Hydrotherm BM-8782 Aquastat Limit

The Hydrotherm BM-8782 Aquastat Limit is a specialized immersion-type temperature controller designed for precise fluid management in hydronic heating boilers. As a critical safety and operational component, this aquastat high limit switch monitors internal water temperatures to prevent overheating conditions that can lead to system fatigue or pressure relief valve discharge. Engineered with a durable liquid-filled sensing element and a robust SPST switching mechanism, the BM-8782 provides reliable boiler temperature control by breaking the burner circuit once the user-defined setpoint is reached.

For technicians servicing old-school cast iron boilers or modern residential hydronic loops, this Hydrotherm replacement part features an adjustable temperature scale and an automatic reset function. The compact housing is built for direct insertion into an immersion well, ensuring high-sensitivity thermal contact. Whether you are troubleshooting a boiler not firing or performing a seasonal HVAC system tune-up, this limit control is the industry standard for maintaining consistent thermal parameters and protecting the heat exchanger from excessive high-limit excursions.

• Precision Thermal Sensing: Utilizes a liquid-filled capillary element for rapid and accurate response to boiler water temperature fluctuations.
• Automatic System Protection: The high limit safety feature cuts power to the burner at the maximum setpoint, preventing dangerous pressure buildup.
• Broad Compatibility: Designed specifically for Hydrotherm and Mestek hydronic units, functioning as a drop-in OEM limit switch.
• Heavy-Duty Construction: Industrial-grade snap-acting switches and a rugged enclosure withstand the high-vibration environment of a mechanical room.

What is the primary function of the BM-8782 in a boiler system?
It serves as a high-limit safety control, breaking the electrical circuit to the gas valve or oil burner if the water temperature exceeds the set limit to prevent system damage.

Does this unit require a manual reset after a high-temperature event?
No, the BM-8782 features an automatic reset, meaning it will re-close the circuit once the water temperature drops below the fixed or adjustable differential.

Can I use this for circulator pump control?
While typically used as a limit, it features SPST switching that makes it compatible with various 120V or 24V control applications depending on your specific wiring schematic.

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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.