Carrier 50PEC09-18 - Manual (Page 36)

36
Checking System Charge — Units are shipped with
full operating charge. If recharging is necessary:
1. Insert thermometer bulb in insulating rubber sleeve on
liquid line near filter drier. Use a digital thermometer for
all temperature measurements. DO NOT use a mercury
or dial-type thermometer.
2. Connect pressure gage to discharge line near compressor.
3. After unit conditions have stabilized, read head pressure
on discharge line gage.
NOTE: Operate unit a minimum of 15 minutes before
checking charge. From standard field-supplied Pressure-
Temperature chart for R-410A, find equivalent saturated
condensing temperature.
4. Read liquid line temperature on thermometer, then
subtract from bubble point temperature. The difference
equals subcooling temperature.
Refrigerant Charging
NOTE: Do not vent or depressurize unit refrigerant to atmo-
sphere. Remove and recover refrigerant following accepted
practices.
Air Coil Fan Motor Removal
Motor power wires need to be disconnected from motor
terminals before motor is removed from unit.
1. Shut off unit main power supply.
2. Loosen bolts on mounting bracket so that fan belt can be
removed.
3. Loosen and remove the 2 motor mounting bracket bolts
on left side of bracket.
4. Slide motor/bracket assembly to extreme right and lift out
through space between fan scroll and side frame. Rest
motor on a high platform such as a step ladder. Do not
allow motor to hang by its power wires.
TROUBLESHOOTING
When troubleshooting problems with a WSHP, consider the
following and refer to Table 15.
Thermistor — A thermistor may be required for single-
phase units where starting the unit is a problem due to low
voltage. See Fig. 32 for thermistor nominal resistance.
Control Sensors — The control system employs 2 nom-
inal 10,000 ohm thermistors (FP1 and FP2) that are used for
freeze protection. Be sure FP1 is located in the discharge fluid
and FP2 is located in the air discharge. See Fig. 33.
WARNING
When replacing the compressor contactor or lockout relay
in a unit with electromechanical controls, use only Carrier
factory authorized parts. Substitution of other components
may result in an inoperative safety circuit and may cause a
hazardous condition.
WARNING
To prevent personal injury, wear safety glasses and gloves
when handling refrigerant. Do not overcharge system —
this can cause compressor flooding.
CAUTION
Before attempting to remove fan motors or motor mounts,
place a piece of plywood over evaporator coils to prevent
coil damage.
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
90.0
-17.7 -6.6 4.4 15.6 26.7 37.8 48.9 60.0
Temperature (C)
Re
s
is
ta
nce (kOhm)
Fig. 32 — Thermistor Nominal Resistance
SUCTIO N
COMPRESSOR
DISCHARGE
COAX EXP ANSION
VA LV E
FP 2 FP 1
LIQUI D
LIN E
WA TER IN WA TER OUT
CONDENSA TE
OVERFLO W
(CO)
AIR COI L
FREEZ E
PROTECTIO N
WA TE R
COI L
PROTECTIO N
THERMIST OR
( °C) ( °C)
AI R
COI L
AIRFLOW AIRFLO W
a50-8163
Fig. 33 — FP1 and FP2 Thermistor Location
LEGEND
COAX — Coaxial Heat Exchanger
Airflow
Refrigerant Liquid Line Flow