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Main fuse or main circuit breaker in an electrical panel:
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.
We include information about How many main disconnect switches are allowed, other main disconnect switch hazards.
We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.
Inspecting the Residential Electrical Main Disconnect Panel or "Box" for Defects
This article and others in the 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.\
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, January 2014, July 2017
Main control center for house
Integrated or separate service disconnect (main breaker or fuses) -
need main disconnect if more than 6 switches
[Click to enlarge any image]
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. Look for these electrical panel hazards when inspecting the main circuit breaker:
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).
More than two main disconnect switches in the main panel are required to turn off the panel (presuming this is a main residential panel hosting more than 6 circuits total - see next bullet.
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 panelboard or electrical panel 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
Wiring condition: Poor electrical panel or main disconnect connections, poor wiring
Illegal taps at the electrical panel or main disconnect
Water leaks: Exterior, electrical panel or main disconnect not weather tight
Specific Electrical Panel Product Defects, see additional articles listed at left and below
How Many Main Breakers are Allowed in a Residential Electrical Panel?
Recently I inspected a ITE Pushmatic main panel box. At the top of each buss line there was a main breaker. What is the current policy regarding this type of main panel box wiring configuration? Is there need for further evaluation by a licensed electrician? - D.B. 1/22/2014
[Click to enlarge any image]
The short answer is that we are allowed up to two main switches to turn off power in the main electrical panel. A sub panel containing 6 circuits or less can omit a separate main breaker and may be switched by the breaker on its input feed circuit.
But there are other issues with Pushmatics that argue for viewing this equipment with caution. I'm not confident that the advice "have the panel examined by an electrician" is at all an adequate warning, since there are surely electricians living by rigid code interpretation who will deem safe electrical panels known to have safety defects but that have not been subject to a government-ordered recall.
Clear examples are FPE Stab-Lok equipment, and two more possible examples are the Bulldog-Pushmatic panel and also Zinsco panels.
Where we have independent, unbiased testing and field reports of comparatively high levels of field failures, an astute home inspector, electrical inspector, or electrician ought to call out those hazards - even where they may call for a costly panel replacement. (The last man in to touch the equipment will be blamed if/when there is a fire or catastrophe).
If I understand your photo, you are pointing (your dangerously close bare fingers made me nervous) to a pair of split-main breakers, an arrangement that lacks a common internal trip or external trip tie. This design would allow one side of the panel to be switched off while leaving the other side "on".
For main disconnects, (using 2002 NEC as an example)
NEC 408.16 Overcurrent Protection.
(A) Lighting and Appliance Branch-Circuit Panelboard Individually Protected.
Each lighting and appliance branch-circuit panelboard shall be individually protected on the supply side by not more than two main circuit breakers or two sets of fuses having a combined rating not greater than that of the panelboard.
Exception No. 1: Individual protection for a lighting and appliance panelboard shall not be required if the panelboard feeder has overcurrent protection not greater than the rating of the panelboard.
[This means that no main is required in the panel if the feeder wires to the panel are protected ahead of the panel itself - that is, in effect there is a separate main breaker ahead of the panel, but there are then separation distance constraints between these switches.]
Your photo shows an electrical panel that uses two main breakers so by my understanding, on this point it would be acceptable.
Further, this particular Pushmatic main breaker design is not visually ambiguous - that is, switching off one side of the panel would not make it look as if both are off.
More discussion about paired or common trip tie or handle tied circuit breakers:
Some experts (http://ecmweb.com) aptly point out that even if a circuit breaker pair could be connected by a common handle (not possible in this Pushmatic case) the level of protection is not the same as that provided by two-pole or double-pole circuit breakers with a common internal trip tie mechanism. A handle-only connection in some designs may leave one breaker "on" and the other "off" - a dangerous condition because of the chance of fooling the electrician or homeowner into thinking that all electrical power is off when it is not.
Common internal trip ties would be required by NEC 240.20(B) for example on a multiwire branch circuit because that code paragraph requires that "... the circuit breaker shall open all ungrounded conductors of the circuit." Tandem circuit breakers (two breakers powering two circuits fit into a single original breaker slot in a panel) also trip together.
NEC also permits a maximum of six disconnects to turn off all power in an electrical panel. We encounter this condition usually in sub-panels or branch panels. If the sub panel contains more than 6 breakers (and is remote from the main switch) it needs to have its own main switch.
NEC 230.71 Maximum Number of Disconnects.
(A) General. The service disconnecting means for each service permitted by 230.2, or for each set of service-entrance conductors permitted by 230.40, Exception Nos. 1, 3, 4, or 5, shall consist of not more than six switches or sets of circuit breakers, or a combination of not more than six switches and sets of circuit breakers, mounted in a single enclosure, in a group of separate enclosures, or in or on a switchboard.
There shall be no more than six sets of disconnects per service grouped in any one location.
For the purpose of this section, disconnecting means used solely for power monitoring equipment, or the control circuit of the ground-fault protection system or power-operable service disconnecting means, installed as part of the listed equipment, shall not be considered a service disconnecting means.
Thank you for your in-depth review and explanation of the issues encountered at this panel box.
[...] and I will revisit these issues with this client. Your comments also prompted me to read other related issues on main panel boxes that were posted on your website.
- D.B. 1/24/2014
About your finger near that Pushmatic breaker, I know you were smart enough not to electrocute yourself.
As a publisher/editor I have to worry about risks to a casual reader, a careless homeowner, or someone who just lacks respect for electricity. The chance that someone else will fail to understand that they need to be careful when inspecting electrical panels is a worry that leads me take opportunity to point out shock hazards where I can see them.
Even though at home inspections I habitually stood blocking my inspection client from direct access to the electrical panel as I examined that component, I once had a client reach right over my shoulder and stick his finger right into a live fuse socket while asking "What the heck is this!" The results were exciting.
Watch out: at a home inspection training seminar we had an electrician tell newbie home inspectors how to inspect the electrical panel by saying "Well the first thing you wanna do is grab a-holt of each of the entry main wires just above where they come into the main breaker - and give them a good shake!"
I could just imagine that with that fool statement he had probably killed one or two of the fellows in the room, sending 240 volts right through their hearts.
Continue reading at MAIN DISCONNECT AMPACITY or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.
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
(A) Location. The· service disconnecting means shall be
installed in accordance with 230.70(A)(l), (A)(2), and
(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
(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_
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).
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.
"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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