AFCI One More Time
Dear Mr. Holt:
I believe your "turn around" opinion of November 5, 2002 based on the limited comparison testing at Cutler-Hammer on 11/4/02 was premature. The concerns that you expressed, items 1-6 on the first page of your AFCI Update (http://www.mikeholt.com/mojonewsarchive/AllSubscribers/HTML\AFCI_-_Update~20021209.htm), in my opinion, remain valid concerns. The test performance that you reported in you newsletter update is far from convincing and is not sufficient to resolve the reality of "loose and glowing connections" and the fires that result.
Based on my years of experience at UL-Melville with wiring devices and the study of "aluminum and copper wire connectablility", I believe that more needs to be done before a reliability / performance claim can be made regarding AFCI/GFI detection and control of fires resulting from "glowing wiring connections".
Since you are going to have Dr. Joe Engle (& company) on December 17, 2002 perform additional testing to demonstrate how an AFCI Circuit Breaker protects against a fire from loose terminals and connections, I suggest that you have the Cutler-Hammer team include the following electrical test / installations in the performance comparison tests:
No. 1. Outlet Box with Duplex Receptacle (w/steel screw) wired with Aluminum Conductor (12 AWG) in a loose connection ("0" in - lbs torque on 1 of the three "BH Screws"). The wiring behind the receptacle in the outlet box should be installed such that the insulated "line" conductor (black), the insulated "neutral" (white) conductor, and the "ground" (bare) conductor are not in contact with each other.
Install the above wiring as in a branch circuit and protect the wiring with a properly rated, standard circuit breaker.
A. Initiate a "glowing connection" at the "0" torqued, "loose" binding head screw terminal.
B. Measure temperatures (via thermocouples) located on the face of the receptacle, the feed through terminal tab near the loose connection, and adjacent wall stud (2" by 4") that supports the outlet box.
C. Measure the time it takes for the circuit breaker to open after the glowing connection is initiated (and also measure the arc cycles that pass before the circuit opens).
No. 2 Same Test as Item 1, except
use a "UL Listed Dual Rated AFCI/GFI Circuit Breaker.
No. 3 Same Test as Item 1, except use a "UL Listed AFCI Circuit Breaker.
No. 4 Repeat Test # 1 except use copper wire, No. 14 AWG.
No. 5 Repeat Test # 2 except use copper wire, No. 14 AWG.
No. 6 Repeat Test # 3 except use copper wire, No. 14 AWG.
No. 7 through 12. Repeat Tests 1 through 6, except use a residential grade Duplex Receptacle with brass screws.
No. 13 through 24. Repeat Tests 1 through 12, except install the receptacle and wiring into the outlet box as in a normal NEC installation, i.e., wiring folded like an accordion behind the receptacle and the receptacle/ wiring gently forced back into the box.
Upon completion of these comparison tests, I believe that those of us trained in the "technical art" will be in a better position to make a preliminary assessment of "AFCI/GFI" Circuit Breaker Performance. A proper analysis of the temperature data, the time it takes for the circuit breaker to activate in each of these test "setups", and an assessment of the "ignition temperature" of the typical materials (determined by UL Test at room temperature & the "lower ignition temperature of the materials" that exists after pre-heating of the materials occur) that are in the proximity of the outlet box will be necessary before one can hope to make the claim as to the effectiveness of a "Dual Rated AFCI/GFI" to detect and control the insidious results of a "glowing loose connection".
Further, regarding your item # 6 concern, "the comprehensive study on the true causes of electrical fires by a Task Force" is valid and is needed. I believe that a "UL-Government-Electrical Industry" research program is long overdue and should be undertaken immediately. In Dr. V. Babrauskas's 2001 research paper "How do electrical wiring faults lead to structure ignitions?1", he states in his Abstract that, "the modes which electrical faults progress to ignitions of structure have not been extensively studied" and that "systematic research has been inordinately scarce on this topic, and that much of the research that does exist is only available in Japanese".
Yet, over 26 years ago, the National Bureau of Standards, in their Report, NBSIR 76-1011 - Exploratory Study of Glowing Electrical Connections, recommended the following:
Consideration should be given to establishing the extent of potential hazards from glow developing in existing buildings and additional laboratory research undertaken to provide resolution of glow phenomena.
1. Research addressing realistic installations and practices involving glowing electrical connections should be undertaken toward achieving the following objectives:
A. Advance quantification of characteristics of glowing connections presented in this report.
B. Scientifically explain reasons for the glow condition.
C. Determine how electrical connections become loose (creep, thermal expansion and contraction, stress relaxation, corrosion, installation procedures, etc.) and determine whether any other mechanisms may lead to the glow condition.
D. Investigate and quantify data concerning loose brass screws -- determine if there are conditions under which copper-brass and aluminum-brass interfaces will develop glows or otherwise overheat under static conditions.
E. Explore the possibility of using a portable device to quickly determine the quality of electrical connections in houses or other buildings.
F. Obtain statistically significant field data on the quality (voltage drop, power dissipation) of electrical connections.
G. In a systematic manner characterizes the fire-starting potential of glowing electrical connections in typical types of building walls.
2. Criteria and tests or other evaluative procedures should be developed and regulations put into effect which will ascertain that electrical connections installed in the future will not be vulnerable to the glow or to other overheating conditions.
3. Determine modifications which can be taken to lessen the vulnerability of existing electrical connections of the glow or other overheating conditions and determine if such modifications are feasible from both technical and economic standpoints.
In my opinion, it would also be of benefit to all parties concerned including the "public" to extend invitations to Mr. Paul Notarian & Chuck Kurten, UL Melville; and Mr. Bill King, CPSC, to attend your December 17 meeting in Pittsburgh.
When the public Cutler-Hammer test demonstration is completed, I would be interested in receiving a copy of the report.
Thomas J. D'Agostino, P.E.
The research paper was presented at the 7th International Fire & Materials Conference, 2001, San Francisco, California, USA, pp. 39-50. You can obtain a copy by contacting Dr. Babrauskas via email: firstname.lastname@example.org
Mike Holts Comment: Thomas, you obviously know more about this subject than I do. What you recommend should be preformed by an independent qualified organization so that we all know the true story. I dont know what organization would be qualified to perform these tests or how much it would cost, but I might be willing to pay to have this study done. If anybody has any recommendations, please let me know.
P.S. Just when I thought this was all over .
Copyright © 2002 Mike Holt Enterprises,Inc.