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Good day.

I hooked up Sense monitor by adding a 240v breaker to my panel (bottom 2 slots on one leg). Problem is Sense has detected that my breaker is sitting on two slots that occupy the same phase/leg of the panel.

How can I tell of there is 2 slots in the electrical panel that will occupy both phase/legs so that Sense will work properly? From reading I suspect Sense monitor power needs to be connected to both phases/legs.

Panel: Stab-lok CAT NO. BE 116-32 MAINS 125 AMP.MAX. 120/240 VOLTS A.C. 1 Phase 3 Wire Y24-863A

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    If it is a 240v (two pole) breaker that is designed for that panel, it should hit both legs. If you test the voltage between the two lugs on the breaker is it 240v? – JPhi1618 May 20 at 15:56
  • Added some images to original post. – Alister55 May 20 at 20:08
  • Sense Response: we noticed that your Sense power wires are drawing from the same phase, or leg. of your electrical panel. It's possible that the power wires were either installed on a tandem breaker or, if you installed on a 240V breaker, Sense is sitting on two slots that occupy the same phase/leg of the panel. While the 240V breaker does ensure that it draws power from two different slots on the panel, depending on where it is placed, those two slots can be drawing from the same phase. To put it into perspective, this is what the phase pattern of the left side of your panel could look like: – Alister55 May 20 at 20:15
  • phase A phase B phase A phase B phase B phase B If your double breaker is attached on a spot where the phase repeats (consecutive phase A), such as towards the bottom, you may run into the issue I've described. I cannot say for sure what your panel phase map is, but you should refer to what is printed on the panel, or reach out to your electrician. – Alister55 May 20 at 20:15
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    This is a straight up guess, but it looks like all of your other 240v breakers straddle one of those thick lines on the breaker numbering label. So the order of the slots could be AA|BB|AA|BB. – JPhi1618 May 20 at 20:22
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Stab-Lok is a PROBLEM

See, for example, What can I do about a breaker that trips frequently on a Stab-Lok panel?

So first read up on Stab-Lok, post a picture of your panel (the pros will recognize it and tell you if it really is a fire hazard, etc.) and determine if this is a concern. If it is a real concern, then dealing with replacement is a much higher priority than hooking up the Sense monitor.

How it SHOULD Work

On many panels (I don't know if Stab-Lok is supposed to work this way or not), a true double (240V) breaker will always hit both legs. The exception is a double-stuff breaker, where it is really two-breakers-in-one. In that case, it normally only hits one leg, and the exception is if it can actually be 1/2 of one leg and 1/2 of the other leg. But that, as I understand it, is only on certain panels where you can have a quad == 4 in one, but really 4 in 2 - i.e., a double-space breaker that has 4 individual breakers, two on one leg, two on the other leg, with the result that the inner breakers can function together as a "double 240V breaker".

FIRST FIGURE OUT THE STAB-LOK!

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    I will have a read on the Stab-lok issue to be sure it isn't a fire hazard. Hate the idea of having to replace the panel but better than the house burning down. I would think that it's not a problem since the panel has been inspected but because it's labeled inspected for the garage power maybe they didn't look into this panel. As far as the Sense issue goes, I noticed an circuit image on the inside of the panel cover I pulled off and will look at that and post if I can make sense of it. – Alister55 May 20 at 20:34
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    "Inspected" can mean: "Inspected at time of initial installation" - which would mean nothing because at the time the hazards were not well known. – manassehkatz May 20 at 20:39
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    Date says inspected 1991. Still reading about the issue and it's a little concerning. Thinking maybe I will contact a local electrician and just have the entire panel replaced. – Alister55 May 20 at 20:45
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    You don't know what that inspection means. The only way to be sure is to get someone familiar with the Stab-Lok problem to look at your panel. There is no room for "maybe" here. You must call an electrician. – longneck May 21 at 13:19
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    Checking with an old buddy that is an electrician to see if he knows anything about the Stab-lok panels. If he doesn't I am going to see if I can find a local electrician that knows of this problem and do an inspection/review so find out if the panel should be replaced. – Alister55 May 21 at 14:13
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The answer from manassehkatz (not related, but we do know each other :-) ) is very important, but it doesn't actually tell you what you want to know.

If you have a voltage meter or multimeter, you can very easily find out whether the poles of this breaker are on the same phase or different phases. (Important: if you are using a multimeter, make sure it is set to voltage measurement, not one of the other settings, before you touch the probes to anything.)

To test, touch one meter probe to one breaker terminal and the other probe to the other terminal. If you read 240v, you are properly on both phases. If you read 0v, you have both on the same phase. You can do this same test on other two-pole breakers too to see what it should look like.

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    Which is probably what the Sense is doing internally. But a multimeter is a lot faster. – manassehkatz May 21 at 13:28
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I did manage to figure out the Sense problem by looking at the specs diagram for the panel. It showed a set of 2 poles with one that used phase A and another that used phase B.

Sense issue is resolved but now I need to get this panel looked at and replace if electrician states it is a problem/fire hazard.

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