Honeywell Boiler aq475a outdoor temperature compensator automatically regulates boiler water temperature and is compatible with contemporary Honeywell electromechanical and electronic 2-wire thermostats. It features:

• Adjustable settings for boiler maximum and minimum temperatures, and for outdoor low (design) temperature.
• Selectable Warm Weather Shut Down (WWSD) at 70°F (21°C) to prevent summer boiler operation.
• Domestic Hot Water (DHW) priority - operates the boiler at the Boiler Maximum Temperature setting to heat domestic hot water and can operate or shut down the system circulator.
• Automatic boiler operating differential.