21
407C and 104 - 121 psi for R 410A. The superheat at the compressor suction line at least 6 inches
away from the compressor should be 8 - 15°.
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
parameters. A system charged to a clear sight glass is often overcharged.
5.2.2. Fan Speed Control System Charging
The standard outdoor air cooled condenser for Data Aire equipment is a Fan Speed Control system.
After the fi eld refrigerant piping is properly completed, connect the refrigerant drum to the low side
and charge with vapor. Charge with approximately three lbs. per nominal ton.
For example, a model DALA 0834-COD is a nominal 8 ton unit but has two nominal four ton circuits.
Charge each circuit with about 12 lbs. of refrigerant to begin. It is likely that more refrigerant will be
required to complete the charging procedure. Make sure all hoses are properly purged. From a
vacuum feed liquid refrigerant into the high side of the system until the pressure equalizes. At this
point there will be about 70 - 80% of the total charge in the system.
Before starting a compressor, the crankcase heater should be energized for a
minimum of 12 hours to reduce the possibility of liquid slugging 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. Start
the system and allow the system to stabilize to room temperature. Bubbles in the sight glass are
not unusual at this point and can be caused by fl ashing from liquid line pressure drop, low sub-
cooling or low charge. It is likely that more refrigerant will be required to complete the charging
procedure. Adjust the refrigerant charge until the sub-cooling is between 8 - 10° F and the superheat
is between 8 - 15° F. There may be fl ashing and/or bubbles in the sight glass when the system is
properly charged.
The unit should be allowed to stabilize for several minutes before meaningful measurements can
be taken. After the system is allowed to stabilize, verifi cation of a few key measurements should be
noted. The discharge should be between 110 - 125° F condensing temperature and the sub-cooling
should be between 8 - 10° F depending on ambient conditions. Suction temperature should be 58
PSI or greater. Measure the superheat at the compressor suction line a least 6 inches away from
the compressor. The superheat should be between 8 - 15° F for units that are water/glycol cooled
and air-cooled units with air-cooled condensers. Units with remote condensing unit should have a
superheat between 20 - 25° F at the compressor. The sub-cooling will be the same 8 - 10° F.
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 parameters. A system charged to a clear sight glass is often
overcharged.
5.2.3. Flooded System Charging
Flooded systems are units having refrigerant circuits with an optional liquid receiver and head
pressure control valve. When the ambient temperature falls during cold weather, the head pressure
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