Carrier 30MP - Operation Methods; Rotation Method Selection; Analog Setpoint Input

Sequence of Operation
30MP Multi-chiller CARRIER CORPORATION ©2018
Installation and Start-up Guide All rights reserved
25
Rotation method
The 30MP Multi-chiller can rotate chillers based on several different methods. You can only use rotation with
equal-sized machines. You can set the rotation method using
Rotation Method Sequence
, and selecting
Never
,
Daily
,
Weekly
,
Monthly
,
Manual
,
Runtime
, or
Runtime Equalization
. The default and preferred method is
Runtime
Equalization
, as it rotates the least-used machine to the lead position, but only when machines are started or
stopped, so that no additional start/stop cycles are incurred.
For unequal-sized chillers, the staging sequence is dependent on the actual machine size and should not be
altered, in order to provide the best water temperature control. For unequal-sized machines, no rotation method is
available. See Configure the controller system (page 18).
Analog setpoint input
The controller has an analog input channel you can use for an external setpoint input. The external setpoint input
range depends on whether the connected chillers are brine or water. Channel AI-2 is used for external setpoint
input and the range is 1 to 5 Volts.
• For water chillers, the range is proportional from 1 to 5 volts where 1 Volt = 40°F and 5 Volts = 65°F.
• For brine chillers, the range is proportional from 1 to 5 volts where 1 Volt = -20°F and 5 volts = 45°F.
NOTE
The lowest allowable setpoint is determined by the highest freeze setpoint of any machine connected to the
controller.
Condenser water temp control
The controller has an analog output channel you can use to operate a cooling tower fan. The control reads the
condenser water temperature from the 30MP chiller UPC Open. To accomplish this, the first chiller (CH1)
must
have the condenser water temperature sensor option and must have a valid status (
Off and Available
or
CCN
Mode and Running
). If that chiller status is invalid, the control will check sequentially for the next available chiller
(CH2 - CH8). We strongly recommend that you install CWT option on at least the first two chillers. You can
configure channel AO-1 to provide a 2-10 Vdc or 0-10 Vdc signal to control a tower fan VFD.
If you have an external control system, you can use the 30MP Multi-chiller to provide the optimum tower setpoint
value to the external control. A network-accessible AV point,
Condenser Water Setpoint
, can provide the desired
condenser water temperature setpoint in °F.