# Residential & PF

Hi,
Can't find much activity on most of the elect.. groups so chose this one, so feel free to redirect me if there's a better place to ask this.
Actually, I might hang around here for a bit; looks interesting. I'm an analog EE with a digital EE experience, now retired for health reasons.
I have the following:
118 Vac average, ~ 2.2A, 205W, 269 VA, 0.78PF (Power Factor), and 0.34 KWH measured over 1.62 hours. (Killa Watt Meter toy - seems pretty accurate, comparing to some of my good equipment)
Total grid charges here are \$0.156/KWH.
That gives me an hourly cost of approximately \$0.0333 to run this appliance, or \$0.79/day.
Do I apply the Power Factor or not for residential costing? Obviously there is no cap bank, etc, but how does the powco look at that? Playing with the meter, the PF is all over the map depending on the appliance, which I didn't expect to find. I'm well aware that PF at the meter would be something entirely different and I've never heard of PF issues for residential service, but ... if I don't ask the stupid question, I remain ignorant<g>.
Yeah, I know, a new toy always exposes the user's ignorances, but hey, I just hadda ask.:^)
What say any power line experienced folk here?
Also: If you know of a group better suited to this sort of discussion, I've be glad to know it.
Twayne
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TWayne wrote:

Don't sweat the power factor. Residential metering is based upon kWH and the metering equipment does not register the reactive or harmonic parts.
There is a tiny 'second order' effect when dealing with constant power loads (motors and switched mode power supplies). The additional current drawn as reactive power will produce a small power loss due to branch circuit I^2R losses. You can make some assumptions about R and calculate this, but the return on investment for p.f. correction isn't economically viable.
I added another newsgroup that might be of interest for this topic, but the traffic there is practically nil.
--
Paul Hovnanian mailto: snipped-for-privacy@Hovnanian.com
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Killa Watt is a great window into measurements that were previously inaccessible to home owners. As you found, it provides a tidy little tidbit of information that may be useful for you to understand just how much an appliance is bleeding from your purse, and thus the nation and the world.
For safety reasons it is probably better that one does not go about modifying appliances to get closer to a resistive load but I understand where you are coming from. You are enlightened enough see your appliance is throwing 54 watt hours per hour to the "terrists" who provide the fuel for our polluting power plants.
Considering that the power delivered to you appliance by the electric utility is a fraction of the energy required to make it and pump it through the distribution system for your appliance to consume, correcting the power factor could save 100 watt hours per hour or close to a megawatt ( 24x365x100W) of prime mover energy per year from being consumed.
If there were ten million of these appliances on line 24x7 that little power correction, to all of them, could prevent the need for one more nuclear power plant. Ten million is how many appliances there would be if one in thirty Americans owned one of them.
peace dawg
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No it's not. The reactive power does not require fuel into the power plants. Reactive power is energy that is "traded" back and forth between your appliance and the power grid, but almost as much is passed back in one portion of the cycle as was taken in another portion of the cycle. It's not real power.
It's not *entirely* free. If the PF was 1, that appliance would draw only 1.74 A, not 2.2 A. The "extra" 0.46 A causes extra resistive losses in the house and utility wiring, and that wastes real power - but only a few watts, not 64 W. (269 - 205 = 64, not 54).
Also, "watt hours per hour" is simply Watts. Why invent a new but useless unit?

Again, reactive power isn't real power and doesn't need prime mover energy, other than the small amount of real-power losses. And the extra current in the wiring happens only between his home and the utility's closest facility that corrects line power factor, not all the way back to the alternator.
Dave
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Wecan do it wrote:

You are apparently confusing "power factor" and "efficiency", which are two different things. The ratio of power delivered over power produced is the efficiency, not the power factor. In fact, the power delivered to your home is a fairly large percentage of the generated power.
Power factor is the ratio of real power (W) to apparent power (VA). Improving power factor reduces reactive power and therefore apparent power, but has theoretically no effect on real power. In reality there is a small effect on real power due to a slight reduction in the conductor losses because the current is reduced. Therefore it has only a small effect on the prime mover energy or your residential meter reading. For a typical residence that operates at fairly high power factor it is insignificant. For large factories operating at low power factors it is much more significant.
--
Benjamin D Miller, PE
www.bmillerengineering.com
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If the load needs 269 VA at .78PF and the generator can only generate 205 watts would the load be getting all the power it needs? Would the generator have to deliver 269 watts to satisfy it?
peace dawg

