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The situation is the following: We had a microwave and a toaster oven connected to the same receptacle in the kitchen – actually, even to the same socket of that 2-plug receptacle, using one of these extender things:

3 outlet extender

Now, I know that’s not necessarily a good idea, but we weren’t planning to use both at the same time. Of course, predictably, at some point we forgot not to do that and ran both the microwave and toaster ovens simultaneously. After a few minutes of that, they both turned off and the top half of the receptacle didn’t work anymore. However, the bottom one still did, so we just used that one instead and I assumed that something in the top part had fried, making a note to replace the receptacle at some point.

Before I got to that, it unfortunately happened again (yes, I know it’s stupid). And here’s the problem: Even after replacing the receptacle, it still doesn’t work! (Tested directly without without the extender, of course.) While replacing it, I couldn’t find any signs of damage (neither on the receptacle nor on the wires), and as far as I can tell, none of the fuses blew and all other receptacles are still working (I can’t really be sure, though).

So it seems clear that the second time around, something different must have happened than the first time, since initially only half of the receptacle stopped working, i. e. the rest of the circuit must’ve been completely unaffected. What are the possibilities here?

  • Blown fuse. Possible, but as I said, everything else in the house still seems to be working, and as far as I can tell I tried replacing each of them individually (house is from the 1980s with old fuses, so it’s not necessarily straightforward to tell if any have triggered.)
  • Damage to the wiring. This answer has some good information, but since there’s no visible damage and the wiring is different, I’m not sure how much applies here. And also, I would think that the fuses should prevent damage if the load becomes too large?
  • Something else?

Wiring: There’s one black and one red (hot) wire, one white neutral, and a bare ground connected to the receptacle.

This is in Ontario, Canada.

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    On the old receptacle, was the tab broken off between the hot wires? How about between the neutral wires?
    – Harper - Reinstate Monica
    Commented Mar 5, 2023 at 22:49
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    Ontario was using circuit breakers back in the 1980s. Usually not the receptacle that goes bad, unless smoke/flame/melting occurs.
    – crip659
    Commented Mar 5, 2023 at 22:50
  • @crip659 Well, I’m not 100% certain about the terminology, but all I can say is that there are fuses – two each in “blocks” that you pull out, as well as screw-in ones for the lights.
    – Socob
    Commented Mar 5, 2023 at 22:55
  • They are fuses, just odd to find in a 1980s house. They were more 1960s(first house). Just don't use pennies to fix.
    – crip659
    Commented Mar 5, 2023 at 23:03
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    @AloysiusDefenestrate Copper, although it turns out to just have been a blown fuse in the end after all!
    – Socob
    Commented Mar 6, 2023 at 4:38

2 Answers 2

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You describe a typical multiwire branch circuit (MWBC) as is normal for kitchen receptacles in the USA & Canada. Each half of the receptacle (red wire-black wire) would be protected by a separate fuse.

You blew the fuse (Egads, really? Still? Fuses? How...quaint) serving one half of it, and then you blew the fuse serving the other half of it.

Unclear if your replacement fuses were already blown before you installed them, or what the issue is there. If you have a multimeter you can check them for continuity to see if they are blown or not.

If you did the usual "person not familiar with MWBCs" trick of not breaking the tab between the hots when you replaced the receptacle, the new fuses would have blown instantly, so it's probably that. The original receptacle is probably fine.

If you either break the hot tab or put back the original receptacle, and install two good fuses, you can plug both devices into the receptacle, top and bottom, and run them without overloading, since top and bottom are two separate circuits. Using the extender to put them both on one of the two circuits was your error, here. Save that for something trivial like a can opener, not a heavy load.

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    Ah! I assumed the purpose of the red/black wires was for linking the electrical boxes together, (as I’ve seen in other boxes in the house), but you may be right that they’re on different fuses! Only trouble is, there’s not that many fuses on the panel, so at least some stuff must be on the same ones. But I will investigate given that information! If this is true I probably just tried the wrong fuses, but I’m probably also guilty of the tab thing you mention…
    – Socob
    Commented Mar 5, 2023 at 22:53
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    After some more thorough fuse tests, you were absolutely correct! The original receptacle was perfectly fine, but I assumed the issue was with that because I didn’t know about MWBCs. And indeed, had I known, I obviously would’ve just put the two heavy loads on the two separate slots, but didn’t bother because I’d assumed that everything was just on the same circuit anyway!
    – Socob
    Commented Mar 6, 2023 at 4:35
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    ...and now you know!
    – Ecnerwal
    Commented Mar 6, 2023 at 13:08
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You overloaded the circuit. Hopefully the repair problem so far is not finding the fuses, not worse. You need to find the fuses and if you cannot you need to trace it back, if it connects to another plug or junction box which I expect it could have burnt the wire off there.

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