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. - ANS
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. - ANS
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. - ANS
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. - ANS
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. - ANS
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. - ANS
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. - ANS
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." - ANS
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. - ANS
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)
• electrical system design process (should be understood for coordination purposes)
• harmonics (as a growing power quality problem)
• reliability, emergency, and standby (as distinct design considerations) - ANS
Important Terminology
• design criteria
• energy budget
• load estimating
• electric load categories
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller ALICE12. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $10.99. You're not tied to anything after your purchase.
