Temperature Reset; Dual Leaving Water Thermistor Well - Carrier AQUASNAP 30RAP010-150 Controls, Start-Up, Operation, Service, And Troubleshooting

MASTER
RETURN
CHILLER
FLUID
SLAVE
CHILLER
*Depending on piping sizes, use either:
• HH79NZ014 sensor/10HB50106801 well (3-in. sensor/well)
• HH79NZ029 sensor/10HB50106802 well (4-in. sensor/well)
Fig. 23 — Dual Chiller Thermistor Location
PART
NUMBER
10HB50106801 3.10 (78.7)
10HB50106802 4.10 (104.1)
A
B
1/4 N.P.T.
Fig. 24 — Dual Leaving Water Thermistor Well
Refer to Table 13 for dual chiller configuration. In this
example the master chiller will be configured at address 1 and
the slave chiller at address 2. The master and slave chillers
must reside on the same CCN bus (Configuration

CCNB) but cannot have the same CCN address (Configu-
 
ration CCN CCNA). Both master and slave chillers must
have Lead/Lag Chiller Enable (Configuration

LLEN) configured to ENBL. Master/Slave Select (Config-
 
uration RSET MSSL) must be configured to MAST for
the master chiller and SLVE for the slave. Also in this example,
the master chiller will be configured to use Lead/Lag Balance

Select (Configuration RSET

ance Delta (Configuration
chiller run-times weekly. The Lag Start Delay (Configura-
 
tion RSET LLDY) feature will be set to 10 minutes. This
will prevent the lag chiller from starting until the lead chiller
has been at 100% capacity for the length of the delay time. Par-
THERMISTOR
WIRING*
LEAVING
FLUID
INSTALL DUAL CHILLER LWT
LEAVING FLUID TEMPERATURE
THERMISTOR (T10) HERE
DIMENSIONS in. (mm)
A B
1.55 (39.4)
1.28 (32.5)
0.505/0.495
6" MINIMUM
CLEARANCE FOR
THERMISTOR
REMOVAL

CCN

RSET

LLBL) and Lead/Lag Bal-

RSET LLBD) to even out the
allel configuration (Configuration
only be configured to YES. The variables LLBL, LLBD and
LLDY are not used by the slave chiller.
Dual chiller start/stop control is determined by configura-
tion of Control Method (Configuration
the Master chiller. The Slave chiller should always be config-
ured for CTRL=0 (Switch). If the chillers are to be controlled
by Remote Contacts, both Master and Slave chillers should be
enabled together. Two separate relays or one relay with
two sets of contacts may control the chillers. The Enable/Off/
Remote Contact switch should be in the Remote Contact
position on both the Master and Slave chillers. The Enable/Off/
Remote Contact switch should be in the Enable position for
CTRL=2 (Occupancy) or CTRL=3 (CCN Control).
Both chillers will stop if the Master chiller Enable/Off/
Remote Contact switch is in the Off position. If the Emergency
Stop switch is turned off or an alarm is generated on the Master
chiller the Slave chiller will operate in a Stand-Alone mode.
If the Emergency Stop switch is turned off or an alarm is
generated on the Slave chiller the Master chiller will operate in
a Stand-Alone mode.
0.61
DIA
The master chiller controls the slave chiller by changing its
Control Mode (Run Status
ing setpoint or Control Point (Run Status
Temperature Reset —
handling leaving-fluid temperature reset based on return cooler
fluid temperature. Because the change in temperature through
the cooler is a measure of the building load, the return tempera-
ture reset is in effect an average building load reset method.
The control system is also capable of temperature reset based
on outdoor-air temperature (OAT), space temperature (SPT), or
from an externally powered 4 to 20 mA signal. Accessory sen-
sors must be used for SPT reset (33ZCT55SPT). The energy
management module (EMM) must be used for temperature
reset using a 4 to 20 mA signal. See Tables 15 and 16.
IMPORTANT: Care should be taken when interfacing with
other control systems due to possible power supply differ-
ences: full wave bridge versus half wave rectification. Con-
nection of control devices with different power supplies
may result in permanent damage. ComfortLink controls
incorporate power supplies with half wave rectification. A
signal isolation device should be utilized if the signal gen-
erator incorporates a full wave bridge rectifier.
37
 
RSET PARA) can
 
OPT1 CTRL) of
 
VIEW STAT) and its operat-
 
VIEW CT.PT).
The control system is capable of