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I consider myself experienced when it comes to electrical wiring; I've replaced a main panel, wired my entire kitchen, added lots of circuits, etc, but this sub panel on the outside of house pains me every time I'm required to cross its path.

This sub panel (fed by another sub panel in my bathroom that was added by the previous owner, different problem, different day) has three 240V breakers on the left side that all deal with my air conditioning. The middle set/green box controls the outside unit, which is perfectly fine. But, both the top and bottom 240V breakers (red boxes) control my inside AC unit.

my horrifying outdoor subpanel

Both breakers in the red boxes are required to be on for the inside AC unit to have power, not "either" (it's like an AND gate). I'm not even sure how someone would do this on purpose if this was the goal.

Three weeks ago the bottom one started tripping at exactly 3:15am once a week. Thought it could be sprinklers or something spraying this panel but it is not. My AC also did not try to start at this time, I have Ecobee thermostats and I know for sure this AC unit was not trying to start then.

Also, this sub panel is fed by a 60 amp (!) breaker that also trips when this bottom AC breaker trips.

Should this whole panel just be replaced/rewired? It should only be controlling the AC unit (inside/outside) and a pool pump, and a detached garage (second breaker from the top on the right).


Bonus question while I'm here. I was trying to figure out which neutral goes with that detached garage breaker so I could control it with a Shelly 1PM (which switches via the neutral wire), but I couldn't find it. In fact, if I disconnect every neutral on that neutral bar, the garage still has power...

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  • The Wagos connectors that are in there were something I added because the two 120V 20amp breakers (the garage breaker and the one below it) had multiple conductors connected to them, and I thought it would be slightly better to just "convert" that to single conductors. Additionally, the ground bar is new, I added that because all the grounds were originally just twisted together near the bottom not mechanically attached in any way. All of the problems I'm describing were there before and after those two changes of mine. Jan 30, 2023 at 16:11
  • Can you give the power specs of the AC? Should be a label on it stating voltage/amps/watts. And the type of AC unit.
    – crip659
    Jan 30, 2023 at 16:16
  • @crip659 yes actually, I have a picture of the sticker on the front. I don't know if there's an indication though of which motor is installed photos.app.goo.gl/3ZHDRk3dsDrzkZd3A Jan 30, 2023 at 16:17
  • Also, there's only one set of conductors coming from the wall, into the disconnect, and to the AC unit Jan 30, 2023 at 16:19
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    Do you appreciate what you have there? Might want to watch Technology Connections' series on heat pumps. youtube.com/watch?v=MFEHFsO-XSI&t=0s Jan 30, 2023 at 19:42

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Also, this sub panel is fed by a 60 amp (!) breaker that also trips when this bottom AC breaker trips.

Since these are plain breakers, they can only be double-tripped by a dead short. If it was an overload, the 30A breaker would trip much sooner than the 60A, so it's a dead short. This indicates a severe and dangerous problem with the wiring or equipment and that 30A breaker should shut off until it is identified. In fact I'd be keen to know if doing so stops the 60A breaker from tripping. (I expect it will but it'd be nice to be sure).

The black and white wire indicates this is powering 240V-only (no 120V loads therefore neutral not needed) equipment. HVAC sounds about right. Generally, such circuits power only a single machine - this is typically a Code requirement. If someone has hung additional stuff off this circuit, it should be removed with extreme prejudice.

Bonus question while I'm here. I was trying to figure out which neutral goes with that detached garage breaker so I could control it with a Shelly 1PM (which switches via the neutral wire), but I couldn't find it. In fact, if I disconnect every neutral on that neutral bar, the garage still has power...

Jumping Jehosephat! That's a question that should not ever be asked!

First let's dismiss the confuser of "switch loops". Prior to 2011 it was common to bring power to a lamp, then use /2 cable (black-white) to bring always-hot and switched-hot to a plain switch. White must be used for always-hot and neutral was not brought down at all. This confuses most novices. The cure here is to replace with /3 cable, as required post-2011.

