Marshall Excelsior Excela-Flo Automatic Changeover Regulator 253 Series. - The Model MEGR-253 Automatic Changeover Regulator automatically redirects LP gas vapor fl ow from an empty service cylinder to a reserve cylinder, without interruption of service. It features an easy to read green indicator which changes to red when the service cylinder needs to be refilled. The MEGR-253 and MEGR-293H Series regulators meet UL, RVIA and NFPA requirements. - Type: Two Stage - Max Inlet Pressure: 250 PSI - Inlet Connection: 1/4in Female Inverted Flare - Outlet Connection: 3/8in FNPT - Exterior Finish: Raw Zinc / Powder Coat - Diaphragm: Fabric Reinforced Molded with O-Ring Bonnet / Body Seal - Diaphragm Type: Internal Relief - Spring Loaded - Bonnet/ Body Material: Die Cast Zinc - Listings: UL Listed / UL 144 - Mounting Holes: 3-1/2in On Center - Primary Cylinder BTU/Hr - Capacity @ 20% Droop: 225,000 (253); 350,000 (253H) - Reserve Cylinder BTU/Hr Capacity @ 20% Droop: 150,000 (253); 200,000 (253H) - Cover: MEGR-862 - Pressure Taps: 1/8in FNPT Plugged. - 51082, 225,000 BTU's, 1/4Ã¢â‚¬Â Inv. Flare x 3/8Ã¢â‚¬Â FPT, Bulk.