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ELECTRICAL INSPECTION, DIAGNOSIS, REPAIR

AFCIs ARC FAULT CIRCUIT INTERRUPTERS
ALUMINUM SECs & WIRING
ALUMINUM WIRING HAZARDS & REPAIRS
AMPS & VOLTS DETERMINATION
AMPACITY - the LIMITING FACTOR
APPLIANCE EFFICIENCY RATINGS

BACKUP ELECTRICAL GENERATORS
BOOKSTORE - ELECTRICAL
BUILDING SAFETY HAZARDS GUIDE

Cadet & Encore Heater Recall
CIRCUIT BREAKER FAILURE
Classified CIRCUIT BREAKER WARNING
CIRCUIT BREAKER SIZE for A/C or HEAT PUMP
Classified CIRCUIT BREAKER WARNING
CUTLER HAMMER PANEL FIRE
CONDUIT, ELECTRICAL
CORROSION in ELECTRICAL PANELS
CORROSION & MOISTURE SOURCES in PANELS

DEFINITIONS of ELECTRICAL TERMS

DIRECTORY OF ELECTRICIANS

ELECTRIC HEAT
ELECTRIC METERS & METER BASES
ELECTRIC MOTOR DIAGNOSTIC GUIDE
ELECTRIC MOTOR OVERLOAD RESET SWITCH
ELECTRIC PANEL AMPACITY
ELECRICAL PANEL INSPECTION
ELECTRICAL INSPECTION SAFETY
ELECTRICAL VOCABULARY
ELECTRICAL SERVICE DROP
  WIRE CLEARANCES
ELECTRICAL SERVICE ENTRY WIRING
  DETERMINE SERVICE AMPACITY
  TABLE OF SERVICE AMPACITY
  SERVICE AMPACITY DEFECTS
ELECTRICAL GROUND SYSTEM INSPECTION
  Electrical Grounding Basics
  Gas Piping Ground Bond
  TABLE OF GROUND WIRE SIZES
  Old House Electrical Grounding
  False Ground at Receptacles
  False Neutral Connections
  Case History: Double Fault Leads to Loss of Power
  Case History:Loss of Neutral Shocks Homeowner
  Electrical Service Grounding Checklist
  Why Grounding is Needed
  ELECTRICAL SYSTEM GROUNDING
  SERVICE GROUNDING DEFECTS
  TABLE OF GROUND WIRE SIZES
  Old House Electrical Grounding
ELECTRICAL SYSTEM GROUNDING
ELECTRICAL 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
EMF RF FIELD & FREQUENCY DEFINITIONS

ELECTRICAL GENERATORS
ELECTRICAL GROUND SYSTEM INSPECTION

ENERGY SAVINGS in buildings

FEDERAL PACIFIC FPE HAZARDS
FIRE SAFETY Checklist, CPSC

GENERATORS, ELECTRICAL
GFCI PROTECTION,Testing GFCIs AFCIs

HEATING COST FUEL & BTU Cost Table
HEAT, ELECTRIC
HEAT TAPE USAGE GUIDE
Hertz - Definitions of KHz MHz GHz THz

KNOB & TUBE WIRING

LIGHTING, INTERIOR GUIDE

LIGHTNING PROTECTION SYSTEMS

LOW VOLTAGE BUILDING WIRING

MAIN DISCONNECT
  MAIN SWITCH LOCATION
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MAIN DISCONNECT AMPACITY
MOISTURE SOURCES in PANELS
MULTI-WIRE CIRCUITS
MURRAY SIEMENS Recall

PHOTOVOLTAIC POWER SYSTEMS
PUSHMATIC - BULLDOG PANELS

REMOTE ELECTRIC POWER, PHOTOVOLTAIC
RUST in ELECTRICAL PANELS

SAFETY FOR ELECTRICAL INSPECTORS

SE CABLE SIZES vs AMPS
SIEMENS MURRAY Recall

SOLAR ENERGY SYSTEMS
SQUARE-D RECALLS

UNDERGROUND SERVICE LATERALS
VOLTAGE MEASUREMENT EQUIPMENT

WIND ENERGY SYSTEMS
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More Information

Service entry wiring (C) Carson Dunlop Electrical Service Entry Wire Inspection & Service Ampacity: How to Inspect
InspectAPedia®  -    

  • How to inspect the electrical service entry wiring for components that limit the electrical service ampacity available to the building - a 200 Amp main panel does not itself assure that 200A is available.
  • How to determine electrical service ampacity - how much electrical power do we have at a building?
  • Electric meter defects that can be determined by visual inspection
  • Questions & answers about electrical service ampacity determination for buildings
InspectAPedia offers impartial, unbiased advice without conflicts of interest. We will block advertisements which we discover or readers inform us are associated with bad business practices, false-advertising, or junk science. Our contact info is at InspectAPedia.com/Contact.htm.