It is axiomatic to all mains electrical work that the neutral must travel with with its partner hot wires. A lot of people with experience in low voltage DC get into a mindset of a "Common" or "Chassis" or "GND" which magically handles all return current because it's 1500 pounds of steel automobile chassis, or because their electronics projects use milliamps. It is not that way with mains electrical. This stuff handles real power. And AC is not DC.

In AC mains, there's a ground alright, but it's nothing but a safety shield. Actual power is wired as an isolated system with the current return path fully wired, and each neutral dedicated to its own circuit ONLY (Due to split-phase or 3-phase power, MWBCs are possible, but an MWBC is one circuit). That is due to simple overloading - when the neutral is the same size as the hot, it can't handle additional current from another circuit! But also for safety, a promiscuous neutral has current on it even when the breaker is off, and that will lift it to 120V when you disconnect it!

Further, due to inductive effects, the neutral must travel with its partner hot(s) in the same cable or conduit. You should be able to put a clamp meter around any cable or conduit, and the reading must always be zero, because neutral current must be equal and opposite from hot currents (or in cases of MWBCs all the currents sum to zero when phase is considered).

It sounds like you inherited a house from someone who just jury-rigged everything and didn't know or care about such details. You're gonna have gremlins until you sort all this stuff out. But I need to call your attention to

Harper's Rule of ignored faults: When you are looking for a problem, and you find another problem that "seems" unrelated to your problem, it often is related and fixing it will fix your problem.

That's especially true in an installation with a spiderweb of code violations and bad practices.

You just need to "steady as she goes" make a plan and fix everything. If you have to downgrade functionality e.g. convert the garage to 120V because you need the white back as a proper neutral, then do it.

I consider myself experienced when it comes to electrical wiring; I've replaced a main panel, wired my entire kitchen, added lots of circuits, etc,

Careful - that kind of talk is going to get you a panel review :) And yes, I know this is not your work.

Since a GE THQP breaker actually fits (and by markings), we can tell this is a GE panel. The THQP230 breaker in green is one of the few proper things in this panel. However I suspect the cover has a gap above and below it; that must be filled with a TFG or the more sturdy THQP120 blank cover plate; actual breakers are the best cover plates. Don't shorten any wires, they're too short already. All those non-GE breakers are aliens and should be replaced at once with GE THQL or THQP.

Now we sometimes find very old GE panels where THQL will not fit. In that case you can only use THQP and Eaton CL (which is UL-Classified for GE panels). Often the best thing is to just have a stack of THQPs and a bunch of empty holes, and use the aliens to fill the empty holes.... they're fine for that. If you're planning to replace the panel, get a nice tall one to #1 hopefully remove need for some wire nuts, and #2 spaces are cheap - more is always better.

I know it's not your work but these are the things you ought to deal with right away.

The Shelly 1PM is not UL-Listed and cannot be installed in a home. Shelly makes UL Listed versions; use those.

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  • The Shelly 1PM is UL listed now actually! shelly.cloud/en-us/products/product-overview/shelly-1pm-ul My plan is/was to use these for power monitoring (power bill is obscenely high and I can't find the culprit ($700+ in the summer), I'm strongly assuming it's because of this mess. Jan 30, 2023 at 19:44
  • "However I suspect the cover has a gap above and below it" lol... There is no cover, it just has a door. Jan 30, 2023 at 20:30
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    @BrianLeishman Wait, there should be a deadfront cover that keeps someone from opening the door and putting fingers on hot things. It also has a key role in keeping the breakers from rocking out when you turn them off. If there's not, search for it! If it can't be found then the panel must be replaced. Jan 30, 2023 at 21:58
  • Got it, there definitely isn't a front cover, and you're right, the breakers do move around. That top GFCI looking breaker (can't figure out what it goes to) is extremely loose and will come out with basically any movement. I believe I've made the decision to have this panel replaced asap based on the responses Jan 30, 2023 at 22:46
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    @Harper-ReinstateMonica That breaker that was tripping being off has seemingly stopped the 60amp sub panel breaker from tripping as well. I've almost completed my new sub panel in a hallway that has plenty of space to replace this outside one and the one in my bathroom closet. photos.app.goo.gl/Fq5zXS2yb9avM3rm8 Feb 7, 2023 at 15:13
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So far you've collected lots of sage advice but not a whole lot focused on how to address what I perceive as your core questions ("what do each of these breakers do for my system, and why does the one keep tripping?").

