Maxitrol MR212D-88 Valve

The Maxitrol MR212D-88 is a high-performance 1" NPT modulating gas valve and regulator engineered specifically for direct fired burners operating under negative pressure (pull-through) conditions. Designed for maximum precision in industrial and commercial HVACR applications, this Selectra series valve features an integral pressure regulator that eliminates the need for an external upstream regulator. It handles a maximum inlet pressure of 5 PSI, providing a stable 5:1 turndown ratio for consistent temperature control without the hysteresis common in motor-driven butterfly valves. The MR212D-88 utilizes a dual-spring mechanism to manage high and low fire settings; the absence of control voltage defaults the unit to its regulated high fire state, while the application of DC voltage modulates the plunger to achieve a precise low fire. This solid-state design ensures rapid, non-fluctuating response times, making it an essential component for Series 14, 24, and 44 modulation systems. Techs should note the negative pressure field-adjustable range of up to -3.5" w.c. to maintain combustion stability in high-demand environments.

• Dual Functionality: Functions as both a modulator and regulator, simplifying gas train piping by removing the requirement for separate pressure regulation components.
• Negative Pressure Optimization: Includes a specific counter-spring design to ensure the valve remains closed against the downward force of pull-through burner suction.
• Solid-State Precision: Provides infinite flame adjustment and immediate response to signal changes from Series 94 or SC11 signal conditioners.
• High Pressure Resilience: Rated for a 5 PSI max inlet with an emergency exposure limit of 12.5 PSI, offering robust Protection against line pressure spikes.
• Field Serviceable: Features field-adjustable bypass and high-fire settings, facilitating exact manifold pressure calibration during startup.

Is an upstream regulator required with the MR212D-88?
No, the MR212D-88 is a modulator-regulator. As long as your inlet pressure does not exceed 5 PSI, the valve handles primary regulation internally.

How does voltage affect the flame height in this model?
For this specific valve, an increase in voltage to the modulator coil corresponds to an increase in outlet pressure, though the underlying mechanical logic uses voltage to lift the plunger and transition from high to low fire regulation.

Can this valve be used for positive pressure burners?
This model is specifically calibrated for direct-fired negative pressure applications. For positive pressure atmospheric burners, the MR251 series is typically the correct choice.

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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.