45
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 refriger-
ant 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 preheat-
ing of the compressor is not necessary.
The variable speed compressor requires a little more care while charging. All unit safeties must be
active while charging the compressor. In order to ensure this, manual bypass switches on the Manual
Override Board MUST NOT be used. Instead the unit must be started in the normal operating mode
based on a call for cooling required by the dap4 controller once an initial charge has been added to
the circuit. Before starting the system, make sure pressure gauges are hooked up and pressure read-
ings are aligned with EEV reading. For dual circuit units, remove the xed speed compressor’s fuses
to prevent it from starting.
If the unit is in OFFbyKEY position, hold the “Esc” button for 5 seconds to start the system via the
dap4 controller. Next, the controlled temperature needs to be higher than temperature setpoint for
the compressor to start. To do this, press the “Menu” button where you will prompted to enter in the
service password before continuing. The default service password is “0000” By utilizing the arrow
keys, scroll up or down to menu “H. Calibrate Sensors” and press ENTER. If the system is being con-
trolled from the return air temperature sensors simply scroll down to the “Return Air Temp Sensor”
menu and press ENTER to move the cursor to the oset value. Use the up and down arrow keys to
change the oset value to +20 °F. Then press ENTER to set the oset. This should allow the tem-
perature to be much higher than the temperature setpoint and the variable speed compressor will
start and run at a full speed of 6000 RPM (or 200Hz). If controlling with discharge air temperature
sensor follow the same steps but use the “Discharge Air Temp Sensor” menu.
When compressor starts, monitor closely the suction pressure, head pressure, compressor VFD dis-
play and the EEV. Watch for any alarms that you might see. During startup, you might see some
alarms such as:
- “C1 Low Pressure”: If suction pressure is below 50 psi, make sure to add more refrigerant per
recommended charge calculation shown above
- “Compressor VFD Alarm”: This alarm shows up when the compressor is called upon for cooling
requirement, but either the VFD has stopped the compressor, or the compressor is experiencing a Low
or High pressure alarm.
Finish charging by slowly opening the valve on the refrigerant manifold set to meter liquid refrigerant
into the low side of the system, with the compressor operating at a speed of 6000 RPM (or 200Hz),
making sure to obtain the required sub-cooling and verify superheat shown in the table below. The
unit should be allowed to stabilize for 15 to 20 minutes to verify key measurements.
Function R-410A Conditions
Discharge Pressure 322 PSIG (2220 kPa)
Suction Pressure
104 PSIG (717 kPa)
or greater
Superheat 10 to 12°F (5.56 to 6.67°C) Dierential
To Next Page
Loading...
