Reduced neutral line to industrial machine

[collins]

I have a power enclosure with a 208/120V input. The pumps are 208v 3ph and require 200amps.
The 120V is tapped off of the 3 hot legs to power a 24vdc power supply and 2 heaters. The power supply draws 3amps and each heater draws 10amps.
Is there a section of the NEC that allows for a reduced neutral drop to the machine or does it need to match the 3 hot legs at 4/0?

 

[don_resqcapt19]

The grounded condutor minimum size is the larger of what is required by 215.2(A)(1) or 220.61. In this case I would expect that the rule in 215 would apply.

 

[BILLY101]

Article 220.61 addresses your issue. It appears that in your situation reduction of the neutral is not permitted.

BILLY

 

[Little Bill]

I have a power enclosure with a 208/120V input. The pumps are 208v 3ph and require 200amps.
The 120V is tapped off of the 3 hot legs to power a 24vdc power supply and 2 heaters. The power supply draws 3amps and each heater draws 10amps.
Is there a section of the NEC that allows for a reduced neutral drop to the machine or does it need to match the 3 hot legs at 4/0?

Are your pump motors 3ph? Do they require a neutral for anything related to them? Does the power enclosure have a main OCPD? If so, what size is it? I don't think you need the neutral sized the same as your pump motor conductors but need more information to be sure.

 

[raider1]

Article 220.61 addresses your issue. It appears that in your situation reduction of the neutral is not permitted.

BILLY

I disagree.

215.2(A)(1) deals with sizing feeder neutrals.

215.2 Minimum Rating and Size.
(A) Feeders Not More Than 600 Volts.
(1) General.........The size of the feeder circuit
grounded conductor shall not be smaller than that required
by 250.122, except that 250.122(F) shall not apply where
grounded conductors are run in parallel.
Additional minimum sizes shall be as specified in
215.2(A)(2) and (A)(3) under the conditions stipulated.

Chris

 

[augie47]

I agree with Chris's assesment.

 

[Little Bill]

I agree with Chris's assesment.

If the conductors come from a panel to a machine, they wouldn't be considered feeders would they?

 

[raider1]

If the conductors come from a panel to a machine, they wouldn't be considered feeders would they?

I am assuming that the control panel at the macine contains overcurrent devices and that the supply is a feeder.

Chris

 

[Little Bill]

I am assuming that the control panel at the macine contains overcurrent devices and that the supply is a feeder.

Chris

That's why I ask the OP for more info. He said "drop to the machine" and that didn't sound like a feeder.

 

[augie47]

When you look at his description: pumpS (plural), heaters, 24v power supply, etc., it's difficult to imagine a scenario with no OCP devices.

 

[collins]

I am assuming that the control panel at the macine contains overcurrent devices and that the supply is a feeder.

Chris

Our machine has a OCPD 200A and individual protection for each 3 ph pump motor. Would like to size the neutral to 4awg since the load on the neutral leg is less than 30A.