Half the house is giving me a major headach.


Old 12-03-13, 04:40 PM
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Join Date: Dec 2013
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Half the house is giving me a major headach.

Hello all,

New to the forum, but seems like a great place..looking forward to contributing as much as possible.

I'm having an issue with my house, I'm homing you all can help.

I recently decided to renovate two of the bedrooms in my home. Since I was ripping everything out to almost the studs, I decided it was time to put some new runs in for the electrical as well, since they were previous tied in to the rest of the house.

When I started, a 3 phase wire ran from the box, the red and black were both hooked into independent breakers (on different legs of the box for that matter). They shared the common neutral. They then split at a box in the basement to go on and power the two rooms, one on the red, and one on the black, then the red powered the living room and the black the hallway lights.

Leg A - Room 1 - Hallway light
Leg B - Room 2 - Livingroom.

Since it ran so much, we were poping breakers. I removed all the lines, put the two bedrooms on each of their own line (new from the breaker both on the same leg) and jumped the connection right from that split downstairs to the livingroom and hallway respectively.

Finished the first room, every things fine. Next day finish the second and we started running into issues. (Keep in mind on the new setup both rooms run off the same leg of the box).

My issue is periodically, half of the house will go out. It is not the half of the main that the two rooms is on but it is the side that the hallway (not living room) is on. I figured I messed up the hallway some how, shut the breaker off and went to bed to figure out in the morning. I woke up in the morning to issues still with that half of the breaker.

The only thing I could imagine was that the main from flipping it on and off so much was bad and needed replacing (its about 50 years old). I called the power company, they cut the power off and I replaced the main this morning.

It is 90% better, but the power still periodically still goes off. Previous to changing the main if I turned the stove on and ran up the Amps, it would kill that half of the breaker. Now, it seems to be running fine with the stove on, but flickers every now and then.

Just went off as I'm writing, I ran downstairs and was only showing .5 volts on that half of the leg when it went out. I shut the main and flipped it back on and everything is up and running again 120v. I shut the main and tried the main lines before the main breaker and one was showing weak like 37v then after a second jumped back up to 120.

Does anyone know of any electrical mistake that could cause a crazy issue like this?

Everything works fine, then all of a sudden like a ghost was in the house it'll flicker and go off from time to time, then come back on, on it's own right away, flipping the main usually gets it back on as well.

Any help would be greatly appreciated.

Note: I am not an electrician but I did work with one for a few years, the things I'm doing are also very basic I've checked and double checked.

Also, the two bedrooms that were run on their own lines are not on the side of the breaker that is having the problem. It's the line with the hallway that I literally ran white to white and black to black, it couldn't be anymore simple.

Sorry for the long winded question, but I wanted to be clear.

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Old 12-03-13, 04:51 PM
Join Date: Aug 2009
Location: USA
Posts: 4,941
Just to clear something up, your original setup was what is called a multiwire branch circuit (MWBC). You can share the neutral with two circuits as long as the circuits are not on the same phase. Typically, two breakers next to each other are each on a separate phase.

I am not quite sure what you did with the new wiring. The bedrooms are now powered on brand new cable that goes all the way back to the service panel? Do the two bedrooms use the same circuit breaker, or do they each have their own? The hallway and living room were both connected to the black wire of the old MWBC?
Old 12-03-13, 04:57 PM
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Join Date: Dec 2013
Posts: 19

Yes, the two rooms both run on their own lines directly to the box. They are in a double switch breaker. So they hook into the same bus on the panel, but are independent breakers.

Just to reinforce, the two bedrooms are not on the leg of the box with the issue.

Old 12-03-13, 05:08 PM
Thread Starter
Join Date: Dec 2013
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Also no, they one was powered the living room was powered by the red, and the hall way by the black.

