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Half of the Condo I rent is losing power sporadically, sometimes for minutes other times for hours. We have power loss to our kitchen lights, microwave, outlet above dishwasher, the dishwasher, entire bedroom, both bathrooms, and the AC unit. Living room lights and outlets, fridge, oven, & foyer light work fine and never go out. We also have occasional flickering lights in the rooms with the power loss. I would say its the breaker, however the issue isn't just on one side of the breaker, its completely random. Also, when the power goes out we are using minimal electricity (usually just a light or two) so we are definitely not overloading the system. It's also important to note that the breaker NEVER trips and we just have to wait until the power just "magically" comes back on. Any thought? 2 electricians have been in and cannot find the issue yet, thank youenter image description here

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Phase/Leg Out

You have lost one phase or leg (terms vary) of your power. 120/240 power comes in on 3 wires - two hots each 120V from the neutral and 240V from each other. Most breaker panels are designed with alternating legs. Left & right in each row are on the same leg. 240V (dryer, oven, A/C, etc.) use a pair of breakers, one on each leg.

Your electrician should have been able to figure this out. In any case, CALL YOUR ELECTRIC UTILITY and tell them you have an intermittent phase/leg out. They'll check it out for free and fix it if it is on their side, which is very often the case.

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    The moment I read "half" (in the context of residential service; it would be "a third" for commercial 3-phase service) this was my first thought. That it affects alternating breakers for 120V circuits cemented that thought. – Monty Harder Nov 13 at 19:36
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    Also, never ever call the two "electricians" who failed to do this again. – J... Nov 14 at 15:13
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Call your utility and report a power outage

It's not random -- you've lost a phase.

Every other breaker in your panel is on opposite phases of 120V, and 240V breakers grab both. The pattern you are showing means that one of those phases is working fine, and the other one is intermittently dead. See the images in Harper's answer here if you want all the details: What is a tandem breaker (aka duplex, cheater, twin, double-stuff, etc.)?

Very often, the problem is on the utility's side, and they'll come out and check it for free. There's also a possibility that the wire is coming loose on one of your panel's main lugs, but I assume your electrician would have caught this.

Note that in the meantime, you should either shut off your main breaker, and/or shut off all 240V breakers -- since the 240V breakers grab both phases, they can backfeed the dead phase with weird voltages (effectively your 240V loads are now in series with half of your 120V loads), which may damage your devices.

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    Given that the electricians did not diagnose a utility-side fault, I think assuming that they would have caught a loose wire on one of the main lugs is ... generous. – Martin Bonner supports Monica Nov 15 at 15:05
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I have a hunch that the following circuits are dead.

enter image description here

The reason I guess this, is how panels work with the two 120V power buses giving 240V. Check out my diagrams on that and a light bulb may go off in your head! Probably not in your kitchen though.

I'm betting the ones you haven't marked are simply ones you haven't had occasion to use, yet. Since you care about A/C, obviously furnace and fireplace aren't on your radar.

Noting that the top 6 breakers (12 spaces) are all 2-pole breakers. It's possible the 2-pole devices have some small amount of performance due to current leaking through the dead 120V devices. Similarly, the dead 120V circuits will somewhat light up due to the low impedance in the large 240V appliances bringing power over from the other leg.

This is a classic "lost pole".

The described pattern is one pole of your AC power, because of how panels work. So I think you have lost it, probably out at the pole, possibly in meter wiring.

Call the power company and report an outage. They should be out in an hour or two and take care of whatever the problem is at the pole.

The good news is, this is something you are allowed to do as a tenant.

If your condo comes off a central transformer with distribution handled by the condo association, then the problem is probably in their bailiwick. Who do you pay your electricity bill to? That is the question.

Don't contact any more electricians until the PoCo swears it isn't them.

Another theory: mangled panel bus.

If the "red" bus had a serious meltdown right there at the 5th row, it would clobber everything below it. The fireplace being opposite the A/C, maybe you just haven't tested the fireplace.

But this is something an electrician should notice immediately after removing breakers in rows 5-8. There should be visible carnage.

