Basic steam heating system parts
The typical residential steam system includes a boiler to produce steam, radiators to release the heat
from the steam into the room, and the piping connecting the two.
The boiler usually burns gas or fuel oil to produce heat to raise the temperature of water to the
In order to properly control the system, three basic components are required. A thermostat tells the system when heat is
required. A pressuretrol turns the burner of the boiler on and off based on the pressure in the system.
This is generally set at between 1 & 3 psi. This setting impacts not only comfort but also the
responsiveness, noise level, fuel economy, and life of the system. Generally speaking, the lower the
pressure is the better it is for the system. In a water based system, a pump circulates the heat while
in a steam system it is accomplished by the pressure of the steam. Enough pressure is required to
overcome the friction of the pipes. A low water cutoff (LWCO) is the third basic control and its purpose
is to keep the boiler from operating without water in it.
A pressure relief valve ("pop safety") is also added to the system to protect from overpressure due to
the boiler failing to shut off. Before these were installed, a steam boiler could explode.