UFC 3 -520-01
June 10, 2002
2-2.5.2 The maximum demand at 125 percent plus the new load does not exceed the
ampacity of the feeder or rating of the service. Determine the required capacity of
feeder or service conductors by adding the new load to 125 percent of the maximum
existing demand load determined above. This value is then compared to the existing
feeder or service capacity to determine whether the existing installation is adequate for
the new load.
2-2.5.3 The feeder has overcurrent protection in accordance with NEC Article 240 .4
(2002 Edition) , and the service has overload protection in accordance with NEC Article
230.90 (2002 Edition) .
The detailed design process requires additional analysis to ensure the facility
is designed properly for the anticipated electrical loads. Refer to the following sections
for further information.
OVERVIEW OF DETAILED ANALYSIS CRITERIA.
Document design decisions throughout the design process. List any special
features and alternatives that were considered. Include the method used for sizing
conductors, conduit, protective devices, and other equipment. As part of the design
analysis process, include a written description of the proposed system and show all
calculations used in determining capacities of electrical systems. When tables from
industry standards are used in the design, indicate the ti tle, source, and date of the
Minor design modifications can often be performed by hand calculations, and
the use of tables from the NEC and industry standards. More complex designs require
a detailed analysis of the system design and operation during normal and abnormal
conditions. The electrical studies to be performed include voltage drop, power flow,
short circuit protection, and coordination. The industry standard for these types of
studies is that they are performed by computer programs designed for such purpose.
Hand calculations usually require simplifying assumptions that limit the accuracy or
usefulness of the results. Figure 2 -1 shows an example of a simplified electrical system
on a computer model.