Building keeps losing a single phase of power

[dparm]

For the third time this year I've woken up to find that my high-rise has lost one of its phases of power. Really annoying since it's effectively the same thing as a total power outage, and each time it's been on a perfectly clear day with no storms to knock down lines or damage equipment. I can always tell because some of the lights dim, the elevators will continue to function, but basically none of my electronics will work.

Back in April, it was at about 3:30am on a Monday morning. I had just gotten out of the shower in preparation to go to the airport for my weekly routine of traveling to NYC. Always fun to try and shave, get dressed, and carry your suitcase down 15 flights of stairs in the dark.

And of course, it being a Monday...same [censored], different day. Fortunately I was not traveling this week (and it was not 90 degrees outside) but I woke up at around 6am and noticed the same power issue. ComEd got it working within a few hours, but this past year has just been a lot of issues like this.

Can anyone explain how and why something like this keeps happening to my building? It's a fairly large high-rise structure with around 450 residents.

 

[JHZR2]

I would imagine improper balance of the loads on the three phases. Too many loads on one of the three - blows that part of the circuit.

Im not a EE, but I believe that household type power (120V) is derived from one of the phases of 480 via a transformer. Each 480V phase is lower voltage but not 120V.

 

[dparm]

Originally Posted By: JHZR2
I would imagine improper balance of the loads on the three phases. Too many loads on one of the three - blows that part of the circuit.



So whose "fault" is that? ComEd? The landlord/building owner?

ComEd's outage map always reports "damaged power lines" though I suspect that's some generic message.

 

[95busa]

Blowing fuses on one phase will do it. I have seen 500amp fuses blow due to loose fuse blocks. Blammo, current asymmetry and no juice.

 

[JHZR2]

Originally Posted By: dparm
Originally Posted By: JHZR2
I would imagine improper balance of the loads on the three phases. Too many loads on one of the three - blows that part of the circuit.



So whose "fault" is that? ComEd? The landlord/building owner?


I guess it depends where something is tripping. If the building is fed with 480, and various apartments are fed via transformer from the different phases, it would be in the building. If three buildings are fed by three different phases, it could be more of an infrastructure issue. Im no expert on this though...

 

[dparm]

I don't think it's something in the building, because each time there was a problem ComEd did not have to enter the building at all.

(I know this because the office was closed during the 3:30am outage and they restored power a few hours later anyways)

 

[crazyoildude]

if its the power going to the building than its con ed if its within the building after the transformers its the building

 

[BigCahuna]

My parents inlaws house used to have an issue like that. Turned out the be they used aluminium wiring during the construction. The electrician told them that the wiring would heat up and contract, making the connections loosen up under the lugs. Cost some big $$$ to correct. But until your buildings owner gets it looked at by a pro, were just guessing at what wrong.,,

 

[spackard]

Older wiring, but a lot more people buying window-shaker AC units?
We used to blow lightning arresters (but not fuses) on the power pole at my old workplace. Eventually we got a new drop and a new transformer.

 

[dparm]

Originally Posted By: spackard
Older wiring, but a lot more people buying window-shaker AC units?
We used to blow lightning arresters (but not fuses) on the power pole at my old workplace. Eventually we got a new drop and a new transformer.


It's a 16-story high-rise built in the 1970s, but it has central air/heat so no window units or anything like that.

 

[pcoxe]

+1 on unbalanced load if it's on the power company side.

 

[zzyzzx]

I am thinking that it's a poor electrical connection on that one phase, but it could really be a lot of things.

 

[dparm]

Originally Posted By: zzyzzx
I am thinking that it's a poor electrical connection on that one phase, but it could really be a lot of things.


Hopefully they've repaired it for good this time...

 

[The_Jeff]

A building that size will have its transformers in the basement. Not sure whose property it is though-- building owner or utility.

The cheaper transformers share "something" so if they lose a phase they still bleed some voltage through, just enough to fry your stuff.

Is power included in rent? IE do you have your own meter?

 

[badtlc]

Originally Posted By: JHZR2
I would imagine improper balance of the loads on the three phases. Too many loads on one of the three - blows that part of the circuit.

Im not a EE, but I believe that household type power (120V) is derived from one of the phases of 480 via a transformer. Each 480V phase is lower voltage but not 120V.


It totally depends. If the residential service is 208/120, 3-phase, it is just a delta:wye transformer 480:208. If the residential is 240/120, 1-phase, it could be done a few different ways.

a 480:208 transformer is going to be owned by the building.

As for what is actually causing the problems, impossible to say. It is weird to lose a phase w/out a breaker tripping all 3 phases. Sounds like bad design all the way around.

 

[dparm]

Originally Posted By: eljefino
A building that size will have its transformers in the basement. Not sure whose property it is though-- building owner or utility.

The cheaper transformers share "something" so if they lose a phase they still bleed some voltage through, just enough to fry your stuff.

Is power included in rent? IE do you have your own meter?



I pay my own electricity bill.

 

[PandaBear]

Originally Posted By: dparm
I pay my own electricity bill.


It doesn't matter who pays the electric bill, it matters who owns the equipment. From my understand at least here, utility is responsible for wiring into the meter for residential, but for commercial like yours it is possible that they have different contracts that will be only responsible to get into the building transformer.

 

[Dave Hess]

Does your wife get mad the building is losing power lately ?

What floor do you live on ?

 

[95busa]

Yeah, if it drops a phase it can push some big amps in the other two....no bueno.