ECN Forum Forums General Topics of the Trade General Discussion Area Typical Engineer's Overkill

George:
Your post jogged my memory. My calcs from 1993 indicated max VD on any circuit to be <2.5%. I had never checked VD physically, only by calcs. I checked the longest, most heavily loaded interior 120V circuit about an hour ago (2:00 P.M. CST). Second floor bath #2, 1500W heat-fan-light combo.
Voltage @ CB=125.2
Voltage @ heater (energized)=122.6
VD <2.1%
I have a POCO dedicated pad mount (50kva) approx 90 ft from service eq.
My recorder indicated that incoming voltage has varied from 127.1 to 123.9 over a period of 12 months.
Rowdy

Dedicated transformer and a voltage recorder? You sure are an engineer!

Aren't those figures a bit high? Sounds as if you could extend the life of your lightbulbs quite a bit by lowering the voltage...


[This message has been edited by C-H (edited 11-03-2002).]

rowdyrudy -- Check your utility's publishsed service conditions, before you call them on it, for your upper reading sounds a bit high. [Make darn sure your meter is accurate beforehand{!) or get ready for some embarrassment.]

At the meter, 126V {er, 252} is the ususal limit per ANSI standard C84.1-1995.




[This message has been edited by Bjarney (edited 11-03-2002).]

Rowdy, RX, MC, ENT, EMT????
John

Rowdy, after ribbing you, at least I should ask some serious questions:

What would the figures over time be for savings due to the over-sized conductors preventing losses due to resistance heating (I-squared times R) as compared to a "cheap" system?

The ads for copper point to turn-around times of a few years for copper Xformers versus Al, any similar savings here?

4160/7200V Wye: just a typical medium voltage system that is fed to some larger factories, and composes most of the power distribution systems in my area. I probably could've cited a better example, and I'm sure I said something to give Bjarney a chuckle! He's the real deal when it comes to medium and high voltages...

Savings? The higher the voltage at the equipment, the higher the losses. Higher voltage at your computer won't make it run any better, it'll just waste the extra voltage as heat. I find this idea of saving money by using bigger wires very strange.

Sparky,
I'm just questioning the voltage relationship. I have seen 2400/4160V and 7200/12470V but never the combo you describe. The math works so I am wondering if your utilities use this voltage?

Nick, Yep, 4160/7200 Wye is the common distribution systems here. 19.9 KV Delta for transmission. Not sure what the voltages are beyond that... Personally, I'm not trained for anything over 480V.

C-H
What I meant was, given the same load and the same source voltage, oversizing conductors (in this case, for the Service Cable, instead of 4/0 Al for a 200A Service, using say, 400 KCM Al in the 400A Service) what savings from resistance heating could one expect?

hey Sparky66,
the downloadable voltage calculator, that was linked a few posts ago, has a calculator in it that, if you plug in the cost of your local electricity, will calculate your savings for you, and let you decide if the savings are worth the money on the oversized wire.

Just used it on a little project I have going here at the 'road.

TW

Thanks Trainwire, I managed to miss that one!