Power Factor. Commercial genset power ratings are
usually based on 0.8 power factor. Select 0.8
unless the application requires one more stringent.
Loading. When specifying engine-generator sets the
designer will analyze the load characteristics and
profiles of the load to be served to determine the
peak demand, maximum step load increase and
decrease, motor starting requirements represented as
starting kVA, continuous and non-continuous
(cyclical/periodic), and the non-linear loads to be
served. This information should be included in the
engine-generator set parameter schedule or on the
drawings for each different unit provided. For this
application, service load is the peak estimated
loading (continuous plus non-continuous) to be
placed on the engine generator set.
Peak demand calculation provides a figure from which
to determine the service load. For prime
applications the service load should include spare
capacity for future load growth and spinning reserve
(reserve generation beyond that required to satisfy
immediate needs and/or system peak demands). Spare
capacity for prime applications should be based on
the facility master plan load projections.
Motor Starting Load. Motor starting requirements
are important to properly size engine generator sets
because the starting current for motors can be as
much as six times the running current, and can cause
generator output voltage and frequency to drop, even
though the genset has been sized to carry the
running load. The designer must analyze the motor
loads to determine if the starting characteristics
of a motor or a group of motors to be started
simultaneously will cause objectionable genset
performance. Provide a motor starting kVA value for
the largest motor or combination of motors to be
started simultaneously. An increase in the size
rating of the genset may be necessary to compensate
for the inrush current. This assists the genset
supplier in properly sizing the engine generator set.
Maximum Speed. The maximum allowable speed is 1800
RPM. If there is not specific requirement or user
requirement for slower speed machines, select 1800
RPM. Selection of the maximum 1800 RPM does not
preclude provision of slower speed machines, for
example, in the larger sizes (above 2000 kW), where
1800 RPM machines may not be available.
Heat Exchanger Type. Fin-tube heat exchangers
(radiators) are the predominate method of cooling.
Specify either a fin-tube or a shell-tube heat
exchanger for each engine-generator set. Heat
exchangers located remote from the engine-generator
set (i.e.,. not mounted on the engine-generator set
SECTION 16263A
Page 18
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