Page 173 - HVAC Pump Handbook

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HVAC Pump Performance

170 HVAC Pumps and Their Performance

(3) ensure that the pump always operates within this flow range, par-
ticularly with constant-speed pumps. It is obvious that one of the great
advantages of a variable-speed pump, properly controlled, is the ability
to operate it near its BEP curve at all loads on the water system.

6.8 Sources of Pump Information
It is obvious that the information included in this chapter on pump
performance requires substantial data from the pump manufacturers
on the selection and operation of pumps on HVAC water systems.
Most of the pump manufacturers active in this market have gone to
great lengths to provide technical information on their pumps.
Traditionally, pump catalogs contain detailed information on pump
physical dimensions and general arrangement as well as pump head-
capacity curves at 1150, 1750, and 3500 rev/min. Data on slower speeds
such as 850 and 720 rev/min are provided for larger-capacity pumps.
The development of computers has enabled pump manufacturers to
provide these data in software form such as diskettes or CD ROM.
Some pump manufacturers are furnishing computer selection programs
where the required pump head and capacity are inserted and the pump
selection is made for the designer. This selection can be on the basis of
(1) the most efficient, or (2) the most economical in first cost.

6.9 Summary

The increase in cost of energy has thrust efficiency of operation to the
forefront. Highly efficient centrifugal pumps are now available at lit-
tle added cost over less efficient pumps. The first and foremost evalu-
ation of HVAC pumps should therefore be efficiency. Since so many of
these pumps are now variable speed, efficiency throughout the oper-
ating range must be considered.
Ease of pump maintenance was of major concern in the past. The
reduction of pump maintenance due to variable speed has lessened
the concern for maintenance capability. Traditionally, pumps have
been given much more space for operation than centrifugal fans.
Many fans are tucked up in air handling units where repair is quite
difficult. With the application of variable speed and greater care in
pump operation, the large spaces around HVAC pumps are no longer
needed. Most HVAC pumps should operate for years without any seri-
ous maintenance.
Along with efficiency and first cost, these pumps should be evaluat-
ed for the space they require. As can be seen in Chap. 5, there are
many different pump configurations for all the applications in the

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