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SERVICING
4. The difference between the thermometer reading and
pressure to temperature conversion is the amount of
subcooling.
Subcooling Formula = Sat. Liquid Temp. - Liquid Line
Temp.
EXAMPLE:
A.
Liquid Line Pressure = 417
B.
Corresponding Temp. °F. = 120°
C.
Thermometer on Liquid line = 109°F.
To obtain the amount of subcooling subtract 109°F from
120°F.
The difference is 11° subcooling. See the specification
sheet or technical information manual for the design
subcooling range for your unit.
See R410A Pressure vs. Temperature Chart
Expansion Valve (TXV) System Two Speed Application
Run the unit on high stage cooling for 15-20 minutes until
refrigerant pressures stabilize. Check charge with unit on
high stage.
Follow Checking Subcooling Instructions.
NOTE: THE TXV PROVIDED IS DESIGNED TO MEET
THE SPECIFICATION REQUIREMENTS FOR OPTIMUM
PRODUCT OPERATION. "NO ADJUSTMENTS NEEDED
TO TXV"
SATURATED LIQUID PRESSURE
TEMPERATURE CHART
Liquid
Pressure
PSIG
200
210
220
225
235
245
255
265
275
285
295
305
325
355
375
405
Saturated Liquid
Temperature °F
R-410A
70
73
76
78
80
83
85
88
90
92
95
97
101
108
112
118
Heat Pump - Heating Cycle
The proper method of charging a heat pump in the heat
mode is by weighing the charge according to the total
charge listed on the rating plate.
Checking expansion valve operation
1. Remove the remote bulb of the expansion valve from
the suction line.
2. Start the system and cool the bulb in a container of
ice water, closing the valve. As you cool the bulb,
the suction pressure should fall and the suction
temperature will rise.
3. Next warm the bulb in your hand. As you warm the
bulb, the suction pressure should rise and the suction
temperature will fall.
4. If a temperature or pressure change is noticed, the
expansion valve is operating. If no change is noticed,
the valve is restricted, the power element is faulty, or
the equalizer tube is plugged.
5. Capture the charge, replace the valve and drier and
evacuate.
Fixed Orifice Restriction Devices
The fixed orifice restriction device (flowrator) used in
conjunction with the indoor coil is a predetermined bore
(I.D.).
It is designed to control the rate of liquid refrigerant flow
into an evaporator coil.
The amount of refrigerant that flows through the fixed
orifice restriction device is regulated by the pressure
difference between the high and low sides of the system.
In the cooling cycle when the outdoor air temperature rises,
the high side condensing pressure rises. At the same time,
the cooling load on the indoor coil increases, causing the
low side pressure to rise, but at a slower rate.
Since the high side pressure rises faster when the
temperature increases, more refrigerant flows to the
evaporator, increasing the cooling capacity of the system.
When the outdoor temperature falls, the reverse takes
place. The condensing pressure falls, and the cooling loads
on the indoor coil decreases, causing less refrigerant flow.
If a restriction should become evident, proceed as follows:
1. Recover refrigerant charge.
2. Remove the orifice assembly and clean or replace.
3. Replace liquid line drier, evacuate and recharge.
Checking Equalization Time
During the "OFF" cycle, the high side pressure bleeds to
the low side through the fixed orifice restriction device.
Check equalization time as follows:
1. Attach a gauge manifold to the suction and liquid line
access fittings.
2. Start the system and allow the pressures to stabilize.
28
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