18 August 1998
Leaving condenser water temperatures.
Condenser water flows (for variable flow systems only).
Instantaneous kW to chillers.
Instantaneous kW to chilled water pumps (if variable).
Instantaneous kW to condenser water pumps (if variable).
Instantaneous kW to cooling tower fans (if variable).
Common chilled water supply temperatures.
(m) Common chilled water return temperatures.
Total chilled water flow.
Chilled water pumps status.
Start/stop signals for chillers (manual or automatic).
Start/stop signals for chilled water pumps (manual or automatic).
Start/stop signals for condenser water pumps (manual or automatic).
Start/stop signals for cooling tower fans (manual or automatic).
Chiller efficiency data.
c. Application notes. The hardware and software inputs described may not be required in every
case. The designer will study the existing or new system to determine which of the parameters are
necessary. Care will be observed when providing automatic start/stop of chillers in lieu of operator
10. CHILLED WATER TEMPERATURE RESET PROGRAM. The energy required to produce chilled
water in a reciprocating or centrifugal refrigeration machine is a function of the chilled water supply
temperature. The refrigerant suction temperature is also a direct function of the supply water
temperature; the higher the suction temperature, the lower the energy input per ton of refrigeration.
Chilled water supply temperature is selected for peak design times; therefore, the supply temperature can
be reset upward during non-peak design operating hours to the maximum which will still satisfy space
cooling requirements. The program resets chilled water temperature upward until the required space
temperature or humidity setpoints can no longer be maintained. This determination is made by
monitoring positions of the chilled water valves on various cooling systems or by monitoring space
temperatures. Design requirements for this applications program will be indicated by the letter X adjacent
to the program listing on the appropriate database table, as shown in Chapters 8 and 9.
a. Field hardware requirements. The hardware requirements are:
UMCS inputs from utility system.
(a) Chilled water valve position (analog position indicator, or fully open indicator on valve
stem) - one per air conditioning chilled water valve.