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So I bought new outlets to replace the old ones in my house and everything was going fine until I reached the kitchen. The panel switch for this particular plug is split between two (a/b) (if that makes any difference). When I put the new plug in, I can’t turn the switch in the panel on as it trips instantly. As soon as I put the old one back, it had no problem.

Why is this happening? I don’t think there’s any difference between the two of them other than the fact that this ones newer.

Any ideas?

Wiring outlet

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    Try reading this. – Harper - Reinstate Monica Feb 1 at 1:44
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    Is that thing called a "plug" in Canada? I would have called it a "receptacle", "outlet" or "socket", but a "plug" means the (male) counterpart to me. – TooTea Feb 1 at 13:31
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    We’ll refer to it as a “wall plug” loosely but was writing quickly and missed that in the title. As you can see at the start of my question, I referred to it as an outlet. – ACanadianCoder Feb 1 at 14:03
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    Usual term is receptacle, but outlet is OK - especially if you pick up last year's model at...the outlet store :-) – manassehkatz-Moving 2 Codidact Feb 1 at 15:26
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    @Freiheit that’s an optical illusion through the photo. There’s no tight loops. – ACanadianCoder Feb 1 at 19:29
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TL;DR Remove the tab on the hot (red/black) side

"A/B" plus the symptoms sounds like you have a Multi Wire Branch Circuit or MWBC. With an MWBC, you can have the top receptacle's hot on one part of the circuit and the bottom receptacle's hot on the other part of the circuit. Each receptacle is then 120V hot-to-neutral but the two hots are 240V apart. With the tab removed on the hot (red/black) side, the two circuits are separate on hot but share neutral. With the tab in place (factory default), you have a short circuit between the two hots - 240V at maximum possible current, which quickly (and correctly) trips the breaker.

Remove the tab, only on the hot side, and everything should work.

While you're at it, check the "A/B". There should be a common shutoff - i.e., either they are part of a double-breaker or have a "handle tie" between the two parts. If you are not sure, upload a picture of the breaker panel.

GFCI

Because this is in the kitchen, it should be (must be on many new installations, depending on location) GFCI-protected. With non-MWBC circuits, this can be done at the receptacle or breaker. With MWBC, this can be done (practically speaking) only at the breaker. If your breaker has a "TEST" button, then you are probably fine. If not, upload a picture to get some advice.

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    Ah this makes sense. Thanks for the thorough answer. Also, there’s a handle tie between the two parts in my panel. – ACanadianCoder Jan 31 at 19:02
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    In some jurisdictions within Canada, kitchen outlets need to be gfci-protected only within a certain distance, about 4 ft of a sink (different provinces have settled on a different precise number of cm); outlets on other counters may be split 15A or single-circuit 20A T-slots at the homeowner's choice. The OP seems to be in Canada (where the split circuits seem to have been rather more common). Given that this pair of breakers have tripped on some number of dead shorts, it might be a good idea to replace it with a new one. – CCTO Feb 1 at 4:24
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    "With the table in place" should say "tab". It's only a 2-character change, so I can't edit it myself. – Graham Feb 1 at 15:05
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    I can't believe the number of MWBC posts I've seen recently. A decade of never seeing it and then wham. I wonder if this was due to construction cost reductions or code changes that now, say 15 years after built, everything is being redone. – J.Hirsch Feb 1 at 15:47
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    @J.Hirsch Probably more to with Covid-19. A lot of people are remodeling/renovating as they have time to spare because they can't go anywhere due to lockdown and money to spare because they can't go on holiday. DIY stores do brisk business these days. – Tonny Feb 1 at 15:53
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You need to remove the tab between the brass screws on the outlet. This will separate the two hot feeds.

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    But only between the brass (hot) screws. Don't remove the tab between the silver (neutral) screws. – AndyB Feb 1 at 4:23

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