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Three−Phase Compressor Rotation
Threephase scroll compressors must be phased se
quentially to ensure that the compressor rotates and
operates correctly. When the compressor starts, a rise
in discharge and drop in suction pressures indicate
proper compressor phasing and operation. If dis
charge and suction pressures do not perform normal
ly, follow the steps below to correctly phase in the unit.
1 − Disconnect the power to the unit.
2 − Reverse any two field power leads to the unit.
3 − Reconnect the power to the unit.
The discharge and suction pressures should operate with
in their normal startup ranges.
NOTE − The compressor’s noise level will be significantly
higher when the phasing is incorrect. The compressor will
not provide cooling when the unit is not correctly phased.
Continued backward operation of the compressor to due to
incorrect phasing will cause the compressor to cycle on in
ternal protector.
IV− CHARGING
HP29 units are field charged with the amount of HCFC−22
refrigerant indicated in the charging procedure. This
charge is based on a matching indoor coil and outdoor coil
with a 25 foot (7.6 m) line set. For varying lengths of line
set, refer to table 3 for refrigerant charge adjustment for
HP29 series units. Units are designed for line sets up to 50 ft.
(15.24 m). Consult Lennox Refrigerant Piping Manual for line
sets over 50 ft. (15.24 m).
WARNING
Never use oxygen to pressurize refrigeration or
air conditioning system. Oxygen will explode on
contact with oil and could cause personal injury.
Use nitrogen only for this purpose and be sure
to use a regulator that can control the pressure
down to 1 or 2 psig (6.9 to 13.8 kPa).
CAUTION
Any nitogen cylinder connected to system must
have a 150 psig maximum setting regulator. Never
introduce pressures greater than 150 psig to any
refrigerant system.
A−Leak Testing
Using an Electronic Leak Detector or Halide
1 − Connect a cylinder of nitrogen with a pressure regulat
ing valve to the center port of the manifold gauge set.
2 − Connect the high pressure hose of the manifold gauge
set to the service port of the suction valve. (Normally,
the high pressure hose is connected to the liquid line
port, however, connecting it to the suction port better
protects the manifold gauge set from high pressure
damage.)
3 − With both manifold valves closed, open the valve on
the HCFC−22 bottle (vapor only).
4 − Open the high pressure side of the manifold to allow
HCFC−22 into the line set and indoor unit. Weigh in a
trace amount of HCFC−22. [A trace amount is enough
refrigerant to equal 3 pounds (31 kPa) pressure].
Close the valve on the HCFC−22 bottle and the valve
on the high pressure side of the manifold gauge set.
Disconnect HCFC−22 bottle.
5 − Adjust nitrogen pressure to 300 psig (2068 kPa). Open
the valve on the high side of the manifold gauge set which
will pressurize the system.
6 − After a short period of time, open a refrigerant port to
make sure the refrigerant added is adequate to be de
tected. (Amounts of refrigerant will vary with line
lengths.) Check all joints for leaks. Purge nitrogen and
HCFC−22 mixture. Correct any leaks and recheck.
7 − If brazing is necessary for repair, bleed enough nitrogen
through the system to ensure all oxygen is displaced.
Brazing with oxygen in the system will create copper ox
ides which may cause restrictions, the failure of compo
nents and will affect the dielectric of refrigerant oil causing
premature compressor failure.
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