Maxitrol M420H-1/2 Modulator Valve for Liquid Propane Gas 1/2" NPT 1/2" PSI
Whether your needs are problem-free stabilized area heating, elevated heating, consistent higher baking/drying temperatures or other process applications, maintaining consistent temperatures is no longer a problem.
The unique Modulator or Modulator/Regulator valve, the heart of the Selectra® Electronic Gas Flame Modulating System, provides precise, non-fluctuating, instantaneous temperature control without requiring a motor or mechanically driven butterfly valve.
These valves are designed exclusively for negative pressure (pull through) applications. They use a counter spring to keep the valve in the closed position despite the downward pull of negative pressure. M411, M511, and M611 valves are set for applications up to 1.5” w.c. and are not adjustable. MR212 valves are factory set for applications up to -1.5” w.c. and are field adjustable for up to -3.5” w.c.
With the main valve closed, an adjustable bypass provides a minimum firing rate to the burner whenever the safety shut-off valve(s) is open. This is low fire to the heater. Since the pressure regulator maintains a constant supply pressure, the minimum firing rate is also held constant. The MR212’s regulator is an integral component while a seperate upstream pressure regulator is required for the M411, M511, and M611. As voltage is applied to the control’s solenoid, a magnetic force is applied to the plunger. The plunger in turn pushes down on the main diaphragm of the M411, M511, and M611 valves or allows pressure to develop in the upper chamber of the MR212 valve. These forces on the main diaphragm are very similar to the spring loading of a gas pressure regulator. When the force is sufficient to overcome the counter spring, the main valve will open and gas will flow through the main valve in addition to flowing through the bypass. With sufficient voltage, the main valve (modulator valve for the MR212) will fully open and the pressure regulator will limit the burner pressure to the desired amount, thus establishing a controlled maximum high fire condition.