Steam Piping and System Sensor Location

In residential steam heating systems, steam rises to the radiators and upper floors using the steam pressure generated by the boiler. Normally, the pressure is low, but sufficient enough to push the steam to the upper floors. In these systems, the boiler must be located below all the piping and all the radiators. Some Heat-Timer controls use an outdoor reset cycling concept that measures the return pipe temperature to measure how far did the steam travel within the piping. Thus, the location of the system sensor is important to the control logic. For optimal operation, the system sensor needs to be installed on the return piping above the water line.

One-Pipe Steam System

In one-pipe steam, gravity-flow steam, each of the radiators has a single pipe connection. The same pipe is used to supply the radiator with steam in addition to delivering the condensed steam back to the boiler. The pipes are pitched away from the boiler to send all the condensate to the return line. If the pitching was incorrect, the piping will generate loud banging noise during the heating period. In addition, steam circulation through the system will be reduced. The noise is due to the steam hitting the condensed water trapped at the pipe elbows.

All one-pipe steam radiators have an air vent to get ride of air trapped in the radiator so it can be replaced by steam. If the air vent is not functioning properly, the trapped air may not allow the radiator to get hot or it may allow the steam to escape and reducing overall system efficiency.

Two-Pipe Steam System

In two-pipe steam, gravity-flow steam, each of the radiators has a two pipes connected. A supply pipe delivers steam to the radiator and a return pipe move the condensate back to the boiler. Both pipes are pitched away from the boiler to send all the condensate to the return line. If the pitching was incorrect, the piping will generate loud banging noise during the heating period. In addition, steam circulation through the system will be reduced. The noise is due to the steam hitting the condensed water trapped at the pipe elbows.

Two-pipe steam radiators have no air vent as all the venting is installted on the piping to or from the boiler. This reduces the number of air vents installed. The air vents in this case are larger. They are deisgned to get ride of air trapped in the radiator and piping so it can be replaced by steam. If the air vent is not functioning properly, the trapped air may not allow a certain part of the system to get hot or it may allow the steam to escape and reducing overall system efficiency.