McDonnell & Miller 349400 Black Y Assembly

The McDonnell & Miller 349400 Black Y Assembly (Model SA159-17) is a critical replacement component for low water cut-off systems and mechanical water feeders. This assembly is engineered to integrate seamlessly with Series 47 and Series 47-2 water feeders, as well as Model 64-A and Model 42S-A controls. As a primary part of the MA-159 and MA-259 quick hook-up fittings, it enables technicians to perform direct installations into gauge glass tappings on a boiler, facilitating accurate water level monitoring. The durable cast construction is designed to withstand the harsh thermal cycling of steam and hydronic systems, ensuring the gauge glass remains perfectly aligned with the unit for reliable visual inspection. Weighing approximately 2.3 lbs, this veteran-standard part is essential for maintaining boiler safety and proper LWCO operation, preventing dry-fire conditions in commercial and residential heating applications.

• Precision Compatibility: Designed specifically for McDonnell & Miller Series 42A, 47, 47-2, 64-A, and 42S-A models.
• Streamlined Installation: Part of the quick hook-up system, allowing for rapid threading into standard boiler gauge glass tappings.
• Enhanced System Integrity: Prevents bypass leaks and ensures accurate low water cut-off triggering by maintaining proper fitting alignment.
• Robust Construction: Built to handle the high-pressure environment of hydronic heating and steam boiler applications.

Is the SA159-17 compatible with both steam and hot water boilers?
Yes, this black Y assembly is designed for boiler controls utilized in both steam and hot water systems, provided the unit model matches the 42, 47, or 64 series specifications.

Does this assembly include the upper and lower hook-up fittings?
The 349400 is the Y-assembly component itself. While it is a foundational part of the MA-159 and MA-259 sets, individual tappings and connectors may need to be inspected for wear separately.

Can this be used to repair a leaking gauge glass connection?
Absolutely. If the leak is originating from the Y-joint or the quick hook-up threads on a compatible McDonnell & Miller control, replacing the assembly is the industry-standard fix.

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.