Chapter 1
Steam System Components
A steam heating system is made up of components
that work together to provide and maintain
comfortable temperature in a structure.
A typical one pipe steam heating system is
shown in Figure 1.
Boiler – the boiler/burner combination is
used to heat water that is converted to steam
and distributed through piping connected to a
variety of heat emitters.
Boiler nameplates contain a significant
amount of information, a typical steam boiler
nameplate is shown in Figure 2.
Input – this tells
us the burner capacity,
or firing rate. In
this case the boiler is
rated for 7.5 gallons
per hour. It’s important
to note that this
is NOT the nozzle
size. To determine
nozzle size fuel unit
pressure must be
considered.
4 National Oilheat Research Alliance
For example, if the pressure is 100 psi, then a
7.50 gph nozzle is correct, however if the pressure
is 145 psi, a 6.25 gph nozzle is correct.
Gross Output (also referred to as “DOE
Capacity”). This shows that this unit is rated
by the US Department of Energy at 868,000
BTU’s per hour when fired at the specified
burner capacity.
Net AHRI Rating (formerly I=B=R). This
is the rating that is used to select a properly
sized boiler based on the heat load calculation
that is performed prior to installation. This
boiler is rated for 651,000 BTUH or 2,713 SQ.
FT. STEAM.
Pressure Relief Valve - the pressure
relief valve protects the system from over pressurization.
If the pressure rises to the systems
maximum operating pressure, the relief valve is
designed to open and release steam/water from
the system.
Most residential steam systems are equipped
with relief valves that open at 15 PSI, but may
actually release and weep around 13 psi.
The relief valve MUST be properly sized, the
rating MUST meet or exceed the boiler’s DOE
heating capacity rating. Figure 3.
Figure 1
Figure 2