McDonnell & Miller 317354 Breaker and Gasket

The McDonnell & Miller 317354 is the critical TC-V vacuum breaker and gasket assembly engineered for high-performance hot water boiler systems. This specific mechanical component is a direct-fit solution for the upper valve of Series TC-4 Test-N-Check configurations, allowing for the rapid evacuation of water from the float chamber during routine diagnostics. By admitting atmospheric air when a vacuum condition occurs, the model TC-V prevents back-siphoning and ensures that low water cut-offs (LWCO) can be tested effectively without requiring a complete system drain. For technicians servicing commercial or industrial boilers, maintaining this 317354 breaker and gasket is essential for meeting ASME CSD-1 code mandates regarding periodic safety control verification.

Constructed with resilient materials, the TC-V vacuum breaker handles a maximum operating pressure of 160 psi (11 kg/cm²) and temperatures reaching 250°F (121°C). Designed for standard 1" NPT connections, this assembly integrates seamlessly into existing equalizing lines, providing the necessary pressure relief for the test check valve to function accurately. Replacing a worn vacuum breaker gasket or the entire 317354 unit is a standard procedure for HVACR contractors to maintain system reliability and prevent the dampers in the TC-4 valve from sticking due to negative pressure. Ensure proper orientation during install: the vacuum breaker must be positioned at the top of the upper equalizing line with the long leg facing the boiler.

• Enhanced Testing Efficiency: Enables rapid float chamber drainage for consistent low water cut-off testing without wasting fuel or boiler water.
• Precise Vacuum Relief: Effectively breaks internal vacuums to prevent backsiphonage and ensure reliable damper closure in TC-4 valves.
• High-Temperature Durability: Rated for severe hydronic heating environments up to 250°F and high-pressure industrial boiler applications.
• Code Compliance: Facilitates adherence to ASME CSD-1 requirements for weekly or monthly LWCO safety checks.

Is the McDonnell & Miller 317354 compatible with all TC-4 valves?
Yes, the model TC-V is the dedicated vacuum breaker and gasket designed specifically for the TC-U (Upper) valve in the McDonnell & Miller Series TC-4 set.

What happens if the 317354 vacuum breaker fails?
A faulty vacuum breaker can prevent the low water cut-off from dropping during a blow-down test, potentially leading to inaccurate readings and failure to detect dangerous low-water conditions.

Can I use standard pipe dope or tape on the 317354 threads?
Yes, but professional HVACR technicians should leave the first thread clear of sealant to prevent debris from entering the vacuum breaker stem or the TC-V internals.

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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.