360
Electrical Distribution: Design Criteria
363
DESIGN CRITERIA
363.1
LOAD DISTRIBUTION
The overall strategy of the electrical network is largely governed by load
distribution patterns. The following schematic diagrams illustrate the
loading pattern of a typical hospital. Figure 360-3 represents the
percentage distribution of total load in the electrical systems at two
existing Veterans Administration hospitals. This data appears
representative for current hospitals of the order of 500 beds.
No attempt was made in the diagram to differentiate between normal and
essential distribution as these tend to vary in proportion with local
engineering practice and codes. But Figure 360-3 shows that the
percentage of the 480Y277 volt system which is transformed and supplied
at 208Y120 volts to be approximately 25% of the total load.
The categories that are responsible for most of the continually increasing
electrical demand in hospitals are generally those shown in this diagram
for the 208Y120 volt distribution. When functional areas such as
laboratories expand within a hospital, their heavier than normal
environmental requirements also boost the electrical load demand for
HVC.
363.2
AVERAGE LOAD DISTRIBUTION
The majority of functional areas within the hospital are supplied with power
in two of the categories shown in Figure 360-3, the transformed power at
120 volts (25% of total load) and fluorescent lighting (12% of total load).
The figures given for these areas are 4.4 and 2.4 watts per square foot
respectively. Therefore it can be assumed for the purposes of general
design that a load of 6.8 watts per square foot is the appropriate mean.
Figure 360-4 is a breakdown in detail of the functions which take
significantly higher loads and therefore represent design maximums. The
high loads demanded by kitchens and laundries would require special
busduct supply and should be located close to a substation.
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