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E. Control Circuit Wiring
Unit internal control circuit voltage is 24 volts. See Table 8
for recommended thermostats. Connect thermostat assembly
and other accessories as shown in unit label diagram and
Fig. 10. Refer to installation instructions shipped with
indoor unit. See Fig. 11 for field-supplied airflow switch wir-
ing if airflow switch is used. The control wiring entrance is
located on right corner post of 541A unit. See Fig. 1. Wiring
connects to a terminal block located at extreme right of con-
trol 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 trans-
formers 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.
IMPORTANT:
BE
CERTAIN
CAPPED. Failure to do so may damage the transformer.
Route thermostat cable or equivalent single leads of no. 18
AWG (American Wire Gage) colored wire from subbase ter-
minals through conduit in unit to low-voltage connections as
shown on unit wiring diagram and Fig. 10.
For wire runs up to 50 ft, use no. 18 AWG insulated wire
(35 C minimum). For 51 to 75 ft, use no. 16 AWG insulated
wire (35 C minimum). For over 75 ft, use no. 14 AWG insu-
lated wire (35 C minimum). All wire larger than no. 18 AWG
cannot be directly connected to the thermostat and will
require a junction box and a splice at the thermostat.
F. Electric Resistance Crankcase Heater
The crankcase heater is inserted into the compressor crank-
case. The crankcase heater is operated from the normally
closed contacts of the control relay (CR1) and is automati-
cally energized when compressor stops. This heater keeps
crankcase warm to prevent oil dilution by refrigerant,
ensures good lubrication, and minimizes loss of oil during
start-up.
G. Airflow Switch
Bryant recommends an indoor airflow switch (field supplied)
be installed and interlocked with the outdoor unit. This pre-
vents the outdoor unit from operating if indoor airflow fails
(broken fan belt, etc.). Operation of the compressor in vac-
uum can damage bearing surfaces. Install indoor airflow
switch in a convenient location at the indoor supply air duct
and wire per Fig. 11.
PRE-START-UP
IMPORTANT: Before beginning Pre-Start-Up or Start-Up,
review Start-Up Checklist at the back of this book. The
checklist assures proper start-up of the system and provides
a record of unit condition, application requirements, system
information, and operation at initial start-up.
CAUTION: Do not attempt to start the heat pump
system, even momentarily, until the following steps
have been completed. Compressor damage may result.
I. SYSTEM CHECK
1. Check all air handler and other equipment auxiliary
components. If unit has field-installed accessories, be
sure all are properly installed and correctly wired. If
UNUSED
WIRES
ARE
—
used, airflow switch must be properly installed. See
Fig. 11.
2. Backseat (open) compressor suction and discharge
valves. Now close valves one turn to allow refrigerant
pressure to reach test gages.
3. Open liquid line service valve.
4. Check tightness of all electrical connections.
5. Compressor oil level should be visible in sight glass.
Adjust the oil level as required. No oil should be
removed unless the crankcase heater has been ener-
gized for at least 24 hours. See Start-Up section, Pre-
liminary Oil Charge on page 12.
6. Be sure unit is properly leak checked, dehydrated,
and charged. See Preliminary Charge, this page.
7. Electrical power source must agree with nameplate
rating.
8. Crankcase heater must be firmly locked into compres-
sor crankcase. Be sure crankcase is warm (heater
must be on for 24 hours before starting compressor).
9. Be sure compressor floats freely on the mounting
springs and that upper flat washers can be moved
with finger pressure. See Compressor Mounting,
page 2, and Fig. 4 for loosening compressor bolts.
II. LEAK TEST AND DEHYDRATION
Leak test the entire refrigerant system using soap bubbles
and/or an electronic leak detector. Evacuate and dehydrate
entire refrigerant system by use of methods described in
GTAC II, Module 4, System Dehydration.
III. TURN ON CRANKCASE HEATER
Turn on crankcase heater for 24 hours before starting the
unit to be sure all refrigerant is out of the oil. To energize
crankcase heater, perform the following steps:
1. Set the space thermostat system switch to OFF, or
adjust the temperature so there is no demand for
cooling.
2. Close the field disconnect.
3. Leave the compressor circuit breaker off. The crank-
case heater is now energized.
IV. PRELIMINARY CHARGE
Refer to GTAC II, Module 5, Charging, Recovery, Recycling,
and Reclamation for charging methods and procedures.
Charge with R-22 by the liquid charging method (through
liquid service valve) on the high side. See approximate
refrigerant charge in Table 4. Charge according to the values
in the Charging Charts, Fig. 12 and 13, on page 14.
V. THERMOSTAT ANTICIPATOR ADJUSTMENT
A. Heating/Cooling Thermostat (HH621606)
The thermostat has an adjustable heat anticipator for both
first- and second-stage heating circuits.
B. Settings
Set adjustment lever for first-stage anticipator at 0.79 (left-
hand side). Set adjustment lever for second-stage anticipator
(right-hand side) at 0.42.
C. Outdoor Thermostat
Refer to 524A-H accessory heater installation instructions
for details of this thermostat (if used).
10
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