Page 12
Approach TXV Charge
DO NOT CHARGE UNIT
(Results of charging at low
temperatures not reliable)
ABOVE
START: Measure outdoor ambient temperature
BELOW
USE WEIGH-IN METHOD
Weigh-in or remove refriger-
ant based upon line length
APPº (Approach) Values(F:+/−1.0°; [C: +/−0.6°])
Outdoor Am-
bient 65ºF
(18ºC)?
If refrigerant added or
removed, retest to
confirm that unit is
properly charged
If value is greater than shown (high
approach), add refrigerant; if less
than shown (liquid temp too close to
ambient temp, low approach), remove
refrigerant.
ºF (ºC)* −018 −024 −030 −036 −042 −048 −060
Any 8 (4.4) 8 (4.5) 9 (5.0) 15 (8.3) 10 (5.6) 6 (3.3) 9 (5.0)
*Temperature of air entering outdoor coil
1.. Confirm proper airflow across coil using figure
11.
2.. Check liquid and vapor line pressures and
compare unit pressures with Normal Operat-
ing Pressures listed in table 2 on page 9.
(Table 2 is a general guide. Expect minor
pressures variations. Significant differences
may mean improper charge or other system
problem.)
3.. Use APPROACH to correctly charge unit or
to verify the charge is correct.
APPROACH METHOD
4.. Set thermostat to call for heat (must have a
cooling load between 70-80ºF (21−26ºC)
5.. Connect gauge set
6.. When heat demand is satisfied, set thermo-
stat to call for cooling
7.. Allow temperatures and pressures to stabilize
8.. Record outdoor ambient
temperature AMBº =_________
9.. Record line temp. LIQº = __________
10.. Subtract to determine approach (APPº):
11.. LIQº_____ − AMBº _____ = APPº_____
12.. Compare results with table to the left
Subcooling TXV Charge
DO NOT CHARGE UNIT
(Results of charging at low
temperatures not reliable)
ABOVE
START: Measure outdoor ambient temperature
BELOW
USE WEIGH-IN METHOD
Weigh-in or remove refriger-
ant based upon line length
SCº (Subcooling) Values (F:+/−1.0°; [C: +/−0.6°])
Outdoor Am-
bient 65ºF
(18ºC)?
If refrigerant added or
removed, verify
charge using the
approach method
BLOCK OUTDOOR COIL
[sometimes necessary with lower temperatures]
Use cardboard or plastic sheet to restrict the
airflow through the outdoor coil to achieve pres-
sures from 325−375 psig (2240−2585 kPa).
Higher pressures are needed to check charge.
Block equal sections of air intake panels and
move coverings sideways until the liquid pres-
sure is in the above noted ranges.
If value is greater than
shown, remove
refrigerant; if less than
shown, add refrigerant
ºF (ºC)* −018 −024 −030 −036 −042 −048 −060
Any 8 (4.4) 8 (4.4) 7 (3.8) 4 (2.2) 8 (4.4) 10 (5.6) 7 (3.9)
*Temperature of air entering outdoor coil
1.. Confirm proper airflow across coil using figure
11.
2.. Check liquid and vapor line pressures and
compare unit pressures with Normal Operat-
ing Pressures listed in table 2.
(Table 2 is a general guide. Expect minor pres-
sures variations. Significant differences may
mean improper charge or other system prob-
lem.)
3.. Use SUBCOOLING to correctly charge unit or
to verify the charge is correct.
SUBCOOLING METHOD
4.. Set thermostat to call for heat (must have a
cooling load between 70-80ºF (21−26ºC)
5.. Connect gauge set
6.. Measure outdoor ambient temperature
7.. When heat demand is satisfied, set thermo-
stat to call for cooling
8.. Allow temperatures and pressures to stabilize
[NOTE − IF NECESSARY, block outdoor coil
to maintain 325 − 375 psig]
9.. Record line temp. LIQº = ______
10.. Measure liquid line pressure and use the val-
ue to determine saturation temperature
(table 4 on page 11) SATº = ______
11.. Subtract to determine subcooling (SCº):
12.. SATº_____ − LIQº _____ = SCº _____
13.. Compare results with table to the left.
+
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