Charging With Fan Speed Control - Data Aire DARC 03 Installation, Operation & Maintenance Manual

perature and the ambient air temperature entering the condenser coil. Air-cooled condensers are
required to operate over a wide range of ambient air temperatures. Provisions must be made to
maintain the overall system balance. Air-cooled condensers tend to run at low head pressure when
operating in low ambient condition. Low head pressure can cause poor expansion valve operation
and poor system performance.
4.3

Charging with Fan Speed Control

As previously noted, the standard Data Aire air-cooled condenser (DARC) comes equipped with fan
speed control on the lead motor (motor number 1, nearest the header). After field refrigerant pip-
ing is properly completed, connect a refrigerant drum to the low side of the system and charge with
vapor (refer to Section 2.5 Leak Testing and Section 2.6 Evacuation prior to charging the system).
Connect the refrigerant drum to the high side and charge with liquid. Charge with approximately
2.55 pounds per nominal ton. Make sure all hoses are properly purged.
NOTE: Before starting the compressor(s) the crankcase 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.
Use the manual override switches (evaporator motor and compressor) on the unit mounted control-
lers (dap4, DAP-III or DAP-II) to switch the units to the ON position (all automatic control will be
disabled but safety switches will remain functional).
Start the evaporator fan and then the compressor. Check the liquid line sight glass to get a feel for
the approximate charge. Bubbles in the sight-glass are not unusual at this point. It is more likely that
more refrigerant will be required to complete the charging procedure.
Adjust the refrigerant charge until the system measures 8 to 10°F of sub-cooling . For system with
Electronic Expansion Valves (EEV), the superheat setpoint defaulted is 6°F and should be between 5
to 10°F. Units with dual refrigerant circuits should have both compressors energized. The unit should
be allowed to stabilize for at least 20 minutes before meaningful measurements can be recorded.
After the system is allowed to stabilize, a few key measurements should be noted. The superheat
should be measured at the compressor suction line, at least 6 inches away from the compressor.
Refrigerant
R-410a
R-410a
With Elec-
tronic Expansion Valves
R-407c
5 Discharge pressure (also called high side pressure or head pressure) is the pressure generated on the output side of a gas compressor
in a refrigeration of air conditioning system. The discharge pressure is affected by several factors: size and speed of the condenser fan, condition
and cleanliness of the condenser coil, and the size of the discharge line.
6 The term subcooling refers to a liquid existing at a temperature below its normal saturation temperature. Subcooling is normally used so
that when the cycling refrigerant reaches the thermostatic expansion valve, it is totally in liquid form, thus, allowing the valve to work properly.
7 In refrigeration and air conditioning systems, the suction pressure (also called the low-side pressure) is the intake pressure generated by
the system compressor while operating.
8 In refrigeration superheat is the amount of heat added to the refrigerant after it has changed from liquid to vapor state.
17 Air Cooled Condenser User Manual
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KEY MEASUREMENTS
Discharge Head
Pressure
5
340 to 415 PSIG
340 to 415 PSIG
245 to 285 PSIG
Sub-Cooling
6
(depending on ambient condi-
tions)
8 to 10°F
8 to 10°F
8 to 10°F
Suction Pressure
7
104 PSIG
or greater
104 PSIG
52 PSIG 8 to 15°F
or greater
Superheat
8
8 to 15°F
5 to 10°F