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My wife and I bought a house and had most of the outlets rewired (to add a ground wire mainly) when we bought the house. Unfortunately, one outlet in the laundry closet (which is there the laundry machine plugs in) did not get rewired for some reason.

The washer was working ok even if the outlet was not grounded (despite having no GFCI and a 3-prong plug -> It's a no-no, but it's how we bought the house).

We recently had our furnace removed and we had a heat pump installed in the attic. A lot of work (including some electrical work) was done and now, the washer is not working any more. I used an outlet tester and the outlet is now dead. The washer works fine when connected with an extension cord to another outlet.

Let's name the broken outlet as outlet A and the outlet that I used to test the washer as outlet B. Outlet B is the closest outlet to outlet A and it is newly rewired 2 years ago by an electrician (it is also grounded).

I called the HVAC company and they sent someone to check it out (since, in my opinion it was their fault: outlet was working before they started the job and not working after). The guy they sent did not speak English so I got some information from his boss (who was acting as a translator over the phone). The worker said he traced the cable from outlet A in the attic and traced it to outlet B (not surprisingly since outlet B was the closest outlet). He opened up outlet A and found two disconnected cables. He hooked them to the outlet and then, the breakers tripped so he gave up.

When I got home, I did the following:
1) I checked for shorts in outlet A (between hot and neutral) -> no short
2) I plugged a cable in outlet A (the broken outlet) and ran it next to outlet B. I then measured connectivity between outlet A (through the cable) and the wires that were in the same box as outlet B. Wires were indeed connected.
3) I removed outlet A and capped the loose cables with wire nuts and connected the cables in the outlet B box (that lead to outlet A) to outlet B. The breakers tripped again.

At this point, I am puzzled. Why would the breakers trip when there is no load? My only potential explanation is that either that outlet is also connected to some other circuit and I am crossing two circuits when I make the connection in the outlet B box or that somehow the Romex cable insulation got punctured and it making some electrical connection to something else.

The HVAC company says the breakers are tripping because the outlet is not grounded and I should replace my ARC breakers with regular breakers. This makes no sense to me (but I am not an expert). How would be breaker know that I have two loose wires connected to hot and neutral when there is no load connected?

Here are some questions: 1) Does anyone know what is going on? This is more out of curiosity as probably the correct fix is to rewire the outlet. 2) Is it possible to fish new Romex cable using the existing cable so I do not have to drill holes in the drywall? One of the walls has insulation.

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    Try disconnecting the A-B cable from your working outlet-B. If that cable is damaged it may be the cause of your problems. – brhans Oct 4 '17 at 21:55
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    What kind of breaker is feeding the circuit in question? – ThreePhaseEel Oct 4 '17 at 22:25
  • Removing the A-B cable definitely fixes the problem of the breakers tripping. Unfortunately, it does not hep with my using the washing machine :(. – Octavian Oct 5 '17 at 0:00
  • To amplify 3PhaseEel's question: Is the circuit breaker for this circuit a GFI or AFCI? – wallyk Dec 12 '17 at 23:36
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Good diagnostic info!

What happened: there is a short in either the cable between outlet A and B, or in the receptacle at outlet B. Have you tested connectivity/resistance between the poles on outlet B? You might find the short. If this setup was kinda sketchy in the first place, other electrical work may have disturbed it just enough to cause a short; it's happened to me when working around around 75-year-old wiring.

If the current wiring was fished through the walls, it is possible to use it to pull new wiring. However, if it was installed while the walls were open, it will probably be stapled in. Horizontal runs are also not likely to be fished. So depending on the location of outlet B, it may be easier to run new wiring (e.g. down the wall into your basement) than replace the existing.

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