External = definitely not my breakers tripping, traffic lights down the street were completely off, and utility notified me of outage.
I was in the middle of a shower when the bathroom lights flickered on and off then completely off. The second bedroom was also affected, but master bedroom, living room, and kitchen were unaffected, so it did not appear that I lost 120V but not 240 or vice versa. I did not test every connection but both lights and wall outlets were affected. Home is a condo, 8-unit buildings. Power was restored at some point later; I was only home briefly but everything seemed to be running.
I know very little about domestic power. Is this a typical occurrence (I have also had total power outages)? Is having half my house on at least two separate systems something I should be worrying about in the long run (building not up to code?) Google is trying to get me to test things that I have already tested.
In the US you have two 120v legs. Your 120v applications can come from either of those legs. Putting them together make your 240v. What probably happened is you lost 1 120v leg. Assuming the loads are balanced correctly, this would result in losing about half of your 120v circuits and all of your 240v circuits.
Assuming there is 220 volt service in your area, there are two feeds coming into your house. For most lines you only use 110 volts. About half of this service should come from each of the feeds. So the outage has probably affected only one of the feeds to your house. Though I guess they’ll probably have to shut it off completely at some point to fix it.
I had something similar happen. Rainwater got into my breaker box and somehow damaged the circuit breaker. :eek: So it wouldn’t let enough power through for the whole house, just…the first two fuses, basically. Very weird.
The other two posters are (in all likelihood) totally correct. If the power is still half out, you shouldn’t run anything that uses 220v. Don’t use your AC, your (electric) stove/oven etc. Shut off all the “double breakers” in your breaker box. It’s not good to run those things with half the voltage that they require.
If you want to verify it, you can look in your breaker box and you’ll find that items in your house that are powered by every other breaker aren’t working. That is, going down one side, one breaker will work, but the next one down isn’t. The one after that is fine, the one below that one is out.
They won’t be tripped, they just aren’t getting any juice.
Losing one leg of a feed to a 220V single or split phase transformer would shut the transformer down entirely. No 110V either. Your 110V in this setup is just a center tap of single coil. What is more likely is that your 8 unit condo is fed by 3phase power. Your 220V in this case is more likely 208V. The 110V for each leg of your panel is then fed by separate transformers tied together at the neutral which gives the 208/220. What happened upstream took out one of the three legs feeding you which in your case left the transformer feeding one sideof your panel energized and the other one not. Actually there were most likely two of the 3 incoming supply lines off otherwise you might have had brownouts on the 110 line instead of nothing. Some of your neighbors probably had no power at all.
PoppaSan is almost certainly correct. There is no possibility that traffic lights down the street share the same 110v legs as a condo unit. The 8 units will almost certainly justify a three phase feed, and internally 110v legs will be created off this feed. Lose a phase and you will lose one third of the 110v legs in the units. In general it is good practice to balance the load across the three phases. So it is no surprise that your unit has power outlets spread across them. A spread load reduces the neutral current and memes the transformers run happier.
As an interesting aside, bigger users typically have three phase power (in which the three wires carry voltage that oscillates high and low in a particular order like you might expect the pistons to do in a three cylinder engine). Three phase power is super neato because it kind of rotates, and it works better for motors, especially when starting them.
If just one of the phases goes out, all the three phase motors that are currently running get very unhappy – weak, hot, noisy. And three phase motors that are not currently running get impossible to start.