Johnson Controls A19 Series temperature controls are designed to cover a broad range of uses for heating and general purpose requirements. Controls have SPST contacts which open on temperature increase or they may be supplied in single-pole, double-throw contact action. Various control ranges are available to cover working temperatures from -30 to 550° F (-34 to 288° C). Closed tank fittings and bulb wells are available for immersion applications. These controls are designed for open low and open high applications. Where critical or high value products are to be maintained within a specific temperature differential, a single control should not be applied to function as both an open low and open high control. In these applications, a separate backup control with alarm contacts should be wired to indicate when the back-up control operates.