1-3/4" 2-stage regulating valve, high fire, 12" WC. The SR Series combines gas pressure regulating and flame staging in a single unit as an ideal replacement for dual manifold systems. Applications include direct-fired heaters with two-speed fans, hi-lo control for outdoor heaters, LP natural gas switchover, and industrial processing. Suitable for natural, manufactured, mixed gases, liquefied petroleum gases, LP gas-air mixtures, and DIN EN 437 gas families 1, 2, and 8