138 Volts!?

[Papa Bear]

We used to be 25 cycle here in Ontario, Canada.
I remember seeing 25 cycle power transformers from radios etc that were switched over to 60 cycle, they were HUGE.

 

[tom slick]

If you are comfortable checking voltages at the panel I'd check both legs of the 120V to neutral and ground make sure one isn't reading low. A bad neutral will show up as high voltage on one leg and low voltage on the other when checked to neutral, they'll be equal when checked to ground as long as the ground is good.

 

[PandaBear]

RMS voltage could be quite a bit different than the peak to peak voltage, but that's about 1.414 times difference, and I don't think yours is at 97.6V.

 

[tom slick]

Originally Posted By: tom slick
If you are comfortable checking voltages at the panel I'd check both legs of the 120V to neutral and ground make sure one isn't reading low. A bad neutral will show up as high voltage on one leg and low voltage on the other when checked to neutral, they'll be equal when checked to ground as long as the ground is good.


This needs to be amended to check for voltage between neutral and ground and isolate the ground as they are probably connected at the main.

 

[SecondMonkey]

Thanks for the replies everyone. The main problem is the building is managed by some dumb woman who knows nothing about industrial property - when I asked if three phase power was available she acted like she'd never heard of such a thing.

I think what I'm going to try and do is have a new power meter/service put in just for me, with my own breaker panel.

Oddly enough, the "220v" outlet reads 230v exactly...which should make each leg 115v, wouldn't it?

I probably should have figured this out before I signed the lease...but I just couldn't pass up the price. Now I've got a shop bigger than Jiffy Lube....you have no idea how long I've wanted my own shop!

Now I have an excuse to buy a fork lift!

 

[SecondMonkey]

One more question - If the outlets are 138v, would that be an electric code violation?

 

[labman]

If you have 230 phase to phase, those suggesting a bad ground may be right.

 

[river_rat]

Originally Posted By: SecondMonkey
Oddly enough, the "220v" outlet reads 230v exactly...which should make each leg 115v, wouldn't it?

Not necessarily.
Picture a Y with equal length and spacing of the three "legs" of the Y.
Picture the center of this Y as grounded and connected to the neutral at the main service panel.
Let each one of these legs from the center out to its end represent one secondary winding of the power transformer(s) supplying this panel.

Now, Picture the voltage coming out of the transformer on each of these legs being 120 volts AC from the tip of the leg to the grounded center.
All these legs can have 120 volts to the center, but they are timed--or "phased"--so that the instantaneous voltage peak (either positive or negative, pick one) occurs at, say the top right one, as the bottom one has already peaked and is heading toward 0 volts. At this moment, the upper left leg has passed 0 volts and is heading back toward its peak voltage of the opposite polarity.
This is three phase--120 degrees of rotation apart.
A motor wired to all three legs will see a rotating current on its windings and want to turn. But if you only want a single phase 120 volt outlet, it would be wired between any one of the leg tips and the grounded (neutral) center of the Y.

OK. Back to voltage. Even though there is 120 volts on each leg to center, there would normally be 208 volts AC between any two outer tips of the Y legs...because they are not at peak opposite voltages at the same time...not maximum push/pull elecron force at the same time.

The math factor is the square root of three. Approximately 1.732.
208 volts (tip to tip) devided by 1.732 is 120 volts (any tip to center).
This is a typical and most common commercial system: 208/120, 3 phase.

If someone wire this for a 240 volt delta system (triangle, not Y--which we won't get into) Then you have 240 volts devided by 1.732 = 138 volts. That is what you are measuring on your receptacles, apparently.

These are just the general principles. You should get an electrician now.

 

[eljefino]

One more check for a loose neutral... bring in a few hair dryers, space heaters, coffee makers, toasters etc and trace your outlets back to the breaker box. Most 2-phase boxes have one phase zig-zag down while the other phase gets the rest. Put an equal load on outlets on both sides, this lightens the influence of the neutral. If that brings your test outlet closer to 119 you're diagnosed.

Of course by this loose neutral theory you should have other outlets on the other phase running around 100-105.

I had a tree branch fall in an ice storm and tug on my service drop just enough to loosen the neutral... so it can happen.

I wouldn't put up with any guff from the management company... read your lease... shoot, read the building codes and find out if they are even ALLOWED to rent property that doesn't meet spec.

 

[dishdude]

Originally Posted By: river_rat
Actually, the more I think about it, someone might have just improperly center-tapped a 277 volt circuit. I really wouldn't get into a panel, especially a 480/277 volt panel, unless you know what you are doing.


This is what I was thinking too, as soon as I read it was a warehouse.

 

[SecondMonkey]

Alright...today I was trying to figure this out, and I ended up getting 180 volts out of the 110 outlet, and 312v from my 220v! Something has got to be totally screwed up somewhere.

I talked to the landlord, who doesn't even know what volts are, and she said she's going to have the utility come out and look at it. Unfortunately my breaker box is in the unit next door with the crazy russian guy...I think I will be installing my own subpanel once I get this all figured out....

Thanks for the help everyone!

 

[labman]

I wonder how the last tenant made out? Was he run out of business replacing electrical stuff?

 

[Pablo]

Maybe I missed it, but did you answer my question?

 

[SecondMonkey]

Originally Posted By: labman
I wonder how the last tenant made out? Was he run out of business replacing electrical stuff?

The guy next door to me used to rent my shop, then he moved over one for some reason. I measured his outlets at around 150v and showed him, he didn't know and was surprised. His tools seem to be working ok though...

Originally Posted By: Pablo
Maybe I missed it, but did you answer my question?

Sorry - I'm using a cheap digital multi-meter. I brought it home to check for 120v at my house and it seems to be reading accurately.

 

[tom slick]

Quote:
Unfortunately my breaker box is in the unit next door with the crazy russian guy...I think I will be installing my own subpanel once I get this all figured out....


who knows what Vladi been up to

I'd certainly be afraid to plug anything in.

 

[SecondMonkey]

Originally Posted By: tom slick
who knows what Vladi been up to

I'd certainly be afraid to plug anything in.

Exactly. I'm going to have to change the locks because I don't know if he still has a copy of the key. He gave me one key by opening my door for me when I got there.

Then again, I've had MUCH worse neighbors!

Youch!

 

[Samilcar]

That's almost 50% higher than nominal voltage.

 

[Papa Bear]

Methinks you need a new meter .....

 

[tom slick]

If, for some stupid reason, that meter was reading peak-to-peak it would display 178v but I doubt that is the problem.

 

[labman]

Originally Posted By: Papa Bear
Methinks you need a new meter .....

If you are getting a higher reading at the shop than at home, I doubt a better meter will help.