Page 9
Refrigerant Charge
ELP units have a factory holding charge of 2 pounds of
HFC-410A. Additional refrigerant will need to be added
during installation (table 2).
TABLE 2. Adding Refrigerant
Models
25 Feet
1
(pounds
Liquid
Line
Dia.
(inches)
Vapor
Line
Dia.
(inches)
Ounces
Adjustment
per foot of
line set
2
ELP090 /
ELA090
23.25
5/8
1-1/8
1.7
ELP120 /
ELA120
31.0
5/8
1-1/8
1.7
1
Total amount of charge necessary to accommodate 25
feet of line set.
2
If line set length is greater than 25 feet, add this amount
to each circuit. If line set is less than 25 feet, subtract this
amount from each circuit. Refer to Lennox Refrigerant
Piping Design and Fabrication Guidelines for more infor-
mation.
NOTE
-
Refrigerant line sets longer than 200 feet (60 me-
ters) are not recommended. For assistance contact Len-
nox Application Department.
To charge the system, use either of the following proce-
dures:
CHARGE PROCEDURE – NORMAL OPERATING
PRESSURES
1 - Connect a manifold gauge set to the service valves:
A - Low pressure gauge to vapor service port.
B - High pressure gauge to liquid valve service port
2 - Operate system in cooling mode until pressures
and temperatures stabilize (5 minutes minimum).
3 -
Use a thermometer to measure the outdoor
ambient temperature. The outdoor temperature will
determine which charging procedure to use.
Outdoor Temp > 65ºF (18ºC)
1 - Apply the outdoor ambient temperature to table
4 or 5 to determine normal operating pressures.
Compare the normal operating pressures to the
pressures obtained from the connected gauges.
If discharge pressure is high, remove refrigerant
from the system. If discharge pressure is low, add
refrigerant to the system.
A - Add or remove charge in increments.
B - Allow the system to stabilize at least 5 minutes each
time refrigerant is added or removed
2 -
Minor variations in these pressures may be
expected due to differences in installations.
Significant differences could mean that the system
is not properly charged or that a problem exists with
some component in the system.
3 -
Switch to heating mode to confirm normal operating
pressures. Let the system stabilize at least 10
minutes, then compare the pressure obtained from
the connected gauges to the normal operating
pressures (heating mode) in table 5.
4 - Verify the charge, as described in the approach
method section.
Outdoor Temp < 65ºF (18ºC)
1 - When the outdoor ambient temperature is below
65F (18C) 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 4).
2 - Charge the unit using the approach method in the
approach method section.
3 - Switch to heating mode and let the system stabilize
at least 10 minutes. Then confirm that the pressures
obtained from the connected gauges match the
normal operating pressures (heating mode) in table 5.
4 -
Minor variations in these pressures may be
expected due to differences in installations.
Significant differences could mean that the system
is not properly charged or that a problem exists with
some component in the system.
CARDBOARD OR
PLASTIC SHEET
OUTDOOR COIL SHOULD BE BLOCKED ONE SIDE AT A TIME
WITH CARDBOARD OR PLASTIC SHEET UNTIL PROPER
TESTING PRESSURES ARE REACHED.
FIGURE 4. Blocking Outdoor Coil
CHARGE PROCEDURE – APPROACH METHOD
Use the following approach method along with the normal
operating pressures to confirm readings.
1 -
Using the same thermometer, compare liquid
temperature at service valve to outdoor ambient
temperature.
Approach Temperature = Liquid temperature minus
ambient temperature
