3phase

   / 3phase #11  
And one other thing that might be mentioned Franz, is that there are no pesky starting circuits or capacitors, or switches, or,...or...or... SO MUCH LESS machinery with the squirrel cage induction motors!!! Three-phase IS nice to have, no doubt about it. The modern conversion to 208V three phase for light industrial uses is an attempt to be able to use all three legs for single phase loads such as in hospitals, office buildings, and schools. Some of the early stuff had a "stinger" leg which was high voltage and useless for the 120V circuits. I have got "burnt" a few times buying used equipment that was 240 volts ONLY and just would not run on 208. In large buildings, even the lighting is three-phase with 480V on the power leg. Good way to get killed if you don't know about it.
 
   / 3phase #12  
Franz, I think we're talking the same language. My question was just how much difference it makes to a Harry Homeowner setup. A real shop / factory would deal in values of a much greater magnitude. Whether a guy with a shop in the barn needs to go 20' with 2# 8's or 3#10's really doesn't matter a whole lot. The 5HP motor in the example would draw roughly 32A on each of two wires or 17A on each of three wires at full load. Power consumption is the same.

I haven't been involved in demand metering to any extent. I have done installations of services with 4000A at 480V three phase though, and all we did was check to insure there weren't any major unbalances between the phases. That never was a problem. You'd almost need to plan to get them unbalanced. I did speak with a couple customers who have load-shedding programs..................chim
 
   / 3phase #13  
Demand charges can be the budget killer for a lot of small businesses, primarily because people never think about them till the bill arrives. About the best site I've found for an explanation of Demand Charges is http://www.niagaramohawk.com/youracct/aboutbill/elecdemand.html
Depending on the utility, getting rid of unjustified demand charges can be an exercize in brutality as it has been with NyMo.
An interesting reality regarding demand charges, is that utilitys are perfectly willing to sell high demand power to municipalitys without demand charge for resale to muni customers, but won't budge for commercial or industrial customers.
I've been away from Peak Shedding machines for a while, since the cost of diesel went above 85 cents a gallon. That was the rough figure we used back in the early 80s when customers considered cogen systems.
 
   / 3phase #14  
Thanks for the <A target="_blank" HREF=http://www.niagaramohawk.com/youracct/aboutbill/elecdemand.html>link</A> Franz.

A bud was telling me his father's shop bill was through the roof because of the three phase service. I couldn't understand why. Your link explained it in such a way that even a dummy like me got it. Makes sense, cents too.
 
   / 3phase #15  
<font color=blue>...Demand charges can be the budget killer for a lot of small businesses... Depending on the utility, getting rid of unjustified demand charges can be an exercize in brutality as it has been with NyMo....</font color=blue>

Hi Franz...

Boy, did we ever find out the hard way... once you get on a demand meter... you're stuck!

Owning worthless stock in the utility company, I think would be cheaper... /w3tcompact/icons/blush.gif
 
   / 3phase #16  
You're not necessarily STUCK, but getting back off the Demand metering is a lot harder than getting on.
I recommend carefully reading your provider's tariffs reletive to Demand metering. Most utilitys routinely violate their own tariffs, after all, they profit from doing so, and SCREW customers who only occasionally meet Demand criteria.
Small businesses often find themselves victims in this game because they regualrly deal with "electricians" who don't offer them all possible alternatives before installing more equipment. A real electrician will be worth his charges because he will show you how to employ things like peak shedding to avoid Demand charges. He also won't do things like run Romex in a commercial situation.
Then again, customers usually get what they pay for, and keep paying for the cheap price forever.
 

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