Service Manual

SERVICING
35
SUPERHEAT AND SUBCOOLING ADJUSTMENT ON TXV
APPLICATIONS
Single Speed Application (*PC1460)
1. Purge gauge lines. Connect service gauge manifold to
access fittings. Run system at least 10 minutes to allow
pressure to stabilize.
2. Temporarily install thermometer on liquid (small) line near
liquid line access fitting with adequate contact and insu-
late for best possible reading.
3. Check subcooling and superheat. Systems with TXV ap-
plication should have a subcooling of 10
+ 2°F and super-
heat of 15 to 18ºF.
a. If subcooling and superheat are low, adjust TXV to
15 - 18ºF then check subcooling.
b. If subcooling is low and superheat is high, add charge
to raise subcooling to10 ± 2ºF then check super-
heat.
c. If subcooling and superheat are high, adjust TXV
valve to 15 - 18ºF then check subcooling.
d. If subcooling is high and superheat is low, adjust
TXV valve to 15 to 18ºF superheat and remove
charge to lower the subcooling to 10 ± 2ºF.
The TXV should NOT be adjusted at light load conditions
55º to 60ºF, under such conditions only the subcooling
can be evaluated. This is because suction pressure is
dependent on indoor airflow, and wet bulb temperature.
NOTE: Do NOT adjust charge based on suction pressure
unless there is a gross undercharge.
4. Disconnect manifold set. Installation is complete.
SUBCOOLING = SAT. LIQUID TEMP. - LIQUID LINE TEMP.
Liquid
Pressure
Saturated Liquid
Tem
p
erature °F
PSIG R-410A
200 70
210 73
220 76
225 78
235 80
245 83
255 85
265 88
275 90
285 92
295 95
305 97
325 101
355 108
375 112
405 118
SATURATED LIQUID PRESSURE
TEMPERATURE CHART
Two Speed Application (*PH1460)
Run the unit on low stage cooling for 10 minutes until refriger-
ant pressures stabilize. Follow the guidelines and methods
below to check unit operation and ensure that the refrigerant
charge is within limits. Charge the unit on low stage.
1. Purge gauge lines. Connect service gauge manifold to
access fittings. Run system at least 10 minutes to allow
pressure to stabilize.
2. Temporarily install thermometer on liquid (small) line near
liquid line access fitting with adequate contact and insu-
late for best possible reading.
3. Check subcooling and superheat. Two stage systems run-
ning on low stage with TXV application should have a
subcooling of 5 to 7 ºF and superheat of 15 to 18ºF.
a. If subcooling and superheat are low, adjust TXV to
15 to 18ºF superheat, then check subcooling.