To elaborate a bit on the Square D QO Tandem Breakers, and the corresponding Bus Kits for QO Load Centers and NQOD Panelboards, which they are used with...
type Tandem Circuit 1 Pole Breakers have a rejection device incorporated with the Mounting clip, which will only fit in the designated locations of the Bus Kit.
The rejection device is a "Hook-Like" Mounting Cam, which fits into a slot under the Mounting Rail's Bead. These Mounting Rail Slots are only found on the first 4 positions on each side of the Bus Kit (or the last 4 positions, depending on the orientation of the Bus). I am referencing a Panel with at least 24 Spaces, and has the "Left = Odd, Right = Even" Numbering scheme.
These "QOT" Frames fit in the "New Style" Buskits (Class 1130 for QO Loadcenters and Class 1630 for QO Panelboards), which are UL listed as Class CTL.
They come in these following flavors:
* 15/15 (QOT1515),
* 15/20 (QOT1520),
* 20/20 (QOT2020),
* Ham ... ooops, that's something else
Ganging handles are available for creating 2 Pole Tandem units if needed.
This will give two 2 Pole Breakers from only 2 Spaces on the Bus.
These Tandem Frames are the typical 1/2" wide 1 Pole QO Frame, with two very thin handles mounted at the "Bus" side of the Frame, corresponding thin Trip Indicating Flags below each handle, and corresponding load side termination lugs, which are side by side.
The Replacement type "QOxxxx"
type Tandem Circuit 1 Pole Breakers have no rejection device - like the "QOT" Tandems do - and are only for use as replacement Tandem Breakers in the "Old-Style" Non-CTL Class of QO Panelboards and Loadcenters.
These Frames are also the "typical" 1/2" width of the QO line, but are very noticably different from the norm, as they have the following differences from normal QO or QOT 1 Pole Frames:
- Overall length is like 25% or 50% longer than the typical QO frame,
- Handles are the normal size - typical of the QO line, except they are "In-Line" of each other - meaning there is one handle at the normal Bus end, and the other handle is about 2 inches down from it,
- Under each reset handle is a "Full-Sized" Trip Indicating Flag - size is same as the typical QO frame's flag (the "newer" models have trip flags, the "older" models have no flags),
- Load side termination lugs are "Stacked" - meaning if you view the frame in a vertical position from the load side's end, the lug for the circuit controlled by the farthest handle (at the Bus end) is the upper-most lug, and the other circuit's lug is below it, and recessed a little.
These are available as:
* 15/15 (QO1515),
* 15/20 (QO1520),
* 20/20 (QO2020),
* 20/30 (QO2030).
If the Panel was made before 1976, it's most likely Non-CTL.
If it predates 1970, it's definitely Non-CTL!!!
edited because my spelling sux!
[This message has been edited by Scott35 (edited 07-24-2005).]