240V split phase weirdness (low V on one phase)

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passedpawn

passedpawn

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OK, it's not brewing related, but you guys are pretty smart so I though I'd give it a shot.

Today, in the middle of the day, the lights started flickering and my computer UPS started freaking out. I checked the voltage in my office and it was 75VAC. That explains it.

Weird thing is, some of the ckts in my house are 120VAC. I put a volt meter across both phases of a 240V connector and verified.

One more data point: the power meter (LCD) on the outside of my house is blank. Normally it's a spasm of numbers doing stuff.

Thoughts? My best guess is the transformer outside my house that converts from X kV to 240V split phase is toast. Irma just went through my neighborhood, so I should be happy to have any power at all.
 
Weird. Got nothin' for you on why, but I'd move the computer to one of the outlets that still has 120V. I'd keep the UPS between the comp and outlet, as the UPS prolly has some protective circuitry as well. If I had a portable GFCI, I'd throw that in before the UPS for good measure.

Brew on :mug:
 
doug293cz said:
Weird. Got nothin' for you on why, but I'd move the computer to one of the outlets that still has 120V. I'd keep the UPS between the comp and outlet, as the UPS prolly has some protective circuitry as well. If I had a portable GFCI, I'd throw that in before the UPS for good measure.

Brew on :mug:
Click to expand...

Yea, I have extensions going to my office from the good phase. Computer and related networking stuff are on the good one.
 
I'm no expert but that sounds like a loose neutral on the main service wires. You should get it looked into (call the power company) it can ruin your 120V appliances and it's a fire hazard. If that circuit had 75V, another one somewhere has 170V.
 
z-bob said:
I'm no expert but that sounds like a loose neutral on the main service wires. You should get it looked into (call the power company) it can ruin your 120V appliances and it's a fire hazard. If that circuit had 75V, another one somewhere has 170V.
Click to expand...

As I said, the good ckt is 120V.

Another odd thing: I pulled the disconnect on the AC, and measuring across the load lines I got about 40VAC. Really weird. I'm going to look at 60 hz waveforms on the scope tomorrow. Something ain't right in Denmark.
 
With no neutral wire to carry the unbalanced load, the split-phase voltages can drift all over the place. The 240V will be rock solid. The main grounding wire is probably carrying a lot of current trying to keep things sorta balanced, and if the ground is saturated with water and it's not too far to the utility pole it can almost do that but it's not safe.

Call the power company. Let them tell me I'm full of it. This is not something you want to mess with yourself.

You asked for advice.:goat:
 
z-bob said:
With no neutral wire to carry the unbalanced load, the split-phase voltages can drift all over the place. The 240V will be rock solid. The main grounding wire is probably carrying a lot of current trying to keep things sorta balanced, and if the ground is saturated with water and it's not too far to the utility pole it can almost do that but it's not safe.

Call the power company. Let them tell me I'm full of it. This is not something you want to mess with yourself.

You asked for advice.:goat:
Click to expand...

I did contact them today. They are busy. You might be surprised how busy they can be sometimes.

Again, 240V isn't steady at all. In fact, the AC isn't working at all. It runs completely on 240V. As you said, missing neutral or ground should have no affect on 240V ckt. My 240 is hosed (I also verified on my brewing ckt, so MUST GET FIXED BY THIS WEEKEND :) )
 
I would be willing to bet that power restoration efforts in Florida have more than just your house's voltage acting a little weird right now.

Seriously, it just might be the result of some maintenance elsewhere on the grid.
 
z-bob said:
Some people got it a lot worse.
Click to expand...

Yea, I'm not complaining. Parts of my county are still dark.

processhead said:
Seriously, it just might be the result of some maintenance elsewhere on the grid.
Click to expand...

Maybe, but neighbors are not having same problem. My neighborhood has underground power feeds to homes, so no exposed wires here.
 
z-bob said:
I'm no expert but that sounds like a loose neutral on the main service wires. You should get it looked into (call the power company) it can ruin your 120V appliances and it's a fire hazard. If that circuit had 75V, another one somewhere has 170V.
Click to expand...

We had that happen in one of our buildings, exactly the same symptoms.
 
passedpawn said:
Weird thing is, some of the ckts in my house are 120VAC. I put a volt meter across both phases of a 240V connector and verified.
Click to expand...

what did it measure across both legs? 240? or less?
the only way to really test it is open up the breaker panel and kill the main and see what the two legs measure where they connect to the panel (no load)

I can't imagine it's Phase related , it's more likely a corroded connection somewhere that drops voltage when a load is applied ;)
 
SleepyCreekBrews said:
what did it measure across both legs? 240? or less?
the only way to really test it is open up the breaker panel and kill the main and see what the two legs measure where they connect to the panel (no load)

I can't imagine it's Phase related , it's more likely a corroded connection somewhere that drops voltage when a load is applied ;)
Click to expand...


50v. None of the 240V devices work now.
 
If the connections are tight coming into the main breaker of your panel and the neutral bond, then you could have a bad connection in your meter panel. Unfortunately, most electric utilities won't let the customer break the seal on a meter panel to do any servicing

Is your service the only one on thepowrr company transformer? .
 
Aha. New data point. I turned off the main breaker and measured what was coming from the meter and verified that one of the lines is completely dead. The good one measures 120V. When I turn on any 240V breaker, the dead line gets lit up a little (through the dryer or something). So, very uncool situation.

I've now turned off all 240 breakers and gotten most of the important house ckts (my home office, kitchen, etc) on the good phase.
 
Have you contacted the utility company yet? That situation is hazardous and I'd bet they'll get there pretty quickly.

Edit: Just noticed that you're in Florida. Doh.
 
