Page 17
If the system is completely void of refrigerant, the recom-
mended and most accurate method of charging is to weigh
the refrigerant into the unit according to the total amount
shown on the unit nameplate.
If weighing facilities are not available or if unit is just low on
charge, use the following procedure:
1 − Connect gauge manifold as shown in figure 12. Con-
nect an R410A drum to center port of gauge manifold.
2 − Record outdoor ambient temperature using a digital
thermometer.
3 − Set room thermostat to 74
F (23
C) in Emergency
Heat" or Heat" position and allow unit to run until
heating demand is satisfied. This will create the nec-
essary load for proper charging of system in cooling
cycle. Change thermostat setting to 68
F (20
C) in
Cool" position. Allow unit to run until system pres-
sures stabilize.
4 − Use the same digital thermometer used to check out-
door ambient temperature to check liquid line temper-
ature.
5 − If outdoor temperature is 60
F (15
C) or above, use
the approach method to check the refrigerant charge.
The difference between ambient and liquid line tem-
peratures should match values given in table 5. Refrig-
erant must be added to lower approach temperature.
Remove refrigerant from system to increase approach
temperature.
TABLE 5
Model Number
Approach Temperature
Liquid Line Temp. − Outdoor Ambient °F (°C)
HPXA12−18
5 (2.8)
HPXA12−24
8.0 (4.4)
HPXA12−30
12.5 (6.9)
HPXA12−36
13 (7.2)
HPXA12−42
13 (7.2)
HPXA12−48
8.5 (4.7)
HPXA12−60
12 (6.7)
6 − If ambient temperature is less than 60
F (15
C), air
flow might need to be restricted to achieve pressures in
the 300−350 psig (2068−2413 kPa) range. See figure
16. These higher pressures are necessary for checking
charge. Block equal sections of air intake panels, mov-
ing obstructions sideways as shown until liquid pres-
sure is in the 300−350 psig (2068−2413 kPa) range.
BLOCKING OUTDOOR COIL
CARDBOARD OR
PLASTIC SHEET
OUTDOOR COIL SHOULD
BE BLOCKED ONE SIDE
AT A TIME WITH CARD−
BOARD OR PLASTIC
SHEET UNTIL PROPER
TESTING PRESSURES
ARE REACHED.
FIGURE 16
TABLE 6
Model Number
Subcooling Values
Conversion Temp. − Liquid Line Temp. °F (°C)
HPXA12−18
8.5 (4.7)
HPXA12−24
12.5 (6.9)
HPXA12−30
5.5 (3.1)
HPXA12−36
8.5 (4.7)
HPXA12−42
8.5 (4.7)
HPXA12−48
7 (3.9)
HPXA12−60
7 (3.9)
7 − Read liquid line temperature. Read liquid line pres-
sure from gauge and convert to heat pump tempera-
ture using the temperature/pressure chart for R410A
refrigerant provided in table 8. The difference be-
tween the liquid line temperature and the conversion
temperature is the subcooling temperature (subcool-
ing = conversion temperature minus liquid tempera-
ture). Subcooling should approximate values given in
table 6. Add refrigerant to increase subcooling and re-
move refrigerant to reduce subcooling. Be aware of
the R410A refrigerant cylinder. It will be light ma-
roon−colored. Refrigerant should be added through
the vapor line valve in the liquid state.
Some R410A
cylinders are equipped with a dip tube which al-
lows you to draw liquid refrigerant from the bot-
tom of the cylinder without turning the cylinder
upside−down. The cylinder will be marked if it is
equipped with a dip tube.
8 − Use table 7 as a general guide when performing main-
tenance checks. This is not a procedure for charging
unit. Minor variations in these pressures may be ex-
pected due to differences in installations. Significant
differences could mean that the system is not properly
charged or that a problem exists with some component
in the system. Used carefully, this table could serve as
a useful service guide.
