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Kevin, Licensed Electrical Contractor
Category: Electrical
Satisfied Customers: 3529
Experience:  30 years Licensed Electrical Contractor in Illinois, Adjunct College Electrical Instructor, Former Electrical Inspector, Diploma: Digital Electronics, FCC Technician License
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Kevin> I am curious, I need to run a 200 amp 3 phase

Customer Question

Hi Kevin> I am curious, I need to run a 200 amp 3 phase subpanel off of a 400 amp main service entrance. I am running about 120 feet away and am curious what size wire to use?
JA: I'll do all I can to help. How long have you been dealing with this?
Customer: about 3 hours
JA: Do you plan on doing the work yourself?
Customer: yes
JA: Anything else we should know to help you best?
Customer: not that I am aware.
Submitted: 9 months ago.
Category: Electrical
Customer: replied 9 months ago.
I plan to run 3 environmental chambers and 3 circulator pumps. EC's run on 50Amp 3 phase and circulators run on 30Amp 3 phase. Will 200amp sub panel be sufficient?
Expert:  Kevin replied 9 months ago.

Hello and welcome to Just Answer. My name is ***** ***** I will be happy to assist you with your electrical question.

1) I will need to know the 3-phase supply voltage in order to perform the voltage drop calculation.

Please provide me with the supply voltage? 208 or 240 or 480 three-phase voltage?

2) Will all 3 chambers and pumps be running simultaneously?

3) What is the FLA (Full Load Amps) rating of each chamber and pump?

Customer: replied 9 months ago.
Hi Kevin,Thanks for your help. I can answer two but if you could tell me how to get #3 I would appreciate it.1. It is 480v 3 phase2. It is possible that they could all be running at the same time3. How would I find this?Thanks
Expert:  Kevin replied 9 months ago.

Thank you for the replies.

1) Electrical equipment such as chambers and pumps will have a nameplate rating located somewhere on the equipment. On the nameplate label, the FLA should be shown.

2) A 200 amp sub-panel will require either 2/0 AWG copper or 4/0 AWG Aluminum conductors. The National Electrical Code recommends that the voltage drop be limited to a maximum of 3%.

Using a 480V 3-phase @ 200 amps and at a 120 foot run with 2/0 AWG copper conductors results in a point eight % (.8%) VD or a loss of 3.9 volts. Therefore, 2/0 AWG Copper is code compliant.

Using a 480V 3-phase @ 200 amps and at a 120 foot run with 4/0 AWG Aluminum conductors results in a point seven % (.7%) VD or a loss of 3.5 volts. Therefore, 4/0 AWG aluminum is also code compliant.

3) The equipment grounding conductor needs to be sized as either 6 AWG Copper or 4 AWG aluminum.

Expert:  Kevin replied 9 months ago.

1) A 200 amp sub-panel feeder is going to be an issue if all the equipment will be running simultaneously and will create an overload on the 200 amp 3 pole feeder breaker.

2) The pumps contain an electric motor and I assume the chambers also contain some type of motor or compressor. On any electric motor, the "in-rush" current upon motor start-up must be accounted for. For a few seconds, there is a higher amount of current upon the motor start-up. The NEC requires that the branch circuits be sized at a minimum of 125% of the motor FLA rating in order to accommodate the "in-rush" current.

3) Totaling the three chambers @ 50 amps each and the 3 pumps @ 30 amps each results in a minimum of 150 amps + 90 amps = 240 amps.

Multiply 240 amps by 1.25 = 300 amps.

This is assuming that the FLA ratings are 50 and 30 amps. If the FLA ratings are higher, then obviously the amperage will increase.

Expert:  Kevin replied 9 months ago.

If you have any additional questions, just let me know and I’ll be glad to answer them for you.

Otherwise, don’t forget to rate me before you log Off.


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