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EZ-ZONE® ST Integrated Solid State Controller

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The EZ-ZONE® ST integrated solid state controller from Watlow®, offers a complete thermal system control solution in a single package. Features include a PID temperature controller connected to a high-amperage solid state relay with the option of adding a properly sized heat sink, an over- and under-temperature limit, a power shut-down contactor and digital communications in one complete and professionally engineered product.

Because the system is modular and scalable, a user only pays for what is needed. Stacking the EZ-ZONE ST integrated controller into multiple configurations enables flexibility to standardize the product platform to solve a wide range of application needs.

Specifications · Features and Benefits


Line Voltage/Power
  • 100 to 240VAC, +10/-15%; (85-264VAC), 50/60Hz, ±5%
  • 24VAC/VDC, +10/-15%; 50/60Hz, ±5%
  • 12VA max. power consumption without mechanical contactor in system
  • 50VA max. power consumption with mechanical contactor used in system, 140VA if using external contactor
  • Data retention upon power failure via nonvolatile memory
  • 0 to 158ºF (-18 to 70ºC) operating temperature
  • -40 to 185ºF (-40 to 85ºC) storage temperature
  • 0 to 90% RH, non-condensing
  • Calibration accuracy and sensor conformity: ±0.1% of span, ±1ºC @ the calibrated ambient temperature and rated line voltage
    • Types R, S, B: 0.2%
    • Type T below -50ºC: 0.2%
  • Calibration ambient temperature @ 77ºF ±5ºF (25ºC ±3ºC)
  • Accuracy span: 1000ºF (540ºC) min.
  • Temperature stability: ±0.1ºF/ºF (±0.1ºC/ºC) rise in ambient max.
Agency Approvals
  • UL®, CSA, CE (zero cross models only), RoHS, W.E.E.E.
  • Limit version features FM approval
  • Microprocessor based user-selectable control modes
  • PID module: single universal input, 2 outputs
  • Limit module: single universal input, 2 outputs
  • Two total additional digital input/outputs shared between PID and limit functions
  • Control sampling rates: input = 10Hz, outputs = 10Hz
  • Isolated EIA 485 Modbus® RTU serial communications
Wiring Termination-Touch Safe Terminals
  • Input, power and controller output terminals touch safe removable 12 to 22 AWG
  • Power load terminals 6 to 12 AWG
    • Tightening torque: 30 in.-lbs
Universal Input
  • Thermocouple, grounded or ungrounded sensors
    • >20MΩ input impedance
    • Max. of 20Ω source resistance
  • RTD 2- or 3-wire, platinum, 100Ω and 1000Ω @ 0ºC calibration to DIN curve (0.00385Ω/Ω/ºC)
  • Process, 0-20mA @ 100Ω, or 0-10VDC @ 20kΩ input impedance; scalable, 0-50mV
  • Inverse scaling
Digital Input
  • Update rate: 1Hz
  • Dry contact or dc voltage
    DC voltage
    • Max. input: 36V at 3mA
    • Min. high state: 3V at 0.25mA
    • Max. low state: 2V
    Dry contact
    • Max. short circuit: 13mA
    • Min. open resistance: 500Ω
    • Max. closed resistance: 100Ω
Current Measurement
  • Accuracy: typical ±1A, max. error ±3A
  • Accuracy and operating range: 0 to 75A
Digital Output
  • Update rate: 1Hz
  • Output voltage: 24V, current limit 10mA
Allowable Operating Range

Type J: 32 to 1500ºF or 0 to 815ºC
Type K: -328 to 2500ºF or -200 to 1370ºC
Type T: -328 to 750ºF or -200 to 400ºC
Type N: 32 to 2372ºF or 0 to 1300ºC
Type E: -328 to 1470ºF or -200 to 800ºC
Type C: 32 to 4200ºF or 0 to 2315ºC
Type D: 32 to 4200ºF or 0 to 2315ºC
Type F: 32 to 2543ºF or 0 to 1395ºC
Type R: 32 to 3200ºF or 0 to 1760ºC
Type S: 32 to 3200ºF or 0 to 1760ºC
Type B: 32 to 3300ºF or 0 to 1816ºC
RTD (DIN): -328 to 1472ºF or -200 to 800ºC
Process: -1999 to 9999 units

Output Hardware
  • User selectable for heat/cool as on-off, P, PI, PD, PID, or alarm action. Not valid for limit controls
  • Electromechanical relay. Form A, rated 2A
  • SSR drive: 20-28VDC low side open collector switch
  • SSR, Form A, 0.5A @ 24VAC min., 264VAC max., opto-isolated, without contact suppression
  • Electromechanical relay, Form A, rated 5A, auxiliary output on PID module, output 2
  • Electromechanical relay, Form C, rated 5A, auxiliary output on limit module, output 3

Features and Benefits

Back panel or DIN-rail mount
  • Provides several mounting options
Compact package
  • Reduces panel size
Touch-safe package
  • Complies with IP2X increasing user safety
±0.1 percent temperature accuracy
  • Provides efficient and accurate temperature control
Agency approvals: UL®, CSA, CE, RoHS, W.E.E.E.
  • Meets applications requiring agency approvals
Three-year warranty
  • Ensures Watlow's reliability and product support
Off-the-shelf designed system solution
  • Improves system reliability and termination reduction
  • Reduces installation cost
  • Eliminates incompatibility headaches often encountered with using many different components and brands
Profile capability
  • Includes ramp and soak with four files and 40 total steps
Ability to communicate with programmable logic controller (PLC), personal computer (PC) or operator interface terminal (OIT)
  • Optional EIA 485 Modbus® RTU
  • RUI/communications gateway with optional EIA 232/485 Modbus® RTU, EtherNet/IP™/TCP Modbus®, DeviceNet™ or PROFIBUS DP.
Solid state relay output
  • Allows faster cycling, more precise control, increased heater life and improves energy efficiency
  • Ability to handle up to 75 amperes
  • Uses either zero-cross or phase angle control modes for flexibility to control resistive loads such as nichrome, tungsten or quartz lamps
  • Utilizes phase angle control mode to prevent load failure or blowing fuses for tungsten or quartz loads
PID temperature control
  • Allows single input/dual output
  • Allows standard PID or adaptive TRU-TUNE+ tuning algorithms for demanding controllability requirements
Optional temperature limit
  • Increases safety in over- and under-temperature condition
Optional definite purpose mechanical contactor
  • Enables circuit safety shut down driven by limit control or PID alarm output signal
Optional current monitoring feature
  • Detects heater current flow and alarm indication of failed solid state relay (SSR) or heater zone
Optional SSR heat sink
  • Sized and engineered for specific applications
  • Factory supplied heat sink is UL® listed
System diagnostics
  • Provides continuous self-monitoring alerts when there is any system trouble to reduce maintenance and service costs
PC Software-EZ-ZONE Configurator
  • Wizard style configuration of controller settings
  • On-line or off-line recipe editing


· Dimensional Drawing of EZ-ZONE® ST with Definite Purpose Mechanical Contactor

· EZ-ZONE® ST with 25 or 40A Heat Sink, without Definite Purpose Mechanical Contactor

· EZ-ZONE® ST with 75A Heat Sink, without Definite Purpose Mechanical Contactor


 width= Specifications for Mechanical Contactor
(PDF, 35KB)