You have an electric lawnmower. Due to you being kind of lazy- this irritates your wife by the way- you haven’t mowed the lawn in several weeks so the grass is particularly shaggy and in need of mowing. Your electric mower, though somewhat beleaguered sounding, seems to be making the best of things until you hit a particularly deep patch and it suddenly falls silent. Try as you might, it cannot be spurred back into action. You assume a circuit breaker has flipped somewhere deep inside the house, resolve to attend to that later, plug the mower in elsewhere, and carry on with the mowing.
Later, you inspect the breaker box and discover that none of the breakers have flipped! You rack your brains for a moment and surmise that, perhaps, an overzealous GFCI somewhere has tripped. But the effort of resetting all the GFCIs is not rewarded; your favorite mowing plug remains dead to the world. In a fit of irritation, you cycle all the breakers in the box. Nothing.
Then, a panic! The chest freezer (apparently on the same nonfunctional circuit) is not running. An extension cord and a hurried effort successfully save the frozen pizzas, but that damn circuit is still dead.
Half an hour later, when you’re about to write the whole thing off and start investing in extension cord manufacturers, the circuit and its many plugs returns to life- for no seemingly no reason at all- of its own accord. …so what gives? The only apparent cause for the circuit’s miraculous recovery seems somehow related to unplugging the chest freezer from the wall. How on earth could that be? It wasn’t a tripped breaker (flipped them all!). It wasn’t a GFCI (reset them all!). The chest freezer is only a year old, has never offered trouble of any sort, and seems to be happily humming along in its new plug.
I’m guessing a bad breaker. Or a bad connection somewhere in the circuit (e.g. a receptacle connection that gets hot – and opens – when lots of current flows through it).
Now that the lights are on I suppose replacing the whole breaker couldn’t hurt as they only cost a couple bucks.
To the second point: Are you suggesting a mechanical interruption in the circuit? Like, it is overpowered and a physical gap forms somewhere? Because that’s a scary proposition and sounds a lot like a fire hazard. I guess replacing the breaker and deliberately overloading the circuit would either A) pop the breaker or B) recreate this mystery scenario and warrant a closer look at all plugs…
That is my suspicion as well. Somewhere in the wiring between the breaker and the receptacle the freezer is plugged into, there’s a poor connection. The load of the electric mower (most of them draw 12 amps or so) combined with the running load of the freezer was enough to warm up something to the point that it moved just enough to break the connection. When everything was turned off or unplugged, it cooled and moved back into contact. In rough order of likliness:
Bad breaker
Bad “backstab” connection at receptacle
Bad connection at a wirenut
You are very lucky. This is the kind of problem that if left to linger, can start a fire. Spend the money that would have gone to your homeowner’s insurance deductible and call an electrician to troubleshoot the bad circuit and add two dedicated circuits - one for the freezer and one outside for the mower.
Yea, a wire nut connection in a receptacle’s enclosure could also be the culprit.
If I were you, I would start pulling receptacles and inspecting. Look for burnt/charred insulation, melted plastic, loose connections, etc. If you can’t find anything, start removing wiring nuts, re-twist the wires, and then install new wire nuts. While you’re at it, you may want to just go ahead and replace the receptacles.
Turn off the breaker before doing this, obviously.
Ok, you guys are freaking me out with this talk of fires now because I’ve already found one receptacle (on a different circuit) where the wires weren’t actually screwed down- it shorted out if you didn’t insert the plug just right- since I bought this place last year…
I’m comfortable dabbling with this stuff (I’ve replaced/added breakers, wired ceiling fans, etc.) but if we’re talking about the house burning maybe I’ll think about bringing in a pro.
Crafter_Man: The house is from the 80s so I should be well beyond the threat of aluminum wiring.
But I guess it’s time open some boxes and see what’s lurking. I kind of had the impulse to do it when I discovered the shotty plug I mentioned earlier but never got around to it.
