Operating Controller for a hot water or warm air heating system • Suitable for line, low voltage or millivolt switching • Maintains proper balance between heating medium temperature and outdoor temperature • Automatically raises heating medium control point as outdoor temperature falls • Does not replace safety high limit control • Not for use in systems requiring above 21OC (70OF) outdoor temperature • Includes 107323ACARD Outdoor Bulb Guard • Bulb size: 10 X 90 mm (3/8 X 3-9/16") • Capillary Length: 3 m indoor/(10') 9 m outdoor/(30') • Switching: SPST • Adjustable Differential: 3.3O to 11.1OC • Approx. dimensions: H X W X D 143 X 51 X 57 mm • Approvals: UL Listed