Partial power outage - some circuits dead, some low voltage, some perfectly fine

Question

Our house is experiencing a strange electrical issue. I'm in the United States (near Cincinnati) and I'm living with roommates in a rental house in a subdivision.

Yesterday morning, I woke up to discover that some circuits in the house have zero power - for example the upstairs bathroom has no lights, no fan, and the outlet is dead. (I checked the GFCI, and it was not tripped.) Other upstairs circuits, such as some (but not all) bedroom outlets, also have no power.

Other circuits in the house seem to be in a "brownout" condition - the voltage is a little low, but drops drastically when a significant load is attached. For example, my Kill-a-Watt reads about 115 volts with little/no load, but when a larger load comes on (such as the refrigerator or a toaster), the voltage drops (as low as ~60 volts). All of the "brownout" circuits seem to drop together - for example, if I turn on the toaster in the kitchen, the LED bulb in the floor lamp in the next room will dim.

Other circuits seem perfectly fine - the Kill-a-Watt reads about 118-119 volts, and the voltage remains steady when a load (such as the refrigerator) comes on.

I checked the breakers, and none of them are tripped. _{There's one "dual" breaker (two breakers tied together) that is physically loose in the breaker box (you can freely move it between OFF and ON with zero resistance, and the label is crossed out, so I guess it's unused?), and another breaker that has always been off as long as I've lived here, but otherwise everything is in the ON position.}

I also felt the breaker box itself, and the entire box is cool to the touch.

Some 240v appliances are functional, but others are not. For example, the electric stove and the heat pump are all working. But the electric water heater is not - there's no hot water. (I attempted to reset it by turning its breaker off, then back on, but that didn't do anything, and there are no controls or indicators that I can find on the heater itself.)

We called the power company, and they came out and verified that everything up to the meter box is working correctly(*). So whatever the issue is, it's within our house.

We currently have the refrigerator on a "good" outlet (with a heavy-duty extension cord), and the remaining items on the "brownout" circuit are relatively lightweight (mostly just LED lights). I've opened a work order with our rental company, and am waiting to hear back on that. So I'm not necessarily looking to fix this myself, but I would like to better understand what could be going on here, and if I should attempt to escalate the work order before Monday.

I don't think this question is a duplicate of any of the various "half my house is without power" questions, because the power company found no issues, and our house seems to be divided into three areas: "out", "brownout", and "normal".

Thanks!

_{* The man from the power company did mention that he found some sort of "temporary" connectors at the weatherhead that are not up to code. They said they'd be sending a 30-day notice that it needs to be fixed and re-inspected, or they'd have to terminate service. He said it would be the landlord's responsibility, fortunately, but that we should be aware of it. I don't think that's related, especially since their load test came back okay, but it seems worth mentioning.}

Updates in response to comments

@crip659, yeah we're trying to get in contact with the rental company. So far they have been frustratingly nonresponsive, despite creating a new "emergency"-level ticket. So... we'll have some thinking to do when the lease is up, but that's another thread. We're not doing any work ourselves, but we'd like to do what we can to avoid burning the house down :)

@A. I. Breveleri- to clarify, the breaker itself is not loose. The switch swings freely with zero resistance, but the full breaker itself is solidly in the panel. I don't know if wires are connected or not, and I'm not sure I want to open the breaker box to look.

@Harper - Reinstate Monica - I just tried this, and everything went dead - both the "weak" circuits and the good ones. The previously-dead ones remained dead. Not a single outlet or light in the whole house had power that I could tell.

As requested, here is a photo of the breaker panel. The 5/7 breaker is the "loose" one I described above.

Update 2

I discovered last night a sequence which got the water heater running. Flip off 9/11 ("main lites"), 23/25 ("water heater"), and 26 ("washer"). Then turn on 23/25, then 9/11. At that point, the water heater started making sounds, and we soon had warm water at the faucet. The water heater breaker was never in the off position for an extended period, and I had tried flipping on just 23/25 previously, but those did not cause the water heater to actually run. So no idea what's going on there.

A company repairman (not an electrician) came out and took a look this morning. We discovered that the "weak" circuits are now behaving perfectly normally (the toaster no longer causes the light in the next room to dim, and the voltage doesn't drop), but the "dead" circuits are still dead. With the "water heater" breaker off, he tried turning on breaker 17 (the one on the bottom-left that's off in my photo), and that caused breaker 9/11 to trip.

I got a photo before he put the cover back on the breaker box, it looks like @NoSparksPlease was right about the split bus panel. 9/11 feeds wires that lead down to the bottom half of the panel. There used to be something connected to the 5/7 240v breaker, but as you can see, the wires were taped off, and when we traced them out of the box, they dead-ended at a junction box near the furnace and water heater.

At this point, now we're just waiting around for the rental company to send an actual electrician to look at the issue. The "weak" outlets issue resolved itself somehow, but the dead circuits upstairs are still dead.

Answer 1

Most of the "half my house" answers are incomplete. Most of the time the problems is in the equipment that is in the utilities jurisdiction, but it certainly can be an issue with the load side of the meter, the wire to the panel, the connection to the main breaker, internal of the main breaker, or connection of the main breaker to the bussing.

