McDonnell & Miller 317350 Valve

As a seasoned tech, you know that ASME CSD-1 code compliance for hot water boilers often means significant downtime. The McDonnell & Miller 317350 (Model TC-U) is a specialized Test and Check Upper Valve designed to eliminate the need for full system drainage during low water cut-off testing. This 1-inch NPT component features an integrated, adjustable vacuum breaker that facilitates the rapid evacuation of water from the float chamber when the blow-down valve is cycled. By restricted water flow through the equalizing lines during a test, this valve ensures the LWCO drops quickly to verify its operating cycle without wasting excessive treated boiler water or fuel. Rated for a maximum pressure of 160 psi and temperatures up to 250°F, this OEM boiler control accessory is built for the high-demand environments where McDonnell & Miller Series TC-4 sets are standard. This upper valve is a exact replacement for the cross in your equalizing line, extending the control unit approximately 2 inches from the boiler shell.

• Efficient LWCO Testing: Simplifies mandated safety checks by isolating equalizing lines, significantly reducing labor hours compared to traditional drainage methods.
• Integrated Vacuum Breaker: The TC-U upper valve includes a built-in vacuum breaker to prevent delayed float drops, ensuring accurate response times.
• Rugged Performance Standards: Engineered to handle 160 psi maximum operating pressure and 250°F maximum temperature for industrial and commercial hydronic systems.
• Streamlined Installation: Designed with a standard 1" NPT connection to directly replace terminal crosses in existing equalizing piping.

Common Questions

How does this valve help with ASME CSD-1 requirements?
It allows technicians to simulate a low water condition by restricting the supply of water to the float chamber during a blow-down, fulfilling the test requirement without draining the entire boiler.

Can the TC-U be used on steam boilers?
While often found in hot water applications, its primary function is isolating equalizing lines in any Test-N-Check configuration compatible with its 160 psi pressure rating; always verify against your specific system's operating parameters.

Why is the vacuum breaker necessary on the upper valve?
The vacuum breaker allows air into the piping to break the vacuum created when water is blown down, ensuring the water level in the float chamber drops immediately rather than being held up by suction.

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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.