Lennox XC21 Installation Instructions Manual page 27

WEIGH IN
Use to initially charge a system when the outdoor unit is void of charge. To verify charge and add or
remove refrigerant use either
START: Determine the correct charge method:
TXV
65ºF
(18.3ºC) and
Above
APPROACH OR
SUBCOOLING
WEIGH IN
CHARGING METHOD
CALCULATING SYSTEM CHARGE FOR OUTDOOR UNIT VOID OF CHARGE
If the system is void of refrigerant, first, locate and repair any leaks and then weigh in the refrigerant charge into the
unit. To calculate the total refrigerant charge:
Amount specified on
APPROACH
or
64ºF
(17.7ºC) and
Below
WEIGH-IN
Figure 13. Determining Charge Method
64ºF (17.7ºC) and Below
Adjust amount. for variation
in line set length listed on
line set length table below.
nameplate
+
Liquid Line
Set Diameter
3/8" (9.5 mm)
*If line length is greater than 15 ft. (4.6 m), add this amount. If
line length is less than 15 ft. (4.6 m), subtract this amount.
NOTE Insulate liquid line when it is routed through areas where the surrounding ambient temperature
could become higher than the temperature of the liquid line or when pressure drop is equal to or greater
than 20 psig.
NOTE The exampled nameplate is for illustration purposes only. Use data listed on actual unit
nameplate for charging.
Figure 14. Using HFC−410A Weigh In Method
SUBCOOLING
WHEN TO CHARGE?
S
Warm weather best
S
Can charge in colder weather
CHARGE METHOD? Determine by:
S
Outdoor ambient temperature
REQUIREMENTS:
S
Sufficient heat load in structure
S
Indoor temperature between 70-80ºF (21−26ºC)
S
Manifold gauge set connected to unit
S
Thermometers:
− to measure outdoor ambient temperature
− to measure liquid line temperature
− to measure suction line temperature
Total charge
=
Refrigerant Charge per Line Set Length
Ounces per 5 feet (g per 1.5 m)
adjust from 15 feet (4.6 m) line set*
3 ounce per 5' (85 g per 1.5 m)
Page 27
methods.
XC21 SERIES