By Tom Baker, Mike Holt
Code Forum Moderator
As a code forum moderator, I see various forum posts and note the trends of them. Early in 2001 there were a lot of posts on AFCIs such as:
Recently, the number of AFCI posts has dropped off considerably. I havent noted one for several weeks, one today was if AFCIs are required for a panel change out.
Comments on AFCI
Early on I did not realize that all AFCIs have a built in Ground Fault Interrupter, set at 30 mA to 50 mA. This is not a Class A GFCI, but functions in the same way. Many of the installations where an AFCI trips is not due to the Arc Fault portion tripping, but rather an inadvertent neutral to ground connection. We had the same tripping of GFCIs when they were first installed, due to the same conditions. GFCI and now AFCIs have shown there are miswired and inadvertent neutral to ground connections.
At least one manufacture makes a listed combination AFCI and GFCI circuit breaker. This device sells for about $38 and offers a lot of protection for the money.
One comment that came up on the forum is the AFCI generates heat and if multiple AFCIs are to be installed in the same panel, they need to be spaced out to reduce heat build up. However this is not necessary, as current loading primarily determines an AFCI circuit breakers temperature.
Several new products were introduced as a result of the AFCI. Insulated staples were marketed to reduce damage for over stapling NM cable. 12-2-2 NM Romex was introduced to allow home runs for two AFCI circuits, as an AFCI can not have a shared neutral (due to ground fault protection). However, at least one manufacturer (Cutler Hammer) offers a 2-pole AFCI for home runs. Standard 12-2-1 NM Romex can be used. The 2-pole AFCIs are available with/without common trip for overcurrent and overload conditions; the trip is always common for an arcing or ground fault.
An AFCI can be tested by using the built in test button. This tests the internal circuitry but not the wiring. AFCI manufactures literature states the branch circuit can be tested using an Insulation Tester (Megger), but an insulation tester can be used to test any circuit prior to being energized, AFCI or not. One testing suggestion was to connect a 100 watt lamp as a load and energize the circuit (this would be at rough-in). With the lamp load this will detect a shared neutral condition.
One That Works, One That
A tester was introduced by Etcon AF120 claming to be an AFCI Tester it actually (if you read the fine print and knew how an AFCI worked) only tested the GFP portion of the AFCI. And this product was subject to a recall by UL, as it was illegally labeled UL Listed http://www.ul.com/media/newsrel/nr092402.html
Fox Meter Inc http://www.arcfaulttester.com introduced a true AFCI tester (now UL Listed). I have not seen it or know of anyone who has, but the initial review is promising. If youve used one, please let me know. A recent post on the Code Forum indicated Etcon is developing an AFCI tester that uses an Arc to test the AFCI.
The Future of AFCI
Certainly there will be more requirements for AFCI installations in the 2005 NEC. Proposals for the 2005 NEC included voluminous documentation and endorsements for AFCIs. While the requirements for AFCIs may be felt by some to be forced upon the industry by special interest groups, the AFCI is here to stay.
More information on AFCIs is available at: http://www.mikeholt.com/articlelist.php?list=AFCI&back=articlecategories.php
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Copyright © 2002 Mike Holt Enterprises,Inc.