Back wired electrical receptacle failures:

Photos of failures occurring at or within back-wired electrical receptacles and switches.

At page top we illustrate a #14 solid copper wire being pushed into the backwire opening of a common electrical receptacle. The wire has not been pushed fully into the connection as I wanted to show the diameter of the wire entering the push-in connector opening.

This article series illustrates and explains possible electrical failures and fire risk when using the push-in rear connectors on some back-wired electrical devices such as receptacles and switches.

Photo-Examples of Failures in Back-Wired Electrical Receptacles Illustrate the Failure Condition

Using the back-wire or push-in type connection points on an electrical receptacle or switch may be just fine, or it may not be reliable nor safe, depending on the age and type of back-wire connector provided.

This article series explains receptacle types, receptacle grounding, connecting wires to the right receptacle terminal screws, electrical wire size, electrical wire color codes, and special receptacles for un-grounded circuits.

The photograph at above-left illustrates a failure of a push-in type back-wired electrical receptacle.

A fault occurred between the live contact assembly and the grounded receptacle mounting strap (center of the photo) causing fire ignition.

The photograph shows the end result of a long-term and multi-step process, where the overheating push-in wire termination caused carbonization of the bakelite around it, which then faulted (probably when it absorbed moisture from the atmosphere during long "off" periods). - J. Aronstein to D Friedman, private email, 10/29/2015

Dr. Aronstein reports having encountered this failure multiple times and in each occasion the receptacle had been push-in backwired.

Low Contact Force is a Key Performance Difference Between Push-In Wire Connections & Clamp or Screw Terminals on Receptacles & Switches

Low contact force between the wire and the receptacle connector where spring-type push-in backwired terminals are used on receptacles is probably the most significant reason that these connections can be expected to deteriorate over many years.

The small contact area afforded by these connectors, documented at RECEPTACLE WIRE-TO-CONNECTOR CONTACT AREA SIZES may increase that risk.

Watch out:

The key performance difference between the push-in and clamp or screw terminals is the rate of deterioration of the electrical connection. The condition of the connection and connector and rate of deterioration become important over a time frame of years in the typical installed environments (which are highly variable).

There may also be considerable variation in the conditions among the 30 or more push-in wire connections in a typical string of receptacles on each receptacle circuit in a home. Those receptacles that are subject to more frequent use and those subject to heavier loads get more disturbance over time.

A push-in spring connection, inherently much weaker than a screw or clamp type connection, will suffer more disturbance, movement, and weakening than the stronger connectors as the receptacle is used, possibly increasing the risk of a subsequent failure.

The time scale of this deterioration usually is years and decades. This means that the fact that electrical failures or problems with these devices were not seen early in their installed life is no assurance whatsoever that the connectors and devices in an older home will continue to remain safe and reliable in the future.

In other words, the probability of a failure, overheating, and a possible fire and loss increase over time. In a 40 or 50 year old home, push-in wired electrical connections on the home's electrical system are not to be trusted. - J. Aronstein Op. Cit.

Below are front and rear view of another push-in type back-wired electrical receptacle failure. These photographs are provided courtesy Jess Aronstein.

and

• Aronstein, Jess,[Personal communication, J.A. to the editor (Daniel Friedman)], 25 October 2015. Dr. Jess Aronstein, protune@aol.com is a research consultant and an electrical engineer in Schenectady, NY. Dr. Aronstein provides forensic engineering services and independent laboratory testing for various agencies. Dr. Aronstein has published widely on and has designed and conducted tests on aluminum wiring failures, Federal Pacific Stab-Lok electrical equipment, and numerous electrical products and hazards.
  
  See ALUMINUM WIRING BIBLIOGRAPHY and FPE HAZARD ARTICLES, STUDIES
  
  and also BACK-WIRED ELECTRICAL DEVICES for examples.
• RECEPTACLE WIRE-TO-CONNECTOR CONTACT AREA SIZES - measurements & calculations of the contact area between an electrical wire and the connecting device on an electrical receptacle or switch explain differences between push-in type backwire connectors, compression plate connectors, and binding head screw connectors, all of which are found on many electrical receptacles and switches.
• Also seeReferences or Citations

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

Reader Field Failure Report: power lost at beach-front home

I read your article on BACK-WIRED ELECTRICAL DEVICES and you indicated an interest in field examples of failures.

We recently stayed at a beach house owned by some friends, and I replaced some failing dimmer switches for them as a favor. I noticed consistent backwiring on these devices to feed downstream loads.

Then on the final day of our stay, there was an electrical failure in a circuit that I had not worked on.

What I discovered when I chased down the fault was very concerning.

The incoming black and neutral were screw connected to the first receptacle in a long circuit, and there were two circuits being fed downstream from the backwire connections on the receptacle.

These failed with evidence of arcing on the wires.

Attached is a paper (with pictures) [now on-line as edited at BACKWIRED RECEPTACLE FAILURE REPORT ] that I put together to help my non electrical friends understand the failure and its potential implications for the safety of their property.

As you will see, I strongly encouraged them to have all of the devices rewired to eliminate backwired connections and connections that use devices as terminal blocks for downstream current flow.

They plan to have this done as soon as possible.

Apparently, there was a house in the same neighborhood that burned to the ground recently and the cause was attributed to an electrical fault (I don’t know that the fault was a backwiring issue, but it would not surprise me if the same electrician did other properties in the neighborhood).

These are multimillion dollar Atlantic beach front properties… not the kind of places you expect such lazy electrical work.

It makes me angry because this house has a zillion receptacles, switches, dimmers and appliances. Some electrician made a pot full of money doing this property and should be ashamed for his laziness.

Anyway, I hope this is useful to your cause. - Anonymous by private email 2018/07/24

Reader comment: field report of backwired device failures

A very large number of my service calls are due to push in receptacles. I have had burn outs as shown above, but usually the result is an open circuit, often causing lack of current in down line receptacles.

I always replace with side clamp wire receptacles and sometimes home owners or landlords have had me remove and replace all of them in the home. 2017/03/20 J W said:

Reply:

JW

Thank you for your important comment. This topic has been a thorn in the side of safe electrical wiring for some time. It is particularly useful (and compelling) to have feed-back from people who have both expertise and field experience with electrical wiring failures.

If you come across a burned, failed backwired device and can send me photos those would be most helpful. My email is at the page top or bottom CONTACT link.

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Continue reading  at BACK-WIRED ELECTRICAL DEVICES - topic home, or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

• BACK-WIRED ELECTRICAL DEVICES - home
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  • BACKWIRED DEVICE SPRING CLIP 1960 DESIGN
  • WIRE-TO-CONNECTOR LIMITATIONS in PUSH-IN ELECTRICAL CONNECTORS
• BACKWIRED RECEPTACLE FAILURE PHOTOS
• BACKWIRED RECEPTACLE FAILURE REPORT
• BACK-WIRING FAQs for RECPTACLES & SWITCHES
• RECEPTACLE WIRE-TO-CONNECTOR CONTACT AREA SIZES
• WIRE-TO-CONNECTOR FORCE COMPARISONS
• WIRE-TO-CONNECTOR PERFORMANCE SUMMARY

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