I’m in an apt. and the power has been shutting off lately. It doesn’t trip any of the breakers in the breaker box inside the apt. but it does trip the master breaker on the box outside. Thought it was an oven issue but it still happens with the oven breaker off.
Visual inspection of the breaker box outside shows one of the wires looks a bit corroded. Wires to/from the rest of the units are a nice copper color. Is that a red flag?
Landlord is dragging their feet and telling us to talk to the electric company, and electric company is saying to call a licensed electrician, so I’m just trying to understand the issue so hopefully the landlord will listen to me.
Electrician here, that’s heat scoring. Happens when the terminal is loose, or the draw is nearing the upper limit of the installed wire for an extended period of time (looks like #8 TW, which is not ideal to run at 50a for more than 3 hours continuously, especially for how old it is). It could also be that the breaker is old enough to not be tripping reliably. Either way, there’s enough resistance with that scoring that I’ll just keep getting worse and continually building up heat until it melts the breaker and/or burns off. An electrician needs to swap that breaker and re-pull the wire (with #6s), that’s not a utility issue.
I assume you are talking about the middle wire?
No, the wire in the bottom terminal that’s blackened
But that’s green copper oxidation
Cause by heat scoring, and beneath the traces of green oxidation is heat blackenng. That leg specifically has been over heated over time, causing the discoloration reaction. If it was natural oxidation (like the statue of liberty, for example), then all the wires would be the same color.
Copper wire for a long time has been manufactured in such a way that it is resistant to ambient oxidation. When excessive heat is induced in the wire, that natural protection is broken down and then it is subject to turning green, but generally only where heat has damaged the wire.
Here is a basic idea of how cables are made to not oxidize when they’re just sitt ng there in normal operation.
Damn, thank you for explaining, I appreciate it.
No worries
What you’re describing is not an issue caused by corrosion on a wire. Corrosion won’t cause overdraw or shorting, so it wouldn’t cause your main breaker to flip.
It’s more likely that you either have a weakening breaker due to age tripping at a lower draw than it was originally rated for or you’re drawing more across the entire system than the main is rated for.
The electric co does not handle anything from the first breaker on and nothing on their end would trip your breaker(it would trip something of theirs upstream), usually so they are right that you should be talking to an electrician. That is something that your landlord should be on the hook for, barring any previous agreements.
If you want to see what your circuits are drawing, consider picking up a digital clamp meter, they will make it possible to see what each circuit, including the main are actually drawing.
Electrical Engineer here, that corrosion doesn’t look too bad, I wouldn’t assume it’s the issue but it’s not impossible it might be a contributing factor since corrosion on connections can cause heat and heat can trip breakers.
If the breaker trips are happening when you do something like turn on the oven or the toaster then it’s just a matter of the electric service to the house being too small for the apartments loads. This can happen if the apartment originally had gas appliances that were later switched to electric or something else (like a hot tub) was later added to increase the electric load beyond what was originally designed for.
If the trips dont seem to correspond to anything you’re doing with electric appliances, then the equipment may be going bad or there may be an intermittent short. Both of which are not something you would be able to troubleshoot (and frankly, if you don’t know what you’re doing, even opening up a panelboard like you’ve done can be deadly).
Either way I highly recommend you either pressure your landlord to bring in an electrician, or pay for one out of pocket if thats not an option.
I definitely won’t make a go of it myself, don’t worry! They also recently moved the sub-panel from inside a closet to a more accessible wall to bring the building up to fire code or something so I wonder if something could be loose from that process. I’ve lived here several years and didn’t even know the unit had a main breaker outside until this year when someone from the electrical company showed me how to reset it.
I’ve experienced this breaker bypass issue a few times and in each case it was a ground fault.
Why this can bypass breaker and trip the mains: In most countries, the common inexpensive breakers in residential panel boxes are not GFCIs. They will catch and interrupt marginal overdraw before it starts a fire but won’t trip fast enough in the case of a ground fault, which is one of the reasons fire codes usually require GFCI outlets anywhere near running water. Since the mains in MDL and housing complexes are GFCI, they can trip faster than the subpanel breakers in the case of a ground fault.
One case that might be relevant to you since you had reason to suspect your oven: a microwave oven door closure sensor became misaligned and would intermittently fail to report closure. It was one of two that controlled a kill-switch relay for the magnetron (the main power drawing component in a MW). The easter egg in their circuit design was that if sensor A failed to report door was closed, the oven would simply act as if door was open, but if sensor B failed to report door was closed, closing the door would instantly cause a ground fault.
Diagnostic recommendation: get some GFCI adapters to use on any big AC appliances you suspect might be causing the fault, like the oven you mentioned, so that next time it happens only the culprit appliance will lose power and you’ll know what to repair/replace.
ETA: the GFCI adapters are common and inexpensive, and your landlord would likely rather pay for a few of those than an electrician visit. Either way, this absolutely is the landlord’s responsibility, especially if your lease includes the appliances.
We only have like 5 outlets in the house, would it be okay to put gfci adapters on all of them and plug extensions into the adapters?
Damn that’s convenient!
Yes, the simplest adapter style is a chunky wall wart, usually cheapest. Otherwise inline modules are common. For either, you just plug them in between the plug and its outlet and press the “reset” button. 15-amp 125v example from a common US supermarket ($14).
And if by extender you mean the multi-outlet strip extenders: yes, the adapter+extender would isolate the fault to just that strip. If ground fault occurs, everything on that strip turns off. You can also find power strips with built-in GFCI.
The only additional consideration re: which GFCI adapters you will need are
- Voltage and amperage rating: you can just copy the rating of the outlet’s breaker
…or, if it’s just handling one appliance, take a picture of the power specification, usually a sticker on the back of the appliance, which should give you minimum amperage rating of GFCI
- Socket type: if you’re in the US, likely all type B or maybe one or two type I (large 220V appliances) from this chart:
Edit: pictures
Excellent, I will grab a couple that will be especially helpful for the kitchen where we occasionally accidentally run the microwave at the same time as the kettle.
I’ll still prod the landlord to have someone come look at the power main issue.
That’s great. And glad youre pressing landlord. They’re very likely obligated to cover expenses related to this, but I understand landlords are shitheads and a PITA.
Just to be clear, re: MW+kettle example, typical GFCI won’t prevent that overload. Circuit breaker should trip. There is a similar component that does both (AFCI) but it’s more expensive and shouldn’t be needed if your breaker is functioning correctly. Adding GFCI is usually inexpensive enough to justify but is only meant to protect against faults, not overloads.
I see, thanks for clarifying!
Not here to directly answer your question, but to recommend that you do an internet search for the name of your location and the phrase rent escrow.
It seems like you could have a somewhat dangerous situation on your hands and escrow is a way to legally withhold your rent until that issue is resolved.
Also, even as a non-electrician that situation looks kind of gnarly and definitely needs to be looked at by an electrician on site. The symptoms alone are definitely concerning.
Best of luck, friend.
Also save your emails and texts. Avoid calls unless your location allows single party consent to record (and test it out on your phone).
