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How to Inspect Residential Electrical Systems, Panels, Grounding, Wiring
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• Class on how to inspect electrical panels
• Home inspection procedures and safety

This document discusses procedures for safe and effective visual inspection of residential electrical systems including electrical panels and other components, when the inspection is conducted by trained building inspection professionals, home inspectors, electrical inspectors, and electricians. It was presented by Daniel Friedman - InspectApedia.com, at the Hudson Valley chapter of the American Society of Home Inspectors - HVASHI Seminar 12 Sept 2002, Updated April 2006, April 2009.

Readers of this article should also be sure to review Safety Hazards and Safe Electrical Inspection Procedures for Inspectors examining Residential Electrical Systems and should pay special attention to the following chapters from that article:   Electrical Panel Interior Inspection -  Removing Electric Panel Covers -  Electrical Panel Cover Screws -  Electrical Panel Interior Hazards -  Testing Main Breakers or Fuses and  Inspect Breakers, Fuses. Carson Dunlop's sketch at page top shows where the electrical inspection starts at a residential property.

© Copyright 2009 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

COURSE SUMMARY - Electric Panel Inspection Course Summary

SAFETY WARNING: Inspection of electrical systems risks death by fatal electrical shock. The procedures discussed in this class require that the cover of the panel be removed in order to expose the panel interior. Homeowners should not attempt this step, and no one lacking proper electrical safety training should remove the electrical panel cover nor attempt to perform the tasks discussed in this class. ELECTRICAL CODE COMPLIANCE WARNING: these inspection procedures are designed to assist in the detection and reporting of electrical service defects which can be recognized by visual inspection. This inspection is not for the purpose of determining compliance with local or national electrical codes. Guidelines given here, such as overhead wire clearances, are based on widely-accepted codes and standards, but local building codes may specify other or different restrictions.

Part I - Electrical Panel Defect Identification - Principles

• Safety Procedures for Electrical Inspectors
• Electrical Power Delivery System
• Common Electrical Panel and Wiring Defects

Part II - Electrical Panel Defect Recognition - Photos of Electrical Defects & Examples

This section of the class contains annotated field photographs of certain electrical panel defects which can be recognized by visual inspection.

That is, no instruments, no measurements, and no insertion of any device into the electrical panel are required to perform these tasks. I have these photos on file and will add them to this presentation if readers request

ELECTRICAL INSPECTION SAFETY - Overview of the Residential Electrical System and Electrical Inspection Hazards

• The Electrical System Function is to power home systems/appliances, providing safe distribution of electrical power throughout the building.
• Costs: operation, repair, updating/expansion

Safety Procedures for Residential Building Electrical Inspectors

SAFETY WARNING: Inspection of electrical systems risks death by fatal electrical shock. The procedures discussed in this class require that the cover of the panel be removed in order to expose the panel interior. Homeowners should not attempt this step, and no one lacking proper electrical safety training should remove the electrical panel cover nor attempt to perform the tasks discussed in this class.

Electrical Panel Inspection Safety - Critical Warnings

Do not:

• touch SEC or other wires
• insert probes/tools into panel
• remove suspect panel covers (more later)
• touch electrical equipment from unsafe location (wet, off balance, grounded - current flows from a hot wire through you, etc.)

Protect nearby observers, clients, etc. from hazards [added by DF 2/13/2006]

• Do not permit observers to touch the inspector while that person is working on or at the electrical panel.
• Do not permit observers to touch the electrical panel nor to insert any tool, pencil, or other object into the panel.
• The inspector should stand with his/her body between observers and the panel, and should be prepared to physically block an attempt by the observer to reach towards or touch the electrical panel while its cover has been removed.
• Explain, calmly and without exaggeration, but accurately, the shock and fire hazards to observers and instruct the observers on what to do if the inspector him/herself is being shocked by the panel. [Don't touch the person being shocked. If a wooden board or stake is nearby, one might attempt to push the inspector away from the panel using that device or to turn off the main breaker or fuse. Call for help immediately.

Safety Warning: Do not attempt to work on your electrical wiring, switches, or outlets unless you are properly trained and equipped to do so. Electrical components in a building can easily cause an electrical shock, burn, or even death. Even when a hot line switch is off, one terminal on the switch is still connected to the power source. Before doing any work on the switch, the power source must be turned off by set­ting a circuit breaker to OFF or removing a fuse. See SAFETY FOR ELECTRICAL INSPECTORS and Electrical Wiring Books & Guides

More Reading on Electrical Inspection Safety

Electrical inspectors planning to examine residential electrical panels, in addition to obtaining proper training, should read the following:

• Safety Hazards and Safe Inspection Procedures for Electrical and Home Inspectors at Residential Electric Panels
• Determining Electrical Service Ampacity, Dan Friedman and Alan Carson, the ASHI Tech Journal Article, Vol.2. No.1, Winter 1992 p. 14-19. (Online, and original reprints available from the American Society of Home Inspectors). Sidebars provided with this article include a table of Electric Wire Sizes provided for the article by ASHI professionals Jules Falcone and Matthew Pinto.

