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Square D backfeed breaker, does it need to be a special kind of breaker?

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  • Square D backfeed breaker, does it need to be a special kind of breaker?

    So I am in the middle of my installation, main panel will be later, but I was just thinking about it. Its a Square D panel, can I use any Square D breaker that is appropriately rated (25A in my case) ? Or does it need to be a special breaker for backfeeding the panel?

    I am connecting Enphase combiner to it (through AC disconnect box). 15 panels at 1.31A

  • #2
    The standard Square D Qo breakers are backfeed rated. I'm not sure about Square D Homeline.
    7kW Roof PV, APsystems QS1 micros, Nissan Leaf EV

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    • #3
      Originally posted by bob-n View Post
      The standard Square D Qo breakers are backfeed rated. I'm not sure about Square D Homeline.
      How would I find out? Would the markings on the breaker indicate it? What makes a breaker backfeed rated? can you tell by just looking at it?

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      • #4
        A breaker sees current, not voltage. If it cannot see both, it does not know which way
        the power flows. Do use good quality, here running at 75% of rating 8 hours of every
        sunny day, I blew one. Maybe it was one of those counterfeit. Bruce Roe

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        • #5
          "How would I find out?"

          The best way to be sure is to contact the manufacturer. That's what I did and learned that almost all of the Qo breakers are back-feed compatible. The only ones I was told to avoid were the ones with sensors, like arc fault sensors. As Bruce said, a normal breaker doesn't know which way the current is flowing.
          7kW Roof PV, APsystems QS1 micros, Nissan Leaf EV

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          • #6
            The Schneider website has lots of information on Square D breakers.
            2.2kw Suntech mono, Classic 200, NEW Trace SW4024

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            • #7
              Are you sure you even need a breaker ? Some AHJ allow inverter AC output to be connected to the service entrance cables between your meter and your load center's main breaker using "line tap connectors". Of course, you would need some sort of over-current protection between the inverter and the line taps, like a fused disconnect box.

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              • #8
                Originally posted by littleharbor View Post
                The Schneider website has lots of information on Square D breakers.
                https://www.se.com/us/en/faqs/FA121271/


                "Any circuit breaker that does NOT have Line and Load (or + and - on DC breakers) identifying markings may be reverse fed. This includes all Square D industrial thermal-magnetic and electronic trip circuit breakers. See the compiled list below:

                Breakers that can be back fed and exceptions (This is a work in process list, it is probably not inclusive and does not yet include legacy breakers): HOM (Excludes those with suffix GFI, EPD, AFI, CAFI and DF.)
                QO and QOB (Excludes those with suffix GFI, EPD, EPE, AFI, CAFI and DF.)
                QOU
                ....

                "

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                • #9
                  The QO breakers are only rated for 12 Vdc systems. The QOU breakers OTOH are rated for up to 48 volt DC systems.

                  QOB breakers are new to me. Going to read up on them.
                  2.2kw Suntech mono, Classic 200, NEW Trace SW4024

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                  • #10
                    Upon further review I see the QOB breakers are miniaturized QO breakers AND they all seem to be rated for 48 volts now. The QOU line boasts "Over current and switching of both AC and DC systems".

                    The HOM Homeline breakers are NOT rated for DC voltage.
                    2.2kw Suntech mono, Classic 200, NEW Trace SW4024

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                    • #11
                      Originally posted by littleharbor View Post
                      Upon further review I see the QOB breakers are miniaturized QO breakers AND they all seem to be rated for 48 volts now. The QOU line boasts "Over current and switching of both AC and DC systems".

                      The HOM Homeline breakers are NOT rated for DC voltage.
                      Im using Enphase microinverters, so its AC current all the way down from the panels. And this is the breaker I am trying to use:

                      square-d-2-pole-breakers-hom230cp-64_1000.jpg

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                      • #12
                        Originally posted by Duxa View Post
                        So I am in the middle of my installation, main panel will be later, but I was just thinking about it. Its a Square D panel, can I use any Square D breaker that is appropriately rated (25A in my case) ? Or does it need to be a special breaker for backfeeding the panel?

                        I am connecting Enphase combiner to it (through AC disconnect box). 15 panels at 1.31A
                        The breaker is to protect the wire and your wire should be at least #10 AWG to carry 20 Amps continuous current. I don't recall the details of your install but if the distance is long you could always upgrade the wire to reduce voltage loss. I think the branch circuits from the combiner to the microinverters are 20 Amp circuits which can carry 16 Amps continuous.
                        9 kW solar, 42kWh LFP storage. EV owner since 2012

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