The Honeywell L4017B 1186 (Model L4017B1186) is a line-voltage combination fan and high-limit safety control designed to regulate blower motor operation and provide over-temperature safety shutdown in forced-air heating systems. Featuring a temperature-actuated helical bimetal element, this surface-mounted controller automatically cycles the circulating air fan based on plenum temperature while monitoring for high-limit thermal fault conditions. Operating on 120/240 VAC systems, the L4017B 1186 ensures energy-efficient heat distribution and reliable high-temperature limit protection across residential, commercial, and industrial forced-air furnaces, boilers, and warm-air ductwork.
Technical Details
- Model / Part Number: L4017B 1186 (L4017B1186)
- Manufacturer: Honeywell
- Device Type: Combination Fan and High-Limit Safety Control
- Electrical Rating: 120 VAC / 240 VAC (Line Voltage) | 50/60 Hz
- Switch Mechanism: Temperature-Actuated Bimetallic Switches (Fan Control & High Limit)
- Sensing Element: Helical Bimetal Sensing Element for Duct/Plenum Insertion
- Reset Mechanism: Automatic Reset (Restores Normal Operation Upon Cooling)
- Mounting Type: Surface Mount / Direct Duct or Plenum Mounting
- Enclosure & Build: Heavy-Duty Metal Housing for Furnace Integration
- Weight: ~1.5 lbs (0.68 kg)
- Standards & Approvals: UL Listed, CSA Certified
Key Features
- Dual-function design combines circulating fan control and high-limit safety protection within a single compact housing.
- Helical bimetal element delivers rapid, accurate thermal response to plenum and duct temperature changes.
- Automates blower activation to ensure warm air delivery and prevents cold air draft circulation during system startup.
- High-limit trip function automatically cuts burner or heating circuit power if unsafe temperatures occur.
- Automatic reset feature safely restores regular system operation once temperatures drop below the high limit threshold.
Applications
- Residential and commercial forced-air heating furnaces and warm-air heating systems.
- Gas-fired, oil-fired, and electric warm air duct heaters, boilers, and process air heating units.
- Industrial air handling units (AHUs), unit heaters, and commercial ventilation control panels.
- Direct maintenance replacement for legacy Honeywell combination fan and limit controls.
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