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".
* 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.
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.