Originally Posted By: jmyers This post was automatically imported from our archived forum.
To everyone:
Double tapped breakers has come up many times in the home inspection industry and I would like to clear up a fact concerning them.
You are allowed to double tap breakers. According to the manufacturers spec sheets on Cutler Hammer (CH Series) and Square D (QO and Homeline Series) it is perfectly acceptable to have two wires under the lug on a breaker while still maintaining the UL listing. I am still researching the Siemens QP series, when I found out anything I will come back and post it here.
It has been presented many times as a NEC code violation and that statement is absolutely incorrect. I could not find any code that referred to double taps at the breaker as being illegal. If you know something that we don't, please pass it along to others can share the wealth.
IMHO....while I personally do not like to see this, mostly because I have witnessed the lugs loosening, with signs of overheating of the wire from arcing or shorts I could find nothing wrong with this.
I do consider this a bad practice and this and shared neutrals, although legal, is personally frowned upon by me.
Originally Posted By: jfarsetta This post was automatically imported from our archived forum.
Guys,
The reason for the confusion has nothing to do with the breaker rating. Whether branch circuit wiring is connected in parallel at the breaker or at a j-box 30-feet away has little to do with the issue. The breaker has a rating, and when that rating is exceeded, there is a heat build-up and the breaker trips. Period.
The question as to double-tapping has more to do with arcing (Joe's point) than anything else. Igor, you're missing the mark entirely.
The issue becomes real when two wires are connected to the same terminal lug on the breaker itself. Let's say that there is a #12 wire connected to a 15A breaker. Now a #14 wire gets connected to the same terminal lug, whether rated for a second connection or not. Bingo; the different wire sizes cause a very basic problem, in that the smaller gauge wire will automatically be looser than the thicker. This type of connection will cause arcing and heat. This is why the practice is frowned upon.
Depending on the Code enforcement official,. they may call it or they may not. To get around this, many electricians simply install a hot pigtail off of the breaker and wire-nut the two pieces of branch circuit cable onto the pigtail. I dont like to see this, especially if there's room in the panel for another breaker. I call it out, though not as a defect. Although a panel is, technically, a giant junction box, I hate to see them used this way.
Back to electrical theory, two hot leads connected in parallel to a single breaker actually decrease resistance in the overall circuit. It matters not whether this connection happens downstream or at the breaker itself; Ohm's law remains constant. When the sum of all device current draw on those wires exceeds the rating of the breaker, excessive heat trips the unit. The issue comes to the tightness of the physical connections and whether the breaker is designed to accomodate more than a single conductor or not.
Oops... time for shock therapy. Hope it's double tapped!
Originally Posted By: jfarsetta This post was automatically imported from our archived forum.
. Better electrical contractors will recommend homeowners install #12 throughout the home, instead of #14 and #12. It usually comes down to a few dollars more. You WANT to oversize the conductors whenever possible. The larger the conductor, the more current it can carry before overheating. Since these conductors are connected to 15A and 20A breakers, all is okay. Besides, the outlets are typically rated for 15-20A anyway. It is more likely that the circuit would be upgraded someday to 20A from 15A anyway. No, to the contrary, a SMART DIY person will install the #12 on a 15A circuit. The DUMB one will install the #14 on a 20A circuit and burn the house down.
Originally Posted By: jmyers This post was automatically imported from our archived forum.
Joe F.
If I am not mistaken it is illegal according to the NEC codes to have any splices in the electric panel, is it not?
You always hit the mark explaining what I am saying to others and you do it so diplomatically! 
HE** NO VOTE FOR JOE, HE** NO VOTE FOR JOE, HE** NO VOTE FOR JOE!
You have my vote. 
Originally Posted By: jfarsetta This post was automatically imported from our archived forum.
Not really. I just dont like to see them, especially where there is room for more breakers. Like I said, I call out the splices, not so much as a defect, but as something they should be aware of. Where there is adequate space and length of wire, I recommend installation of a new breaker to attach the spliced cable to.
I just think that, unless there is a valid reason to do so, splicing within the panel itself is sloppy workmanship. Servicability of that splice is extremely dangerous sue to the live panel, whereas in a j-box you simply shut down the affected circuits.
Joe, I am making a genuine effort to clarify my feelings, rather than Code. This is just a preference.
Originally Posted By: jmyers This post was automatically imported from our archived forum.
Joe F.
Makes good sense to me, although I thought I remembered reading it is illegal to make splices in the service panel according to the NEC codes.
Anyway, good point! Connections are much safer to work on in a J-box outside of the panel. But then again, if you are in need of electrical shock therapy like me, could save you some bucks! 