How to Inspect Residential Electrical Systems, Panels, Grounding, Wiring
InspectAPedia® -
Class on how to inspect electrical panels
Home inspection procedures and safety during electrical system inspection
Questions & answers about visual inspection of electrical panels, panel installation, defects, repairs
Electrical panel inspection guide: This electrical wiring article 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. We include questions and and answers about common defects in electrical panels that may be discovered by visual inspection, that is, without performing electrical tests.
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This material was first 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, August 2011.
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.
touch electrical equipment if you can see evidence of existing dangerous conditions (such as the missing electrical grounding electrode shown at left)
touch SEC or other wires
insert probes/tools into panel
remove suspect panel covers. Later we explain that visual clues of water, leaks, short circuits, spring-loaded panel faces, all present possible electrocution hazards that can occur merely from touching or attempting to remove the panel cover).
touch electrical equipment from unsafe location (wet, off balance, grounded - current flows from a hot wire through you, etc.)
continue to touch or inspect the panel if you feel a charge, tingle, shock
stand in water or in wet conditions while touching electrical equipment
Watch out: 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 a 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 setÂting 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:
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.
Frequently-Asked Questions (FAQs) about visual inspection of electrical panels, panel installation, defects, repairs
Question: can an electrical panel be mounted upside down?
Can a circuit breaker panel be installed upside down and still pass national and local electrical code inspections? - Mike
Reply: Circuit breakers that operate vertically should be mounted so that "up" is "on" and "down" is "off"
How to Mount an Electrical Panel: Panel Position and "upside down" electrical panel code provisions:
Mike:
According to a number of electricians forums we reviewed, contemporary electrical panel circuit breakers will function correctly in any position, and there are quite a few electricians who mount panels "upside down" with the mains at panel bottom, in particular if the SEC cables are entering from the bottom of the unit. Just be sure that all panel labels including MAINS are properly oriented and legible so that the homeowners are not confused about which breaker controls which circuit.
There may however be both code (NEC) and user issues about breaker positions: in particular about clear "off" and "on" positions of circuit breakers in some electrical panel designs.
If the electrical panel MAINS switch operates "side to side" then you can mount the panel with either end "up" but if the MAINS switch operates "up and down" then putting the panel "upside down" would mean that "off" would be "up" - which is unsafe because that's not how most users think about switch on and off positions.
Perhaps part of the "off is down" convention derives from older knife-switch mains that were installed with "off = down" because of a concern that in the opposite position a worn or loose knife switch might fall from "off" (up) into "on" (down) in a panel - an unsafe condition.
See NEC 404.7. Also see NEC 240.81. That provision requires vertically-operating circuit breaker switches to be mounted so that "Up" is "On and "Down" is in the "Off" position.
Question: How do we know if an electric panel fuse has blown?
How do you know if say a solid type 40 amp four inch fuse on the condenser outside fan is blown? - Bruce
Reply: swap in a new fuse; remove the fuse and test it for continuity.
Bruce you're right that it may be impossible to tell that a cartridge type fuse is "blown" by simple visual inspection, unless by chance the fuse is discolored or deformed.
By contrast, round Edison-based fuses include a glass window through which you can observe the melted fusible link if that type of fuse has "blown".
In some countries cartridge type fuses actually use a re-usable cylinder into which a fusible link is inserted, can be removed, and can be inspected.
But a blown cartridge fuse will not conduct electricity from one end to the other - one could test such a fuse OUT OF THE PANEL (not in place in the panel, for safety reasons) using a multimeter or VOM in the Ohms setting.
Most homeowners simply swamp in a new fuse and see if that restores power.
Question: Is it safer to turn off all of the circuit breakers when inspecting an electrical panel?
If i want to visually inspect the wires behind the panel cover, could i just turn off all breakers to reduce the chances of shock if the panel hits a hot wire? Thanks!- JMW
Reply: Yes, ... and not exactly - electrical panel inspection tips
A competent onsite inspection by an expert usually finds additional clues that help accurately diagnose a problem or spot an unsafe condition at the electrical panel, even before it is touched (see Touching Electrical Equipment).
That said, here are some things to consider:
Once an external inspection of the electrical panel, surrounding wiring and devices, and the panel cover and even other site clues of amateur workmanship or poor maintenance have been considered, if you turn off the main circuit breaker to the panel it should de-energize all of the circuits below, making it unnecessary (and probably a mistake) to turn off individual circuit breakers.
Watch out: because there are serious safety hazards and risk of injury or death to the inspector or bystanders during an electrical inspection, be sure to review SAFETY for ELECTRICAL INSPECTORS
Watch out: turning off the main circuit breaker in an electrical panel will not de-energize the main service entry lugs nor possibly other electrical panel components so potentially fatal electrical shock hazards remain.
Watch out: do not turn off circuit breakers at an electrical panel that is in use supporting an active, occupied building. There are risks of disabling or even damaging computer equipment and also certain medical equipment that might be kept running to support the health, safety, even life of building occupants in some situations.
Watch out: in certain electrical panels such as FPE Stab-Lok equipment, operating the circuit breakers by switching them on and off can actually increase the risk that later the breaker may fail to trip in response to an overcurrent, risking a buildng fire. See FEDERAL PACIFIC FPE HAZARDS
Questions & Answers regarding this article
Questions & answers about visual inspection of electrical panels, panel installation, defects, repairs
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Electric Service
Installation Manual,
A guide for successful installation of residential, commercial and industrial electrical services, 5th Ed.,
Hawaiian Electric Company
Hawaii Electric Light Company
Maui Electric Company,A guide for successful installation of residential,
commercial and industrial electrical services, original web search 08/15/2011, source: http://www.heco.com/vcmcontent/Energy%20Services/
Business%20Services/Customer%20Installations/ESIM_manual.pdf
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.
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.
"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.
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)
"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.