McDonnell & Miller 344100 Tube Assembly

The McDonnell & Miller 344100 (Model SA66-35) is a high-precision upper tube assembly engineered for the maintenance and repair of Series 67 low water cut-offs. As a critical safety component for steam boiler systems, this assembly ensures the operational integrity of the LWCO by housing the internal mechanism that responds to water level fluctuations. It is designed for seamless integration into existing 67 and 67-G models, facilitating a direct replacement of degraded or scaled tubing that can impair float movement and switch activation. Built for the rigors of commercial and industrial environments, the SA66-35 tube assembly utilizes robust materials to withstand standard operating pressures and high-temperature steam applications. This OEM replacement part is essential for technicians tasked with restoring the reliable dry-fire protection required in hydronic heating systems, ensuring the burner circuit is interrupted precisely when water levels fall below safe thresholds.

Key Benefits

• Precise Compatibility: Specifically manufactured for McDonnell & Miller Series 67 units, ensuring the mechanical tolerances match original specifications.
• Streamlined Installation: Designed to fit within the standard quick hook-up fittings, reducing labor time during system overhauls.
• Enhanced System Safety: Restores the vital connection between the float chamber and the electrical switch, critical for preventing boiler dry firing.
• Durable Construction: Engineered to hold up under fluctuating steam pressures and prevent premature corrosion or sediment buildup.

Common Questions

Is the SA66-35 compatible with the 767 series?
While both are float-type controls, the 344100 tube assembly is specifically listed for the 67 and 67-G series. Always verify the part number against the specific casting on your device before installation.

What is the maximum operating pressure for this assembly?
This assembly is rated for use within the standard Series 67 parameters, which typically support a maximum steam pressure of 20 psi.

Does this include the float and bellows?
No, the SA66-35 is the upper tube assembly only. If you require the float or the switch mechanism (such as the No. 11 switch), those must be sourced separately as part of a complete rebuild kit like the MA559.

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.