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• * Safety Hazards and Safe Inspection Procedures for Electrical and Home Inspectors at Residential Electric Panels
• Additional technical contributors & reference sources for this article are listed below.

Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

ELECRICAL PANEL INSPECTION
COURSE SUMMARY
ELECTRICAL INSPECTION SAFETY
ELECTRICAL VOCABULARY
SERVICE DROP
  WIRE CLEARANCES
SERVICE ENTRY WIRING
DETERMINE SERVICE AMPACITY
  TABLE OF SERVICE AMPACITY
  SERVICE AMPACITY DEFECTS
ELECTRICAL GROUND SYSTEM INSPECTION
  TABLE OF GROUND WIRE SIZES
  SERVICE GROUNDING
MAIN DISCONNECT
  MAIN SWITCH LOCATION
  MAIN SWITCH
SYSTEM GROUNDING
DISTRIBUTION PANELS
  PANEL COVER
  CIRCUIT WIRING AMPS FUSING
  PROBLEM-BRAND ELEC PANELS
  ELEC PANEL LOCATION
  FUSES vs CIRCUIT BREAKERS
  MAIN DISCONNECT INSPECTION
  OTHER PANEL DEFECTS
ELECTRICAL BASICS

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

• Our recommended books about building design, inspection, and repair, and about indoor environment testing, diagnosis, and cleanup are at the InspectAPedia Bookstore.
• ...

More Information on Building Diagnostic Inspections and Repairs

• Aluminum Wiring Information Website Aluminum Electrical Wiring Hazards and Repairs: in-depth authoritative info, photos, documents including selection of proper vs. ineffective repair methods. E.g.: Ideal 65 "Twister" purple connector fails in field and lab testing with aluminum wire.
• Ampacity of an Electrical Service: How to determine the electrical service size or ampacity entering a building
• Circuit Breaker, a bad one fails to trip failure at aluminum bus-to-circuit breaker connection - field report and photographs
• Electrical Panels, How to Inspect in Buildings, safety for electrical inspectors, electrical panel, fusing, wiring defects, defective products. Inspection Class Presentation
• Federal Pacific Electric (FPE) Stab-Lok Circuit Breaker Panel Hazards Website - Latent fire hazards, in-depth authoritative research, documents, advice on Stab-Lok electric panel and circuit breaker failures and what to do when this equipment is found in buildings.
• Lightning Strike Risk Assessment, Protection Systems & Services
• Multi-wire branch circuit inspection and defects
• Zinsco Electrical Circuit Breaker Failures: overheating, failure to trip, burn-ups involving Zinsco and certain Sylvania electrical panel components - page under development March 2006.
• "Electrical System Inspection Basics," Richard C. Wolcott, ASHI 8th Annual Education Conference, Boston 1985.
• "Simplified Electrical Wiring," Sears, Roebuck and Co., 15705 (F5428) Rev. 4-77 1977 [Lots of sketches of older-type service panels.]
• "How to plan and install electric wiring for homes, farms, garages, shops," Montgomery Ward Co., 83-850.
• "Electrical System Inspection Basics," Richard C. Wolcott, ASHI 8th Annual Education Conference, Boston 1985.
• "Simplified Electrical Wiring," Sears, Roebuck and Co., 15705 (F5428) Rev. 4-77 1977 [Lots of sketches of older-type service panels.]
• "How to plan and install electric wiring for homes, farms, garages, shops," Montgomery Ward Co., 83-850.
• "Home Wiring Inspection," Roswell W. Ard, Rodale's New Shelter, July/August, 1985 p. 35-40.
• "Evaluating Wiring in Older Minnesota Homes," Agricultural Extension Service, University of Minnesota, St. Paul, Minnesota 55108.
• "Electrical Systems," A Training Manual for Home Inspectors, Alfred L. Alk, American Society of Home Inspectors (ASHI), 1987, available from ASHI. [DF NOTE: I do NOT recommend this obsolete publication, though it was cited in the original Journal article as it contains unsafe inaccuracies]
• "Basic Housing Inspection," US DHEW, S352.75 U48, p.144, out of print, but is available in most state libraries.
• Rust and Corrosion in Electrical Panels, A Study and Report on Frequency and Cause for Electrical and Home Inspectors at Residential Electric Panels


• Directory of Home Inspectors accessible via internet
• Electrical System & Wiring Hazard Inspection, Detection, Cause, Remedy, Prevention - Main Electrical Page

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