Table of Contents
Advertisement
CSRA-SVX02A-EN
System Start-Up
With Lead/Lag enabled, HGBP operation (if applicable) will be bypassed and
the system will go directly into pumpdown when the last subtract command
is initiated.
When the UCM is powered up (after a power loss), or any time the
compressor's start time and run time are equal, the number one (Lead)
designated compressor will be the first "On" and the number two (lag)
designated compressor will be the first "Off" on single circuit units (20 - 30
Tons).
For dual circuit units (40 through 60 Tons), the "On" sequence will be A-C-B-
D and the "Off" sequence will be D-B-C-A under the previously described
conditions. Refer to Figure 23 for compressor locations.
Sequence of Operation
Condenser Fan Control
The CGM condenser fan control logic is dependent on the number of
compressors operating per circuit and the saturated condensing
temperature. Fan logic is not initiated until the low ambient start time has
elapsed.
The condenser fan contactors, located in the unit control panel, initiate fan
operation when energized. Refer to Figure 22 for the condenser fan
locations and fan contactor designators. Dashed lines connecting pairs of
fans indicate instances where one contactor controls both fans.
Sequence of Operation
Low Ambient Dampers
Low Ambient Dampers are used to extend the operation of these units from
the standard operational temperatures to a minimum of 0°F without hot gas
bypass or 10°F with hot gas bypass. (These values apply when wind speed
across the condenser coil is less than 5 m.p.h.). If typical wind speeds are
higher than 5 m.p.h., a wind screen around the unit may be required. By
restricting the airflow across the condenser coils, saturated condensing
temperatures can be maintained as the ambient temperatures change.
The low ambient damper actuator controls damper modulation for each
refrigerant circuit in response to saturated condensing temperature.
Chilled Water Circulating Pump
Once the system has been filled, complete the following chilled water system
start-up procedures.
1. Turn the 115 volt control circuit switch 1S1 and the 24 volt control circuit
switch 1S70 located in the unit control panel to the "Off" position.
2. Turn the chiller circuit breaker (1CB1) and the pump circuit breaker on the
pump starter panel, to the "On" position.
3. Close the field supplied main power disconnect switch or circuit protector
switch that provides the supply power to the unit's circuit breaker (1CB1).
59
Advertisement
Table of Contents
