Specifications

31
CIRCUIT/COMPRESSOR LOADING — The control can
be configured to stage the circuit/compressors. The Loading
Sequence Select (Staged Loading Sequence, LOAD) setting
determines how the control will perform loading. The configu-
ration can be set to Equal or Staged.
Equal Loading
— With Equal loading, the lead circuit will
start and maintain the minimum stage of capacity with the slide
valve fully unloaded. As additional capacity is required, the
slide valve will be adjusted in approximately 5% increments to
match capacity requirements. The lag circuit will not start until
the lead circuit reaches 70% capacity. The lead circuit will re-
main at 70% and the lag circuit will increase in capacity until it
also reaches 70% capacity. The control will alternate between
circuits to maintain the same percentage of capacity on each
circuit until they reach 100%.
Staged Loading
— If staged loading is selected, the lead cir-
cuit will start and maintain the minimum stage of capacity with
the slide valve fully unloaded. As additional capacity is re-
quired, the slide valve will be adjusted in approximately 5% in-
crements to match capacity requirements until the circuit is ful-
ly loaded. Once the circuit is fully loaded and additional capac-
ity is required, the control will start the lag circuit fully
unloaded. The control will continue load the lag circuit in ap-
proximately 5% increments to match capacity requirements
until both circuits reach 100% capacity.
To configure this option with the Touch Pilot™ display:
To configure this option with the Navigator™ display:
Minimum Load Control — Minimum Load Control
can be a factory-installed option or a field-installed accessory.
If installed, and its operation is desired, the Minimum Load
Control must be enabled. Once enabled, the valve will be oper-
ational only during the first stage of cooling.
To configure this option with the Touch Pilot™ display:
To configure this option with the Navigator™ display:
Dual Chiller Control — The dual chiller routine is
available for the control of two units installed in series or paral-
lel supplying chilled fluid on a common loop. One chiller must
be configured as the master chiller, the other as the slave chill-
er. For parallel applications, an additional leaving fluid temper-
ature thermistor (dual chiller LWT) must be installed in the
common chilled water piping as described in the Installation
Instructions for both the master and slave chillers. See the Field
Wiring section in the 30XW Installation Instructions for dual
chiller LWT sensor control wiring.
The control algorithm relies on several parameters that must
be field configured for operation. Both chillers must be on the
same Carrier Comfort Network
®
bus with different addresses.
On both chillers, Master/Slave Select (Master/Slave Select,
MSSL) must be enabled. The water piping arrangement, Chill-
ers in Series (Chiller in Series, SERI), must be configured.
The master chiller must be programmed with the Slave Chiller
Address (Slave Address, SLVA). Additional optional pro-
gramming parameters may be configured to meet application
requirements.
Lead/Lag Balance Select (Lead Lag Select, LLBL) deter-
mines which chiller is the lead machine. The options are Al-
ways Lead, Lag if Fail, and Runtime Select. Under Runtime
Select control, the lead chiller will change based on the time in-
crement selected in the Lead/Lag Balance Delta configuration
(Lead/Lag Balance Delta, LLBD). If the run hour difference
between the master and the slave remains less than the Lead/
Lag Balance Delta, the chiller designated as the lead will
remain the lead chiller. The Lead/Lag changeover between the
master and the slave chiller due to hour balance will occur dur-
ing chiller operating odd days, such as day 1, day 3, and day 5
of the month, at 12:00 a.m. If a lead chiller is not designated,
the master chiller will always be designated the lead chiller.
The dual chiller control algorithm has the ability to delay
the start of the lag chiller in two ways. The Lead Pulldown
Time parameter (Lead Pulldown Time, LPUL) is a one-time
time delay initiated after starting the lead chiller, before
checking whether to start an additional chiller. This time delay
gives the lead chiller a chance to remove the heat that the
chilled water loop picked up while being inactive during an un-
occupied period. The second time delay, Lead/Lag Delay (Lag
Start Timer, LLDY) is a time delay imposed between the last
stage of the lead chiller and the start of the lag chiller. This pre-
vents enabling the lag chiller until the lead/lag delay timer has
expired.
A quicker start of the lag chiller can be accomplished by
configuring the Start if Error Higher parameter (Start if Error
Higher, LL.ER). If the difference between the common leav-
ing water temperature and the set point is greater than the con-
figured value, then the lag chiller will start.
A minimum on time for the lag chiller can be programmed
with the Lag Minimum Running Time configuration (Lag
Minimum Running Time, LAG.M). This parameter causes
the control to run the lag chiller for the programmed minimum
on time. The Lag Unit Pump Select (Lag Unit Pump Control,
LAGP) can be configured such that the pump can be on or off
while the chiller is off. This parameter is only active in Parallel
Chiller Operation.
For units with a Touch Pilot™ display, two additional steps
must be completed to start the machine. On the master chiller,
the Master Control Type must be configured for the start con-
trol defined in the Machine Control configuration. To start the
machines, the master chiller must be started with the Start/Stop
button and Master Mode selected. The slave chiller must be
started with the CCN Mode selected.
Each application, Parallel and Series, are described sepa-
rately below.
DUAL CHILLER CONTROL FOR PARALLEL APPLI-
CATIONS — To configure the master chiller for parallel
applications using the Touch Pilot™ display, see Table 25. To
configure the master chiller for parallel applications using the
Navigator™ display, see Table 26.
To configure the slave chiller for parallel applications using
the Touch Pilot™ display, see Table 27. To configure the slave
chiller for parallel applications using the Navigator™ display,
see Table 28.
DUAL CHILLER PUMP CONTROL FOR PARALLEL
CHILLER APPLICATIONS — It is recommended that a
dedicated pump be used for each unit. The chiller must start
and stop its own water pump located on its own piping. If
pumps are not dedicated for each chiller, chiller isolation
DISPLAY NAME PATH
LINE
NO.
VALUE
Staged Loading
Sequence
Main
Menu Config USER
4
Default = No
No (Equal)
Yes (Staged)
ITEM ITEM EXPANSION PATH VALUE
LOAD
Loading Sequence
Select
Configuration OPTN
Default = Equal
Equal
Staged
DISPLAY NAME PATH
LINE
NO.
VALUE
Hot Gas
Bypass Select
Main
Menu Service
FACTORY
14
Default = No
No (No Minimum
Load Control)
Yes (Minimum Load
Control Installed)
ITEM
ITEM
EXPANSION
PATH VAL U E
HGBP
Hot Gas
Bypass Select
Configuration UNIT
No = No Minimum
Load Control
Yes = Minimum Load
Control Installed
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