McDonnell & Miller RB-122-E Guard-Dog 144676 Low Water Cut-Off 110Volt

Original price was: $208.94.Current price is: $143.79.

77 in stock

SKU: 284135 Category:


The McDonnell & Miller RB-122-E Guard-Dog 144676 is a Low Water Cut-Off (LWCO) specifically designed for residential hot water boilers. It plays a crucial role in ensuring boiler safety by automatically shutting down the burner if the water level falls below a critical point, preventing overheating and potential explosions. Here’s a breakdown of its key features and benefits:


  • Automatic safety device: Monitors the water level in your boiler and shuts down the burner if it falls below a safe threshold.
  • Prevents damage: Stops the boiler from operating under low water conditions, which can lead to overheating, warping, and cracking of internal components.
  • Protects against explosions: Low water conditions can cause steam pockets to form, increasing the risk of a dangerous explosion. The RB-122-E helps prevent this by shutting down the boiler before such situations arise.

Operating Principle:

  • Electronic: Utilizes a solid-state conductivity probe to detect water presence instead of the traditional float and switch mechanism.
  • Reliable detection: The probe is less prone to wear and tear compared to mechanical components, offering consistent and reliable operation.
  • 120 VAC operation: Compatible with most residential boiler control systems.

Key Features:

  • Easy installation: Features a compact design and “plug-and-play” wiring harness for quick and straightforward setup.
  • Automatic reset: Automatically resumes operation once the water level rises to a safe point, eliminating the need for manual intervention.
  • LED indicators: Green LED indicates power, while red LED signifies low water and boiler shutdown.
  • Self-cleaning probe: Minimizes maintenance needs by reducing the frequency of cleaning the probe.
  • Durable construction: Built with high-quality materials for long-lasting performance and reliability.


  • Enhanced safety: Provides critical protection against the dangers of low water conditions in your boiler.
  • Peace of mind: Continuously monitors the water level and automatically responds to ensure boiler safety.
  • Reliable performance: Solid-state technology offers dependable operation with minimal moving parts.
  • Low maintenance: Self-cleaning probe and automatic reset require minimal attention.
  • Cost-effective: Prevents potential damage and repairs associated with low water events.

Things to consider:

  • Compatibility: Ensure the RB-122-E matches your boiler’s voltage requirements and control system compatibility.
  • Installation: Proper installation by a qualified technician is crucial for safety and optimal function.
  • Testing: Regular testing is recommended to ensure the LWCO is working correctly.

Overall, the McDonnell & Miller RB-122-E Guard-Dog 144676 is a valuable safety device for any residential hot water boiler. Its combination of advanced technology, ease of use, and reliable performance makes it a popular choice for protecting your boiler and ensuring the safety of your home.

Additional information

Weight 2.11 lbs


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