Refrigerant Charging; Air Coil Fan Motor Removal; Troubleshooting; Thermistor - Carrier Aquazone 50RHE 006 Installation, Operation And Maintenance Instructions

6. Compare the subcooling temperature with the normal
temperature listed in Table 9. If the measured liquid line
temperature does not agree with the required liquid line
temperature, ADD refrigerant to raise the temperature or
REMOVE refrigerant (using standard practices) to lower
the temperature (allow a tolerance of ± 1.7 K).

9.9 - Refrigerant charging

WARNING: To prevent personal injury, wear safety glasses
and gloves when handling refrigerant. Do not overcharge
system - this can cause compressor flooding.
NOTE: Do not vent or depressurise unit refrigerant to atmos-
phere. Remove and reclaim refrigerant following accepted
practices.

9.10 - Air coil fan motor removal

CAUTION: Before attempting to remove fan motors or motor
mounts, place a piece of plywood over evaporator coils to
prevent coil damage.
Disconnect motor power wires 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.
Air flow
Air
coil

Thermistor

Condensate
overflow (CO)
Legend
Air flow
Refrigerant liquid line flow
28
Fig. 21 - FP1 and FP2 thermistor location
Air flow
Expansion
valve
FP1
FP2
Liquid line
Water in
Air coil freeze
Water coil
protection
protection

10 - TROUBLESHOOTING

(Figs. 20 and 21 and Table 16)
When troubleshooting problems with a water-source heat pump,
consider the following.
10.1 - Thermistor
A thermistor may be required for single-phase units where
starting the unit is a problem due to low voltage. (See Fig. 20
for thermistor nominal resistance.)

10.2 - Control sensors

The control system employs 2 nominal 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. 21).
Fig. 20 - Thermistor nominal resistance
90.0
80.0
70.0
60.0
50.0
40.0
30.0
20.0
10.0
0.0
0 -6.7
0.0 20.0
Tube-in-tube
heat
exchanger
Water out
4.4 15.6 26.7 37.8 48.9
40.0 60.0 80.0 100.0 120.0
Temperature (degF)
Temperature (°C)
Suction
Compressor
Discharge
60.0
140.0