TABLE 67 (cont.) MCA/MOCP DETERMINATION NO C.O. OR UNPWRD C.O.
580J
LEGEND: |
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C.O. | Convenience outlet | |
DISC | Disconnect | |
FLA | Full load amps | |
IFM | Indoor fan motor | |
LRA | Locked rotor amps | |
MCA | Minimum circuit amps | |
MOCP | ||
P.E. | Power exhaust | |
UNPWRD CO | ||
NOTES: |
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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 the percentage of voltage imbalance.
% Voltage Imbalance = 100 x | max voltage deviation from average voltage | |
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average voltage | ||
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Example: Supply voltage is
AB = 224 v
BC = 231 v
AC = 226 v
Average Voltage = | (224 + 231 + 226) | = | 681 | |
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3 | 3 | |||
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=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 | |
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227 | |||
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| = 1.76% |
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This amount of phase imbalance is satisfactory as it is below the maxi- mum allowable 2%.
IMPORTANT: If the supply voltage phase imbalance is more than 2%, contact your local electric utility company immediately.
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