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Unsafe sub panel bonded ground and neutral (C) Daniel Friedman Main Electrical Panel Disconnect Switch
Inspection & Defects List

  • MAIN ELECTRICAL DISCONNECT - CONTENTS: 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. Electrical code citations regarding the main electrical disconnect at buildings. Two main breakers allowed - code citations. The six circuit breaker rule as main electrical panel disconnect, electrical code requirements.
  • POST a QUESTION or READ FAQs about the main power switch or main disconnect switch at electrical panels
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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.



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Inspecting the Residential Electrical Main Disconnect Panel or "Box" for Defects

Unsafe sub panel bonded ground and neutral (C) Daniel FriedmanThis 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

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Electrical Service Box Location Defects

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:

How Many Main Breakers are Allowed in a Residential Electrical Panel?

Split main breaker design in Pushmatic electrical panel (C) InspectApedia DBReader 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

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Reply:

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.

(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.

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.

(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.

Reader follow-up:

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

Reply:

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.

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Continue reading at MAIN DISCONNECT AMPACITY or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see ELECTRICAL INSPECTOR SAFETY PROCEDURES important basic safety procedures, clothing, and equipment for home inspectors and electrical inspectors.

Or see ELECTRICITY TURN ON AFTER BREAKER TRIP

Or see Step 5. RESTORE UTILITIES AFTER FLOODING

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