Lennox HP40, Installation Instructions Manual

Page: 9 / 16

Page 9
System Evacuation
WARNING
Unit contains a NITROGEN holding charge. The
holding charge must be purged and the system
must be evacuated prior to charging with R407C.
Evacuating the system of non−condensables is critical for
the unit to operate properly. Non−condensables are de-
fined as any gas that will not condense under temperatures
and pressures present during operation of an air condition-
ing 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:
low pressure gauge to suction line service valve
high pressure gauge to liquid line service valve
IMPORTANT − Compliant scroll compressors (as with
any refrigerant compressor) should never be used to
evacuate a refrigeration 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.
2 −The nitrogen holding charge in the unit must be re-
leased. Open both manifold valves to release the ni-
trogen from the unit. See the liquid and suction line
service valves section for how to operate the service
valves.
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, condensing unit, and indoor
unit to an absolute pressure of 23 mm (23,000 mi-
crons) of mercury. During the early stages of evacua-
tion, it is desirable to close the manifold gauge valve
at least once to determine if there is a rapid rise in
ab-
solute pressure . A rapid rise in pressure 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
minus vacuum pressure.
6 −When the absolute pressure reaches 23 mm (23,000
microns) of mercury, close the manifold gauge
valves, turn off the vacuum pump, and disconnect the
manifold gauge center port hose from the vacuum
pump. Attach the manifold center port hose to a nitro-
gen cylinder with the pressure regulator set to 150
psig (1034 kPa) and purge the hose. Open the man-
ifold gauge valves to break the vacuum in the system.
Close the manifold gauge valves.
WARNING
Danger of Equipment Damage.
Avoid deep vacuum operation. Do not use com-
pressors 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 man-
ifold gauge hose from the cylinder. Open the manifold
gauge valves to release the nitrogen from the system.
8 −Reconnect the manifold gauge to the vacuum pump,
turn the pump on and continue to evacuate the system
until the absolute pressure does not rise above .5 mm
(500 microns) of mercury within a 20−minute period af-
ter shutting off the vacuum pump and closing the man-
ifold gauge valves.
9 − When the absolute pressure requirement from step 9
has been met, disconnect the manifold gauge hose
from the vacuum pump. Then, weigh in a LIQUID
charge of R407C through the liquid and suction ser-
vice valves.
Refer to the unit nameplate for the correct liquid
charge. If you can not measure in the total amount, re-
fer to the start−up section and set the final system
charge according to the charging instructions.
The
R407C refrigerant cylinder should be chocolate
brown.
Start−Up
Cooling Start-Up
1 − Check the unit disconnect switch to make sure power
is off.
2 − Rotate the fan to check for frozen bearings or binding.
3 − Inspect all factory and field-installed wiring for loose
connections.
4 − Replace the stem caps. Tighten finger tight, then
tighten an additional 1/6 turn.
5 − Check the 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
you have consulted the power company, and the volt-
age condition has been corrected.
6 − Set the thermostat for cooling demand, turn on the
power to the indoor blower coil, and close the heat
pump unit disconnect switch to start the unit.