Do not connect the heater directly to a boiler or furnace coil or any other uncontrolled temperature source, or the thermostat could be damaged causing the unit to overheat. Unit is not weatherproof. For safe and proper operation the unit must be located indoors where the ambient air temperature is constant and is a minimum of 70°F (21°C). CAUTIONS Hatco requires that two temperature/pressure gauges, Hatco part number 03.01.003.00, be installed to assure proper operation. Install one in the supp