Page 29
DO NOT CHARGE UNIT
(Results of charging at low
temperatures not reliable)
START: Measure outdoor ambient temperature
USE WEIGH
‐
IN METHOD
ant based upon line length
1. Confirm proper airflow across coil using figure
19.
2. Compare unit pressures with normal operating
pressures provided on applicable charging
sticker as reference in table 1.
3. Set thermostat to call for heat (must have a
cooling load between 70
‐
80ºF (21-26ºC).
4. Connect gauge set.
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 applicable charging
sticker located on unit access panel or copy
located at the end of this manual. See table 2 for
to determine applicable charging information for
specific model.
ABOVE or
BELOW
If value is greater than
shown (high approach),
add refrigerant; if less
than shown (liquid
temperature too close to
ambient temperature,
low approach), remove
refrigerant.
If refrigerant is added
or removed, retest to
confirm that unit is
properly charged.
64ºF
(17.7ºC) and
Below
65ºF
(18.3ºC) and
Above
APPROACH TXV
FIGURE 21. HFC-410A Approach TXV Charge
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
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. Confirm proper airflow across coil using figure
19.
2. Compare unit pressures with normal operating
pressures provided on applicable charging
sticker as reference in table 1.
3. Set thermostat to call for heat (must have a
cooling load between 70
‐
80ºF (21-26ºC)
4. Connect gauge set
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 4):
SATº = ______
10. Subtract to determine subcooling (SCº):
SATº_____ - LIQº _____ = SCº _____
11. Compare results with applicable charging sticker
located on unit access panel or copy located at
the end of this manual. See table 3 for to
determine applicable charging information for
specific model.
MORE
or
LESS
If value is
LESS
than shown, add
refrigerant.
If refrigerant is
added or removed,
verify charge using
the
Approach
Method
.
ABOVE or
BELOW
64ºF
(17.7ºC) and
Below
65ºF
(18.3ºC) and
Above
CARDBOARD OR PLASTIC SHEET
SUBCOOLING TXV
FIGURE 22. HFC-410A Subcooling TXV Charge
