Lennox Elite ELS Series, Installation Instructions Manual

Page: 19 / 24

Page 19
Refrigerant Charge
ELS units have a factory holding charge of 2 pounds of
HFC-410A in each circuit. Additional refrigerant will need
to be added during installation.
To charge the system, use the following procedure:
1 - Measure actual length of liquid and vapor lines for
each circuit.
2 - Add refrigerant to each circuit based on measured
liquid and suction line lengths.
A - If the measured line length is greater than 25 feet,
add refrigerant (refer to table 2).
B - If the measured line length is less than 25 feet,
remove refrigerant (refer to table 2).
TABLE 2. Adding Refrigerant
Models
Total lbs –
Stage 1 with
25ft line set
Total lbs –
Stage 2 with
25ft line set
Liquid Line
Diameter
Ounces
Adjustment per
foot of liquid line
Suction Line
Diameter
Ounces
Adjustment per
foot of suction line
ELS072S4S 18.5 N/A 3/8 0.5 1-1/8 0.2
ELS090S4S 21.75 N/A 5/8 1.5 1-1/8 0.2
ELS120S4S 23 N/A 5/8 1.5 1-1/8 0.2
ELS120S4D 12 12 3/8 1.5 1-1/8 0.2
ELS150S4D 15 15.5 3/8 0.5 1-1/8 0.2
ELS180S4D 23.75 23.5 5/8 1.5 1-1/8 0.2
ELS240S4D 22.5 23.5 5/8 1.5 1-1/8 0.2
3 - Check normal operating pressures:
A - Connect a manifold gauge set to the service valves:
• Low pressure gauge to vapor valve service port
• High pressure gauge to liquid valve service port
B - Operate the system until pressures and
temperatures stabilize (5 minutes minimum).
C - Use a thermometer to measure the outdoor ambient
temperature.
D - If the outdoor temperature is greater than 65 º F
(18 º C):
• Apply the outdoor ambient temperature to tables
4, 5, or 7 to determine normal operating pressures.
Compare the normal operating pressures to the
pressures obtained from the connected gauges. If
liquid pressure is high, remove refrigerant from the
system. If liquid pressure is low, add refrigerant to
the system.
• Add or remove charge in increments.
• Allow the system to stabilize at least 5 minutes each
time refrigerant is added or removed.
• Minor variations in these pressures may be expect-
ed due to differences in installations. Significant dif -
ferences could mean that the system is not properly
charged or that a problem exists with some compo-
nent in the system.
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).
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 10. 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.