<P> These systems depend on the proper operation of thermostatic air - venting valves located on radiators throughout the heated area . When the system is not in use , these valves are open to the atmosphere , and radiators and pipes contain air . When a heating cycle begins , the boiler produces steam , which expands and displaces the air in the system . The air exits the system through the air - venting valves on the radiators and on the steam pipes themselves . The thermostatic valves close when they become hot ; in the most common kind , the vapor pressure of a small amount of alcohol in the valve exerts the force to actuate the valve and prevent steam from leaving the radiator . When the valve cools , air enters the system to replace the condensing steam . </P>
<P> These systems depend on the proper operation of thermostatic air - venting valves located on radiators throughout the heated area . When the system is not in use , these valves are open to the atmosphere , and radiators and pipes contain air . When a heating cycle begins , the boiler produces steam , which expands and displaces the air in the system . The air exits the system through the air - venting valves on the radiators and on the steam pipes themselves . The thermostatic valves close when they become hot ; in the most common kind , the vapor pressure of a small amount of alcohol in the valve exerts the force to actuate the valve and prevent steam from leaving the radiator . When the valve cools , air enters the system to replace the condensing steam . </P>
where is air vented from a hydronic heating system
where is air vented from a hydronic heating system
valves located on radiators throughout the heated area
valves located on radiators throughout the heated area