Question? Just ask us!
Free Encyclopedia of Building & Environmental Inspection, Testing, Diagnosis, Repair
InspectAPedia ® Home
ELECTRICAL INSPECTION, DIAGNOSIS, REPAIR
ACCURACY vs PRECISION of MEASUREMENTS
AFCIs ARC FAULT CIRCUIT INTERRUPTERS
ALUMINUM SECs & WIRING
ALUMINUM WIRING HAZARDS & REPAIRS
AMPS VOLTS DETERMINATION
AMPERAGE MEASUREMENT METHODS
AMPACITY - the LIMITING FACTOR
APPLIANCE EFFICIENCY RATINGS
BACKUP ELECTRICAL GENERATORS
BACK-WIRED ELECTRICAL DEVICES
BOOKSTORE - ELECTRICAL
BUILDING SAFETY HAZARDS GUIDE
Cadet & Encore Heater Recall
CIRCUIT BREAKER FAILURE
CIRCUIT BREAKER SIZE for A/C or HEAT PUMP
Classified CIRCUIT BREAKER WARNING
CORROSION in ELECTRICAL PANELS
CORROSION & MOISTURE SOURCES in PANELS
CUTLER HAMMER PANEL FIRE
DEFINITIONS of ELECTRICAL TERMS
DIRECTORY OF ELECTRICIANS
DMM Digital Multimeter HOW TO USE
ELECTRIC METERS & METER BASES
ELECTRIC MOTOR DIAGNOSTIC GUIDE
ELECTRIC MOTOR OVERLOAD RESET SWITCH
ELECTRIC PANEL AMPACITY
ELECTRIC PANEL INSPECTION
ELECTRIC PANEL MOISTURE
Electric Power Frequency Table
ELECTRIC WATER HEATER TIMERS
ELECTRIC WATER HEATERS
ELECTRICAL DISTRIBUTION PANELS
ELECTRICAL GROUND SYSTEM INSPECTION
ELECTRICAL SERVICE DROP
ELECTRICAL SERVICE ENTRY WIRING
EMF RF FIELD & FREQUENCY DEFINITIONS
FEDERAL PACIFIC FPE HAZARDS
FIRE SAFETY Checklist, CPSC
GFCI PROTECTION,Testing GFCIs AFCIs
HEATING COST FUEL & BTU Cost Table
HEAT TAPE USAGE GUIDE
Hertz - Definitions of KHz MHz GHz THz
KNOB & TUBE WIRING
LIGHTING, EXTERIOR GUIDE
LIGHTING, INTERIOR GUIDE
LIGHTNING PROTECTION SYSTEMS
LOW VOLTAGE BUILDING WIRING
LOW VOLTAGE TRANSFORMER TEST
MAIN ELECTRICAL DISCONNECT
MAIN SWITCH LOCATION
MAIN DISCONNECT AMPACITY
MOISTURE SOURCES in PANELS
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
THERMAL EXPANSION of HOT WATER
THERMAL EXPANSION of MATERIALS
UNDERGROUND SERVICE LATERALS
VOLTS / AMPS MEASUREMENT EQUIP
VOLTAGE MEASUREMENT METHODS
WIND ENERGY SYSTEMS
WIND TURBINES & LIGHTNING
ZINSCO SYLVANIA ELECTRICAL PANELS
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.
Green links show where you are. © Copyright 2014 InspectApedia.com, All Rights Reserved.
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
[Click to enlarge any image]
How Many Main Breakers are Allowed in a Residential Electrical Panel?
Reader Question: 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). Details and an expanded discussion of these hazards can be found at PUSHMATIC - BULLDOG PANELS.
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.
[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.
Separately, 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.
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.
And 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.
Green link shows where you are in this article series.
Frequently Asked Questions (FAQs)
No FAQs have been posted for this page. Try the search box below or CONTACT US by email if you cannot find the answer you need at InspectApedia.
Questions & answers or comments about the main power switch or main disconnect switch at electrical panels.
Use the "Click to Show or Hide FAQs" link just above to see recently-posted questions, comments, replies, try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.
Search the InspectApedia website
HTML Comment Box is loading comments...
Technical Reviewers & References