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3. Unit is shipped with valve stem(s) front seated and caps
installed. Replace stem caps after system is opened to refrig-
erant flow (back seated). Replace caps finger tight and tighten
additional 1/12 turn (20 ft-lb torque) with wrench.
4. Close electrical disconnects to energize system.
5. Set room thermostat at desired temperature. Be sure the set
point is below indoor ambient and is set low enough to
energize desired speed.
NOTE: Carrier electronic thermostats are equipped with a 15-
minute staging timer. This timer prevents the 2-speed system from
operating at high speed until unit has been operating in low speed
for 15 minutes unless there is at least a 5°F difference between
room temperature and thermostat set point. To force high speed
(after a minimum of 2 minutes in low speed), adjust the set point
at least 5° below room ambient for cooling or 5° above room
ambient for heating.
6. Set room thermostat to COOL or HEAT and fan control to
AUTO or ON as desired. Wait for the appropriate time
delay(s) and the 2-minute minimum low-speed run time.
Operate unit for 15 minutes. Check refrigerant charge.
Step 12—Check Charge
Service valve gage ports are not equipped with Schrader
valves. To prevent personal injury, make sure gage manifold
is connected to the valve gage ports before moving valves off
fully back seated position. Wear safety glasses and gloves
when handling refrigerant.
UNIT CHARGE
Factory charge is shown on unit rating plate. To check charge in
cooling mode, refer to Cooling Only Procedure. To check charge
in heating mode, refer to Heating Check Chart Procedure.
NOTE: When 2-speed unit is operating in low-speed cooling,
system vapor (suction) pressure will be higher than a standard
single-speed system or high-speed operation. This normal opera-
tion is due to the reduced capacity operating with typically larger
indoor and outdoor coils.
Adjust charge in both heating and cooling by following procedure
shown on charging tables located on unit information plate on back
side of access panel.
COOLING ONLY PROCEDURE
1. Operate unit a minimum of 10 minutes before checking
charge.
2. Measure liquid service valve pressure by attaching an accurate
gage to service port.
3. Measure liquid line temperature by attaching an accurate
thermistor type or electronic thermometer to liquid line near
outdoor coil.
4. Refer to unit rating plate for required subcooling temperature.
5. Refer to Table 6. Find the point where required subcooling
temperature intersects measured liquid service valve pressure.
6. To obtain required subcooling temperature at a specific liquid
line pressure, add refrigerant if liquid line temperature is
higher than indicated or reclaim refrigerant if temperature is
lower. Allow a tolerance of ± 3°F.
HEATING CHECK CHART PROCEDURE
To check system operation during heating cycle, refer to the
Heating Check Chart on outdoor unit. This chart indicates whether
a correct relationship exists between system operating pressure and
air temperature entering indoor and outdoor units. If pressure and
Table 6—Required Liquid-Line Temperature (°F)
LIQUID
PRESSURE AT
SERVICE VALVE
(PSIG)
134
141
148
156
163
171
179
187
196
205
214
223
233
243
253
264
274
285
297
309
321
331
346
359
temperature do not match on chart, system refrigerant charge may
not be correct. Do not use chart to adjust refrigerant charge.
NOTE: When charging is necessary during heating season,
charge must be weighed in accordance with unit rating plate ± 0.6
oz/ft of 3/8-in. liquid line above or below 15 ft respectively.
EXAMPLE:
To calculate additional charge required for a 25-ft line set:
25 ft - 15 ft = 10 ft X 0.6 oz/ft = 6 oz of additional charge
Step 13—System Functions and Sequence of
Operation
The outdoor unit control system has special functions. The
following is an overview of the 2-speed control functions:
COOLING OPERATION
This product utilizes a 2-stage cooling indoor thermostat. With a
call for first stage cooling (Y1), the outdoor fan and low-speed
compressor are energized. If low speed cannot satisfy cooling
demand, high speed is energized (Y1 and Y2) by the second stage
of indoor thermostat. After second stage is satisfied, the unit
returns to low-speed operation until first stage is satisfied or until
second stage is required again.
HEATING OPERATION
This product utilizes a 2-stage heating indoor thermostat. The first
stage of heating is heat pump operation (Y1), while auxiliary or
back up heat is controlled by second stage (W2). The control board
determines speed of heat pump operation. See Table 7 for ambients
at which high-speed and low-speed operations occur.
NOTE: The values in Table 7 are valid unless the ZONE option
has been selected on the 2-speed control board STAGE 2 LATCH
pot. See Zoning Selection section for details.
15
REQUIRED SUBCOOLING
TEMPERATURE
(°F)
5
10
15
71
66
61
74
69
64
77
72
67
80
75
70
83
78
73
86
81
76
89
84
79
92
87
82
95
90
85
98
93
88
101
96
91
104
99
94
107
102
97
110
105
100
113
108
103
116
111
106
119
114
109
122
117
112
125
120
115
128
123
118
131
126
121
134
129
124
137
132
127
140
135
130
20
56
59
62
65
68
71
74
77
80
83
86
89
92
95
98
101
104
107
110
113
116
119
122
125
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