Just got my Sense home energy monitor and was going to do the install when I realized that the space I thought I had free in my (Square D) electrical panel was actually occupied by a double wide, double pole breaker:

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I had not seen these before so I did some research and found that these breakers were made by Square D back in the 60s/70s but have since been obsoleted. From what I've read, you can replace these double wide breakers with the QO style breakers which only take up one side of the panel.

Doing this will free up the space I need to install the double-pole breaker for the Sense. My question is, does anyone know if this is kosher? Note: this breaker feeds a sub-panel.

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  • I don't know the exact model you are asking about but square d makes "double stuff" 2 breakers in 1 slot for 15, 20 & 30 amp breakers, 120v for the smaller loads ,iIf your panel can accept them. Then you can have room to add your new double pole breaker .
    – Ed Beal
    Commented Oct 14, 2016 at 1:54
  • Can you post a photo of the panel directory/wiring diagram label? Commented Oct 14, 2016 at 2:03
  • I updated my post with a photo of the wiring diagram. Unfortunately there is a wire obscuring it but this is the best one I have on hand.
    – Jason
    Commented Oct 14, 2016 at 3:49
  • If by "double stuff" you mean a tandem breaker, my panel does not support that.
    – Jason
    Commented Oct 14, 2016 at 3:55

1 Answer 1


Go ahead and replace the Q12100 with a QO2100 and install the breaker for the Sense. You'll be fine.

P.S. regarding double-stuff/tandem breakers: since your panel is class CTL, it does not support them in any slots.

  • The panel is a CTL class panel. There is a sticker that says: "CLASS C.T.L. PANELBOARD ISSUE NO. 8213 SQUARE D COMPANY"
    – Jason
    Commented Oct 14, 2016 at 16:48
  • 1
    Thanks, for your reply. Sounds like my plan is kosher. Quick question, is there a trick to getting these Q1 breakers out or do you just pull really hard?
    – Jason
    Commented Oct 14, 2016 at 16:50

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