Replies

1. 
   WayneL5 | Dec 20, 2002 12:52am | #1

   It's possible with 3 phase that you have 480 volts.  Many industrial buildings do.  You're probably best off with an electrician.  Choose one with industrial experience, not one that does only residential work.

2. 
   booch | Dec 20, 2002 05:39am | #2

   I'm with Waynel5 on this. I'd bet the panel is 3 phase 480.

   You say "plain box" after the initial meter. Size of a desk?, a computer?, some size inbetween? Chances are it is a 3 phase transformer with lower voltage taps to provide 277, 240 or 120 or some combination. 277 on lighting (wye) would be common in some applications. 240 3 phase would be common in others. 120 is of course there as well.

   Square D alone has 3000 varieties of transformers that are used in small industry. Some are custom made some are shake em out of the box standards.

   Then again you could have an electrical enclosure that has multiple transformers inside of it. That is one larger one to split the 480 into a lower buss voltage then lower level transformers to take that and drop it further.

   Too bad your name isn't Pandora. You have much the same story as her here. Although played right you have a tits shop.

   If you open it there will be lots of issues to deal with. In the least you need to clean off the nameplate on each transformer to see what it is. Then you have to see how the installer tapped it and what voltage was delivered on the secondary. Danger Danger. This isn't like the toaster where you have to be stupid to put yourself at risk. Each transformer has a terminal strip (the smaller ones) and the larger ones have taps that come directly from the windings. Every connection and screw without connection is to be considered hot. If everything is clean well marked and neatly wired it can be figured out. I doubt it, it sounds like older gear with paper labels and little information provided.

   The thing that tips me to the age is: First you have no High voltage tags. Second there is no voltage identification labeling anywhere. And third I haven't heard much talk about what kind of fusing / breakers are in the panels / safety switches.

   Call a buddy get a reference and get a real electrician. Not the guy that fixes apartment outlets but someone who works  in industrial or mixed trades. You'll drop a couple hundred to hear him talk. You need to be there to write notes on what is what circuit and is it protected.

   Your real danger here is that there could be multiple circuits in the box and throughout the shop that are not identified. Plus I would bet the legacy stuff you have there could be misapplied. Not expensive to fix but consider that some schmuck could have but a 300 volt rated fuse in a 480 volt fuseblock... etc. Seems like a small issue, but you need to know that the rating is your only assurance that when the fuse blows it stays contained. I can't tell you how many NON style fuses I see in 480 volt slots. It is like a stick of dynamite if it blows..maybe. Have him/her check out the wiring protection as they explain the circuitry to you.

   It could be that all is well and nothing needs be done. The problem is that 480 is nothing to screw with. Most of us that actually do something have gotten poked by 120 and have seen or participated in a 240 screwup that generated some smoke. 480 puts you in a box unless you treat it with respect.

   Last thought really simply put: 60amps 480 3P converted to 120v 1phase is 720 amps. That is a pile of juice! Good Luck!

1. 
   riverr1 | Dec 20, 2002 06:10am | #3

   Booch,

   Yea, I pretty much resigned myself to calling some one in after Wayne's post. The question in itself would be like me wanting you to know what color of car my neighbor has in her garage. Silver by the way. The lines were cut at the pole about 5 years ago, and it took me 6 weeks to get the power connected because they kept telling me they were there and I had power. Finally took them giving me the local service yard supervisor's telephone number to get them to realize what power I was asking for. Seems they didn't even know this pole was there. Because of the previous 3 phase power to the shop, that is why this pole was not taken out and power run with the rest of the power in the street.

   As for the box between the meter and the panels, it's not that big. Maybe 4 inch thick and 12" x 14". One panel is breakers, the other two are glass fuses with paper cartridge behind them. There are also 2 paper cartridge subpanels before the fuse panels. That's a total of 5 boxes. You're right about the paper. Long past anytime when they were readable. Some you can tell they once had color and writing on them though. I would guess what's in there is pre WWII. But that's just a guess. The original power drop is still there also. Old knob and tube right through the solid brick walls, 4 lines. There is also an old mast from another previous power drop. I don't think this meter is anywhere near that old though. Maybe from the 60's.

