10
Step 4 — Complete Electrical Connections
POWER SUPPLY — Electrical characteristics of available
power supply must agree with nameplate rating. Supply volt-
age must be within tolerances shown in Tables 7A and 7B.
Phase imbalance must not exceed 2%. Operation of unit on
improper supply voltage or with excessive phase imbalance
constitutes abuse and is not covered by Carrier warranty.
Per local code requirements, provide an adequate fused dis-
connect switch within sight of unit and out of reach of children.
Provision for locking switch open (off) is advisable to prevent
power from being turned on while unit is being serviced. The
disconnect switch, fuses, and field wiring must comply with lo-
cal requirements. Refer to Tables 7A and 7B for electrical data.
Route power wiring through entrance in right-hand corner post
of unit. The power terminal block is sized to handle either cop-
per or aluminum wires. Unit must be grounded. Affix crank-
case heater warning sticker to unit disconnect switch.
POWER WIRING — All power wiring must comply with
applicable local requirements. Install a field-supplied branch
circuit disconnect switch that can be locked off or open. Run
power wires from disconnect switch through unit power open-
ing and connect to terminal block inside the unit control box.
See Fig. 9.
UNBALANCED 3-PHASE SUPPLY VOLTAGE — Never
operate a motor where a phase imbalance in supply voltage 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
average voltage
EXAMPLE: Supply voltage is 380-3-50.
AB = 385 v
BC = 373 v
AC = 377 v
Average Voltage =
385 + 373 + 377
3
= 378 v
Determine maximum deviation from average voltage:
(AB) 385 – 378 = 7 v
(BC) 378 – 373 = 5 v
(AC) 378 – 377 = 1 v
Maximum deviation is 7 v. Determine percentage of voltage
imbalance:
% Voltage Imbalance = 100 x
7
378
= 1.85%
This amount of phase imbalance is satisfactory as it is be-
low the maximum allowable of 2%.
GENERAL WIRING NOTES
1. A crankcase heater is wired in the control circuit so it is
always operable as long as power supply disconnect is
on, even if any safety device is open or unit stop/start
switch is off.
2. The power-circuit field supply disconnect should never be
open except when unit is being serviced or is to be down
for a prolonged period. When operation is resumed,
crankcase heater should be energized for 24 hours before
start-up. If system is to be shut down for a prolonged peri-
od, it is recommended that the suction and discharge
valves be closed to prevent an excessive accumulation of
refrigerant in the compressor oil.
3. Terminals for field power supply are suitable for copper,
copper-clad aluminum, or aluminum conductors.
CONTROL CIRCUIT WIRING — Unit internal control cir-
cuit voltage is 24 volts. See Table 8 for recommended thermo-
stats. Connect thermostat assembly and other accessories as
shown in unit label diagram and Fig. 10A-10C. Refer to instal-
lation instructions shipped with indoor unit. See Fig. 11 for
field-supplied airflow switch wiring if airflow switch is used.
The control wiring entrance is located on right corner post of
38AQS unit. See Fig. 1. Wiring connects to a terminal block
located at extreme right of control box.
Transformers no. 1 and 2 are wired for a 230-v unit. If a
208/230-v unit is to be run with a 208-v power supply, the
transformers must be rewired as follows:
1. Remove cap from red (208 v) wire.
2. Remove cap from orange (230 v) spliced wire.
3. Replace orange wire with red wire.
4. Recap both wires.
DUPLEX 38AQS WITH 40RMQ024 OR 40RMQ028 — In
order to properly connect two 38AQS heat pump condensing
units to a single 40RMQ packaged air handler, it is necessary
to add 3 field-supplied Fan Coil Relay Boards, P/N
33ZCRLYBRD. Relay board no. 1 and no. 2 should be
installed in the control box of condensing unit A and relay
board no. 3 should be installed in the control box of condens-
ing unit B. The condensing units may be controlled in two dif-
ferent ways:
1. If a face split coil is desired in cooling, connect the wiring
as shown in Fig. 10B.
2. If a full face active coil is desired in cooling, connect the
wiring as shown in Fig. 10C.
IMPORTANT: Contact your local electric utility com-
pany immediately if the supply voltage phase imbalance
is more than 2%.
Unit cabinet must have an uninterrupted, unbroken electrical
ground to minimize the possibility of personal injury if an
electrical fault should occur. This ground may consist of elec-
trical wire connected to unit ground lug in control compart-
ment, or conduit approved for electrical ground when
installed in accordance with NEC (National Electrical Code)
(U.S.A.), ANSI/NFPA (American National Standards Insti-
tute/National Fire Protection Association) (U.S.A.), and local
electrical codes. Failure to follow this warning could result in
the installer being liable for personal injury of others.
IMPORTANT: Operation of unit on improper power
supply voltage or with excessive phase imbalance con-
stitutes abuse and is not covered by Carrier warranty.
IMPORTANT: BE CERTAIN UNUSED WIRES ARE
CAPPED. Failure to do so may damage the transformer.