Page 171 - HVAC Pump Handbook

Rishel_CH06.qxd 20/4/06 6:06 PM Page 168

HVAC Pump Performance

168 HVAC Pumps and Their Performance

6.7 Pump Noise

Pump noise in HVAC water systems is objectionable since it can
travel through the piping to other areas of the building outside the
equipment rooms. Also, the noise may indicate trouble in the pump
or its motor with the possibility of expensive maintenance. Further, a
noisy pump often indicates inefficient pump operation. An interest-
ing article appeared in the September 2004 issue of HPAC
Engineering Magazine on how low-frequency noise impairs learning.
There is absolutely no reason to allow noisy pump operation; noise in
pumps comes from improper installation, selection, or faulty opera-
tion. Pump noise is much more prevalent in constant-speed pumps
than in variable-speed pumps. Pump noise originates from outside of
or inside the pump.

6.7.1 Noise outside the pump
The outside noises stem from the motor or misalignment of the pump
and motor. Motor noise comes basically from speed. Most HVAC pump
motors operate quietly at either 1200 or 1800 rev/min synchronous
speeds. At these speeds there should not be any objectionable noise.
Often, there are opportunities to achieve higher pump efficiencies by
operating the pumps at 3600 rev/min synchronous on high-head, vari-
able-speed applications. Care should be taken, in this case, to ensure
that objectionable noise will not travel outside the equipment room
when the pump must operate near its design condition.
The other major outside sources of noise are caused by misalign-
ment of the pump and motor or distortion of the pump by the con-
nected piping. These are easily corrected by realignment of the
pump and its motor and checking the piping to ensure that it is
supported properly. Standard procedures for pump alignment are
available from pump manufacturers and the Hydraulic Institute.
Misalignment may also be caused by a poor pump foundation or the
pump base itself. See Chap. 25 for the proper installation of HVAC
pumps.
Most of the pump companies and the Hydraulic Institute have very
good instructions and diagrams for proper design of pump founda-
tions. Pump bases vary; some have more than adequate strength to
maintain pump and motor alignment while others may be question-
able. The design of pump bases should be scrutinized carefully to ensure
adequate construction. Dowling of pump bases is not required in most
HVAC installations other than large cooling tower pumps and some
large chilled water pumps. Likewise, vibration and temperature detec-
tors are seldom required on HVAC pumps and motors.

Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)
Copyright © 2006 The McGraw-Hill Companies. All rights reserved.
Any use is subject to the Terms of Use as given at the website.