Carrier 48MPD Installation, Start-Up And Service Instructions Manual page 15

Disconnect must be located within sight of the unit and read-
ily accessible from the unit in compliance with NEC
Article 440-14.
All field wiring must comply with NEC and all local codes.
Size wire based on MCA (Minimum Circuit Amps) value
shown on the unit informative plate. See Fig. 12 for power
wiring connections to the unit power terminal block and equip-
ment ground.
Operating voltage to the compressor must be within the volt-
age range indicated on the unit nameplate. Voltages between
phases must be balanced within 2%, and the current must be
balanced within 10%. See Table 5 for unit electrical data.
Use the following formula to determine the percent voltage
imbalance.
% Voltage Imbalance
max voltage deviation from average voltage
= 100 x
average voltage
EXAMPLE: Supply voltage is 460-3-60.
AB = 452 v
BC = 464 v
AC = 455 v
Average Voltage =
Determine maximum deviation from average voltage:
(AB) 457 − 452 = 5 v
(BC) 464 − 457 = 7 v
(AC) 457 − 455 = 2 v
Maximum deviation is 7 v.
Determine percent voltage imbalance:
% Voltage Imbalance = 100 x
= 1.53%
452 + 464 + 455
3
1371
=
3
457
=
7
457
This amount of phase imbalance is satisfactory as it is be-
low the maximum allowable 2%.
IMPORTANT: If the supply voltage phase imbalance
is more than 2%, contact local utility immediately.
Unit failure as a result of operation on improper line volt-
age or excessive phase imbalance constitutes abuse and may
cause damage to electrical components.
LEGEND
EQUIP — Equipment
GND — Ground
NEC — National Electrical Code
TB — Terminal Block
Fig. 12 — Field Power Wiring Connections
15