Chiller Controller


The SZ2166 is a microprocessor based chiller controller. It is designed for use on multi-stage chiller applications and includes boiler support and control.


  • Stand-alone or network operation
  • 365-day time clock with two holiday schedules, automatic leap year and daylight savings correction
  • No backup battery required for control parameters, schedule or clock
  • Hot water supply and return temperature inputs
  • Chilled water supply and return temperature input
  • Two digital outputs for boilers
  • One digital output for alarm
  • Mixed water temperature input
  • Outdoor air temperature input
  • Separate set point for thermal storage sequence
  • Outdoor air reset control
  • Two digital inputs for pump status
  • External time clock input
  • Six digital outputs for chillers, pumps and chiller stages
  • Adjustable offsets and differentials on digital outputs
  • Lead/Lag sequencing of up to six chillers
  • Two modulating analog outputs for valves and VFDs
  • Adjustable P+I+D control on modulating outputs
  • LEDs for monitoring status
  • Automatic rotation of pumps
  • Automatic rotation of chiller and boiler stages
  • Pump lube feature
  • Local and remote override capability

Call to order:


Specs & Docs



Accuracy: +/- 0.5%
Programming: EIA RS485 interface
Communications: RS485, half duplex
Memory backup: Non-volatile EEPROM, no battery required


Operating temperature: 32 to 131°F (0 to 55°C)
Operating humidity: 0 to 100% RH, noncondensing
Storage temperature: 14 to 140°F (-10 to 60°C)


Supply voltage: 24 VAC +/-20%
Inputs: Six 1000 Ω PtRTD, momentary override and five digital (dry contact)
Range: Chilled water supply and return: 0 to 100°F
Hot water supply and return: 40 to 240°F
Mixed water: 20 to 220°F
Outdoor air: -40 to 160°F
Outputs: Nine digital (SPST dry contact, 24 VAC @ 2A) and two 4 to 20 mA DC analog
Max. load resistance (analog output): 600 Ω
Common mode rejection: 100 db @ 60 Hz
Power consumption: 15 VA max.

Specifications subject to change without notice.