Lennox ELP Series User Manual page 14

4 - If the outdoor ambient temperature is below 65ºF
(18ºC) it may be necessary to restrict the air flow
through the outdoor coil to achieve liquid pressures
in the 325-375 psig (2240-2585 kPa) range. These
higher pressures are necessary for checking the
charge. Block equal sections of the outdoor coil on
all coil sides until the liquid pressure is in the 325-
375 psig range (figure 10).
OUTDOOR COIL SHOULD BE BLOCKED ONE SIDE AT A TIME
WITH CARDBOARD OR PLASTIC SHEET UNTIL PROPER
TESTING PRESSURES ARE REACHED.
FIGURE 15. Blocking Outdoor Coil
Models
ELP090S4S / ELA090
ELP120S4S / ELA120
*Approach temperature method valid at full load.
TABLE 6. HFC-410A Normal Operating Pressures – Cooling Mode (Liquid ±10 and Suction ±5 psig)*
ELP090 / ELA090
Outdoor Air
Temp
Liquid
65º F (18º C) 226
75º F (24º C) 261
85º F (29º C) 303
95º F (35º C) 349
105º F (41º C)
404
115º F (46º C) 462
125º F (52º C)
525
SCFM
*pressures at 80°F dry bulb and 67°F wet bulb.
CARDBOARD OR
PLASTIC SHEET
TABLE 5. HFC-410A Approach Temperatures*
Approach Temperature (ºF) (+/-1)
ELP120 / ELA120
Suction Liquid
119 247
125 291
129 333
133 370
135 437
137 495
136 562
2760 4000
A - Charge the unit using the approach method in the
next section:
• Using the same thermometer, compare liquid tempera-
ture at service valve to outdoor ambient temperature.
Approach Temperature = Liquid temperature minus
• Approach temperature should be as indicated in ta-
bles 3 or 6 for each stage. An approach temperature
greater than this value indicates an undercharge.
An approach temperature less than this value indi-
cates an overcharge.
• Add or remove charge in increments.
• Allow system to stabilize at least 5 minutes each
time refrigerant is added or removed.
• Do not use the approach method if system pres-
sures do not match pressures in table 4, 5, or 7
except when the outdoor ambient temperature is
below 65ºF (18ºC).
• The approach method is not valid for grossly over or
undercharged systems.
7.0
6.0
Suction Stg 1 Liquid
132 221
136 260
138 304
140 354
142 403
144 462
146 526
Page 14
ambient temperature
Approach Temperature (ºC) (+/-.05)
3.9
3.3
(2) ELP090 + ELA240
Stg 1 Suction Stg 2 Liquid
137 223
140 261
142 305
145 357
147 406
150 469
152 538
6125
Stg 2 Suction
134
136
138
141
143
146
150