McDonnell & Miller RB-24E-L Control

The McDonnell & Miller RB-24E-L (Part Number 144690) is a specialized residential low water cut off designed for 24V hot water boiler systems. This electronic LWCO utilizes a 3/4" NPT probe-style sensing element to monitor for hazardous low-water conditions, ensuring the burner circuit is interrupted before equipment damage occurs. Unlike manual reset models, this unit features an auto reset function that restores operation once the water level returns to the probe, making it ideal for standard residential applications. The RB-24E-L is engineered with a built-in test switch to verify function without draining the system and includes a dedicated burner control wiring harness to simplify field installation. Its compact design and integrated 24V low water cut off technology provide reliable protection against dry-firing, effectively managing boiler safety in modern hydronic heating infrastructures.

• Simplified Wiring: Includes a factory-supplied wiring harness specifically for burner control integration, reducing diagnostic and installation time.
• Self-Cleaning Probe: The McDonnell & Miller 144690 utilizes a probe designed to minimize scale buildup, ensuring long-term sensing accuracy in diverse water conditions.
• Internal Testing Logic: The integrated test button allows for immediate verification of the internal relay and electronic circuitry during routine maintenance.
• Compact Footprint: Fits into tight boiler jackets and manifold configurations where 3/4" NPT tapping is required.

Does the RB-24E-L require periodic maintenance?
Yes, the probe should be removed and inspected annually for scale or sediment accumulation to ensure proper conductivity between the probe and the boiler water.

Can this unit be used on steam boilers?
No, this specific model is engineered strictly for hot water (hydronic) heating systems. Steam applications require different sensing technologies due to the presence of foam and surging.

What does the green LED indicator signify?
A solid green light indicates that the water level is sufficient and the 24Vac low water cut off is permitting burner operation. If the light flashes or turns off, the system has detected a low water event or a probe failure.

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.