I hope someone can help me understand what I’m looking at. Please refer to the partial picture of a main residential panel below. I don't have a web page so it seems that I cannot include an image but I would be happy to e-mail the image to anyone interested. I hope that my word picture is enough.
I have not taken the panel cover off (yet) to see what the OCPDs in question look like from the rear.
Each of the top two branch circuit breakers appears to be a double pole breaker and each breaker has one 20A and one 40A breaker in the same housing. Both the water heater and the range are 240V appliances and each is served by the two corresponding halves of each of the breakers. Both breakers have handle ties, the inside 40A ones for the range (one pole from each breaker) are linked with looks like a more or less conventional handle tie, and the outside 20A ones (again, one pole from each breaker) for the water heater are linked with what I think is a made tie. It may not be but I haven’t seen anything like this before.
My question is why would this system be used instead of the more conventional way, one double-pole 20A and one double pole 40A breaker? Why would one even use a double pole breaker with different ratings for each of the poles? I didn’t even know such beasties were manufactured.
I’m sorry folks but my ignorance is vast and I hope for some enlightenment

I bet you are talking about one of these:


http://www.google.com/url?source=imgres&...2G3CSrr5l6KfUjQ

If so, the only real purpose is to simply save space. You basically get 4, 1-pole circuits or 2, 2-pole circuits using just two slots in the panelboard.

So imagine you have full panelboard but still have load capacity and want to add another circuit or two. This breaker would allow you to do that...

It is just a double piggy back breaker. (Two 240v circuits in 2 slots.) I have seen them from SqD.

Agree. I used to call them "a quad breaker." Purpose is to save space or to create space if the panel is maxed. Quad breakers for different manufacturers may look slightly different but basically still have the center tie and the outer tie.

Just a note to remember:

That Quad breaker, like the single pole twin, may only be used in panels that have the notched buss or v-slot as I call it. The panel style will be a 30/40 circuit. A straight 30 circuit, or straight 40 circuit panel does not have a notched buss so the Quad breaker, or single pole twin, will have to be modified to fit since is is manufactured with a rejection feature. As we all know that is a violation of 110.3b.

The older SqD piggyback breaker is stacked in line with full sized operating handles and can be paired with the regular handle ties (or the 10 penny nail trick). The condo I had in Treasure Island (Pinellas Co) had a panel with these in it from day one.
I never understood why they put in such a small panel but that was 1967 and things were looser then I guess.

Today, even the square D piggybacks have a rejection tab. But a hacksaw will take care of that for the old panels.

Just kidding on recommending cutting the tab.

I have seen a few with the hook cut off.

I am guilty as charged from past years.
Prior to knowing better.

Thanks to all of you for the enlightening information. Yes, Brian, it was exactly one of those. And yes, the panel was maxed out. And the panel was in a mobile home, and I've been in only a few of those.
Curiously, I live in a double-wide but I have the luxury of one whole spare slot so I don't have any 'quads.'
Thanks to all for once again broadening my appreciation of the wide, wide electrical real world.
Heinz R.

Thanks for posting the question. You brought back memories of when I was back in business and Bryant panelboards and I believe they had the "quads" as well. I think I even used a couple here and there, if memory serves me correctly.

Quads were also popular in split buss panels. In the top half when people added central air.

I know it was wrong back then also, more that six devices, but that is what people did to get out of installing another panel or a sub panel.

I remember those well, even installed a few, never liked them much, felt like cheating the system

I know what your saying.
And of course it was only a murray breaker available for quads.
And some old bulldog ge breakers.

So out comes the hacksaw, sidecutters and etc to make it fit on the buss.
I wonder how many have failed over the years due to modifying the breaker to fit.

Many years ago it was thought that the mark of a good electrician was one who could make things work. Like making breakers fit in panels where they were not designed to fit in. And I did it myself.

Back in 1987 when I became an electrical inspector for The New York Board of Fire Underwriters I learned that this is not proper. Now when I teach at my seminars, I tell everyone that the mark of a good electrician is one who reads the directions, and the manufacturer's label.

I think that those of us who worked in the field, all did some things that at the time seemed clever and inovative and as Mike said made us good electricians able to adapt to adverse situations, but looking back are things that we as inspectors now know are unacceptable practices