Page 13
IMPORTANT
The following procedures require accurate
readings of ambient (outdoor) temperature, liquid
temperature and liquid pressure for proper
charging. Use a thermometer with accuracy of +2
°
F and a pressure gauge with accuracy of +5 PSIG.
APPROACH METHOD (TXV SYSTEMS)
(Ambient Temperature of 60
_
F [16
_
C] or Above)
1 – Connect gauge manifold. Connect an upright
R–22 drum to center port of gauge manifold.
2 – Record outdoor air (ambient) temperature.
3 – Operate indoor and outdoor units in cooling
mode. Allow outdoor unit to run until system
pressures stabilize.
4 – Make sure thermometer well is filled with
mineral oil before checking liquid line
temperature.
5 – Place thermometer in well and read liquid line
temperature. Liquid line temperature should
be a few degrees warmer than the outdoor air
temperature. Table 9 shows how many
degrees warmer the liquid line temperature
should be.
Add refrigerant to make the liquid line
temperature cooler.
Recover refrigerant to make the liquid line
temperature warmer.
11
TABLE 9
Model
Liquid Line
°
F Warmer Than Outside
(Ambient) Temperature
APPROACH METHOD – EXPANSION VALVE SYSTEMS
AMBIENT TEMPERATURE OF 60
_
F (16
_
C) OR ABOVE
7
14
11
5
6
11
7
14
10HP18
10HP30
10HP48
10HP12
10HP60
10HP42
10HP36 (CAN)
10HP24
10HP36
SUBCOOLING METHOD (TXV SYSTEMS)
(Ambient Temperature Below 60
_
F [16
_
C] )
NOTE- It may be necessary to restrict air flow in order
to reach liquid pressures in the 200-250 psig range
which are required for checking charge. Block equal
sections of air intake panels as shown in figure 22,
moving obstructions sideways until liquid pressures
in the 200-250 psig range are reached.
Block outdoor coil one side at
a time with cardboard or
plastic sheets until proper
testing pressures are reached.
BLOCKING OUTDOOR COIL
FIGURE 22
CARDBOARD OR
PLASTIC SHEET
1 – Connect gauge manifold. Connect an upright
R–22 drum to center port of gauge manifold.
2 – Operate indoor and outdoor units in cooling
mode. Allow outdoor unit to run until system
pressures stabilize.
3 – Make sure thermometer well is filled with
mineral oil before checking liquid line
temperature.
4 – Read liquid line pressure and convert to
condensing temperature using temperature/
pressure conversion chart.
Condensing temperature (read from gauges)
should be a few degrees warmer than the
liquid line temperature.
5 – Place thermometer in well and read liquid line
temperature. Table 10 shows how much
warmer the condensing temperature should be.
Add refrigerant to make the liquid line
temperature cooler.
Recover refrigerant to make the liquid line
temperature warmer.
TABLE 10
Model
Condensing Temp
°
F Warmer Than
Liquid Line
SUBCOOLING METHOD – EXPANSION VALVE SYSTEMS
AMBIENT TEMPERATURE BELOW 60
_
F (16
_
C)
4 + 2
9 + 2
13 + 2
9 + 2
8 + 2
6 + 2
7 + 2
9 + 2
13 + 2
10HP18
10HP30
10HP48
10HP12
10HP60
10HP42
10HP36 (CAN)
10HP24
10HP36
6 – When unit is properly charged liquid line
pressures should approximate those given in
table 11.
IMPORTANT
Use table 11 as a general guide for performing
maintenance checks. Table 11 is not a procedure for
charging the system. Minor variations in pressures
may be expected due to differences in installations.
Significant deviations may mean the system is not
properly charged or that a problem exists with some
component in the system. Used prudently, table 11
could serve as a useful service guide.
