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Percentage
Max Voltage Deviation From
Voltage
=
Unbalance
Example:
Avg. Voltage:
Maximum Deviation from Average
% Voltage Unbalance
MAXIMUM ALLOWABLE LENGTH IN FEET TO LIMIT
VOLTAGE DROP TO 2%
Wire
Minimum Circuit Ampacity (MCA)
Size
(AWG)
10
15
14
77
51
12
122
81
10
193
129
8
307
205 154 123 103
6
489
326 244 195 163 140 122 109
Example:
A 7 ½ Ton unit is to be installed. The distance from the
building to the unit is 75'. Calculate the minimum wire size
assuming no more than 2% voltage drop.
MCA for 7 Ton 230V unit = 43.3 (from S&R plate).
Applying previous table wire sizes less than #8 AWG
cannot be used for circuits which have a rating of 45A. The
#8 wire is not suitable since the maximum length for a 45A
circuit is 68'.
Solution: Use a #6 AWG wire suitable up to 109'.
NOTE: It is the contractors's responsibility to follow the
NEC (USA) or CEC (Canada) when sizing the service wire
for this unit.
*Always refer to the unit's S&R plate for actual ratings.
Local codes often require a disconnect switch located
near the unit; do not install the switch on the unit. Switch
shall be provided to ensure all-pole disconnection from
the supply mains. Refer to the installation instructions
supplied with the indoor furnace/air handler for specific
wiring connections and indoor unit configuration. Likewise,
consult the instructions packaged with the thermostat for
mounting and location information.
Average Voltage
Average Voltage
L1 – L2 = 220 V
L2 – L3 = 216 V
=
(220+216+213) / 3
=
649 / 3
= 220 – 216 = 4
= 100 x (4 / 216)
= 400 / 216
20
25
30
35
38
NR
NR
NR
61
49
NR
NR
97
77
64
55
88
Overcurrent Protection
The following overcurrent protection devices are approved
for use.
• Time delay fuses
• HACR type circuit breakers
These devices have sufficient time delay to permit the
motor-compressor to start and accelerate its load.
Refer to the unit serial plate and this table for the maximum
overcurrent protection permitted.
Run all line voltage wiring and conduit from the service
disconnect box to the unit. Refer to the NEC (USA) or CEC
(Canada) codes for the correct size conduit based on the
wire size. The conduit enters the control box through the
hole provided in the bottom. NOTE: The control box hole is
sized for 3/4" conduit. If permitted by code, a flexible conduit
is preferred to minimize vibration transmission from the unit
to the building.
Connect the line voltage wires to the L1, L2, and L3
40
45
terminals of the definite purpose contactor (located in the
NR
NR
unit control box). Refer to the wiring diagram attached to
the unit when making these connections.
NR
NR
NR
NR
Three Phase Compressor Rotation
77
68
Use care when handling scroll compressors. Dome
temperatures could be hot.
Three phase scrolls are power phase dependent and can
compress in more than one direction.
Verify proper rotation for three phase compressors by
ensuring the suction pressure drops and discharge
pressure rises when the compressor is energized.
NOTE: When operated in reverse, a three phase scroll
compressors is noisier and its current draw substantially
reduced compared to marked values.
To correct, disconnect power and switch any two leads at
the unit contactor and re-observe.
High Voltage Connections
Route power supply and ground wires through the high
voltage port and terminate in accordance with the wiring
diagram provided inside the control panel cover.
Low Voltage Connections
Low voltage control wiring should be no smaller than
18 AWG. Field connections must be made inside the
control box with solder-less connectors (wire nuts). See
the following diagram for a typical low voltage wiring
schematic. The wires running to the condensing unit can
be sourced from either the indoor unit's terminal block, or
the thermostat.
6
CAUTION
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