MEEB Chapter 17 - ELECTRIC WIRING DESIGN Exam Study Guide.
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Course
Electrical Wiring
Institution
Electrical Wiring
MEEB Chapter 17 - ELECTRIC WIRING
DESIGN Exam Study Guide.
Summary
This chapter addresses the topic of electrical wiring design within the context of design criteria that
provide for appropriate performance within the safety requirements established by codes. As there are
numerous acceptable s...
MEEB Chapter 17 - ELECTRIC WIRING
DESIGN Exam Study Guide.
Summary
This chapter addresses the topic of electrical wiring design within the context of design criteria that
provide for appropriate performance within the safety requirements established by codes. As there are
numerous acceptable solutions for most design situations, general guidelines and suggestions from
practice are often provided. Conformance to local code requirements is emphasized. - answer✔
General considerations that will influence wiring system design include: expectations for flexibility, a
desire for reliability, demands for safety, first cost and life-cycle cost considerations, and energy
conservation requirements and desires. Space availability and requirements for systems installation and
maintenance must be considered. Any special circumstances pertaining to a given facility also need to
be identified. - answer✔
The wiring design process generally starts with an estimate of building electrical load. Data tables and
suggestions to assist in this process are provided. Building electrical loads may be categorized as follows:
lighting, miscellaneous power, HVAC, plumbing/piping, vertical transportation, kitchen equipment,
special equipment. The magnitude of loads in each category will vary from building type to building
type. - answer✔
System voltage selection will greatly influence wiring design. System voltage is the voltage capability
provided by the utility service or building transformer. Several standard system voltage and wiring
arrangements are in use in North America and include: 120 volt, 1-phase, 2-wire; 120/240 volt, 1-phase,
3-wire; 120/208 volt, 1-phase, 3-wire; 120/208 volt, 3-phase, 4-wire; 277/480 volt, 3-phase, 4-wire; and
2400/4160 volt, 3-phase, 4-wire. Typical applications for each of these arrangements are discussed.
Transformer voltage standards establish system voltages, motor voltage standards establish utilization
voltages; the two are in reasonable agreement. - answer✔
Grounding and ground-fault protection are discussed in some detail, including background and typical
practices. Energy conservation considerations are also surveyed. General design procedures that will
lead to energy-conserving designs are outlined. - answer✔
A generic step-by-step process applicable to the design of wiring for a range of facility types is
presented. The process proceeds from load estimating, to equipment placement and sizing, to wire
sizing for branches and feeders, and concludes with drawings and coordination. Location of electric
spaces (including electric closets), the properties of such spaces, and the effect of circuit lengths
resulting from location decisions are discussed. Equipment layout and the development of lighting and
power drawings are explored. General rules for the application of overcurrent protection equipment are
reviewed. - answer✔
Rules of good practice for the design of branch circuits are presented and discussed. Guidelines for
branch circuits in residential and nonresidential (school and office) occupancies are considered in
substantial detail. Rules of practice for tabulating panel loads are presented. The concepts of demand
factor and spare capacity are introduced. Feeder capacity and sizing is discussed and illustrated by
worked examples. Voltage drop is considered. The development of riser diagrams is discussed. The
importance of coordination in the development of electrical systems is emphasized. A caution is given
regarding the use of computer programs for sizing calculations. - answer✔
Harmonic currents (as an element of power quality) are described as a growing problem in modern
buildings. Although the issue of harmonics is complex, an overview of the problem and potential
solutions is given. Passive solutions have historically been employed, but there is movement to active
solutions such as "active line conditioning." The need for—and relationships between—emergency,
legally required standby, and optional standby systems is explored. Reliability is distinguished from
"emergency." - answer✔
Grounding and ground-fault protection are discussed in some detail, including background and typical
practices. Energy conservation considerations are also surveyed. General design procedures that will
lead to energy-conserving designs are outlined. - answer✔
Key Concepts
• design criteria (as benchmarks for design decisions and analyses)
• flexibility (as an important design objective)
• reliability (as an important design objective)
• safety (as a mandatory design consideration)
• economic factors (as a decision-making tool)
• energy conservation (as a societal and personal design objective)
• space allocations and locations (as design issues throughout the design process)
• load estimating (as a design tool)
• service versus system versus utilization voltages (as design issues)
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