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manivs
Participant

Join Date: Mar 2009
Posts: 1

Incommer Selection for mCC Panel

07/13/2010 3:56 AM

I have a MCC panel with 4 No of 4kW motor with DOL start, 2nos of 30kW motor feeder with star/delta start and 2 no of 15kw motor feeder which are controlled start with VFD,

Plz somebody guide me how to calculate incommer protection(SDF/MCCB) for this MCC panel,

Thanx in advance
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san win
Participant

Join Date: Jul 2010
Posts: 1
#1

Re: Incommer selection for mCC panel

07/13/2010 6:12 AM

Hi Manvics,

What is your operation criteria for these fans ?
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Anonymous Poster
#2
In reply to #1

Re: Incommer selection for mCC panel

07/13/2010 9:17 AM

basically these are radial fans in hvac system,

Any other details required plz let me know
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msamad
Guru

Join Date: Feb 2009
Location: Houston, USA
Posts: 946
Good Answers: 244
#3
In reply to #2

Re: Incommer selection for mCC panel

07/13/2010 6:36 PM

Per NEC 430.62, the feeder circuit breaker rating or setting (whichever is minimum) should be equal to (but not greater than) the rating or setting of the largest short circuit protection of the motors plus sum of the full load current of other motors.

Let's say for a feeder of 4 motors, the short circuit setting of breaker of each of the motors is 35A and FLA is 15.4A. The MCC incoming feeder circuit breaker rating should be 35 + 3 x 15.4 = 81.2A. So, 80A breaker can be selected.

In your case, the MCCB rating (or setting) = Short circuit protection setting of the one 30KW motor + sum of the FLA of all other motors.

- MS

__________________
 "All my technical advices in this forum must be consulted with and approved by a local registered professional engineer before implementation" - Mohammed Samad (Linkedin Profile: http://www.linkedin.com/in/msamad)
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Anonymous Poster
#4

Re: Incommer Selection for mCC Panel

01/19/2011 12:39 AM

TOTAL CAPACITY IS 106KW tOTAL AMPS WILL BE 205AMPS PLEASE USE = 250AMPS MCCB AT INCOMMER
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