Boiler Controller


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


• 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 inputs • Two digital outputs for chillers • One digital output for alarm • Mixed water temperature input • Outdoor air temperature input • Outdoor air reset control • Two digital inputs for pump status • External time clock input • Local override and remote override capability • Six digital outputs for boilers, pumps and boiler stages • Adjustable offsets and differentials on digital outputs • 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 • LEDs for monitoring status • 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

Call to order:


Specs & Docs


General Accuracy: +/- 0.5% Programming: EIA RS485 interface Communications: RS485, half duplex Memory backup: Non-volatile EEPROM, no battery required Environmental Operating temperature: 32 to 131°F (0 to 55°C) Operating humidity: 0 to 100% RH, non-condensing Storage temperature: 14 to 140°F (-10 to 60°C) Electrical Supply voltage: 24 VAC +/-20% Inputs: Six 1000 Ω PtRTD, momentary override, five digital (dry contact) and one 4 to 20 mA DC analog Range: 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 Outputs: Nine digital (SPST dry contact, 24 VAC @2 A) and Two 4 to 20 mA DC analog Analog input impedance: 250 Ω 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.