Evacuation & Dehydration - Lennox HS29-072 Installation Instructions Manual

2 − Open the high pressure side of the manifold to allow
the HCFC 22 into the line set and indoor unit. Weigh in
a trace amount of HCFC 22. [A trace amount is a maxi
mum of 2 ounces (57 g) refrigerant or 3 pounds (31
kPa) pressure]. Close the valve on the HCFC 22 cylin
der and the valve on the high pressure side of the man
ifold gauge set. Disconnect HCFC 22 cylinder.
3 − Connect a cylinder of nitrogen (that has a pressure
regulating valve) to the center port of the manifold
gauge set.
4 − Connect the high pressure hose of the manifold gauge
set to the service port of the suction valve.
NOTE − Normally the high pressure hose is connected
to the liquid line port. However, connecting it to the suc
tion port more effectively protects the manifold gauge
set from high pressure damage.
5 − Adjust the nitrogen pressure to 150 psig (1034 kPa).
Open the valve on the high side of the manifold gauge
set which will pressurize the line set and indoor unit.
6 − After a few minutes, open a refrigerant port to ensure
that the amount of refrigerant you added is large
enough to be detected. (Amounts of refrigerant will
vary with line lengths.) Check all joints for leaks. Purge
the nitrogen and HCFC 22 mixture. Correct any leaks
and recheck.
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
the unit to operate properly. Noncondensables are gases
that will not condense under temperatures and pressures
which are present while an air conditioning system is oper
ating. Noncondensables and water vapor combine with re
frigerant to produce substances that corrode copper piping
and compressor parts.
1 −Remove the suction valve actuation/stem cap. Turn
the stem unit it is fully open. To open the liquid valve,
remove cap and turn the valve stem until it is fully open.
2 −Connect the manifold gauge set to the service valve
ports as follows:
low pressure gauge to suction line service valve
D
high pressure gauge to liquid line service valve
D
3 −Purge the system of dry air, helium, or nitrogen.
Never use compliant scroll compressors (as with
any refrigerant compressor) to evacuate a refrigera
tion or air conditioning system!
NOTE − Use a temperature vacuum gauge, mercury
vacuum, or thermocouple gauge. The usual Bourdon
tube gauges are inaccurate in the vacuum range.
4 −Connect the vacuum pump (with vacuum gauge) to the
center port of the manifold gauge set.
5 −Open both manifold valves and start the vacuum pump.
6 −Evacuate the line set, outdoor unit, and the indoor unit
to an absolute pressure of 23 mm (23,000 microns) of
mercury or approximately 1 inch of mercury. During the
early stages of evacuation, 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 test.
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.
7 −When the absolute pressure reaches 23 mm (23,000
microns) of mercury, do the following:
close the manifold gauge valves
D
turn off the vacuum pump
D
disconnect the manifold gauge center port hose
D
from the vacuum pump
Attach the manifold center port hose to a nitrogen cyl
inder with the 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.
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.
8 −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 the indoor unit.
Page 19
IMPORTANT
CAUTION