Page 16
1 − Expansion Valve Systems
The following procedures are intended as a general guide for
use with expansion valve systems only. For best results, in-
door temperature should be between 70
°
F and 80
°
F (21
C
and 26.5
C). If outdoor temperature is 60
F (16
°
C) or above
the approach method of charging is used. If outdoor tempera-
ture is less than 60
°
F (16
°
C) the subcooling method of
charging is used. Slight variations in charging temperature
and pressure should be expected. Large variations may indi-
cate a need for further servicing.
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 Above 60
F [16
C] )
1 − Connect gauge manifold. Connect an upright HCFC-22
drum to center port of gauge manifold.
2 − Record outdoor air (ambient) temperature.
3 − Operate indoor and outdoor units in cooling mode. Al-
low outdoor unit to run until system pressure 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 temper-
ature. Liquid line temperature should be a few de-
grees warmer than the outdoor air temperature. Table
9 shows how many degrees warmer the liquid line
should be.
Add refrigerant to make the liquid line cooler.
Remove refrigerant to make the liquid line warmer.
TABLE 9
Model
Liquid Temp. Minus
Ambient Temp.
F (
C)
HP27−042
HP27−024
HP27−030
HP27−036
8 + 1 (4.4 + .5)
5 + 1 (2.8 + .5)
5 + 1 (2.8 + .5)
8 + 1 (4.4 + .5)
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 18, moving obstruc-
tions 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 18
CARDBOARD OR PLASTIC SHEET
1 − Connect gauge manifold. Connect an upright HCFC-22
drum to center port of gauge manifold.
2 − Operate indoor and outdoor units in cooling mode. Allow
units to run until system pressures stabilize.
3 − Make sure thermometer well is filled with mineral oil be-
fore checking liquid line temperature.
4 − Read liquid line pressure and convert to condensing tem-
perature using temperature/ pressure conversion chart.
Condensing temperature (from gauges) should be a few
degrees warmer than the liquid line.
5 − Place thermometer in well and read liquid line tempera-
ture. Table 10 shows how much warmer the condensing
temperature should be.
TABLE 10
Model
Subcooling
F (
C)
HP27−030
HP27−036
8 + 2 (4.4 + 1)
HP27−024
7 + 2 (3.9 + 1)
HP27−042
7 + 2 (3.9 + 1)
8 + 2 (4.4 + 1)
Add refrigerant to make the liquid line cooler.
Recover refrigerant to make the liquid line warmer.
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.
D−Oil Charge
Refer to table 1 on page 3.
