Lennox XP14 SERIES Unit Information page 16

4 − Open both manifold valves and start the vacuum
pump.
5 − Evacuate the line set and indoor unit to an absolute
pressure of 23,000 microns (29.01 inches of mercu-
ry). During the early stages of evacuation, it is desirable
to close the manifold gauge valve at least once to deter-
mine if there is a rapid rise in absolute pressure. A
rapid rise in pressure indicates a relatively large leak. If
this occurs, repeat the leak testing procedure.
NOTE − The term absolute pressure means the total
actual pressure within a given volume or system,
above the absolute zero of pressure. Absolute pres-
sure in a vacuum is equal to atmospheric pressure mi-
nus vacuum pressure.
6 − When the absolute pressure reaches 23,000 microns
(29.01 inches of mercury), close the manifold gauge
valves, turn off the vacuum pump and disconnect the
manifold gauge center port hose from vacuum pump.
Attach the manifold center port hose to a nitrogen cylin-
der with pressure regulator set to 150 psig (1034 kPa)
and purge the hose. Open the manifold gauge valves to
break the vacuum in the line set and indoor unit. Close
the manifold gauge valves.
CAUTION
Danger of Equipment Damage.
Avoid deep vacuum operation. Do not use compres-
sors to evacuate a system.
Extremely low vacuums can cause internal arcing
and compressor failure.
Damage caused by deep vacuum operation will void
warranty.
7 − Shut off the nitrogen cylinder and remove the manifold
gauge hose from the cylinder. Open the manifold
gauge valves to release the nitrogen from the line set
and indoor unit.
8 − Reconnect the manifold gauge to the vacuum pump,
turn the pump on, and continue to evacuate the line set
and indoor unit until the absolute pressure does not rise
above 500 microns (29.9 inches of mercury) within a
20−minute period after shutting off the vacuum pump
and closing the manifold gauge valves.
9 − When the absolute pressure requirement above has
been met, disconnect the manifold hose from the vacu-
um pump and connect it to an upright cylinder of
HFC−410A refrigerant. Open the manifold gauge valves
to break the vacuum from 1 to 2 psig positive pressure in
the line set and indoor unit. Close manifold gauge valves
and shut off the HFC−410A cylinder and remove the
manifold gauge set.
C − Charging
Refrigerant Charge
This system is charged with HFC−410A refrigerant which
operates at much higher pressures than HCFC−22. The
recommended check expansion valve is approved for use
with HFC−410A. Do not replace it with a valve that is de-
signed to be used with HCFC−22. This unit is NOT ap-
proved for use with coils that include metering orifices or
capillary tubes.
Units are factory-charged with the amount of HFC−410A re-
frigerant indicated on the unit rating plate. This charge is
based on a matching indoor coil and outdoor coil with 15 ft.
(4.6 m) line set. For varying lengths of line set, refer to table
3 for refrigerant charge adjustment. A blank space is pro-
vided on the unit rating plate to list the actual field charge.
Check Indoor Airflow before Charging
IMPORTANT
Check airflow before charging!
NOTE − Be sure that filters and indoor and outdoor coils are
clean before testing.
HEATING MODE INDOOR AIRFLOW CHECK
Blower airflow (CFM) may be calculated by energizing elec-
tric heat and measuring:
temperature rise between the return air and supply air tem-
peratures at the indoor coil blower unit,
voltage supplied to the unit,
amperage being drawn by the heat unit(s).
Then, apply the measurements taken in following formula
to determine CFM:
Amps x Volts x 3.41
CFM = CFM =
1.08 x Temperature rise (F)
COOLING MODE INDOOR AIRFLOW CHECK
Check airflow using the Delta−T (
Check indoor airflow using the step procedures as illus-
trated in figure 20.
Page 16
DT)
process (figure 20).