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4 - If the outdoor ambient temperature is below 65ºF
(18ºC) it may be necessary to restrict the air ow
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 (gure 10).
CARDBOARD OR
PLASTIC SHEET
COIL SHOULD BE BLOCKED ONE SIDE AT A TIME
H CARDBOARD OR PLASTIC SHEET UNTIL PROPER
G PRESSURES ARE REACHED.
FIGURE 15. Blocking Outdoor Coil
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
ambient temperature
• 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.
TABLE 5. HFC-410A Approach Temperatures*
Models Approach Temperature (ºF) (+/-1) Approach Temperature (ºC) (+/-.05)
ELP090S4S / ELA090 7.0 3.9
ELP120S4S / ELA120 6.0 3.3
*Approach temperature method valid at full load.
TABLE 6. HFC-410A Normal Operating Pressures – Cooling Mode (Liquid ±10 and Suction ±5 psig)*
Outdoor Air
Temp
ELP090 / ELA090 ELP120 / ELA120 (2) ELP090 + ELA240
Liquid Suction Liquid Suction Stg 1 Liquid Stg 1 Suction Stg 2 Liquid Stg 2 Suction
65º F (18º C) 226 119 247 132 221 137 223 134
75º F (24º C) 261 125 291 136 260 140 261 136
85º F (29º C) 303 129 333 138 304 142 305 138
95º F (35º C) 349 133 370 140 354 145 357 141
105º F (41º C) 404 135 437 142 403 147 406 143
115º F (46º C) 462 137 495 144 462 150 469 146
125º F (52º C) 525 136 562 146 526 152 538 150
SCFM 2760 4000 6125
*pressures at 80°F dry bulb and 67°F wet bulb.
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