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Small rectangular limit control with plenum mounting tabs, silver metal finish, two terminals visible

SUPCO

SUPCO Fixed Temp Auto Reset Plenum Mount Limit Control 130-170F

SKU CH-3CYJ-BAF30

Fixed-temperature auto-reset limit control opens on temperature rise at 130-170°F with 40°F differential for 120/240/480V systems

  • typeFixed Temp, Auto Reset Plenum Mount
  • Automatic reset restores operation without manual intervention
  • Fixed temperature limits protect equipment at 130°F and 170°F
  • 40°F differential prevents rapid cycling of connected systems
  • Compact 1 7/8 in insertion fits standard plenum openings
  • Rated for 120/240/480 V across residential and commercial circuits

SUPCO Fixed-Temp Plenum Limit Control

The SUPCO limit control is a fixed-temperature, auto-reset switch designed for plenum mounting in HVAC systems. It opens on temperature rise with SPST action to interrupt power when the set point is reached. Installers use it as a high-limit safety device for electric heat sections or fan-coil units. The control resets automatically once the plenum temperature falls back within range.

Operating Range and Voltage Limits

The switch operates between 130 °F and 170 °F with a 40 °F differential between open and close points. It is rated for 120 V, 240 V and 480 V circuits, with current ratings of 15 A resistive at 120 V and 10 A resistive at 240 V. Inductive ratings are 3 A at 120 V and 1.5 A at 240 V. The device is not suitable for voltages outside the listed range or for three-phase loads without additional contactors.

1 7/8-Inch Insertion Depth Decides Fit

The sensing element inserts 1 7/8 inches into the plenum, so the duct or housing must accommodate that depth without obstruction. The overall housing measures 2 7/8 inches high by 1 7/8 inches wide. If the available plenum wall thickness or internal clearance is less than the insertion length, the control cannot be installed correctly and a different mounting style is required.

Highlights

  • Automatic reset restores operation without manual intervention
  • Fixed temperature limits protect equipment at 130°F and 170°F
  • 40°F differential prevents rapid cycling of connected systems
  • Compact 1 7/8 in insertion fits standard plenum openings
  • Rated for 120/240/480 V across residential and commercial circuits

Specifications

BrandSupco
typeFixed Temp, Auto Reset Plenum Mount

Questions about this item

Should I choose the 130 °F or 170 °F limit for my furnace?

The control opens on rise; 130 °F shuts the burner earlier for tighter spaces, while 170 °F allows higher plenum temperatures before opening.

What does the 40 °F differential mean once installed?

After opening at the set point, the switch auto-resets only when the plenum cools 40 °F below that temperature.

How do the 120 V, 240 V and 480 V ratings affect wiring?

The SPST contacts are rated 15 A at 120 V, 10 A at 240 V and 3 A at 480 V; size the circuit accordingly.

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