I’m looking at a new to me shop building. It’s actually a old barn. The building currently has no electrical service. It was once electrified, but for safety reasons I do not plan on reusing any of the existing wiring or fixtures. At the road there is 3 phase power. It will proably be 200′ of above ground service to the building. My question is about power. I currently have 100amps of 220v power at my current shop. I’ve never had a problem with the low amperage as I only use one tool at a time. That said, I’m interested in 3 phase power at my new building. I currently don’t own any 3phase tools, but I see them all the time on ebay. The nice thing about 3 phase tools is that you can buy the old industrial grade tools that nobody wants (cheap!) because of the power requirements. Great! Sign me up! However, I’ve been warned that I can get into some expensive meter or meter rates. I’m also concerned about the cost of running the 3 phase service and the panels. I was honestly planning on wiring most of the shop myself, but I would need to hire out the 3phase equipment as it’s beyond my knowledge base. How low of a amperage can we get in 3 phase? What about my 120/220v panel? I don’t want to go below 100amps of 220v. Does the 120/220v just come off one leg? ie when I do my own work, can I just shut off the main breaker to safe the 120/220 volt panel? Thoughts?
Certified boat fetish.
Replies
For starters you wont have 240 any more, you will have 208 volts. If you have electric stove or similar, you'll probably need to buy an autotransformer or you will never have a 'high' setting on the stove. Same thing with your welder.
3 phase often has a demand charge that can really jack your bill depending where you are/ utility provider.
Advise would be to stay with single phase, buy a surplus 15 HP 3 phase motor and build yourself a rotary converter if you want to run the old 3 phase tools.
For your application the best is probably a 4-wire delta service.
That consists the 3** transformers, one on each leg connected in a delta.
http://www.federalpacific.com/university/transbasics/chapter3.html 2nd picture.
Except one of the transformers has a centertap, just like the single phase 120/240 systems. That center tap is grunded and is the neutral. So you have 240 between any 2 legs of the 120 between the neutral and the two 'lower' legs. The 3rd leg is called the wild leg.
** They might also use a open delta configuration, which only uses 2 transformers. Specially as you have limited 3 phase loads (at this time).
Wiring is not too much different, except for 3 phase loads you run 3 hots and a ground. The main thing is that rotation is controlled by the order in which the hots are connected.
In a case like yours I would get a 3 phase main panel and the run a 120/240 sub-panel off it.
But you need to contact the power company and see what there cost will be to install this service. Specially since you don't have any 3 phase loads now they might not do it, charge full cost of the extransforers, and/or have a large minimum fee.
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
There are a number of major issues involved here; the involvement of the Utility and a licensed electrical contractor are unavoidable.
The Utility is going to have a minimum requirement for their meter; 100 amp is likely. Even if someone were only extending a line from their home, it would be foolish to feed less than 60 amps to the panel.
I've said it before, and it bears repeating here: BURY the lines, and bury them deep. If they come from the Utility transformer, their standards will apply. Most likely, that will be a ditch three foot deep- after the bottom is covered with sand. Whatever the size of the service, I advise running separate wires - NOT cable - in as large a pipe as you can. This will greatly ease pulling the wires, and replacing them later on. Since we're talking about 100 amps, I don't think 3" pipe is unreasonable - especially with the length of your run.
Your local codes are likely to require a disconnect on the outside of the building. A nipple straight through the wall, to the panel, is the easiest way to go from there.
There's not much savings in using a small panel. I recommend at least 24 spaces - 12 0n each side. You'll fill them fast. I have a bias in favor of "bolt in" types of breakers.
You will need a ground rod.
Finally, you need to be SURE of the power you are receiving. "3 phase" is available in several varieties, all of which make a difference to the electrician. It may be best for you to also have a transformer of your own, depending on the type of 3 phase the utility provides.
I don't know about commercial power, but for a residental service the utility owns the lines and transformer up to and including the meter. I provide the socket though. After the meter, the cost is on me. The utility also doesn't charge anything for a buried service. I kinda forgot about that option. I don't know if they charge a premium for a commercial buried service though. I actually like disconnect switches as they keep me from frying my butt when I take the panel cover off, but even a small 3 phase disconnect can't be cheap.
Certified boat fetish.
I went to the utility website and looked up this information:
View ImageOverview This is the default rate plan. Your monthly energy usage is billed at a flat rate.
Charges Standard: General Secondary-CG1 Facilities Charge (one meter)
Single-phase service $0.26175 per day
Three-phase service $0.52350 per day
Each additional meter $0.04110 per day
Energy Charge: 9.988 cents per kWh Fuel Adjustment: 0.00 cents per kWh Transmission Adjustment: 0.00 cents per kWh
Their residental pricing:
View ImageElectric
OverviewWith standard price, your monthly energy usage is billed at a flat rate. Temporary charges and adjustments may appear as line items on your bill. A 1 percent per month late payment charge (1.5 percent in Michigan) is applied to outstanding charges past due.ChargesWisconsin
Facilities charge: $0.22027 per day
Energy charge: 9.988 cents per kilowatt-hour
Non-taxable fixed charge: 3 percent of monthly charges or $2.97, whichever is less.
Fuel Adjustment: 0.00 cents per kWh
Transmission Adjustment: 0.00 cents per kWh
So if I'm reading this correctly, my meter cost is doubled for 3phase, but the actual energy usage is the same. The extra meter cost seems to be offset by the absense of the monthly $2.97 charge. Thoughts?
Certified boat fetish.
Pretty simple to just run a rotary converte for the three phase tools you want. I have all mine set up to turn the converter on automatically when the switch is turned on. A 1.5 sec time delay relay allows the phase converter get to get up to speed before the machine comes on. Works great and I only run the converter when it's needed.
"The utility also doesn't charge anything for a buried service. "In general that is not true.Many POCO's will provide a nominal distance, either above or below ground. Past that point you have to pay for it..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
I guess that's what I meant. I don't remember the distance, but I'm sure that 200' is over it.
I briefly looked at some rotary converters years ago, but I had trouble separating the BS from the chaff and gave up. Care to educate me some more?
Certified boat fetish.
There is a fair amount of info on doing it yourself on rotary converters. Somewhere I have several articles stashed but don't have the time to chase them down. Here are a couple from a quick Google search:http://www.essortment.com/hobbies/rotaryphasecon_sflv.htm
http://www.cnczone.com/forums/archive/index.php/t-7859.html