If I'm tracing the wires in the photo correctly, the green-box breakers are connected to a cable that exits in the conduit at the right edge of the panel. I would have guessed that's the one that goes to the outdoor HVAC unit.

It appears the conductors from both red-box breaker pairs leave through the hole in the rear wall of the panel. I would guess those both go to the furnace.

Have a look at your indoor/furnace unit. Inspect how its supply conductors are connected: is there a disconnect switch? More than one, or multiple poles on the one disconnect? How many sets of supply conductors are wired to the furnace? What voltage(s) does the furnace require?

There are many ways you can match up the supply conductors at the furnace with those in the breaker panel. One way is to disconnect conductors from breakers, disconnect conductors from furnace, then (at the furnace) check the voltage between the black and white conductors in the same cable. If it's approximately zero volts then measure the resistance between them. If it's infinite, then go out to the panel, pick one of the disconnected A/C-related cables, and short the black and white together. Check the resistance from the furnace end again. After a few iterations you'll have positively identified where the cable from the frequent-tripping breaker goes, and from there you'll be able to ask better questions such as "Is this equipment causing the breaker to trip? Why?"

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  • The green box breakers are the ones that go to the outside unit, you are correct. There is only one disconnect switch, with one pair of black/white coming in, and one pair of black white going out. The AC takes 240V. I will debug further! I almost think they just used one conductor from each, and the other conductors go "somewhere" Jan 30, 2023 at 21:01
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  • the breaker in your green outline is called a tandem breaker, and is putting 120v out on a black and a white 14 gauge (looks like 14ga size). Then that begs the question what is being used as the neutral for that circuit, did they use the bare ground wire?
  • I suspect the tandem breaker was used to put 120v service out to whatever unit, because they didn't run 10/3 they couldn't legally make it happen with 10/2 wire
  • should only be controlling the AC unit (inside/outside) and a pool pump, and a detached garage : all on 14 gauge wire?
  • having wire nuts inside the panel is allowed, but with what your pic depicts... that's pretty bad and an indicator of a hack job
  • Should this whole panel just be replaced/rewired? It should only be controlling the AC unit (inside/outside) and a pool pump, and a detached garage.
    • yeah, and also seeing how you seem to not be sure of what is actually wired from it. I count 8 breakers and you mention 4 things.
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    Actually, the Tandem breaker appears to be “hacked”by placing it a half-breaker-space down. It may actually be acting as a full-sized 240 volt breaker. At a minimum, it should be replaced with a true 240 volt breaker.
    – DoxyLover
    Jan 30, 2023 at 18:42
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    That's not a tandem. This is a GE panel Jan 30, 2023 at 18:46
  • The wires are actually mostly 12 gauge, which is only slightly better. For example the green conductors being used as grounds near the bottom are 14. The offset center breaker(s) for the outside unit might be "right", it reminds me of these 120+240 tandem breakers amzn.to/3kJqGYQ Jan 30, 2023 at 18:58
  • My guess is that with the grounds are used as neutrals for the garage because they garage circuit continues to work after disconnecting the neutrals. Jan 30, 2023 at 19:00
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    @BrianLeishman it sounds like you inherited a real mess. I got an old pallet factory in similar electrical disarray - fortunately all EMT conduit and it's hard to screw that up irrreparably. You may have to downgrade some functionality temporarily to make it safe and legal in the wires available. Did you just buy it? Were these defects disclosed on the seller paperwork? You might have recourse. Jan 30, 2023 at 19:34

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