WaterSense at Work: Best Management Practices for Commercial and Institutional Facilities
Introduction to Mechanical Systems
Mechanical systems are used in nearly every type of commercial and institutional
facility to provide building heating and cooling. Some facilities also use mechanical
systems to cool specific pieces of equipment, such as vacuum pumps, X-ray equip-
ment, and ice machines. In many instances, these mechanical systems use water as
the heat transfer medium. As a result, the use of water for building and equipment
heating and cooling can be significant, in some cases as much as 30 percent of the
total water use within a facility, as shown in Figure 6-1 for various commercial facility
Figure 6-1. Water Use Attributed to Mechanical Equipment for Heating and
Cooling in Various Commercial Facility Types
Common mechanical systems that use water as the heat transfer medium include
single-pass cooling, cooling towers, chilled water systems, and boiler and steam
systems. When looking to reduce mechanical system water use, facilities should first
eliminate single-pass cooling or reuse that water, then evaluate other cooling and
heating systems to maximize efficiency. Single-pass cooling systems use water to re-
move heat and cool specific pieces of equipment. However, after the water is passed
through the equipment, it is typically discharged to the sewer, rather than being re-
cooled and recirculated. In some cases, single-pass cooling can be the single largest
water user at a facility, using approximately 40 times more water to remove the same
heat load than a cooling tower operating at five cycles of concentration.
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