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Evacuation & Dehydration
IMPORTANT
Units are shipped with a holding charge of dry air and
helium which must be removed before the unit is
evacuated and charged with refrigerant.
Evacuating the system of noncondensables is critical for
proper operation of the unit. Noncondensables are gases
that will not condense under temperatures and pressures
present during operation of an air conditioning system. Non
condensables and water vapor combine with refrigerant to
produce substances that corrode copper piping and com
pressor parts.
1 - Connect manifold gauge set to the service valve ports
as follows: low pressure gauge to vapor line service
valve; high pressure gauge to liquid line service valve.
IMPORTANT - Compressors (as with any refrigerant
compressor) should never be used to evacuate a refrig
eration or air conditioning system.
NOTE - A temperature vacuum gauge, mercury vacu
um or thermocouple gauge should be used. The usual
Bourdon tube gauges are inaccurate in the vacuum
range.
2 - Open the vapor line and liquid line valves to evacuate
the unit.
3 - Connect the vacuum pump (with vacuum gauge) to the
center port of the manifold gauge set.
4 - Open both manifold valves and start vacuum pump.
5 - Evacuate the outdoor unit, the line set, and the indoor
unit to an absolute pressure of 23 mm of mercury or
approximately 1 inch of mercury. During the early
stages of evacuation, it is desirable to close the man
ifold gauge valve at least once to determine if there is a
rapid rise in absolute pressure. A rapid rise in pres
sure indicates a relatively large leak. If this occurs, the
leak testing procedure must be repeated.
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 mm of mercu
ry, close the manifold gauge valves, turn off the vacu
um pump and disconnect the manifold gauge center
port hose from vacuum pump. Attach the manifold cen
ter port hose to a nitrogen cylinder with pressure regu
lator 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.
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,
indoor unit, and the outdoor unit.
8 - Reconnect the manifold gauge to the vacuum pump.
Turn the pump on and continue to evacuate the out
door unit, line set, and indoor unit. Evacuate until the
absolute pressure does not rise above .5 mm (500 mi
crons) of mercury within a 20-minute period after you
shut off the vacuum pump and close the manifold
gauge valves.
10- 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
HCFC 22 refrigerant. Open the manifold gauge valves
to break the vacuum in the outdoor unit, line set, and in
door unit. Close manifold gauge valves. Shut off
HCFC 22 cylinder and remove the manifold gauge set.
Start-Up
IMPORTANT
Crankcase heater should be energized 24 hours be
fore unit start-up to prevent compressor damage as
a result of slugging.
1 - Rotate the fan to check for frozen bearings or binding.
2 - Inspect all factory and field-installed wiring for loose
connections.
3 - Refer to charging section to accurately charge and
check the charge on this unit.
4 - Check voltage supply at the disconnect switch. The
voltage must be within range listed on unit nameplate.
If not, do not start equipment until the power company
has been consulted and the voltage condition cor
rected.
5 - Set thermostat for a cooling demand, turn on power to
blower and close heat pump unit disconnect switch to
start.
6 - Recheck unit voltage with unit running. Power must be
within range shown on unit nameplate. Check amper
age draw of unit. Refer to unit nameplate for correct
running amps.
Page 17
CAUTION
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