Evacuating The System - Lennox Merit Series13HPD Units Installation Instructions Manual

5. Close the valve on the HCFC−22 cylinder and the valve
on the high pressure side of the manifold gauge set.
6. Disconnect the HCFC−22 cylinder.
7. Connect a cylinder of dry nitrogen with a pressure
regulating valve to the center port of the manifold
gauge set.
NOTE − Amounts of refrigerant will vary with line lengths.
8. Adjust dry nitrogen pressure to 150 psig (1034 kPa).
9. Open the valve on the high side of the manifold gauge
set in order to pressurize the line set and the indoor unit.
10. After a few minutes, open one of the service valve
ports and verify that the refrigerant added to the
system earlier is measurable with a leak
11. Check the indoor and outdoor units and line set for
leaks using the leak detector mentioned in paragraph
10.
12. Proceed with evacuation as outlined in the Evacuating
the System.

Evacuating the System

WARNING
Danger of Equipment Damage. Avoid deep
vacuum operation. Do not use compressors to
evacuate a system. Extremely low vacuums can
cause internal arcing and compressor failure.
Damage caused by deep vacuum operation will
void warranty.
IMPORTANT
Use a thermocouple or thermistor electronic vacuum
gauge that is calibrated in microns. Use an instrument
capable of accurately measuring down to 50 microns.
Evacuating the system of non−condensables is critical for
proper operation of the unit. Non−condensables are
defined as any gas 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 compressor parts.
1. Connect manifold gauge set to the service valve ports
as follows:
S
low pressure gauge to vapor line service valve
S
high pressure gauge to liquid line service valve
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 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
mercury).
NOTE − During the early stages of evacuation, it is
desirable to close the manifold gauge valve at least once to
determine if there is a rapid rise in sure 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 pressure in a
vacuum is equal to atmospheric pressure minus 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
detector.
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.
7. Shut off the dry nitrogen cylinder and remove the
manifold gauge hose from the cylinder. Open the
manifold 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
vacuum pump and connect it to an upright cylinder of
HCFC−22 refrigerant. Open the manifold gauge valve
1 to 2 psig in order to release the vacuum in the line set
and indoor unit.
10. Close manifold gauge valves and shut off the
HCFC−22 cylinder and remove the manifold gauge
set.
SERVICING UNITS DELIVERED VOID OF CHARGE
If the system is void of refrigerant, clean the system using
the procedure described below.
1. Use nitrogen to pressurize the system and check for
leaks. Repair all leaks.
2. Evacuate the system to remove as much of the
moisture as possible.
3. Use nitrogen to break the vacuum and install a new
filter drier in the system.
4. Evacuate the system again. Then, weigh the
appropriate amount of HCFC−22 refrigerant as listed
on unit nameplate into the system.
5. Monitor the system to determine the amount of
moisture remaining in the oil. It may be necessary to
replace the filter drier several times to achieve the
required dryness level. If system dryness is not
verified, the compressor will fail in the future.
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13HPD SERIES