The McDonnell & Miller 193D is a heavy-duty combination low water cut-off and pump controller designed for commercial and industrial steam boilers. Engineered for high-demand environments, this float-operated control manages pump activation while providing critical low water protection to prevent boiler dry-firing. The 193D model features alternate tappings, specifically 1" NPT connections for equalizing pipes and integrated ports for gauge glass and tri-cock sets, facilitating a streamlined water column installation. With a maximum steam pressure of 150 PSI and a 345 VA pilot duty rating at 120 or 240 VAC, this unit is built for reliability. It utilizes two snap-acting SPDT switches (No. 5 Switch) to ensure positive making and breaking of circuits, eliminating the common failure points associated with mercury-based or bellows-style controls through a permanent magnet repulsion mechanism. Key Benefits Dual-Function Reliability: Operates as both a primary pump controller and a secondary low water fuel cut-off (LWCO) for comprehensive boiler safety. Eliminates Bellows: Features a magnetic repulsion switch mechanism that removes the need for flexible bellows, significantly reducing the risk of mechanical fatigue and leaks. Simplified Installation: The alternate tappings (163900) allow for flexible piping configurations and direct mounting of water level monitoring accessories. Versatile Application: Suitable for boilers of any steaming capacity requiring high-pressure management up to 150 PSI. Common Questions What is the difference between the 193 and the 193D? The McDonnell & Miller 193D includes specific 1" NPT alternate tappings for additional mounting flexibility compared to the standard model, making it ideal for retrofitting into existing water column setups. Can this unit be used for manual reset applications? This specific part (163900) is an automatic reset model. If your local code requires manual reset for the low water cut-off, a 193-M series or a 5-M switch assembly must be specified. What maintenance is required for the 193D? Technicians should perform a daily blow-down when operating above 15 PSI to clear sediment from the float chamber and ensure the float mechanism moves freely within the casting. 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.
