Need advice for clarifying HP and kVA of mechanical equipment schedule

[David Christian]

Hi guys,

I just begin my power engineering career after graduation this August. I have worked in an engineering consulting firm for two months. I lack of working experience and I really need your help and advice for my design.
When I design panel schedule for residential projects.I just want to make sure the power output for some mechanical equipment.

When I see the equipment schedule, for example:
AC unit:
Fan HP:1/3
V/PH/HZ: 230/1/60
MOCP: 25
MCA: 17

Could you help me to check whether my understanding is correct.

Based on my understanding:
MOCP means maximum over current protection size. Therefore, the size of breaker is 25A/2P?
MCA means maximum current. Therefore, the maximum current is 17A.

For power output, I have two different understanding:
1. 1HP=1kVA, therefore the power output is 334VA.
2. Power output=Voltage x MCA=230x17=3910VA.

Could you tell me which understanding is correct?

Thanks

 

[infinity]

MCA is the minimum circuit ampacity and is used to size the conductors. The MaxOCPD is there for ground fault and short circuit protection only so it does not need to correspond to the conductor size.

 

[JFletcher]

1HP = 746W, or .746KW, or ??? VA, depending on power factor of the motor.

MOCP is maximum breaker size, in this case, 25A.
MCA is minimum circuit ampacity, which is 17A.

Breakers for AC units are allowed to be sized larger than the wiring to account for motor inrush.

The unit you are looking at is a 3 ton? You would go by nameplate, but your second calculation is much more accurate. Even the smallest 5,000 BTU window unit draws about 6 amps from a 120V source (720VA). A 334VA AC would barely cool a coat closet. The fan is just one part; the compressor draws much more current.