36 ● gForce Ultra User Manual 10-2014
At this point, the unit and compressor will need to be started. Use the VFD “Hand on”
key (7.5.1 Local Control for Charging) of the VFD controller to adjust the speed of the
compressor to minimum frequency. Make sure to set the airflow of the unit to its full
capacity.
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 (3.12
Manual Override Switches). Switch the fan and compressor manual
switches to the ON position. All automatic control is disabled but safety
switches will remain functional.
Start charging (slowly open the service valve to feed liquid refrigerant into the low side
of the system) the unit with the compressor at its minimum frequency until the desired
subcooling and superheat are met. Using the and buttons on the VFD, slowly
ramp the compressor up to its maximum frequency while slowly feeding the system
more refrigerant. When the compressor is at its maximum frequency, make sure to
maintain the required subcooling and superheat shown in the table below. The unit
should be allowed to stabilize for 15 to 20 minutes before meaningful measurements
can be taken. After the system is allowed to stabilize, verification of a few key
measurements should be noted. A properly charged system operating at typical
parameters will have the following pressures:
340 to 415 PSIG (2344 to 2861 kPa)
104 to 165 PSIG (717 to 1138 kPa)
6 to 12°F (3.33 to 6.67°C) Differential
8 to 10°F (4.44 to 5.55°C) Differential
Depending on ambient conditions
Measure the superheat at the compressor suction line at least 6 inches (152 mm) away
from the compressor.
When done charging, press the “Auto on” key on the VFD local display to return to
normal operation controlled by the dap4™ controller. Also adjust the fan speed
potentiometer back to the original position and set the slide switches OFF on the
Manual Override Module.
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