What Is the Aquastat on a Boiler?

Features

• Heated water from a boiler may circulate through pipes under the floors or into radiators or baseboard heaters. Under-floor heating pipes typically are located within the concrete slab foundation or the floor's joist system. A pipe system has the advantage of providing consistent heat throughout a room as the hot water flows through the pipes. In the United States, residential boiler heating systems are more common in parts of the country where access to natural gas is limited.

Function

• Aquastats function like thermostats. While wall thermostats monitor the temperature inside rooms of your home, the aquastat monitors the temperature inside the boiler. When the temperature in the boiler drops to a certain level, the aquastat signals the boiler to heat the water to a higher temperature. The wall thermostat tells the heating system when the building's temperature drops to a certain level, and the aquastat then signals the pump to circulate water.

Modulating Aquastat

• An aquastat keeps boiler water between a low and high limit at all times, typically maintaining the temperature around 180 degrees Fahrenheit. To save energy, you can buy a modulating aquastat. This item reduces energy usage when you still need heat but the weather isn't so cold, such as in spring and fall. The equipment senses when the outside temperature is warmer and lowers the temperature inside the boiler accordingly. For this reason, it's also called an outdoor reset. If you'd rather not spend extra money on a modulating aquastat, you can manually lower the temperature on a regular aquastat.

Triple-Acting Aquastat

• Triple-acting aquastats also are available to add the ability to heat your domestic water for bathing and other uses. This equipment has more complicated heat settings for safety reasons. A water temperature of 111 degrees Fahrenheit or higher can cause skin scalding, according to an article published in February 2008 issue of "Fuel Oil News."