Trane IntelliPak CG-SVX02B-EN, Installation & Operation Manual

Page: 45 / 64

45
System Start-Up
Table 8C
Chilled Solution Reset Schedule based on Entering Solution Temperature
Active Leaving
Solution Setpoint
Reset
Amount = Maximum
LSS = ALSS + Maximum
Reset
Amount = Zero (0)
LSS = ALSS
Adjustable
Reset
3 - 16 F
End Temperature
Range 4 - 19
Factory Preset = 8
Start Temperature
Range 4 - 19
Factory Preset = 10
EST - LST
Temperature
Entering Solution Reset
Factory
Preset = 5
Sequence of Operation
Lead/Lag (Standard)
When Lead-Lag is enabled, for each capacity add request,
the CGM will begin sequencing the compressors “On” that
have:
a. the least number of starts; or,
b. the least run time (if number of starts are equal)
At each capacity subtract request, the CGM will begin se-
quencing the compressors “Off” that have:
a. the most run time; or,
b. the least number of starts (if more than one
compressor has the same run time)
If a compressor is locked out for any reason when a capac-
ity add request occurs, the next available compressor which
meets the specified criteria will be started.
If a compressor can not be turned “Off” due to the minimum
“On Time”, the next compressor which meets the specified
criteria will be turned “Off”.
On dual circuit units, as the first two capacity add requests
are initiated, one compressor on each circuit will start be-
fore any additional compressors on any circuit is started.
When staging down from three compressor stages to two
compressor stages, the CGM will turn a compressor “Off”
on the circuit that has the most compressors operating.
The Lead/Lag function is ignored (treated as disabled)
when the Hot Gas Bypass option is installed and enabled.
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” se-
quence will be A-C-B-D and the “Off” sequence will be D-B-
C-A under the previously described conditions. Refer to Fig-
ure 16 for compressor locations.
Sequence of Operation
Hot Gas Bypass (HGBP)
The Hot Gas Bypass (HGBP) option prevents compressor
short cycling. The HGBP option can only be installed on cir-
cuit #1. With HGBP installed and enabled, the unit will al-
ways stage the circuit #1 compressors “On” first, if operable
and stage them “Off” last. Hot Gas Bypass is never initiated
when staging compressors “On” (adding capacity), only
when staging compressors “Off”.
HGBP is initiated when the last compressor on circuit #1 is
operating, and the capacity control algorithm generates a
subtract command.
Sequence of Operation
Condenser Fan Control
The CGM condenser fan control logic is dependent on the
number of compressors operating per circuit and the satu-
rated 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 Fig-
ure 15 for the condenser fan locations and fan contactor
designators.