Evacuation; Start−Up; Refrigerant Charging - Lennox HPXA16-024 Installation Instructions Manual

Evacuation

Evacuating the system of noncondensables is critical for
proper operation of the unit. Noncondensables are defined
as any gas that will not condense under temperatures and
pressures present during operation of an air conditioning
system. Noncondensables and water vapor combine with
refrigerant to produce substances that corrode copper pip-
ing and compressor parts.
IMPORTANT
Use a thermocouple or thermistor electronic vacuum
gauge that is calibrated in microns. Use an instrument
that reads from 50 microns to at least 23,000 microns.
1. Connect manifold gauge set to the service valve ports
as follows:
D low pressure gauge to vapor line service valve
high pressure gauge to liquid line service valve
D
2. Connect micron gauge.
3. Connect the vacuum pump (with vacuum gauge) to
the center port of the manifold gauge set.
4. Open both manifold valves; 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 desir-
able to close the manifold gauge valve at least once to
determine 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 dry nitrogen
cylinder 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.
WARNING
Danger of Equipment Damage! Avoid deep vacu-
um operation. Do not use compressors to evacu-
ate a system. Extremely low vacuums can cause
internal arcing and compressor failure. Damage
caused by deep vacuum operation will void war-
ranty.
7. Shut off the dry nitrogen cylinder and remove the man-
ifold gauge hose from the cylinder. Open the manifold
504954M 08/06
gauge valves to release the dry 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 vac-
uum 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.
Start−Up
IMPORTANT
If unit is equipped with crankcase heater, it should
be energized 24 hours before unit start−up to pre-
vent compressor damage as a result of slugging.
1. Rotate fan to check for frozen bearings or binding.
2. Inspect all factory− and field-installed wiring for loose
connections.
3. After evacuation is complete, open the liquid line and
vapor line service valves (counterclockwise) to re-
lease refrigerant charge (contained in outdoor unit)
into the system.
4. Replace stem caps and secure finger tight, then tight-
en an additional (1/6) one-sixth of a turn.
5. Check voltage supply at the disconnect switch. The
voltage must be within the range listed on the unit
nameplate. If not, do not start the equipment until the
power company has been consulted and the voltage
condition has been corrected.
6. Set the thermostat for a cooling demand. Turn on pow-
er to indoor blower unit and close the outdoor unit dis-
connect to start the unit.
7. Recheck voltage while the unit is running. Power must
be within range shown on the nameplate.

Refrigerant Charging

This system is charged with HFC−410A refrigerant which
operates at much higher pressures than HCFC−22. The
field−provided check expansion valve for the indoor unit
must be approved for use with HFC−410A. This unit is NOT
approved for use with coils which include metering orifices
or capillary tubes.
Factory Charge
The unit is factory−charged with the amount of HFC−410A
refrigerant indicated on the unit rating plate. This charge is
based on a matching indoor coil and outdoor coil with a 15
foot (4.6 m) line set. For varying lengths of line set, refer to
table 3 for refrigerant charge adjustment.
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