"bud--" wrote in message
eb.com...
On 2/26/2014 4:59 AM, Robert Green wrote:
I was mostly concerned at the time
that the inspector would disallow the dual skinnies because of the
potential
to overload the panel.
Panels will have a rating something like 10/16. There are 10 full size
breaker positions and you can put 16 "poles" in it. A tandem breaker is
2 poles, so you could install up to 6 tandem breakers. The label should
tell you the rating.
Panel is a QO CAT QO BW - 20M - 100 - 5
I believe that the 20 refers to the max # of breakers and the 100 is the max
current. Otherwise the catalog number don't seem to agree with the listing
in the PDF. No idea what BW means. It's hard to read the label because
it's a) faded, b) upside down and c) obscured by neutral and ground wires.
The panel is tested with the maximum number of poles - 16 above - and UL
does not allow installing more poles than that. That is done by only
allowing tandem breakers in certain positions (6 in the example above).
The label will indicate which positions tandem breakers can be installed
in. In a 10/20 panel it is all positions. It may also be no positions. A
SquareD tandem breaker has a bar on the bottom that has to fit into a
slot through the gutter rail, which exists only in the positions where
tandem breakers are allowed. These are class CTL panels and breakers
(circuit limiting) and they have been around a long time.
This has to be a pre 1985 panel and I haven't found it yet although I found
a few like it in this PDF:
www.farnell.com/datasheets/1626663.pdf
The inspector wants to know that tandem breakers were installed in
positions where they are allowed.
From what I can see, that's not an issue with my panel. As I recall, the
hot bar (not sure of the technical name of the alternating metal "fingers"
running down the center) was the same from the top to the bottom - no
specialized slots for tandems (why would there be?). The replacement
breakers have a very different connection mechanism that the original ones.
The ones that came with the panel have two pronged clips that make the
connection to the rail but the replacements have a single claw-like
"grabber" - so different looking that I was sure I bought the wrong
breakers.
There are also non-class CTL tandem breakers that can be installed in
any position - for older panels that are before CTL came out. I know no
one here would ever install one of them in a class CTL panel.
I am pretty sure that at least on of the labels on the panel has the letters
CTL but if it came out after 1985, then I definitely don't have a CTL panel.
From what I can see of the PDF listed above, the breaker panels that support
special slots for tandems look quite different from the box I have which is
a series of alternating metal fingers running down the heavy black plastic
"spine" of the panel.
http://en.wikipedia.org/wiki/Circuit_total_limitation
Talks about CTL being in place since 1969 and replacement breakers being
non-CTL. Even if the panel ends up "dangerously overloaded" isn't the main
breaker supposed to trip before anything bad happens?
--
Bobby G.