Explanation of Example 1:
- A Demand Factor is applied to the Possible Maximum Demand to
calculate the Probable Maximum Demand. The Probable Maximum Demand is
the rate at which the heater shall generate hot water, or the recovery
- The Probable Maximum Demand is factored by the Storage Capacity
Factor to determine the Storage Tank Capacity. The Storage Tank Capacity
is the capacity required being available for use. Storage tanks are not
considered to be 100% usable and thus, a usable storage tank factor shall
be applied to the calculated storage tank capacity; the percent capacity
considered usable for most tanks is 70, thereby resulting is a 1.43
usable storage tank factor. The usable storage tank factor for systems
utilizing instantaneous generators or multiple tank arrangements shall be
coordinated with the Design Agent.
Additional Note: The fixture-unit method is adequate for typical usage.
Expanded usage for food service, non-standard fixtures, or abnormal usage
patterns (extreme low or high demand peaks or erratic peak duration and
occurrence) shall be factored into the sizing calculations. For example,
food-service fixture demand factors need to be adjusted if disposable
service ware is used.
Concentrated patient treatment for sick call, or
other instance of high-peak usage, is another example of fixture hot
water demand adjustment.
The Demand Factor and Storage Capacity Factor are listed in
References 9h and 9i for given building types, which include a hospital
but not medical clinic, dental clinic, nor laboratory. A Demand Factor
of 0.40 and Storage Capacity Factor of 1.00 are considered representative
for a clinic upon review of the factors for the building types shown.
Factors for MTF's with laboratory space greater than 10% of the total
facility space shall be coordinated with the Design Agent.