Honeywell L8100B1128 Aquastat Controller

The Honeywell L8100B1128 Aquastat Controller is a high-limit immersion controller engineered for precision hydraulic system protection. This SPST aquastat is designed to break the circuit on temperature rise, specifically serving as a secondary safety limit for hydronic heating systems. It features a broad 100-180 degree F operating range with a factory-set 190 degree energy cutoff (ECO) to prevent boiler overheating. The unit utilizes a 3/8-inch x 2-7/8-inch sensing bulb and a 39-inch capillary length, allowing for flexible mounting configurations in standard immersion wells. With a 5 degree fixed differential and a 20 degree ECO switch differential, this controller ensures stable operation without excessive short-cycling. This model is technically identical to the L8100B1128/U, making it a direct Honeywell replacement part for existing boiler high-limit controls. For contractors, the aquastat wiring is straightforward, integrating seamlessly into 120V or 240V control circuits to maintain safe water temperatures in residential and light commercial applications.

Key Benefits

• Critical High-Limit Protection: Integrated 190°F Energy Cutoff (ECO) provides an essential safety layer for pressurized hydronic systems.
• Fixed Thermal Differential: Maintains a tight 5°F differential to ensure consistent system response and prevent temperature overshoots.
• Flexible Installation: The 39-inch capillary allows for remote sensing bulb placement when standard direct-mount configurations are restricted.
• Broad Compatibility: Functions as a universal replacement for the L8100B series, supporting various boiler manufacturers.
• Simplified Field Replacement: Identical specifications to the "U" suffix model streamline inventory and installation for service technicians.

Common Questions

What is the difference between the L8100B1128 and the L8100B1128/U?
There is no functional or technical difference; the "/U" denotes a universal trade-packed version, while both share the same sensing range and ECO setpoints.

Can this be used as an operating control instead of a high-limit?
This specific model is designed as a high-limit safety because the contacts break on temperature rise and it includes a non-adjustable ECO safety switch.

Does this unit come with an immersion well?
Standard L8100B units are usually designed to fit existing immersion wells; verify your current well depth and diameter (3/8") match the bulb specifications for proper heat transfer.

Disclaimer: While we strive for 100% accuracy, product data and specifications are subject to change. Please contact our team to confirm compatibility or technical details before purchasing.