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SERIES LV Limit Controller

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Watlow's family of microprocessor-based limit controllers provides an economical solution for applications requiring temperature limit control. Limits are available in a broad range of packaging options, allowing selection of the best version for an application. Limits are available with an operator interface and can be ordered in 1/8 DIN-square panel mount or DIN-rail mount design configurations.

The SERIES LV limit family incorporates a microprocessor design platform. This design provides significant improvements in the performance, repeatability and accuracy offered by Watlow's current line of analog limit controllers.

The variable SERIES LV limit includes an operator interface for viewing and selecting the set point. A red, four-character seven segment LED displays the set point. Set point selection is made with a continuous turn rotary encoder. Operating range temperature values are customer defined in the product configuration part number.

The limit controllers are factory mutual (FM) approved with special UL® approval for the open board potted versions. Watlow's limit controllers include industry leading service and support and are protected by a three-year warranty.

Specifications · Features and Benefits


  • DIN-rail model can be DIN-rail or chassis mount DIN-rail spec DIN 50022, 1.38 in. x 0.30 in. (35 mm x 7.5 mm)
Limit Controller
  • Microprocessor-based limit controller
  • Nominal switching hysteresis, typically 3ºF (1.7ºC)
  • High or low limit, factory selectable
  • Latching output requires manual reset upon over or under temperature condition
  • Manual or automatic reset on power loss, factory selectable
  • Internal front panel or external customer supplied momentary reset switch
  • Input filter time: 1 second
Operator Interface
  • Four digit, seven segment LED displays, 0.28 in. (7 mm) high
  • ºF or ºC indicator LED
  • Alarm indicator LED
  • Continuous turn, velocity sensitive rotary encoder for set point adjustment
  • Front panel SET/RESET
Standard Conditions For Specifications
  • Rated line voltage, 50 to 60Hz, 0 to 90% RH non-condensing, 15-minute warm-up
  • Calibration ambient range: 77ºF (25ºC) ±3ºC
Sensor Input
  • Grounded or ungrounded
  • Type E, J, K, T thermocouple
  • >10 MΩ input impedance
  • 250 nV input referenced error per 1Ω source resistance
  • 2-wire platinum, 100Ω
  • DIN-curve (0.00385 curve)
  • 125µA nominal RTD excitation current
Input Accuracy Span Range

Type E: -328 to 1470ºF (-200 to 800ºC)
Type J: 32 to 1382ºF (0 to 750ºC)
Type K: -328 to 2282ºF (-200 to 1250ºC)
Type T: -328 to 662ºF (-200 to 350ºC)
RTD (DIN) -328 to 1472ºF (-200 to 800ºC)

Thermocouple Input
  • Calibration accuracy: ±1% of input accuracy span, ±1º at standard conditions and actual calibration ambient. Exception: Type T, ±2.4% of input accuracy span for -328 to 32ºF (-200 to 0ºC)
  • Temperature stability: ±0.3º per degree change in ambient
RTD Input
  • Calibration accuracy ±1% of input accuracy span ±1º at standard conditions and actual calibration ambient
  • Temperature stability: ±0.2º per degree change in ambient
Allowable Operating Ranges

Type E: -328 to 1470ºF (-200 to 800ºC)
Type J: -346 to 1900ºF (-210 to 1038ºC)
Type K: -454 to 2500ºF (-270 to 1370ºC)
Type T: -454 to 750ºF (-270 to 400ºC)
RTD (DIN) -328 to 1472ºF (-200 to 800ºC)

Electromechanical Relay, Form C
  • Min. load current: 100mA
  • 8A @ 240VAC or 30VDC max., resistive
  • 250VA pilot duty, 120/240VAC max., inductive
  • Use RC suppression for inductive loads
  • Electrical life 100,000 cycles at rated current
External Reset Switch
  • Momentary, dry contact closure
Agency Approvals
SERIES LV (potted version only)
  • UL® 991 recognized temperature limit for cooking industry
  • UL® 60730-1
SERIES LV (including potted version)
  • UL® 873 recognized temperature regulator
  • UL® 197 reviewed for use in cooking appliances
  • UL® 991
  • UL® 50 IP65 for tactile key models
  • ANSI Z21.23 Gas appliance thermostat approval
  • CSA C22.2#24 approved limit control
  • FM Class 3545 temperature limit switches
  • RoHS, WEEE
  • 0.25 in. (6.3 mm) quick connect, push on terminal or removable screw terminals
  • 24VAC +10%; -15%; 50/60Hz, ±5%
  • 120VAC +10%; -15%; 50/60Hz, ±5%
  • 230 to 240VAC +10%; -15%; 50/60Hz, ±5%
  • 10VA max. power consumption
  • Data retention upon power failure via nonvolatile memory
Operating Environment
  • 32 to 158ºF (0 to 70ºC)
  • 0 to 90% RH, non-condensing
  • Storage temperature: -40 to 185ºF (-40 to 85ºC)

Features and Benefits

Adjustable set points
  • Offers control flexibility
Four character LED display
  • Improves set point selection accuracy
Multiple mounting options
  • Minimizes installation time
High or low limit with auto or manual reset
  • Provides application flexibility
Fahrenheit or Celsius operation with indication
  • Offers application flexibility
Sensor break protection
  • Provides positive system shutdown
Agency approvals
  • Meets certification requirements/compliance
Microprocessor based technology
  • Ensures accurate, repeatable control


· Dimensions Table of SERIES LV Limit Controller (PG 74 + 96)