You need to get your landlord to get somebody out to investigate the customer side of the service before some more damage results.

More explanation is needed about how the connection at the weatherhead is not utility jurisdiction.

Edit: You have a split bus "rule of six" panel that up to 6 "main" breakers were allowed to shut off all power. One of the six 2-pole breaker usually near the middle of the panel feeds all the small breakers in a sub-section of the panel. In your panel it is likely the 9,11 marked "main/lights". As long as that one is off none of the lower breakers will do anything. After turning off all 2-pole breakers turn only the 9,11 on and half your circuits will come on, turn on the lower water heater breaker and weird stuff will start. You're missing a leg and the 120v circuits connected to the dead leg are being fed reduced voltage through the water heater.

I would suspect that when 5,7 failed it also caused damage where it attaches to the bussing, so they added the bottom 2-pole breaker to the "lighting" sub-section and moved wires down to it.

Still, you need an electrician to find the faulty connection. I absolutely recommend only people with electrical training and flash retardant suit risk removing panel cover when a likely failed wire termination lug is possibly hot enough to come apart. Seriously.

Answer 2

TL;DR: I think we have a fried squirrel in our walls

Well it's been quite some time since all this happened, and the rental company has yet to send an electrician out to diagnose the original problem. There was at least one incorrect assumption I made, as well as a lot I've learned from browsing other questions on this site, and I now have a theory that makes sense to me based on everything I know now.

The incorrect assumption: The "another breaker that has always been off as long as I've lived here", number 17. Turns out, that breaker controls the bedroom and bathroom outlets that were "dead".

What explains the behavior we saw?

I believe that something** happened on the upstairs bedroom/bathroom circuit, either a short or an overload, which caused breaker 17 to trip and half of the 9/11 "main lites" breaker.

_{The 9/11 breaker is two physically separate breakers with a handle tie. So it's possible that one could have tripped internally but mechanical resistance from the other breaker prevented the handle from moving to the tripped position externally. I didn't save the link, but I read elsewhere on this site that if you physically hold a breaker in the ON position, it will still trip if you overload it, which aligns with this theory.}

Once the panel entered that state, that caused the wonky behavior that I described at the beginning of my question: most 240v appliances worked fine (since they don't go through the "main lites" breaker), but half of the 120v outlets were getting their power through the heating element of the water heater, which would explain what I was calling "brownout".

When I flipped all the 240v breakers off, then back on, this reset the tripped half of the "main lites" breaker, restoring normal power to most of the house. (I didn't notice until the following morning that the toaster no longer caused the lights to dim.) I didn't touch #17 because I incorrectly believed it to be irrelevant. When the first repairman came out, he turned on breaker 17 which caused "main lites" (9/11) to trip immediately because that mysterious fault** was still a problem.

Later in the week, another company repairman came out, and he was able to flip on breaker 17 with no problem whatsoever. After this, everything in the house worked. That was also the last useful contact we had with the rental company about it: they sent out a few electrical contractors to get quotes about replacing the panel, but that's the last we've heard.

**What caused it in the first place??

It's now winter, and the past few weeks we've heard some rustling and scratching in the ceiling that sounded like a squirrel was making itself at home between our 1st and 2nd floors. Apparently, before I moved into this house, there had been similar squirrel problems before, and my roommates (who have lived in this house a year before I moved in) know roughly where they're getting in. The squirrel entry point is on the same exterior wall as the outlets on breaker 17.

I suspect some poor critter crawled up into our walls and tried to have some electrical wires for lunch. In the process, he shorted out the wires, causing both of the breakers (17 and one pole of 9/11) to trip as I described above. When company repairman #1 showed up, the wires were still shorted out (maybe the critter survived but left them shorted? or died with his teeth in the cable?). By the time repairman #2 showed up, something had jostled the fault in the walls (possibly more critters crawling around the now-de-energized cable?), the fault was no longer present, so now the breaker doesn't trip.

Thanks again for everyone who answered and commented! I have learned a LOT through this experience, both through this question and all the other great answers on this site!

Answer 3

I know this is a old post but wanted to share a problem I had with random brownouts. I been in my home since 2000, had it built new. About a month ago PEC (Kyle, Texas) came out and swapped my meter out (everyone in the area got new ones). It took me a bit to realize my problems started with the meter swap. The brownouts would generally happen in the morning when I gave Alexa my "I'm up" command that turns on various lights and my entertainment system but not always. The last few days the problem started to get a bit worse, so much so, when it happened most of the house would reset. Once I was able to catch the voltage drop on my DMV to around 60 volts!

I sent a message into PEC and they came out the next morning with parts on hand - seems I am not the only one that has called this problem in. The meter's socket was not happy, the upper left had been sparking/burning to where the meter's socket had to be replaced. Also, one of the lugs wasn't really fully engaged since the 2000 install (lower right).

I am so relieved it was the meter's connection. For a month I have going over the whole house looking for the problem and for anything that I had done over the years to be the cause.

So if your power company comes by and swaps out your meter (of for whatever reason) be on your toes as that work could have allowed a long standing issue to bubble up! I also would like to say the PEC guys were awesome and said not to wait so long to report something like this in the future. They are there to come by and look - doesn't matter which side of the meter the problem ends up being - safety first, who's to blame later.