Power factor correcting capicitors?

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dacflyer
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Power factor correcting capicitors?

Post by dacflyer » Mon Jul 29, 2002 10:40 am

is it too complicated to to use pfcc<p>i have several sodium and mercury lamp fixtures here,, and they all show that the use of a pfcc can cut down the current a lot,, most of these are connected across the input ( 120v )<p>i was thinking if i can use such caps on other appliances in my home...like well pump /
air conditioner / or anything that uses a lot of current... i do not think they whould help on a resistive load..but maybe can on a induction load,,as in motors and transformers,,ballast...
is this feasiable? and is it too complicated to figgure out what size cap to use?
and anyone shed some light on this so i can have a idea...i need to get my electric bill down !...lol
3 window a/c's and a well these are all 220v, too

russlk
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Re: Power factor correcting capicitors?

Post by russlk » Mon Jul 29, 2002 2:44 pm

Correcting the power factor will not change your electric bill one bit. The power meter only measures "real" power, the out of phase component does not register. There are power factor correction circuits for motors which lower the voltage to make the load current larger relative to the inductive current.

bobsRAC
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Re: Power factor correcting capicitors?

Post by bobsRAC » Tue Jul 30, 2002 2:08 pm

Power factor is only measured for large commercial/industrial services (therefore, there's no point in correcting it for a residential service). If you are trying to steal power, on the other hand, go somewhere else and ask :) .<p>[ July 31, 2002: Message edited by: bobsRAC ]</p>

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Re: Power factor correcting capicitors?

Post by L. Daniel Rosa » Tue Jul 30, 2002 4:12 pm

I'm not sure how much it will help reduce your power bill, but it may have other benefits. You're right about resistive loads, there's nothing to correct because the PF is 1 with those.<p>The math is fairly simple, but hard to explain. The result is finding what inductive reactance exists and matching it with capacitive reactance in parallel.<p>If you'd like, I can scan some pages out of my schoolbook that deal with that.

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Re: Power factor correcting capicitors?

Post by Michael Vickers » Tue Jul 30, 2002 7:11 pm

"Correcting the power factor will not change your electric bill one bit. The power meter only measures "real" power, the out of phase component does not register. There are power factor correction circuits for motors which lower the voltage to make the load current larger relative to the inductive current. "<p>By reducing his load current, he could reduce his I^2*R losses in his lines, saving a full kWh a year, despite only being billed for "real power".

russlk
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Re: Power factor correcting capicitors?

Post by russlk » Tue Jul 30, 2002 7:50 pm

I think power in North Carolina is cheaper than here where it is 6.2 cents per KWH.

bobsRAC
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Re: Power factor correcting capicitors?

Post by bobsRAC » Wed Jul 31, 2002 5:45 am

Up to 8c/kWH in Jax, FL

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Crowbar
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Re: Power factor correcting capicitors?

Post by Crowbar » Wed Jul 31, 2002 5:58 pm

I agree with Micheal Vickers in what may be saved by reducing I^2*R Losses, however you need also to look into the cost of the required capacitors (they will need to be oil filled run type) and in the larger sizes are not cheap. Once you multiply that by how many appliances you want to correct and your savings vs. payback becomes an issue since you don't pay a penalty for poor pf. If you were to use a central bank to correct the pf of your whole house a bank of capacitors may or not be more economically feasible, and may have the the effect of increasing your mains voltage when demand is low. All in all I think its best left to the industrial electricians to properly apply.
Keep Prying...

Crowbar

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Re: Power factor correcting capicitors?

Post by Michael Vickers » Wed Jul 31, 2002 7:57 pm

Crowbar:
There isn't near enough reactance in a house to save any money. While I've never seen it measured on a house, the power factor on your average residential substation is usually quite good, about .95.<p>Adding caps for voltage reasons though, is another story. However, your utility company should have a minimum voltage level requirement that they should be required to supply, so once again this is probably silly (but interesting to me anyhow).

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Re: Power factor correcting capicitors?

Post by dacflyer » Wed Jul 31, 2002 8:16 pm

i am not trying to steal power,, i do not know where you got this idea,,, i am just trying to reduce my bill... its killer here,,
i have more 220v breakers in my box than 110v breakers,,,
220v items....
2 window a/c's
i new deep 1 hp well
water heater
dryer..<p>110v items heavy .....
fridge
small window ac
attic fan ( furnace blower type )<p>Hmmmm what to do with out spending a fortune..//

billdar
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Re: Power factor correcting capicitors?

