Page 9
If weighing facilities are not available or if unit is just
low on charge, the following procedure applies.
The following procedures are intended as a general
guide for use with expansion valve systems only. For
best results, indoor temperature should be between
70
°
F and 80
°
F. Outdoor temperature should be 60
°
F or
above. Slight variations in charging temperature and
pressure should be expected. Large variations may in-
dicate a need for further servicing.
APPROACH METHOD (TXV SYSTEMS)
(Ambient Temperature of 60
F [16
C] or Above)
1– Connect gauge manifold. Connect an upright
HCFC-22 drum to center port of gauge manifold.
IMPORTANT
The following procedure requires accurate read-
ings of ambient (outdoor) temperature, liquid
temperature and liquid pressure for proper charg-
ing. Use a thermometer with accuracy of +2
°
F and
a pressure gauge with accuracy of +5 PSIG.
2– Record outdoor air (ambient) temperature.
3– Operate indoor and outdoor units in cooling mode.
Allow units 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 tem-
perature. Liquid line temperature should be a few de-
grees warmer than the outdoor air temperature.
Table 5 shows how many degrees warmer the liquid
line temperature should be.
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 in table 6.
TABLE 5
Model
HS25–261
HS25–311
APPROACH METHOD – EXPANSION VALVE SYSTEMS
7+1
3+1
HS25–211
7+1
Liquid Line
°
F Warmer Than Outside
(Ambient) Temperature
HS25–411
HS25–461
4+1
5+1
HS25–511
HS25–651
3+1
4+1
IMPORTANT
Use table 6 as a general guide for performing main-
tenance checks. Table 6 is not a procedure for charg-
ing the system. Minor variations in these pressures
may be expected due to differences in installations.
Significant deviations could mean that the system
is not properly charged or that a problem exists
with some component in the system. Used pru-
dently, table 6 could serve as a useful service guide.
D–Oil Charge
Refer toTable 1 on page 5.
VI–MAINTENANCE
At the beginning of each heating or cooling season, the
system should be cleaned as follows:
A–Outdoor Unit
1– Clean and inspect condenser coil. (Coil may be
flushed with a water hose).
2– Visually inspect all connecting lines, joints and
coils for evidence of oil leaks.
IMPORTANT
If insufficient heating or cooling occurs, the unit
should be gauged and refrigerant charge checked.
B–Indoor Coil
1– Clean coil if necessary.
2– Check connecting lines and coil for oil leaks.
3–Check condensate line and clean if necessary.
C–Indoor Unit
1– Clean or change filters.
2– Adjust blower cooling speed. Check static pressure
drop over coil to determine correct blower CFM. Re-
fer to Lennox Engineering Handbook.
3– Belt Drive Blowers - Check condition/tension.
4– Check all wiring for loose connections.
5– Check for correct voltage at unit.
6– Check amp–draw on blower motor.
Unit nameplate_________Actual_________.
TABLE 6
NORMAL OPERATING PRESSURES
OUTDOOR COIL
ENTERING AIR
TEMPERATURE
HS25–261
HS25–311
HS25–411
65
°
F (TXV)
75
°
F (TXV)
85
°
F (TXV)
95
°
F (TXV)
LIQ.
+ 10
SUC.
+ 10
PSIG
PSIG
LIQ.
+ 10
SUC.
+ 10
PSIG
PSIG
LIQ.
+ 10
SUC.
+ 10
PSIG
PSIG
105
°
F (TXV)
LIQ.
+ 10
SUC.
+ 10
PSIG
PSIG
HS25–211
HS25–461
SUC.
+ 10
PSIG
LIQ.
+ 10
PSIG
138
162
189
222
255
78
79
80
82
84
143
167
195
229
263
73
77
80
82
84
140
160
186
216
254
69
74
78
80
81
136
160
191
225
260
74
76
78
79
80
149
176
209
244
275
69
72
74
76
78
HS25–511
LIQ.
+ 10
SUC.
+ 10
PSIG
PSIG
LIQ.
+ 10
SUC.
+ 10
PSIG
PSIG
HS25–651
138
163
182
222
255
73
75
76
78
79
138
164
185
228
260
69
73
74
75
76
