McDonnell & Miller RB-24E-S Control

The McDonnell & Miller RB-24E-S (Part Number 144693) is a heavy-duty, 24VAC conductance-type low water cut-off designed specifically for residential hot water boiler applications. Engineered for reliability in the field, this unit features a 3/4" NPT connection with brass threads to ensure a secure, leak-free metal-to-metal seal. The RB-24E-S includes a specialized control board wiring harness, allowing for efficient "plug and play" integration with modern boiler control boards, including those from United Technologies and Honeywell. This automatic reset LWCO protects the heat exchanger by interrupting the burner circuit immediately upon detecting an unsafe water level. With a 15,000-ohm probe sensitivity and a patented self-cleaning probe, this control minimizes scale build-up and reduces maintenance intervals. Transitioning between states is easily monitored via the integrated LED status indicators (Green for Power, Red for Low Water), while the built-in test switch confirms proper operation without needing to drain the system.

• Plug-and-Play Integration: Includes a dedicated control board wiring harness designed for rapid installation on common residential gas boilers.
• Reduced Maintenance: The McDonnell & Miller 144693 features a patented self-cleaning probe to prevent mineral accumulation.
• Operational Reliability: Automatic reset functionality ensures the system resumes safely once water levels are restored.
• Robust Construction: Rated for a maximum water pressure of 160 psi and temperatures up to 250°F.
• Field Diagnostics: Test switch and dual LED indicators provide instant visual verification of the burner circuit status.

Is the RB-24E-S compatible with glycol systems?
Yes, the McDonnell & Miller RB-24E-S is rated for use with water/glycol mixtures up to a 50% concentration.

Can I use this low water cut-off on a steam boiler?
No, the RB-24E-S GuardDog is specifically designed for residential hot water boilers and should not be applied to steam systems.

Does this unit require a manual reset after a low water event?
This model features an auto reset, which automatically restores burner operation once the probe detects that water has returned to a safe level.

This item is not eligible for free shipping.

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.