Catalogue

18 RLC-PRC042D-EN
Controls
Tracer UC800 Controller
Today’s Stealth™ chillers offer predictive controls that anticipate and compensate for load changes.
Other control strategies made possible with the Tracer UC800 controls are:
Feedforward Adaptive Control
Feedforward is an open-loop, predictive control strategy designed to anticipate and compensate
for load changes. It uses evaporator entering-water temperature as an indication of load change.
This allows the controller to respond faster and maintain stable leaving-water temperatures.
Soft Loading
The chiller controller uses soft loading except during manual operation. Large adjustments due to
load or setpoint changes are made gradually, preventing the compressor from cycling
unnecessarily. It does this by internally filtering the setpoints to avoid reaching the differential-to-
stop or the demand limit. Soft loading applies to the leaving chilled-water temperature and demand
limit setpoints.
Adaptive Controls
Adaptive Controls directly sense the control variables that govern the operation of the chiller:
evaporator pressure and condenser pressure. When any one of these variables approaches a limit
condition when damage may occur to the unit or shutdown on a safety, Adaptive Controls takes
corrective action to avoid shutdown and keep the chiller operating. This happens through
combined actions of compressor and/or fan staging. Whenever possible, the chiller is allowed to
continue making chilled water. This keeps cooling capacity available until the problem can be
solved. Overall, the safety controls help keep the building or process running and out of trouble.
Rapid Restart
A Rapid Restart is performed after a momentary power loss occurs during operation. Similarly,
if the chiller shuts down on a non-latching diagnostic and the diagnostic later clears itself, a Rapid
Restart will be initiated.
AdaptiSpeed Control
Compressor speed is used to control capacity of the chiller, optimizing mathematically with the
condenser fan speed to provide the highest level of performance. The increased performance of
the UC800 Controller allows the chiller to operate longer at higher efficiency, and with greater
stability.
Variable-Primary Flow (VPF)
Chilled-water systems that vary the water flow through chiller evaporators have caught the
attention of engineers, contractors, building owners, and operators. Varying the water flow
reduces the energy consumed by pumps, while having limited affect on the chiller energy
consumption. This strategy can be a significant source of energy savings, depending on the
application.