Dang, hope they get it sorted out for you soon.

as inconvenient as that is, I was working with a customer in St Maarten yesterday, they got back in the office on Thursday when power was restored and they were ordered to evacuate again Saturday night because of Hurricane Maria :smack:

I sincerely hope that aint headed for the US
 
SleepyCreekBrews said:
Dang, hope they get it sorted out for you soon.

as inconvenient as that is, I was working with a customer in St Maarten yesterday, they got back in the office on Thursday when power was restored and they were ordered to evacuate again Saturday night because of Hurricane Maria :smack:

I sincerely hope that aint headed for the US
Click to expand...

I understand that others have it a lot worse. That doesn't make me feel much better though. I'm self employed from home - I like the AC.
 
Got power back yesterday. Temporary fix.

Because one of the 120 phases was dead, the power company installed a large wheeled transformer next to my house. I believe it's a 120 -> 240 transformer that is operating off that single phase and recreating the split phase for my house. The only connections to it are to my meter and a ground rod that they staked into the ground. That means that that single phase is carrying double the current it used to, but it looks pretty fat so I imagine that's fine.

I would guess they will come in later and trench a new line back to the transformer at some point, but I don't much care as long as the lights are on now.

Thanks for listening :)
 
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Glad you have power back on. My guess is they are short of permanent transformers as they recover from storm damage.
They will probably be back to pull them temp unit out when they can replace your old one with a new one.
 
BrunDog said:
Glad your back to normal. Why do you think they would retrench? Probably just need to replace the transformer.
Click to expand...

There might be a broken underground line. Happened to my neighbor. He put two large palms in front of his house and nicked a line, and a year later lost power. They retrenched around the cul-de-sac, under driveways, to bring him new service.

The power guys told me that I share a the transformer secondary with my neighbors, and that if that secondary was broken the neighbors would have trouble too.
 
yep, sounds like a bad line. more than likely the utility has aluminum running to your house and when those get nicked, it can take some time before the aluminum corrodes and a problem manifests itself. it could have been damaged when first installed, perhaps taking years to become an issue. they may locally cut it and put in a splice but for short, simple runs, they'll likely replace the whole thing, especially if the conductors are old anyway.
 
itsnotrequired said:
yep, sounds like a bad line. more than likely the utility has aluminum running to your house and when those get nicked, it can take some time before the aluminum corrodes and a problem manifests itself. it could have been damaged when first installed, perhaps taking years to become an issue. they may locally cut it and put in a splice but for short, simple runs, they'll likely replace the whole thing, especially if the conductors are old anyway.
Click to expand...

They will run it back to the transformer - I'm not letting them put a big splice box in my front yard. Not sure what "simple is", but it's relatively close except for 3 wide driveways they need to tunnel under.
 
passedpawn said:
There might be a broken underground line. Happened to my neighbor. He put two large palms in front of his house and nicked a line, and a year later lost power. They retrenched around the cul-de-sac, under driveways, to bring him new service.

The power guys told me that I share a the transformer secondary with my neighbors, and that if that secondary was broken the neighbors would have trouble too.
Click to expand...

Oh! Ya something is funny then.
 
Yeah that changes the scenario.
If they did need to splice anything, I doubt they would put any kind of splice box in your yard. Most low voltage underground splices are direct burial and below grade.
 
processhead said:
Yeah that changes the scenario.
If they did need to splice anything, I doubt they would put any kind of splice box in your yard. Most low voltage underground splices are direct burial and below grade.
Click to expand...

They put a big box in my neighbors yard when he lost power a few years ago. I talked to him about it when he got home. He was steaming: "Andrew, you know why they did that? They're being f'ing lazy. I guarantee you that box will be gone tomorrow." And, it was :)
 
Closing the loop...

Power company finally came and remove the large transformer on the side of my house that was giving me split phase off the one remaining good leg coming into my house. They used a neat instrument to find the break in the bad leg. It was right under a sprinkler head. Apparently it had been nicked a long time ago (I've been here since 2001 and I don't think I've worked on that sprinkler). The tech cut out the offending 6" piece and patched. Back in business.

The nick went through the insulator and eventually the internal aluminum wire turned into a massy knuckle of AlO2. I removed the oxide and there's almost a 1" gap between conductors. I'm guessing that the final thin conductor vaporized in an I^2R flash.

upload_2017-12-3_22-5-43.png
upload_2017-12-3_22-6-24.png
upload_2017-12-3_22-6-47.png
 
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The good news is that you have a hard failure to point to.Your story is a good one to tell to people who say that underground utilities fix all problems. It does fix tree limb problems, but opens up a whole 'nother can of worms.
 
That was a cool story.

Reminded me of a service call once with similar power issues except it was winter in the UP. The first thing we noticed was a fairly good size patch of ground where the snow had completely melted and the dirt was steaming.

Must have taken a few watts to heat up the ground like that.
 
lschiavo said:
That was a cool story.

Reminded me of a service call once with similar power issues except it was winter in the UP. The first thing we noticed was a fairly good size patch of ground where the snow had completely melted and the dirt was steaming.

Must have taken a few watts to heat up the ground like that.
Click to expand...

Hopefully, the fault was on the utility's side of the meter. That likely would have had the customer's meter spinning pretty good.
 
lschiavo said:
That was a cool story.

Reminded me of a service call once with similar power issues except it was winter in the UP. The first thing we noticed was a fairly good size patch of ground where the snow had completely melted and the dirt was steaming.

Must have taken a few watts to heat up the ground like that.
Click to expand...

sort of like looking for a leaking underground gas line, look for the big patch of dead grass :yes:
 
Several years ago, the plant where I worked decided they had a leak in an underground anhydrous ammonia line where it crossed a large grassy field. The give-away was a large dead spot of grass surrounded by super tall, dark green, lush, healthy grass in a field of otherwise mediocre grass.
 

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