If you’ve already found problems elsewhere, I’d say definitely get the whole place checked out. Somebody didn’t do their job. Unfortunately you’ll probably end up paying for it, but it’s better then having more serious problems come of it.
Before calling a pro, I would just go ahead and start pulling receptacles. Try to figure out which connections (hot *and *neutral) are “feeding” the receptacle for the freezer and the receptacle you were using for the mower. Take a close look at these.
Just to be sure, you may want to just go ahead and start replace wire nuts and receptacles as a matter of course. Parts are cheap. Just takes a little time.
backstab connections (straight wire inserted to make a connection) are failures and fires waiting to happen.
screw down connections if made speedily or sloppily can be or come loose. a high current circuit, like a freezer, can also loosen with thermal effects.
remember to turn off the breaker and test for voltage before touching wires.
In my first appartment, I once lost all power except for my bathroom. When the power guy came to fix it I went out to talk with him. He said that power to the building comes in on three phases and only only phase had died. The other two phases were working.
Another possibility is a broken neutral. This would allow the circuit to mostly work as long as the loads between the two hots on that branch were reasonably balanced. This is a dangerous one because even though things seem to be mostly working, the neutral ends up “floating” between the two hots and as it floats down on one side (causing things not to work) it floats up on the other side, causing a dangerous overvoltage that can destroy things and cause a fire.
A loose connection (already discussed pretty well in the above posts) is also a potential fire starter, even if most things seem to be working correctly now.
This needs checked out ASAP. I would shut off the breaker to the circuit that had the fault and run a temporary heavy duty extension cord for the freezer so you don’t lose all the food in it.
One of the buildings I used to work in was famous for having a brownout on one of its three phases. This ended up being very deadly to a lot of our computer equipment. Brownouts can be worse than blackouts in that respect.
Three phase is common in larger buildings but it’s not common in residential service, although it does still exist in some areas. An easy way to tell if you have 3 phase is if your line to neutral voltage is 120 but your line to line voltage (typically found on dryers and ovens) is 208 instead of 240. There’s nothing inherently wrong with three phase service, except that your clothes take longer to dry and your oven takes a bit longer to heat up.
Most residential service is a split (center tapped) single phase. You have 120 volts from either line to neutral and 240 volts from line to line. Similar to dropping a phase, as you had, you can drop one line and not the other. Your oven and dryer probably won’t work, and since the outlets in your home should be roughly evenly distributed between the two lines, roughly half of your outlets won’t work either. It’s not that uncommon of a problem.
So assuming that I have a multimeter and don’t mind digging around behind wall plates, is there something I could look for to confirm (or not) this possibility?
We’re not talking about a short. We are talking about an open that correlates with the magnitude of current.
A bad connection has a contact resistance that is too high. As the current flows through the connection, the temperature of the connection increases due to I[sup]2[/sup]R heating. It may even increase to the point that it becomes a “glowing contact,” which is a pretty dangerous situation. Or it may simply open due to mechanical separation brought upon by thermal expansion. Either way, the root cause of failure is a connection with too much resistance.
I underlined and bolded the clue to your problem. I doubt that you have a breaker problem, The outlet that you need to check out is the one the freezer was plugged into. If there is a loose wire and daisy chained through the outlet (a bad procedure) it probably heated up and then broke the conectioneverything went dead. Until you unplugged the freezer, the jar of unplugging the freezer caused the wires to rremake contact and a=every thingis now hot. This could be either the hot or the neutral.
Unless you have a Zinsco panel breakers seldom go bad normally it is the wirring.
To check for a neutral problem is easy. Check the voltage between the hot and neutral, between the hot and the ground, and the voltage between the neutral and ground. first two should be arround 120 VAC and the third neat zero.
Measure the voltage between hot and neutral in the outlets that were having a problem and compare it to the line to neutral voltage from each line measured at the breaker box. If the outlets are at a significantly higher or lower voltage then the neutral is likely floating. If the voltage looks correct, plug something that draws a lot of current into the outlet (like a hair dryer) and turn it on, then measure the voltage again.