How to Inspect Residential Electrical Panels - Part 7
the Distribution Panel

How to inspect electrical panels - the main panel
Inspecting the electrical distribution panel
Questions & Answers about procedures for and defects found in inspection of the electrical distribution panel
References

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Main electrical panel inspection procedures & defects: this article summarizes inspection of the building electrical panel, main panel, or electrical distribution and sub panels. This article series 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.

PANEL COVER - Residential Electrical Panel Cover Inspection and Special Safety Hazards - Look before you touch!

Information in this electrical inspection article series was presented by Daniel Friedman - InspectApedia.com, and discussed by 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.

Before Touching or Opening the Electrical Panel for Inspection

Look (and test? before touching, open door, look again (rust, burns, gaps, unsafe stance)
Block client from touching equipment
May be unsafe to remove upper cover of combination panels (service main at top)
Sheet metal screw shorts, shocks, fires
Swing-out covers can pinch wires

CIRCUIT WIRING AMPS FUSING - Electrical branch circuit wiring amps/fusing defects - Copper electrical wiring

Match wiring gauge to ampacity - the following describe copper wire sized or gauges and the matching circuit ampacity or overcurrent protection that is required to be provided by fuse or circuit breaker:

14 gauge - 15Amps
12 gauge - 20 Amps
10 gauge - 30 Amps
8 gauge - 40 Amps

Exceptions to these wire sizes and fusing occur for special circumstances such as air conditioners whose motors produce a brief current surge during startup.

Aluminum electrical branch circuit wiring size guide: for a circuit of the same amperage, an aluminum solid conductor branch circuit wire must be 1 size larger than copper. Currently (since the 1970's) aluminum electrical wiring is used only in the form of multi-strand on single-use circuits like range /DHW/AC older solid conductor AL may be present in next gauge.
Solid conductor aluminum branch circuit wiring is unsafe, a fire hazard, and requires repair - see The Aluminum Wiring Website

PROBLEM-BRAND ELEC PANELS - Problem-Brand Electrical Panels

Federal Pacific Electric Stab-Lok breaker panels - see FEDERAL PACIFIC FPE HAZARDS
Zinsco electric panels - see ZINSCO / SYLVANIA HAZARDS
Bryant electric panels
Challenger replacement breakers/panels
Other problem-prone panels or breakers (more research needed)

ELEC PANEL LOCATION - Electrical Panel Location Defects

Mains: Not in: bathroom, clothes closet, kitchen cabinets, stairwells (same as service disconnect)
Should be at eye level, easily accessible, 3 ft. clearance
Subs: may be located almost anywhere (still some Sub panels are improper as above).
Finding hidden sub panels: Look for feeder-breaker/fuse or wires leaving main

FUSES vs CIRCUIT BREAKERS - Relative Electrical Safety of Fuses versus Circuit Breakers

Fuses more reliable to "blow" - not mechanical BUT easier to over-fuse (reduce with S-type retro)
Breakers more convenient to reset can be tested without having to then replace the safety device - less likely to be over-fused (but over fusing still happens - compare wire gauge to breaker ampacity)

MAIN DISCONNECT INSPECTION - Electrical Panel Main Disconnect Inspection - Do you Pull the Main Fuse or Test the Main Breaker?

may be necessary to get some panel covers off
may be unsafe or may not want to shut power off to building
ask occupant/owner before killing power
report limitations to inspection
re-set accidentally-tripped breakers and leave note

OTHER ELECTRICAL PANEL DEFECTS - Other Electrical Panel Defects Discoverable by Visual Inspection

Obsolete and/or fused neutrals
Damaged panel/components
Loose panel
Inappropriate support material
Unprotected panel openings/knockouts
Undersized panel - physical size/crowded
Overheating - look at mains, breakers, bus, neutrals, wires
Rust or water - look for rust, corrosion, overheating, subtle spots, suspect hidden damage to bus or breakers, look for water trace marks on entering SEC
circuits not labeled
panel overcrowded
poor access to panel
panel upside down or switches on in down position (obsolete)
Panel used-with and not suitable for AL wiring

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Technical Reviewers & References

Related Topics, found near the top of this page suggest articles closely related to this one.

* Safety Hazards and Safe Inspection Procedures for Electrical and Home Inspectors at Residential Electric Panels

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.

The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.

Or choose the The Home Reference eBook for PCs, Macs, Kindle, iPad, iPhone, or Android Smart Phones. Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter INSPECTAEHRB in the order payment page "Promo/Redemption" space.

Building inspection education & report writing systems from Carson, Dunlop & Associates Ltd

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)
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.
"Simplified Electrical Wiring," Sears, Roebuck and Co., 15705 (F5428) Rev. 4-77 1977 [Lots of sketches of older-type service panels.]
"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.
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