Page 18
DO NOT CHARGE UNIT
(Results of charging at low
temperatures not reliable)
START: Measure outdoor ambient temperature
USE WEIGH-IN METHOD
Weigh-in or remove refrigerant
based upon line length
APPº (Approach) Values(F:+/−1.0° [C: +/−0.6°])
1.. Connect gauge set as illustrated in figure 17.
2.. Confirm proper airflow across coil using figure 18.
3.. Compare unit pressures with table 6, Normal
Operating Pressures.
4.. Set thermostat to call for heat (must have a cooling
load between 70-80ºF (21−26ºC).
5.. When heat demand is satisfied, set thermostat to call
for cooling.
6.. Allow temperatures and pressures to stabilize.
7.. Record outdoor ambient temperature:
AMBº =_________
8.. Record liquid line temperature:
LIQº = __________
9.. Subtract to determine approach (APPº):
LIQº_____ − AMBº _____ = APPº_____
10.. Compare results with table below.
FIGURE 21
64ºF and
BELOW
65ºF
and
ABOVE
ABOVE or BE-
LOW
If value is MORE
than shown, remove
refrigerant.
If value is LESS
than shown, add
refrigerant.
If refrigerant is added
or removed, verify
charge using the
Subcooling Method.
MORE or
LESS
ºF (ºC)* −018 −024 −030 −036 −042 −048 −060
65 (18) 4 (2.2) 2 (1.1) 2 (1.1) 2 (1.1 6 (3.3) 7 (3.9) 8 (4.4)
75 (24) 5 (2.8) 4 (2.2) 4 (2.2) 5 (2.8) 8 (4.4) 8 (4.4) 9 (5.0)
85 (29) 6 (3.3) 4 (2.2) 6 (3.3) 8 (4.4) 8 (4.4) 8 (4.4) 9 (5.0)
95 (35) 5 (2.8) 4 (2.2) 5 (2.8) 7 (3.9) 8 (4.4) 8 (4.4) 9 (5.0)
105 (41) 3 (1.7) 4 (2.2) 5 (2.8) 6 (3.3) 8 (4.4) 8 (4.4) 9 (5.0)
115 (45) 3 (1.7) 3 (1.7) 4 (2.2) 6 (3.3) 8 (4.4) 9 (5.0) 9 (5.0)
*Temperature of air entering outdoor coil
B
Once refrigerant charge is
correct, disconnect gauge set
and replace service port caps.
APPROACH TXV
DO NOT CHARGE UNIT
(Results of charging at low
temperatures not reliable)
START: Measure outdoor ambient temperature
USE WEIGH-IN METHOD
Weigh-in or remove refrigerant
based upon line length
SCº (Subcooling) Values (F:+/−1.0° [C: +/−0.6°])
BLOCK OUTDOOR COIL: [sometimes necessary with lower
temperatures] Use cardboard or plastic sheet to restrict the airflow
through the outdoor coil to achieve pressures 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 pressure is in the above noted ranges.
If value is MORE
than shown, remove
refrigerant.
1.. Connect gauge set as illustrated in figure 17.
2.. Confirm proper airflow across coil using figure 18.
3.. Compare unit pressures with table 6, Normal
Operating Pressures.
4.. Set thermostat to call for heat (must have a cooling
load between 70-80ºF (21−26ºC)
5.. Measure outdoor ambient temperature
6.. When heat demand is satisfied, set thermostat to
call for cooling
7.. Allow temperatures and pressures to stabilize.
NOTE − If necessary, block outdoor coil to maintain
325 − 375 psig.
8.. Record liquid line temperature:
LIQº = ______
9.. Measure liquid line pressure and use the value to
determine saturation temperature (see table 5):
SATº = ______
10.. Subtract to determine subcooling (SCº):
SATº_____ − LIQº _____ = SCº _____
11.. Compare results with table below.
FIGURE 22
MORE or
LESS
If refrigerant is added or
removed, verify charge
using the Approach
Method.
64ºF and
BELOW
65ºF
and
ABOVE
ABOVE or BE-
LOW
ºF (ºC)* −018 −024 −030 −036 −042 −048 −060
65 (18) 10 (5.6) 10 (5.6) 11 (6.1) 13 (7.2) 10 (5.6) 8 (4.4) 8 (4.4)
75 (24) 6 (3.3) 7 (3.9) 8 (4.4) 9 (5.0) 7 (3.9) 8 (4.4) 7 (3.9)
85 (29) 6 (3.3) 8 (4.4) 6 (3.3) 7 (3.9) 7 (3.9) 8 (4.4) 8 (4.4)
95 (35) 6 (3.3) 9 (5.0) 6 (3.3) 8 (4.4) 7 (3.9) 8 (4.4) 7 (3.9)
105 (41) 10 (5.6) 9 (5.0) 7 (3.9) 9 (5.0) 7 (3.9) 8 (4.4) 6 (3.3)
115 (45) 10 (5.6) 10 (5.6) 8 (4.4) 10 (5.6) 7 (3.9) 7 (3.9) 6 (3.3)
*Temperature of air entering outdoor coil
C
If value is LESS
than shown, add
refrigerant.
Once refrigerant charge is
correct, disconnect gauge set
and replace service port caps.
CARDBOARD OR
PLASTIC SHEETS
SUBCOOLING TXV
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