I understand that some double-lugged SquareD breakers are allowed and that others are not. Can anyone tell me from looking at this picture if they are allowed on these breakers or not?
yes these are ok for double taps if the wire is the same size. Roy Cooke
If it is a “set screw” tpe of connection it is a single wire.
If it has a “screw and plate” connector it can accept two.
The picture is now attached to my original post. Sorry guys.
This is what to look for:
post images not downloads…much easier and safer!
That was just a PDF. If you don’t have Adobe you won’t open it.
This is a JPG
just better to have pictures posted…rather than downloadable files is all I am sayin.
I agree with Paul. Pictures not large PDFs.
I just look for the saddle clamp under the screw.
Same size wires (as Roy said) and saddle clamp = OK
No clamp, no double tap.
As in Larry’s picture above.
Square D has a breaker with a clamp like that. So does one other manufacturer, is it Cutler Hammer???
Whether it is “allowed” to double tap or not isn’t always the point.
The other concern is that the added circuit may overload the breaker, and cause it to trip regularly during normal use.
It always catches my attention when I find double taps no matter who makes the breaker. It often represents a homeowners attempt at electrical.
(…I have never seen double tapped breakers in new construction, and/ or remodeling where it was both performed by a licensed electrician, and it was inspected by the AHJ)
I personally prefer to see a duplex breaker replace the double tapped breaker.
How can a double tap overload a breaker any worse than a single circuit? If so, where is the harm? The conductors are doubled too so the load will be split across two instead of one. 240.4(D) provides more than adequate overload protection.
i believe harold was saying that when a 2nd circuit is added, it could potentially double the load, potentially causing the breaker to trip more often.
if the loads have been taken into consideration prior to installing the 2nd circuit, then it should be no problem.
I think what greg is saying is…if the breaker trips at lets say at a certain point…it will do it regardless of what it connected to it…granted it will have more load on it when it is doubled up…but the breaker itself knows not what it does…just what it is supposed to do…lol…
and thats trip in an overload…
The bad part is like cc stated…if the homeowner has taken into consideration the loads prior…and we all KNOW they do not…they see an open space and WHAMO…add another circuit…lol
How can a double tap overload a breaker? I see homeowners do this all the time. There is a reason that certain appliances have a dedicated circuit. Tap into one of these circuits with another high draw appliance, and run them at the same time. How about an outlet for a window unit air conditioner on the microwave circuit? Just an example of the many possible combinations I can think of. I am sure there are better examples.
I don’t have a problem with an electrician performing legitimate double taps on approved breakers. But I never see that in my area…it is always the weekend warrior trying their hand at electrical with no regard for what they are doing.
Sometimes it is a double tap on a 20 amp circuit breaker with 14 guage copper wiring, or better yet the installer was aware that the load was being increased on a 15 amp circuit, and so they install a 30 amp 120 vac breaker to serve two 15 amp conductors…brilliance 
I guess I am just saying if you see a double tap…don’t stop looking…there is often more to the picture.
I think PDF files are great! I like them because there are so many things one can do with them, the file posted as a PDF file here is not a problem, but then when it is as large as this one
http://www.ul.com/regulators/2006WhiteBook.pdf
it could take some time, about 6 MB’s for sure but worth the time spent and it will have the specific answers to the original question here, again I think that PDF full version files are the best for those who have the software which is free anyway.
If it is just one indication in a more complex investigation that is fine but there are plenty of HIs that say “double tapped breaker” with no other justification for calling it out. Bearing in mind there is no load restrictions on a general lighting circuit in a dwelling the only real question is if it is a general lighting load on a “dedicated” circuit.
Another comment on Greg’s picture, I would have noted that the white wire on the adjacent double pole breaker should have been marked with tape to signify that it is an ungrounded conductor and not a neutral.
That is the original PDF from the top note loaded as a JPG