24
Legend and Notes for Tables 12-15
LEGEND
* Motors are designed for satisfactory operation within 10% of normal
voltage shown. Voltages should not exceed the limits shown in the
Voltage Limits column.
NOTES:
1. Minimum circuit amps (MCA) and maximum overcurrent protection
(MOCP) values are calculated in accordance with The NEC. Article
440.
2. Motor FLA values are established in accordance with Underwrit
-
ers’ Laboratories (UL). Standard 1995.
3. Unbalanced 3-Phase Supply Voltage
Never operate a motor where a phase imbalance in supply voltage
is greater than 2%. Use the formula in the example (see column to
the right) to determine the percentage of voltage imbalance.
4. Installation with Accessory Electric Heaters
Size the Field Power Wiring between the heater TB1 and the
40RU indoor fan motor per NEC Article 430-28 (1) or (2) (depends
on length of conduit between heater enclosure and 40RU power
entry location). Install wires in field-installed conduit.
Example: Supply voltage is 230-3-60
Determine maximum deviation from average voltage.
(AB) 397-393 = 4 v
(BC) 403-397 = 6 v
(AC) 397-396 = 1 v
Maximum deviation is 4 v.
Determine percent of voltage imbalance.
This amount of phase imbalance is satisfactory as it is below the maxi
-
mum allowable 2%.
FLA
— Full Load Amps
HACR
— Heating, Air Conditioning, and Refrigeration
%Voltage
Imbalance: = 100 x
max voltage deviation from average voltage
average voltage
AB = 394 v
BC = 403 v
AC = 396 v
Average Voltage =
(393 + 403 + 396)
=
1192
3
3
=
397
% Voltage Imbalance = 100x
6
397
= 1.5
IMPORTANT: If the supply voltage phase imbalance is more than 2%,
contact your local electric utility company immediately.
A
B
C
MOTOR
