36
At this point there will be approximately 70-80% of the total charge in the system. It is likely
that more refrigerant will be required to complete the charging procedure. Close the valve on
the refrigerant manifold gauge set.
WARNING: Before starting a compressor, the crankcase heater should be
energized for a minimum of 12 hours to reduce the possibility of liquid slug-
ging on start-up. Failure to energize the crankcase heater could result in
compressor damage. If the system is charged from a vacuum, the preheating
of the compressor is not necessary.
NOTE: A quick and easy way to run the fans and compressor is by using
the manual slide switches provided by the Manual Override Module (Exclu-
sively for oor mounted units. Ceiling mounted units are not equipped
with Manual Override Module!) All automatic control is disabled but safety
switches will remain functional.
Before turning the system on to nish charging the circuit make sure you check for voltage phasing.
For more information on this refer to section 5.3.
NOTE: Charging to a full liquid line sight glass should never be the sole
means of determining the correct refrigerant charge. Other parameters such
as superheat, suction pressure, head pressure, sub-cooling and ambient
temperature are also important. A system charged to a clear sight glass is
often overcharged.
Manually start the system by rst sliding the “Blower” switch to ON position on the manual override
board. Allow time for all fans to start and come up to a constant airow before starting the constant
speed compressor. Then manually start the constant speed compressor by sliding the “Cool 2” switch
to the ON position on the manual override board to turn on the constant speed compressor. Allow the
system to stabilize to room temperature. Bubbles in the sight glass are not unusual at this point. It
is likely that more refrigerant will be required to complete the charging procedure.
Finish charging by slowly opening the valve on the refrigerant manifold set to meter liquid refrigerant
into the low side of the system.
Adjust the refrigerant charge to the sub-cooling value shown in the table below and the sight glass
has sparse bubbles. The unit should be allowed to stabilize for 15 to 20 minutes to verify key mea-
surements in the table below.
Function R-410A Conditions
Discharge Pressure 340 to 415 PSIG (2344 to 2861 kPa)
Suction Pressure 104 to 121 PSIG (717 to 834 kPa)
Superheat
6 to 12°F (3.33 to 6.67°C) Dierential
Sub-Cooling
8 to 10°F (4.44 to 5.55°C) Dierential
Depending on ambient conditions, at com-
pressor’s maximum speed
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