Page 211 - WaterSense at Work

WaterSense at Work: Best Management Practices for Commercial and Institutional Facilities
Boiler and steam systems are used in large building heating systems for heating
water or to produce steam for industrial processes, cooking, or other operations. Hot
water boilers are a subset of commercial and industrial boilers used to heat water.
Steam boilers, which include water-tube and fire-tube systems, produce steam by
boiling water. Low-pressure boilers are used most for commercial applications and
heating water, while high-pressure boilers are more common for power generation
and industrial processes.
Hot Water Boilers
Hot water boilers are used to provide hot water for bathing, laundry, dishwashing,
or similar operations. Unlike steam boilers, however, they do not produce steam.
Instead, hot water boilers essentially act as commercial- or industrial-scale water
Hot water boiler distribution systems can be open or closed. Open systems provide
hot water to end uses, such as hand washing, bathing, and laundry. These can either
be direct-supply systems or have loop piping, whereby the hot water is recirculated
back to the hot water boiler. Open systems are typically found in food service or laun-
dry operations. Recirculating systems are most commonly used in applications that
need hot water instantaneously, such as hotels.
Closed systems are often used for heating buildings. Hot water is circulated in a
closed loop for space heating, using either air heat-exchange or hydronic floor-heat-
ing systems. Water in closed-loop systems is typically treated to prevent corrosion
and scaling. Additional water is needed only to make up for leaks and periodic addi-
Because water efficiency isn’t a primary concern for hot water boiler systems,
they are not discussed further in this section.
Water-Tube Boilers
Water-tube boilers (see Figure 6-5) are used for high-pressure boiler applications.
In these systems, water circulates through tubes that are indirectly heated by fire.
Exhaust gases remain inside the boiler shell and pass over tube surfaces to heat the
water. The heated water then rises as steam to be used for cooking, as process steam,
or for other operations. Water-tube boilers are lighter by design and thus able to
withstand higher pressures. They are also capable of high efficiencies and generating
saturated or superheated steam.
Boiler and Steam Systems
East Bay Municipal Utility District (EBMUD). 2008.
WaterSmart Guidebook—A Water-Use Efficiency Plan Review Guide for New Businesses
Pages THERM10-14.