Page 123 - HVAC Pump Handbook

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Physical Description of HVAC Pumps

120 HVAC Pumps and Their Performance

this type of pump are furnished in a compact assembly and vertically
mounted, which saves equipment room space. The smaller pumps are
flexibly coupled through an integral bracket to a vertical, solid-shaft
electric motor. A slightly larger pump of this configuration can be fur-
nished mounted vertically with the same motor, or it can be supplied
mounted horizontally and connected through a flexible coupling to a
standard, horizontally mounted motor. The motor and pump are
mounted on a structural base, as is the case with many volute-type
pumps. These small turbine pumps are equipped with high-temperature
mechanical seals for 250°F water.

5.4 Positive-Displacement Pumps
Positive-displacement pumps as used in HVAC applications are small
in size because, typically, they are used only for chemical feed service in
other applications where a positive amount of material is required.
Most of these pumps are of the rotary or reciprocating type. Since these
pumps seldom enter into the overall performance of HVAC water sys-
tems, no further discussion of them will be included. Hydraulic
Institute’s Centrifugal Pump Standards is an excellent reference man-
ual for these pumps.

5.5 Regenerative Turbine Pumps
A specialty pump that cannot be classified as a centrifugal pump or a
positive-displacement pump is the regenerative turbine pump, as
shown in Fig. 5.11. This pump is used in the HVAC field primarily for
low-flow, high-head applications such as boiler feed service. It has very
tight clearances and, therefore, must be equipped with a very good
suction strainer. Its efficiency is lower than other centrifugal pumps of
similar size. It has been replaced on many applications by the small,
multistage, turbine-type centrifugal pump, as shown in Fig. 5.10.

5.6 Pump Construction
Most centrifugal pumps for the HVAC industry do not require the
rugged construction found in industrial and power plant installa-
tions. Compared with other pump applications, HVAC pumping is
easy pump duty. All the major liquids used in this field should be
noncorrosive and nonabrasive. Therefore, these pumps must offer
long life with very little in the way of repairs. Chapter 25 on mainte-
nance of pumps will review, in detail, the causes for abnormal wear
in pumps.

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