplies a multure wire branch circuit to the fans. All the fans have a single receptacle at each fan location. One leg of the split phase system supplies two receptacles or two fans and the other leg of the split phase system supplies the other two receptacles or two fans. So the circuit has two ungrounded conductors and one neutral. All conductors are #12 THHN. The multi wire branch circuit supplies no other loads.

A double pole 20 amp breaker is the circuits OCPD. The fans are thermally protected. The circuit is energized by a double pole motor rated switch.

Can a motor circuit be supplied by a multi wire branch circuit? For the neutral conductor does not have an ampacity as required by 430.24.

Does the total rating of fastened in place utilization equipment have to remain 50% or less of the branch circuit rating as described in 210.23(A) (2)?

 

[Dennis Alwon]

The neutral only carries the difference between the phases so a #12 neutral should not be an issue

210.23 does not apply since there is no lighting load or other loads besides the motors.

 

[infinity]

You have two 1/2 HP, 9.8 amps fans per circuit that means that your conductors must be 125% of the largest (in this case either one) plus the amp rating of the other.

9.8 * 125% = 12.25 + 9.8 = 22.05 amps #12 THHN @ 75° C is good for 25 amps so your conductors are large enough. The neutral will carry near 0 volts when all four fans are running so it's not relevant. As Dennis stated you can use two fastened in place fans on each circuit.

 

[ActionDave]

That's how I would have wired it. There's no reason to waste the copper on a dedicated neutral for all four fans. Save those natural resources for future generations.