I needed to add a circuit to my Murray 200A panel. The panel was installed 10 years ago.
I purchased a Murray twin breaker from Lowes, and I installed in the panel with no problem.
Then I did some reading that most 40 ckt panels will not accept a twin breaker. And then I read the inside label of my panel, it did not indicate any twin breakers could be used
So now I'm confused. How was this twin breaker able to be installed? I thought these panels had provisions or interlocks that prevented these breakers form being installed?
The article does point out that the NEC removed the 42 pole limit on
panelboards so these are a little murkier. When the panel was listed
adding a tandem breaker might have exceeded the 42 limit, now it
I would bet that there are 2 slots in that 40 breaker panel where CTL
breakers are allowed. (probably right next to the main)
That is an old style that are fairly hard to find these days but they
did allow using handle ties to get a tandem 240 v pair. It is not
legal to do that now. Breakers on 240v circuits require internal trip
for both poles. You could use the handle tied breakers on a multiwire
circuit. (AKA Edison, Shared neutral etc)
If the panel indicates so, yes, in those locations.
If it doesn't say it is, it isn't... :)
And, the pictures at the top indicate it doesn't allow _any_ tandem
breakers (they're no double lines in any locations). See how the
samples in the previous link show where they are/aren't allowed...
On Sunday, September 28, 2014 7:21:11 PM UTC-4, dpb wrote:
Confusing to say the least. Even though its not shown on the label, I thoug
ht the article says something to the effect that if the panel is not CTL ra
ted ( which it does not appear to be because I do not see anything on the l
abel saying "MAX circuits 42'), then I was under the assumption it could be
On Sunday, September 28, 2014 6:25:50 PM UTC-4, Mikepier wrote:
*The catalog number says it all. 40 spaces, 40 circuits, period. One thin
g that I noticed on that label is the notation indicating the location wher
e a backfed circuit breaker must go in slots #1 and #3. This may limit the
use of third party generator interlock kits which tend to be located in th
e #2 and #4 slots. Most likely Murray (Siemens) has their own interlock ki
t for this panel. Just an observation. Sorry to digress.
That would appear to be the case. Ok no big deal. I actually used a twin breaker to re-arrange some breakers in my panel to accommodate putting a 30A backfed generator inlet on the top right.
I actually have plenty of spaces left in my panel, but one of the 15A circuits in the panel would not reach to the new spot of the breaker, so to avoid extending it with another wire and wire nut, I just used a twin.
Interesting thread. I never knew that there technically could be a legal or
other issue when using a tandem breaker in a panel. I just assumed that if
it fit in the slot and it worked, it was okay to use.
But, since you have plenty of extra spaces, and you can put in a regular
breaker by just using a wire nut inside the panel extending the existing
wire, I think that I would have chosen that option rather than buying and
putting in a tandem breaker. That would eliminate the whole question or
issue of whether using a tandem breaker in that panel is proper or legal
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