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Yes, the generator only needs to generate the real power, although the current flowing in the wires (and thus the resistive losses due to that current) is about 30% higher than it would be with a power factor of 1.
Think of the reactive power as energy that is oscillating back and forth between the motor (or whatever inductive device is in the appliance) and the grid. The motor "borrows" it for part of a cycle, then "returns it" in another portion of the AC cycle. It doesn't contribute to useful output, but it doesn't load the generator either.
Dave
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Would a 205 megawatt generator set be able to drive 269 MVA load?
does 205 W @ .762 PF = 296 VA?
is that the same as 205W @ - 40.35 degrees?
is that the same as (205 -j174) watts load?
peace dawg
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Although, in the case of thermally-generated power, the power delivered to your home is apparently only about 30% of the original heat energy produced by burning fuel (or fission of atoms, concentrating the sun, or whatever source of heat was used). That's because the process of converting heat into electrical energy is inherently inefficient.
So burning fuel to generate electricity which is transmitted to your house and then converted back to heat takes about 3 times as much fuel as if you burned the fuel in your house in a 90% efficiency furnace. Electric resistance heating is 100% efficient, and the transmission grid is pretty good too, but the fuel->heat->electricity step is not. And "efficiency" depends a great deal on what you choose to measure as the input and output.
Dave
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LOL! Wow, this is an interesting thread to greet a newcomer with. It only took one post to identify the egos, louts and misfits even if a few of them do know what they're talking about. Obviously several participants are parrots and the others like their buzzwords and guess a lot, while a few actually know what they're talking about. That tells me, don't ask a question here if you really want a professional and accurate response to most things.
Maybe I'll see you all again, dunno.
Twayne
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TWayne wrote:

Aha! A newcomer. I'm surprised that some of the folks here didn't try to sell you on the latest financial scam or flat earth theory.
You've got to lurk on a newsgroup for a while in order to figure out who the goofs, trolls and troublemakers are. In the final analysis, the advice you get is worth every penny you pay for it.
--
Paul Hovnanian mailto: snipped-for-privacy@Hovnanian.com
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On Sun, 07 Sep 2008 21:04:53 -0700, "Paul Hovnanian P.E."

Flawless.
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lol, well, then again, there is the experience factor. Like I said, several personalities stood out immediately; much faster than on most groups. So, no, one doesn't necessarily have to lurk in a group to figure out who the goofs, trolls, etc. are. But I do admit it's a LOT faster to happen here than on any other group I've worked on. Now, about that flat eart theory: How could something so sensible and so obviosly evident be debatable in any way? Heck, every high school kid knows the earth isn't round; far from it, in fact! But I digress, don't I? Well, don't I? I've decided this group does have some value after all, BTW. Reading through tonite's episode was truly amusing, even somewhat interesting in a comedic sort of way. At least I haven't heard anyone make any snips about hole theory being dismissed; now, that would be funny. How many electrical engineers participating in this group does it take to change a lightbulb? None. All but one don't know how and the other person is too smart to bite. How many electrical engineers participating here does it take to kill someone? None. Anyone standing too close to this group will die by default.
Were there ever any real, actual electrical engineers in this group? Are there now? Stand up and identify yourself if you are actually an electrical engineer. Here's a test question for you: Does an electrical engineer's career ever encompass nothing but digital transmission circuits? I'll bet over half of you don't know the correct answer, or if you do, you don't know why it's the correct answer.
Cheers all, & thanks for making me feel so much a genius by inference,
Twayne
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TWayne wrote:

Yes & yes. Real and actual ones too.

I have some paper that says I am actually one, so I guess I am. Sometimes I even get to sound the train whistle.

Ooh, a test, and I forgot to study. Can I make it up a different time?
--
Benjamin D Miller, PE
www.bmillerengineering.com
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Ben Miller wrote:

Big deal! They sell clocks that do that on the hour. My retired dad has one with a steam locomotive & whistle. :)
<http://www.thingsyouneverknew.com/product/usefulthings/clocks/steam+engine+train+sounds+clock.do

Sure, when you finish building that time machine. ;-)
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aioe.org, Goggle Groups, and Web TV users must request to be white
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Michael A. Terrell wrote:

<http://www.thingsyouneverknew.com/product/usefulthings/clocks/steam+engine+train+sounds+clock.do
Oh well, there goes my job. Replaced by a machine.
--
Benjamin D Miller, PE
www.bmillerengineering.com
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Ben Miller wrote:

What can I say? It happens to us all, sooner or later. :(
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Ben@somewhere says...

Electric train, I hope. Otherwise you'll get the steam union mad.

Don't worry. It's open (note)book.
--
Keith

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Tha's OK; wasint ment fer a reel engine ear neway<g>; I usta dreama bein a infrared engineer and now I R one.
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wrote:

Perhaps you should actually attempt to word the question correctly then, dipshit.