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I changed three very old electrical outlets in my grandmother's home today, and was thinking afterward about how they were wired. After finishing they did work when tested, with a simple desk lamp, but I haven't tried anything more complex or sensitive to wiring.

The outlets I removed did not appear to have break off tabs at all, and the outlets are not switched. I was thinking that they were just ancient, at least 70's era, and the screw plates shared an unrestricted contact on both hot and neutral.

The two outlets in question have two hot wires, two neutral, and a ground. I wired up the new outlets and left the metal tabs intact. I am worried now that that may eventually cause a problem, and hopefully someone can confirm or deny for me. If it is suggested that I should remove the hot side's metal break-off tab, I will do so immediately. If it will not cause issues, then I will leave it as-is.

What should I do?

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    Can you post photos looking into the back of the boxes for said outlets please? – ThreePhaseEel Oct 5 at 1:44
  • I want a photo looking into the back of the box in the wall, not of the tab on the receptacle – ThreePhaseEel Oct 5 at 2:01
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    It can cause big trouble. Have any light switches stopped working? Did any breakers insta- trip when you first turned them back on? – Harper - Reinstate Monica Oct 5 at 3:10
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    I can't imagine that this could be a problem without immediately blowing a breaker when you installed it. – Glenn Willen Oct 5 at 3:56
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    @Gleen, Harper all light switches seemed to work, the breakers did not trip once reset nor with a lamp plugged in to test. – John M Oct 5 at 4:09
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If the outlets test correctly and are functioning as intended then you should leave the break off tabs alone.

The break off tabs are there so that you can power the top and bottom outlets differently. Most commonly so that you can have one of the outlets on a switch. A less common and generally inadvisable reason is so that you can have each outlet on a different circuit.

If you aren't trying to do either of these things then leave the tabs intact. Older outlets often don't have break off tabs. The only thing I would check to make sure of is that your outlet is rated to handle the amperage of the circuit.

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"The two outlets in question have two hot wires, two neutral, and a ground."

Are you saying that when not connected, the two "hot wires" both supplied voltage?

If so, the tabs should definitely be removed. E.g. perhaps one of them is controlled by a wall-switch elsewhere in the room (and it might have been removed and plastered over years ago).

But in the more common situation where only one of them is actually powered, the other one supplies power to the next outlet in the chain. In this case the tab should definitely not be removed.

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It's not that unusual for the two sets of connections on the back of an outlet to be used to connect the wires coming from the breaker panel to the wires going to other outlets on the same circuit. However, as you've noted, it's also possible that the wires were on completely separate circuits. If they were on separate circuits, then there are negative consequences to leaving them connected. The negative consequences can be anything from breakers that are immediately tripped (which indicates a hazardous condition) to various other hazardous conditions which could be harmful/annoying now and/or hazardous in the future (various possibilities are discussed in other answers).

Ultimately, the only way that you are going to know if the circuits were connected is to test. You can do that testing by either testing the circuits as they exist in the home (which can be quite inconvenient), or, assuming the outlets you were replacing were functional, you can test the replaced outlets to determine how they were actually connected.

Testing the old outlets

If you still have the old outlets which you removed and you have a continuity meter (e.g. an ohmmeter, or Ohm meter; multimeter; etc.), then you can test and be certain whether the original outlets had the top and bottom plugs connected together or disconnected. Testing the old outlets will allow you to be 100% certain if the top and bottom sockets were connected prior to you doing work.

If you don't have a continuity meter of some sort, then you can probably get assistance from someone at a local hardware store to test the outlets. Just be upfront with the person helping you as to what you are wanting to find out. Most such stores will provide assistance.

However, IMO, you should own something that will serve this testing function if you are wanting to do this type of work. Testers which will perform this function can be quite inexpensive. Having something to do this type of test can resolve many types of situations.

If you have a meter of some sort:
With no wires connected to the back of the outlet, check the continuity (i.e. resistance) between the connections in the same position in both the top and bottom plugs. You can do this either by using the screw connections where the wires were actually connected prior to removal, or you can insert the probes for the tester/meter into the holes where plugs would normally go (i.e. actually insert the test probes into the holes in the face of the outlet, where you'd insert normal plugs, but between where you'd insert two different plugs). If inserting into the socket slots, using the test probes available on most meters, you will often need to wiggle the probes around to actually make contact inside the slots the plugs go in.

If the upper and lower sockets are connected, you should easily read 0 Ohms across the connections for the top and bottom sockets. If they were disconnected, then you should be unable to read a low resistance between at least one pair of slots/screws on either the left or right side of the outlet.

Ideally, you would do this testing as you removed each individual outlet and either break off the tabs, or not, as indicated for each outlet as you were replacing the old one. Given that you have already removed the outlets and almost certainly have not tracked which outlet came out of which electrical box, doing this testing now will only tell you A) If all of the outlets have the top and bottom connected, then there's no need to worry; or B) the number of outlets which you need to identify and break the tabs off of; and/or C) that you need to break the tabs off of all of the outlets.

If your situation is not (A) or (C), then you will need to go through and test each location where you replaced an outlet to determine which one had the top and bottom on separate circuits. It will be quite helpful to have an appropriate tester in order to do that. But, at least you know from your testing of the removed outlets how many of the outlets you need to positively identify as the ones which need the tabs broken off (i.e. if only one of the old ones had the top and bottom disconnected, you only need to find one box where that needs to be the case and can stop investigating once you've found it).

  • Guys, I cannot thank you all enough for your time and advice. I dug the old outlets out of the recycle bin and ran resistance through them with my multimeter, pinned on the same side screws as well as the same side slots, top and bottom, and found them to zero out both ways, either side. I have to admit, I felt really stupid at not thinking of that before asking for help. I promise, I'm not a complete idiot. Thank you all again. – John M Oct 5 at 21:37
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"The two outlets in question have two hot wires, two neutral, and a ground."

That could be the abovementioned "two different circuits". If the two hot wires are not supplied via the same breaker, and if they both supply power (as opposed to powering something else downstream) that is the case.

Bridging two circuits is bad news. In a single phase system, it interferes with the functionality of the breakers - in a way that can allow a plugged in device to get away with drawing severe overcurrent, or create a false sense of safety when only one breaker is switched off but the user assumes that is sufficient to make the circuit safe to work on. In a two or three phase system, if both circuits are supplied from different phases, you create a capital short circuit.

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John, don’t take this the wrong way but please get someone qualified to repair/replace the electrical outlets, switches, etc that need to be replaced in your grandmothers house before you run into an issue.

The answer to your question was in your post but your electrical knowledge did not present it to you. “The screw plates had an unrestricted contact on both the hot and neutral”. So many here giving you complicated answers that are missing the simplicity of it as well.

You had a standard outlet prior to the addition of the break off tab which allows independent power to each side of the outlet. One set of wires was the IN for power and the other set was the OUT to feed power to the next “item” in the circuit. The unrestricted plate allowed the power come in on one set of wires and leave on the other just as the break off tab does on modern outlets. Last item in the circuit will only have one set of wires to it.

Leave the tabs or you will kill power to the remaining items on the circuit.

  • Hello, and welcome to Home Improvement. Thanks for the answer; keep 'em coming. And, you should probably take our tour so you'll know how best to contribute here. – Daniel Griscom Oct 7 at 0:09

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