   Thanks for the attempt at helping me though. I appreciate it. Geeesh, If I have 720 amps, you think I'll ever have to worry about dimming lights when I turn my General cabinet saw on? haha

   Don

1. 
   booch | Dec 20, 2002 06:49am | #4

   It won't be hard to sniff out once it is looked at.

   As for the fuses.

   Paper (actually some composite material now) fuses aren't all that bad. They need to be spec'd right is the problem. Back in the day they were probably proper. The problem is that ace hardware doesn't carry 600 volt rated fuses so the fly by night repairman will get what is available and put them in. That is why they now require rejection type fuses in new installations. You can't put a lower rated fuse in the higher rated slot.

   Fuses always blow. They age as well. After near blown status on a fuse and / or storage in high temperature areas, the amp capacity of the fuse drops. Some as much as 80 percent depending on the ageing. The beauty is that they blow prematurely. Breakers quite the other way, again, sometimes.

   PS on the glass fuses. Generally they are on the secondary of a transformer. Most have a 250 volt max rating. Some, from the hardware store again, only have a 50 volt rating (they are designed for DC) if they are mis-specified. Even small fuses now days are rejection type.

   Ask the electrician how balanced the transformer load is (assuming there is more than one transformer). If you go back to three phase, then each phase needs to be balanced for load. Otherwise you get some awful power bills. three phase is monitored for peak, powerfactor, and usage. You get billed on each. Usage is just like home. Powerfactor relates to your power balance (this is really a glazing of the topic), and the peak is what will cost a fortune.

   As an example a buddy of mine does welding out in the sticks, where he lives, for his hobbies. He also does it for local farmers when their combine takes a dump. Peak usage is determined over the highest 15 minutes of the month. Whatever that peak demand usage value is, determines the bill for the whole month. Peak is paid on top of the usage(wattage) bill. My buddy had bills over 300 dollars several months. That could have bought lots of tools.

   You are buying power with the big boys when you buy 3 phase. (GM, Ford, and any other industry) The rules were made for them to stay in line and not cause inadvertent peaks that require more power plants to be built. Time of day also plays in to the billing. Ask your power company how they will bill you and what type of metering they have on you if it isn't already obvious. Amazingly they do have sympathy for the little guy. They want you to get big so they can really clean you out.

1. 
   riverr1 | Dec 20, 2002 03:31pm | #5

   Booch,

   Thanks again. Can you tell me how to use a vom on a 3 phase outlet?

   Don

1. 
   booch | Dec 20, 2002 05:58pm | #6

   First wear rubber soled shoes (leather is a good conductor) and don't lean on anything when you are working. You don't want to be a wire in this equation.

   Set the meter to AC and make sure the wires are plugged into the right locations on the meter.

   Set it to 600 volt range. If it is a modern meter it may have an autorange feature but be certain. You could smoke your meter if you pick too small a range.

   There are different models out there. Some are made for household current (radio shack lower end models). If it doesn't provide for 600 volts don't use the meter.

   Lay the meter on a solid surface then hold the probes by the insulated handles and begin measurements by reading the ground to the surrounding enclosure voltage.

   Phase to phase and phase to ground measurements are the measurements you are interested in. You'll need to check each phase to ground as well as each phase to each phase. Some assumptions could be made but assume everything is hot. Even the ground and common wires are suspect in a old wiring application. That is why you start at the ground and common voltage readings.

   If you don't have a meter and need to buy one then get a "Wiggy" which is the first autoranging meter that uses sound and visual indication to tell you the voltage. Most electricians have one of these.

   If you are nervous that is good. If you are scared then call the electrician that would be safer.

   start measuring