Honeywell Immersion Temperature Controller – SPST Aquastat, 100–240°F Range, Bulb & Capillary Type, Surface/Well Mount

Honeywell Immersion Temperature Controller – SPST Aquastat, 100–240°F Range, Bulb & Capillary Type, Surface/Well Mount

Condition: Used. Moderate wear from prior installation; unit shows discoloration and residue on the housing and sensing bulb. Capillary appears intact with no kinks. Cover may have minor surface scratches.

This Honeywell Immersion Controller (Aquastat) is a mechanical temperature control device with a 100°F to 240°F adjustable range, commonly used to regulate water temperature in hydronic heating systems, boilers, indirect water heaters, and other HVAC applications. It operates using a capillary bulb sensor immersed directly in the fluid, triggering an SPST (Single-Pole Single-Throw) switch when the setpoint is reached. This design provides reliable temperature control without the need for external power to operate the sensing mechanism.
It’s designed for immersion in water or glycol solutions via a well or strap-on mount, depending on the system configuration. This model is favored in both residential and commercial systems due to its simplicity, durability, and compatibility with a wide range of equipment.

🔧 Features:
Temperature Range: 100°F to 240°F
Switch Type: SPST (Single-Pole, Single-Throw)
Application: Open-on-rise or close-on-rise (model-dependent)
Sensing Element: Liquid-filled bulb with capillary tube
Mounting: Immersion well (threaded) or strap-on
Electrical Rating: Typically 120V/240V AC, 10A resistive (verify model tag)
Control Dial: Front-access, adjustable with Fahrenheit scale
Housing: Steel or plastic casing with removable cover
Sensor Type: Copper or nickel-plated bulb with 5–6 ft capillary (approx.)

🏭 Applications:
Boiler temperature control (hydronic heating)
Domestic hot water circulation control
Solar water heating systems (backup control)
Freeze protection circuits
Fan or pump switching based on water temp
Indirect water heater limit control
Geothermal system loop monitoring

🔄 Cross-Referenced Models:
Honeywell L6006A1145 – Commonly seen immersion Aquastat, 100–240°F, SPST
Honeywell L6006C1018 – SPDT version with similar range
White Rodgers 11B30-1 – Mechanical immersion controller equivalent
Johnson Controls A19ABA-40 – Comparable temp range, different mounting
Robertshaw 110 Series – Classic mechanical water temperature control

📌 Comparable Products:
Honeywell L4006A1967 – Snap-acting immersion controller, 100–240°F
White Rodgers 11A30-11 – Adjustable immersion control with fixed differential
Taco HydroStat 3250 – Digital replacement with integrated boiler control
Johnson Controls A19ABC Series – Wide-range temperature controllers for immersion
Tekmar 256 – Digital boiler control (more advanced applications)

🧩 Part of Larger Systems:
This immersion controller is typically used within:
Residential or commercial hydronic boiler systems
Solar thermal collector systems
Indirect domestic hot water heaters (Buderus, Lochinvar, Amtrol, etc.)
Geothermal water-to-water systems
Pump relay systems where water temp dictates operation
It can be used as:
High-limit cut-out
Circulator control
Boiler enable switch based on water temp
Works with threaded immersion wells from Honeywell or compatible brass/stainless steel wells.

⚠️ Trademark Disclaimer:
All product names, logos, brands, and other trademarks mentioned are the property of their respective owners. These names are used solely for identification purposes and do not imply endorsement or affiliation.

Related:
immersion temperature controller
aquastat 100-240F range
Honeywell SPST boiler thermostat
mechanical hot water controller
strap-on water temperature switch
hydronic control temperature sensor

Common Requests:
“Honeywell Aquastat 100–240°F replacement”
“Used boiler immersion controller with capillary sensor”
“Temperature controller for indirect water heater”
“How to wire Honeywell SPST aquastat”
“Immersion well thermostat for hydronic heating systems”

All product names, trademarks, and registered trademarks are the property of their respective owners. Use of these names does not imply any affiliation or endorsement.

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