Post by billdar » Thu Aug 01, 2002 1:09 pm

you could switch to 'green' power sources.<p>In my lastest edition of "Sandle-Wearing, Tree-Hugging Hippy Engineers Weekly" (July 22, vol 23) they state:
"within 13 months renewable resources energy
production will overcome fossil fuel and
nuclear production. And withing 24 months
will render them completely obsolete, thus
increasing the supply of cheap power and
lowering costs."<p>Of course you need to write to your congress man, or local TV/Movie personality, to remove the government cover up on green technology.

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Re: Power factor correcting capicitors?

Post by haklesup » Thu Aug 01, 2002 6:13 pm

There is not much you can do to your existing appliances to make them cheaper to run but you can identify the worst offenders and manage when you use them (perhaps you can spot a particular power hog and replace it with a more efficient unit and save$). A quick search in a search engine with "Save Power" turned up several power management plug in modules (with cute names like "kill-a-watt" and "power Monitor") that monitor your motorized appliances and adjust something to make it more efficient (read the websites for details. Unfortunately these cost about $40 each. Maybe you could get 1 or 2 and then use it to rate each of your appliances. Try switching to a gas water heater and dryer (can probably find a used dryer). <p>A few suggestions: Of course there were hundreds of websites dealing with energy saving, just look. Try putting in some doors to isolate certain living areas so that you can turn down some of your air conditioners. Make sure the air filters are clean too, that wastes lots of energy<p>CO

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Re: Power factor correcting capicitors?

Post by Michael Vickers » Thu Aug 01, 2002 8:57 pm

Billdar,
While I don't agree that we can replace existing power sources at the same demand levels, I'm very interested in the technology. Tell me more of the mag you put out, is it a technical publication?

billdar
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Re: Power factor correcting capicitors?

Post by billdar » Fri Aug 02, 2002 9:34 am

"Sandle-Wearing, Tree-Hugging Hippy Engineers Weekly" (July 22, vol 23)? You can find it at your local "tabaco water pipe" store.<p>Sorry man, I was attempting a joke on the green power propaganda machine. It just irks me that green proponents are usually movie stars or political science majors and base their arguments on some mythical eutopia rather than scientific fact.<p>This is completly my opinion, and I relize I had a lapse in judgement posting it in this forum.<p>My apologies.

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MrAl
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Re: Power factor correcting capicitors?

Post by MrAl » Sun Aug 04, 2002 5:45 am

Hello,<p>I have to agree with the other post
that said you wont see any (or much) change
in your electric bill by correcting
the pf of any of your home appliances.
If you had something that ran with a phase
angle of 90 degrees you might see some
savings if you corrected the pf, but even
with pf correction the savings due to
the reduced i^2 * R losses would still be
minimal because there isnt that much power
involved with a home appliance.<p>For example, if you had 10 amps flowing
(about 1200 watts) through a line who's
resistance was 0.5 ohms you would see 50 watts
lost in the line.
Now if you correct the pf you still see
maybe 9 amps, which means now 40 watts is
lost in the line. While this is surely less
then 50 watts, the difference is only 10 watts.
This leads to a cost savings over any time
period of less then 1 per cent.
If you are lucky and you see 8 amps after the
correction, you will get roughly about 1.5
percent savings over any time period.
This means if you now pay $100.00 a month
for electrical power and your main power use
was this appliance alone, you would now pay
$98.50 a month. Problem with this is that
you have other devices you cant correct for.
Let's say the devices you can correct for
constitute 50% of the total energy use in
your home. Now if you pay 100.00 per month
before pf corrections on all devices that
can be corrected you will now pay $99.25
per month.<p>
Conclusion<p>If you think saving $0.75 to $1.50 per month
is good, then you should look into correcting
all your home devices pf's. If not, do what the
rest of us do :-)<p>One way to reduce costs is to replace old
appliances with newer energy efficient
devices.<p>Unplug two night lights and you will probably
save more then pf correcting. The newer LED
night light circuits draw much less power:
typically 1 watt compared to 4 to 6 watts of
the old incandescent types.<p>
I hope this sheds some light on the subject.<p>Good luck with all your circuits,
Al
LEDs vs Bulbs, LEDs are winning.

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