There's a remote possibility: a hacked Rule of Six panel melting down

After all, if we presume that your search was systematic, your outage looks more like this:

enter image description here

And that looks like a classical "Rule of Six" panel. This type avoided having a an expensive >60A main breaker by having 6 large "main breakers" in the top 12 spaces of the panel. The rest of the panel (lower area aka lighting circuits) was fed by one of those breakers, typically in the lower right (where you are having a problem).

My theory is someone "hacked" this Rule of Six panel to feed the lower area without using that lower right breaker, freeing it up for use as a general breaker. Something went wrong with the hack, breaking one leg of the lower area and the breaker in that spot.

However, against that theory is the fact that I see hints of a space for a main breaker. Rule of Six panels did not have main breakers; that was the whole point.

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Could also be a broken neutral. This causes "intermittent" behavoir as you described. In the open neutral case whats going on is that with nothing to force a balanced center between the single 240V split phase, the voltage each side sees becomes a function of what's loading the service at any given moment, fridges kicking on and off, lights being switched on and off as one passes through the house, etc. What was a balanced system forced by the center tap of the utility transformer carrying any imbalance current, ie; the difference current between the sum of sub-phase A loads and sub-phase B loads, now becomes a voltage divider dependant on the total series current A-B squared multiplied by the effective imedence of each segment and then dived between the segments When A and B are truly balanced the neutral doesn't have anything to do. Truly balanced doest make a stable showing in the real world world for long, but Mostly balanced does and can let a missing neutral go unnoticed for quite a while. Maybe a subtle, poltergiesty feel about the place as minor shifts in the center take place in circuits power the visual voltmeters, the lights. The someone plugs in a space heater into phase A and on phase B the tv's, stereos, game consoles, fancy appliances, routers, modems, IOT crap, yada yada all smoke thier input voltage regulators as the voltage goes over 200V. OK, Maybe its not that bad these days, A lot of power supplies are self adjusting to input these days.

I would unplug anyting I loved none the less. With that done a couple of quick and dirty tests could lock in the diagnosis.

If you can measure the voltage on the meter side of the main breaker, or as close to the point where its thier baby and not yours as is possible (the demarkation point), and you have full voltage across the 2 lines, go turn on a decent single phase load just long enough to get a measurment at the demark, between either sub=phase and the neutral. Test 1) If the neutral is broken upstream a hair dryer on an otherwise unloaded system will swing the center way off center, donating voltage to the other leg until it starves itself enough to act as a regulator. You will observe a significant difference in the the voltage between L1-N and L2-N. Of couse a lamp plugged in would give you the same info but not confirmation all the way out to the demark.

If test 1 does not show a shifting middle, What does it show? If you get 120v-N on either side, and you are experincing the fault....

Test 2) If you have an electric (240V) dryer turn it on high heat. if the affected lights come on suddenly its a missing sub-phase, or portion of it between the panel feeding said area and the main, if they were both present in test 1, which should have been test 0, or "Does it show low or no voltage on one leg at the sevice entrance." The low impedance of the dryers heater coils will couple A to B with the live one holding up the dead one, within limits. Good for a test or even an emergency but I wouldn't run it like that for long.

Of course, There is a possibility for the same type of problems to occuring as a result of the same problems but on a sub-feeder or even branch circuit breaker within the "your baby" territory of your own panels. On a multiwire branch ciruit both conditions are possible and the overpriced arc fault breakers wont help your poor equipment in an open neutral case.

The bad thing about the open neutral case is the likely chance of a big voltage ending up on expensive electronics during one of those center shifting events. It doesnt even have to be on, just plugged in. In microseconds the damage is done.

The utilty here, PGE, used to provide a claim form for equipment failure in a "thier baby" case, but well, they got a lot of babies currently. I don't know if its effected their claims department as much as it has thier sabre rattling, grid switching department.

  • 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 Nov 13 at 16:51
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I've seen the loss of one leg (as others have described) during windy weather due to a loose connection at the utility pole. The wind causes the aerial wire to sway, and the movement is just enough to break the connection intermittently. The remedy is the same as others have mentioned: report the power loss to the electric company. If it's a loose connection at the utility pole, the fix takes just a few minutes.

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I've had this problem twice. The first time one of the legs failed inside the breaker box and things were starting to short/melt. Electrician estimated we were minutes away from a major house fire. The second time one of the legs became disconnected at the pole and the utility company fixed it.

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