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TABLE 67 (cont.) MCA/MOCP DETERMINATION NO C.O. OR UNPWRD C.O.
LEGEND:
C.O. --- Convenience outlet
DISC --- Disconnect
FLA --- Full load amps
IFM --- Indoor fan motor
LRA --- Locked rotor amps
MCA --- Minimum circuit amps
MOCP --- Maximum over current protection
P.E. --- Power exhaust
UNPWRD CO --- Un --- powered convenient outlet
NOTES:
1. In compliance with NEC requirements for multimotor and
combination load equipment (refer to NEC Articles 430 and
440), the overcurrent protective device for the unit shall be fuse
or HACR breaker. Canadian units may be fuse or circuit break-
er.
2. Unbalanced 3-Phase Supply Voltage
Never operate a motor where a phase imbalance in supply volt-
age is greater than 2%. Use the following formula to determine
thepercentageofvoltageimbalance.
% Voltage Imbalance = 100 x
max voltage deviation from average voltage
averagevoltage
Example: Supply voltage is 230-3-60
AB = 224 v
BC = 231 v
AC = 226 v
Average Voltage =
(224 + 231 + 226)
=
681
3
3
= 227
Determine maximum deviation from average voltage.
(AB) 227 – 224 = 3 v
(BC) 231 – 227 = 4 v
(AC) 227 – 226 = 1 v
Maximum deviation is 4 v.
Determine percent of voltage imbalance.
% Voltage Imbalance = 100 x
4
227
= 1.76%
This am oun t of phase im balance issatisfactory as it is below the maxi-
mum allowable 2%.
IMPORTANT: If the supply voltage phase imbalance is more th an 2%,
contact your local electric utility company immediately.
580J