Boiler Controller



The SZ2165 is a microprocessor-based boiler controller for use in multi-stage boiler applications. It includes chiller support and control functions.



  • Six 1000 Ω PtRTD, momentary override
  • Five digital (dry contact)
  • One 4 to 20 mA DC analog
    • Hot water supply and return: 40 to 240°F
    • Chilled water supply and return: 0 to 100°F
    • Mixed water: 20 to 220°F
    • Outdoor air: –40 to 160°F


  • Nine digital (SPST dry contact, 24 VAC @2A)
  • Two 4 – 20 mA DC analog

Maximum load resistance (analog output):


Common mode rejection: 

100 db @60Hz


  • Stand-alone or network operation
  • 365-day time clock with two holiday schedules
  • Hot water supply-and-return temperature inputs
  • Chiller support
  • Two digital inputs for pump status
  • Local override and remote override capability
  • Digital outputs for boilers, pumps, and boiler stages with adjustable offsets and differentials
  • Lead/Lag sequencing of up to four boilers
  • Analog input for pressure control
  • Two modulating analog outputs for valves and VFDs
  • Adjustable P+I+D control on modulating outputs
  • Automatic rotation of pumps
  • Automatic rotation of boiler and chiller stages
  • Domestic hot water function
  • Pump lube feature
  • Selectable normally open or normally closed relay outputs