Old Set Up

Phase A - Red Line - Bedroom 1 - Hallway
Phase B - Black Line - Bedroom 2 - Living room

New Set Up

Phase A of box - New Line - Bedroom 1 switch one of breaker A
Phase A of box - New Line - Bedroom 2 switch two of breaker B
Phase A of box - Black Line - Living room - Independent breaker (share neutral)
Phase B of box - Red Line - Hall Way - Independent breaker (share neutral)

Phase B of box is the one with the issue.
Old 12-03-13, 05:19 PM
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I am still confused as to what you did. The new lines do not go to the service panel?
Old 12-03-13, 05:25 PM
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Are you using tandem breaker or a two pole breaker? It makes a difference.

A properly wired MWBC will have the breakers on both hot legs of the panel. Most tandems only grab one leg.
Old 12-03-13, 05:27 PM
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Sorry, I know I am using incorrect terminology and it is probably confusing you.

Each bedroom has its own line, all the way to the panel. The hot on each hooks into its own breaker, but its a double switch breaker that plugs into one tab in the panel, so they are on the same phase.

The MWBC now runs from the panel to a junction box in the basement. At the panel, each is hooked into its own breaker, on its own tabs, different phases of the panel.

Once it reaches the junction box, I ran new lines to connect it to where the living room starts, and where the hallway starts, eliminating the rooms from the circuit.

To reinforce the issue, everything works fine, just had dinner after using the stove, then all of a sudden I'll get a flicker, and it'll go out for a second then come back on. No breakers flip.

Old 12-03-13, 05:30 PM
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Join Date: Dec 2013
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The MBWC is hooked into their own legs of the panel on independent breakers.

However, each bedroom is hooked into independent sides of the tandem breaker, but they do not share a neutral anywhere in the circuit and are both functioning just fine during the momentary outage as they (and the living room) are on Side A of the breaker, the hallway (side with the issues) is on Side B which entirely goes out.
Old 12-03-13, 05:52 PM
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I think its worth it to note, I turned off the breaker to the hallway one morning which is the only line I worked on, on the effected side, and the problem persisted even with it off.

Is their really something that can make the electric just shut off for a second and then come back, without popping a breaker?
Old 12-03-13, 06:25 PM
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Power on that leg just went out again, ran downstairs with my volt meter and shut the main all together.

Tested the lines with the house disconnected all together, hooked up the volt meter to the lines from outside directly from the meter and the bad line was all over, 17v, 37v, .5v, 12v, 17v...the other was a steady 120.

Has to be a problem outside the house and just a coincidence it happened as I was doing some electrical work.

Calling the POCO now....
Old 12-03-13, 07:39 PM
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Posts: 9,379
Your partial power outage is probably caused by a loose connection or bad main breaker. You said the panel is 50 years old and you replaced the main breaker, but was it new or a used one. Have you told the power company about the problem and asked them to check for loose connections? I'd do that first and then move on to the meter socket and then to the main breaker. It sounds as if the problem is at the main breaker, but it really could be anywhere.

When I started, a 3 phase wire ran from the box, the red and black were both hooked into independent breakers (on different legs of the box for that matter)
You do not have 3-phase power.

When you added these new circuits to the bedrooms, did you put them on AFCI breakers as required by code?
Old 12-04-13, 10:32 AM
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Join Date: Dec 2013
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POCO came this morning and swapped all the wires to the pole, and cleaned the contacts on the meter. Everything seems to be running normal now since they left a few hours ago.

As far as the three phase, I understand I don't have three phase electric, I have two, but it was a 12-3 wire.

And yes, they are the correct breakers, whenever I do new runs to the panel I change the breaker. I'm going to swap them all out soon enough, just want to buy them in bulk (since most are 15AMP tandum) rather then getting ripped off one at a time at home depot.

Thanks for all the help!
Old 12-04-13, 10:41 AM
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Glad the electric company got you fixed up. Thanks for letting us know.
I have two [phase]
No Single phase. 2-phase is obsolete and was commercial only. 3-phase replaced it.

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