The Johnson Controls A19ADB-2 is a heavy-duty hot water immersion temperature control engineered for precision high-limit cutout in commercial and industrial boiler systems. This mechanical thermostat features a single-pole, single-throw (SPST) switch configuration designed to open on temperature rise, providing a critical safety lockout when temperatures exceed the defined setpoint. With a robust 100 to 240 degree F setpoint range, it is the standard for contractors managing hydronic heating and process water applications. The unit is equipped with a manual reset mechanism, ensuring that a professional technician must evaluate the system before operation resumes after a high-temperature event. The package includes a 1/2 inch NPT well connector for direct immersion and a knob range adjuster for easy field calibration. Compatible with voltages ranging from 24 to 277Vac, this Johnson Controls A19 series controller offers versatile integration into various electrical control circuits while maintaining high-accuracy thermal sensing through its liquid-filled element. Key Benefits High-Temperature Cutout: Ensures system safety by interrupting the circuit when water temperatures exceed the 100-240?F setpoint. Manual Reset Safety: Provides a "trip-free" lockout that requires manual intervention, preventing hazardous automatic restarts. Universal Voltage Compatibility: Field-ready for 24V, 120V, 208V, 240V, and 277Vac applications. Durable Construction: Features a NEMA 1 general-purpose enclosure and dust-tight Pennswitch contacts for long-term reliability in mechanical rooms. Direct Immersion Design: Includes a 1/2" NPT well for rapid thermal response and easy installation in boiler tappings. Common Questions Does the A19ADB-2 reset automatically? No, this specific model is a manual reset control. Once the high-limit temperature is reached and the switch opens, it must be manually depressed to close the circuit again. What is the maximum bulb temperature for this unit? While the operating range is 100 to 240?F, the sensing element can typically withstand infrequent overshoot temperatures up to 290?F during shipping or system spikes without losing calibration. Can I install this on a rough or uneven surface? For the best results and to prevent case twisting that might affect calibration, it is recommended to use only the top two mounting holes when installing on irregular surfaces. 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.
