Carrier 17/19EX - Manual (Page 97)

Common Point Sensor Installation
Lead/lag operation does not require a common chilled water point sensor. Common point
sensors can be added to the 8-input option module, if desired. Refer to the certified drawings for
termination of sensor leads.
Note: If the common point sensor option is chosen on a chilled water system, both machines
should have their own 8-input option module and common point sensor installed. Each
machine will use its own common point sensor for control, when that machine is desig-
nated as the lead chiller. The PIC cannot read the value of common point sensors
installed on other machines in the chilled water system.
When installing chillers in series, a common point sensor should be used. If a common point
sensor is not used, the leaving chilled water sensor of the upstream chiller must be moved into
the leaving chilled water pipe of the downstream chiller.
If return chilled water control is required on chillers piped in series, the common point return
chilled water sensor should be installed. If this sensor is not installed, the return chilled water
sensor of the downstream chiller must be relocated to the return chilled water pipe of the
upstream machine.
To properly control the common supply point temperature sensor when chillers are piped in
parallel, the water flow through the shutdown chillers must be isolated so that no water by-pass
around the operating chiller occurs. The common point sensor option must not be used if water
bypass around the operating chiller is occurring.