Noise produced by backup power systems can
be a serious problem if not addressed properly. Standby generators,
motor-generator sets, and UPS systems produce noise that can disturb building
occupants and irritate neighbors and/or landlords.
The noise associated with electrical
generation usually is related to the drive mechanism, most commonly an internal
combustion engine. The amplitude of the noise produced is directly related to
the size of the engine-generator set.
First consider whether noise reduction is a
necessity. Many building owners have elected to tolerate the noise produced by
a standby power generator because its use is limited to emergency situations.
During a crisis, when the normal source of power is unavailable, most people
will tolerate noise associated with a standby generator.
If the decision is made that building
occupants can live with the noise of the generator, care must be taken in
scheduling the required testing and exercising of the unit. Whether testing
occurs monthly or weekly, it should be done on a regular schedule.
If it has been determined that the noise
should be controlled, or at least minimized, the easiest way to achieve this
objective is to physically separate the machine from occupied areas. This may
be easier said than done.
Because engine noise is predominantly
low-frequency in character, walls and floor/ceiling construction used to
contain the noise must be massive. Lightweight construction, even though it may
involve several layers of resiliently mounted drywall, is ineffective in
reducing low frequency noise.
Exhaust noise is a major component of
engine noise but, fortunately, it is easier to control. When selecting an
engine-generator set, select the highest- quality exhaust muffler available.
Such units often are identified as “hospitalgrade” mufflers.
Engine-generator sets also produce
significant vibration. The machine should be mounted securely to a
slab-on-grade or an isolated basement floor, or it should be installed on
vibration isolation mounts. Such mounts usually are specified by the
manufacturer.
Because a UPS system or motor-generator set
is a source of continuous power, it must run continuously. Noise must be
adequately controlled. Physical separation is the easiest and most effective
method of shielding occupied areas from noise. Enclosure of UPS equipment
usually is required, but noise control is significantly easier than for an
engine-generator because of the lower noise levels involved.
Nevertheless, the low-frequency 120 Hz
fundamental of a UPS system is difficult to contain adequately; massive
constructions may be necessary. Vibration control also is required for most UPS
and m-g gear.
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