Main Electrical Disconnect Switch & Switch Location InspectAPedia® -
How to inspect the main electrical disconnect - the "main switch" for defects
Electrical service switch or panel location errors
Requirement for main disconnect switch in electrical panels
The six breaker rule as main electrical panel disconnect
Online Course on how to inspect electrical panels
Questions & answers about the main power switch or main disconnect switch at electrical panels
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This article summarizes inspection of the main electrical switch - the main switch at buildings and also outlines other electrical panel and switch defects that can be found by visual inspection. 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.
Integrated or separate service disconnect (main breaker or fuses) -
need main disconnect if more than 6 switches
Electrical Service Box Location Defects
OK indoors our outside (if weather tight)
NOT OK bathroom, clothes closet, kitchen cabinets
Should Be at eye level, easily accessible, with 3 ft. working clearance
Inspecting the Electric Service Panel & Main Disconnect Switch for Condition Defects
The Implications: electrical shock or fire
Missing Main Disconnect Switch - note that at some installations the main disconnect may be located separately from the main electrical panel, particularly if the main electrical panel is distant from the electric meter (NEC Ref 1).
No main disconnect switch in electrical panels with six or more breakers. If the "six-breaker" rule is allowed locally, the six switches must be together in the same panel enclosure.
That is, if six or fewer breakers are in the main panel, that panel can be counted as a service disconnect (NEC Ref 2).
We and others believe this requirement originated with fire fighting departments, to assure that no more than six manual operations would be required to turn off electrical power in an emergency. Note that local jurisdictions and codes may require that a single main switch be provided. - Ed.
Poor access to the electrical panel; panel not secured
Rust, corrosion in the electrical panel or main disconnect
Overheating signs in the electrical panel or main disconnect enclosure
Over fusing or box rating too small for the service entry wiring or building or circuit load
Inappropriate. mounting surface for the electrical panel or main disconnect / not secure
Damaged electrical panel or main disconnect parts
Poor electrical panel or main disconnect connections, poor wiring
Illegal taps at the electrical panel or main disconnect
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U.S. National Electrical Code, NEC Reference (1): [QUOTING 2008 NEC]
National Electric Code is Article 225 Part II.
225.31 Disconnecting Means. Means shall be provided for
disconnecting all ungrounded conductors that supply or pass through
the building or structure.
225.32 Location. The disconnecting means shall be installed either
inside or outside of the building or structure served or where the
conductors pass through the building or structure. The disconnecting
means shall be at a readily accessible location nearest the point of
entrance of the conductors. For the purposes of this section, the
requirements in 230.6 shall be utilized.
VI. Service Equipment - Disconnecting Means
230.70 General. Means shall be provided to disconnect all
conductors in a building or other structure from the service entrance
conductors.
(A) Location. The· service disconnecting means shall be
installed in accordance with 230.70(A)(l), (A)(2), and
(A)(3).
(1) Readily Accessible Location. The service disconnecting
means shall be installed at a readily accessible location
either outside of a building or structure or inside nearest the
point of entrance of the service conductors.
(2) Bathrooms. Service disconnecting means shall not be
installed in bathrooms.
(3) Remote Control. Where a remote control device(s) is
used to actuate the service disconnecting means, the service
disconnecting means shall be located in accordance with
230.70(A)(1).
(D) Marking. Each service disconnect shall be permanently
marked to identify it as a service disconnect.
(C) Suitable for Use. Each service disconnecting means
shall be suitable for the prevailing conditions. Service
equipment installed in hazardous (classified) locations shall
comply with the requirements of Articles 500 through 517
U.S. National Electrical Code NEC Reference (2): Requirement for main circuit breaker if more than six switches in the panel: See NEC Section 230-71.
Article 225: A readily accessible disconnect is required at the remote building, located either outside or nearest the point of entrance inside [225-8]. There shall be no more than six disconnects mounted in a single enclosure, or up to six separate enclosures [230-71]. The disconnects must be grouped and each disconnect must be marked to indicate the load served [110-22 and 230-72].
1993 NEC (Quoting from Orlando Florida Code of Ordinances, web search 01/18/2011, original source: http://search.municode.com/html/13349/level3/TITIICICO_
CH22ELCO_ARTIIINAELCOAM.html#TITIICICO_CH22ELCO_
ARTIIINAELCOAM_S22.49SE230-71NAELCOAM
Section 230-71 of the National Electrical Code of 1993 is amended to read as follows: (a) No building shall have more than six (6) operations of the hand for a main disconnecting means. (b) Commercial buildings. The 100A or over service disconnecting means shall comply with Article 230 of the National Electrical Code and shall be installed on the outside of the building as near the point of entrance of service wires as possible considering the type of building and accessibility in case of fire or other reason for opening the service switch and disconnecting the building. Upon special application to the inspecting authority, before any work is started, approval may be granted for the meter and/or service disconnecting means to be installed inside the building if accessible and available for meter reading, servicing and disconnecting in case of emergencies. (c) On commercial or residential buildings, if the service disconnecting means is not readily apparent on the exterior of the building, it shall be properly indicated by a reasonable sign constructed of permanent materials with no less than one and one-half (1½) inches high letters designating its exact location. The sign shall be located on the exterior of the building at the service doorway. If the service disconnecting means is located at a point that is not accessible and available for meter reading, servicing, and disconnecting in case of emergencies, there shall be a shunt trip switch installed and so noted as above. (d) Where a property comprises more than one building under single management or in multiple occupancy buildings, a separate switch at service entrance equipment for each building must be installed (it may be a toggle switch) to disconnect the "House Lighting" circuits. This switch may be locked. It shall have an indicating sign at or on the switch.
Outside electrical service feeder wires: see Article 225, not Article 230 (Service conductors).
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)
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.
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.
"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.
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