The Fisher 289 series release valves are set in a pressure range of 0.5 to 2.25 psig / 34 to 155 mbar. They are throttling release valves downstream of the regulator to prevent overpressure in the downstream system. Smooth throttling action minimizes pressure shock in the system during emergency operations. The unit is equipped with a pitot tube amplifier to provide the highest possible release capacity while ensuring a small increase in system pressure. The Model 289H release valve is installed between a large two-regulator (e.g. CS800 or CS400 series) and the burner to provide high release capacity. Series 289 Release valves are ideal for low pressure environments because their large membranes provide increased sensitivity.