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 2012 InspectAPedia.com, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use page top links to major topics or use links at the left of each page to navigate within topics and documents at this website. Green links show where you are in a document series or at this website.

Inspecting the Electrical Service Entry Wiring bringing electrical power to the electric meter

Service entry wiring (C) Carson Dunlop

Readers of this section should see ELECTRIC METERS & METER BASES for details. Sketch courtesy of Carson Dunlop.

  • Mast, conduit, cable: weather tight
  • service cap
  • roof flashing
  • conduit required at roof penetrations
  • conduit joints
  • top and base of meter
  • at wall penetration
  • well connected to service entrance cable (SEC)
  • frayed SEC cables, abandoned SEC cables

A study by the author (Reporting Extent and Sources of Rust and Corrosion in Electrical Panels, HOLM Conference) showed that very common sources of water leaks into and damaging electrical panels include frayed SEC, leaks at the top of the meter, and leaks at the building wall where the SEC passes from the bottom of a meter pan into the building electrical panel.

How to Determine Residential Electrical Service Ampacity

Readers of this section should see AMPS & VOLTS DETERMINATION for a detailed article on how to determine the amps and volts of a building's electrical service.

Do not rely on the ampacity printed on the main fuse or breaker, though that information is important. Examine the following:

  • service drop wire size
  • mast diameter
  • 1-inch 60A mast
  • 2-inch 200A lateral
  • meter base size
  • meter rating
  • service box rating
  • distribution panel rating
  • total of all fuses or breakers in panel (the sum is NOT the service ampacity as % utilization applies)

So what determines the actual service ampacity at a building?

  • Smallest link in the chain determines
  • Best indication is size of SEC + id CU/AL
  • IF SEC is not visible, look at service disconnect
  • Specify if unable to determine, and why

A General Table of Electrical Service Ampacity vs. Service Entry Cable Sizes

AMPS Copper Aluminum
30 10* 8*
60 6* 6*
70 6* 4*
100 4 2
125 2 1/0
150 1/0 2/0
200 2/0 4/0

More Reading:
Ampacity of an Electrical Service - Details of how to determine electrical service ampacity and voltage by visual inspection and/or safe use of test instruments.

Electrical Service Ampacity Defects

  • Inadequate / marginal total capacity for the modern use of the building. Some lenders require a minimum of 100A.
  • Some utility companies will not replace an old 60A service (and meter) and will require that service be upgraded.
  • load calculation of required service ampacity for buildings is not required during a home inspection but the inspector should be familiar with that procedure

Electric Meter Defects

Obsolete electric meters (C) Daniel Friedfman

  • Loose electric meter - watch for attachment screws falling inside, shorting, causing a fire (Arnold Rd. Pok)
  • Water Leaks into electric meter top from frayed SEC or defective seal at meter top
  • Water leaks from electric meter pan into service conductors into main electrical panel - see RUST in ELECTRICAL PANELS
  • Obsolete electric meters - change out required by utility company in some circumstances
  • Electric meter rated only for copper wire connected to aluminum SEC

 

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Technical Reviewers & References

  • InspectAPedia.com® - Daniel Friedman - Publisher & Editor.
  • Critique, contributions wanted: Contact Us to suggest corrections or additions to articles at this website, and if you wish, to receive online listing and credit as a contributor. Particular thanks are due to the many experts and also consumers who read and critique technical articles at InspectAPedia.com.
  • * 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.

ELECTRICAL SERVICE ENTRY WIRING
  DETERMINE SERVICE AMPACITY
  TABLE OF SERVICE AMPACITY
  SERVICE AMPACITY DEFECTS

ELECTRICAL BASICS

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

  • Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
  • Recommended books on electrical inspection, electrical wiring, electrical problem diagnosis, and electrical repair can be found in the Electrical Books section of the InspectAPedia Bookstore. (courtesy of Amazon.com)
  • * Safety Hazards and Safe Inspection Procedures for Electrical and Home Inspectors at Residential Electric Panels
  • 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
  • Rust and Corrosion in Electrical Panels, A Study and Report on Frequency and Cause for Electrical and Home Inspectors at Residential Electric Panels
  • "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.
  • Electrical System & Wiring Hazard Inspection, Detection, Cause, Remedy, Prevention - Main Electrical Page
  • ...
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