Power factor Correction

[jeschien]

PF correction lowering electric bill

I found this randomly while researching capacitors for your home. I have found that they do indeed work if installed correctly. If a capacitor is active during run time of an inductive motor and goes offline with the motor you will see a reduction on your electrical consumption. If Amps x volts =watts divide by 100 = KW, then a capacitor that lowers the amps pulled through your electrical panel will thus reduce the whole equation, lowering your KWH/month. I have NASA testing and US Dept of Energy.

 

[leitmotif]

Since on single phase AC P = I x E x PF
then by correcting PF using capacitors you will reduce the load.

However look at the previous posts. As I said if the utility does not meter and bill for it is it worth the time & material??
Most likely it is not cost effective.
Is it worth installing $5 of capacitor to save a nickel??


Dan Bentler

 

[jeschien]

Its not always cost effective for the home owner if they have a high power factor. Here in california you must have at least a 95% PF to not get a penalty. PG&E claims to deliver clean energy; however, once you turn an inductive motor on your PF goes way down. The best application of a capacitor is to 'connect' it at your AC or pool pump, whatever is your biggest hog. The ROI on these products is around 18-24 months, bigger bill would equal bigger savings, but savings is savings none the less. The utility company has to make up for the reactive power you need, but this really only happens in large industrial facilities.

There is a lot of talk these days about capacitors, the proof is there, its all about the installation. A panel mount system usually only will save about 5%, but one at your AC or pool we see upwards of 20-30%. There are many knock off companies claiming to do this or that and they have created a bad taste for capacitors; however when done correctly these absolutely do work.

 

[ivo.maenen]

I like the horse-example:

http://www1.eere.energy.gov/industry/bestpractices/pdfs/mc60405.pdf

This link is good for single-fase-systems:

http://openbookproject.net//electricCircuits/AC/AC_11.html

also interesting:

http://powerelectronics.com/power_management/motor_power_management/705PET23.pdf

 

[Lancie1]

There is a lot of talk these days about capacitors, the proof is there, its all about the installation. A panel mount system usually only will save about 5%, but one at your AC or pool we see upwards of 20-30%

Jeschien,

Whoa!, you were doing great, but now you have mixed in a little fiction with your facts. Any realized savings are not dependent on the location of the capactior, but on its size in KVAR and on when it is energized. You may have remembered the results bass ackwards.

Fact: A capacitor is a parallel device. Mounted somewhere on the power line (downstream of the power meter), it has the same basic effect. The same size capacitor mounted at an Air Conditioner or at the main panel will have the same effect on the power meter FOR THE POWER FACTOR OF THE AIR CONDITIONER.

I can make a convincing arguement that a Capacitor will save MORE power mounted at the main panel and energized all the time (that the main breaker is on). That way, it will be in effect all the time and work for all household motors, where if you install it on the AC contactor so that it is only connected when the compressor is running, then it will only effect the power factor when the AC is running. If there are some other motors in your house (refrigerator compressor, shop tools, vacuum cleaner, and so on), then mounting ON the AC will cause you to loose the benefit of the capacitor for the other motors.

A large capacitor can cause the household voltage to run higher than normal if all your motors are not running (very rare that they are all running at once).

For home use, it is probably best to settle for a slighly smaller capacitor that brings the "average" power factor up to 0.95 lagging. At times when NO motors are on with a capacitor, the home power factor may go above 1 (leading) and the voltage could rise to 15% above normal.

 

[leitmotif]

Its not always cost effective for the home owner if they have a high power factor. Here in california you must have at least a 95% PF to not get a penalty. PG&E claims to deliver clean energy; however, once you turn an inductive motor on your PF goes way down. The best application of a capacitor is to 'connect' it at your AC or pool pump, whatever is your biggest hog. The ROI on these products is around 18-24 months, bigger bill would equal bigger savings, but savings is savings none the less. The utility company has to make up for the reactive power you need, but this really only happens in large industrial facilities.

There is a lot of talk these days about capacitors, the proof is there, its all about the installation. A panel mount system usually only will save about 5%, but one at your AC or pool we see upwards of 20-30%. There are many knock off companies claiming to do this or that and they have created a bad taste for capacitors; however when done correctly these absolutely do work.

Are you really telling me that California utilities meter residential (single family) for power factor?? I am only familiar with NW utilities and to my best knowledge none meter a single family for power factor.

Capacitors are NOT the only means to correct power factor you can overexcite a synchoronous motor for power factor correction but if I recall correctly it is only cost effective when the motor is larger than 3 or 400 HP. Caps are of course the best choice method for the single family.

IF you place the cap (single family) at the line to the panel then with no inductive load your system PF will go capacitive (leading). The power factor meter does not care whether inductive or capacitive (lag or lead PF) it will measure either and you will get charged for either one.

I would think that unless they really ding you for power factor charge it is still not worth your time nor effort. Here in Seattle most industry will not mess with it and just pay the charge.

Dan Bentler

 

[ivo.maenen]

"Here in Seattle most industry will not mess with it and just pay the charge"

Not very wise or economic. The solution should always be simple and clear for the 'electric brains' of the companey. If not you should appeal to the man who pays the bills. You can always buy an automatic PF-correction-cabinet what will cost you x dollars and than you have the fine: y dollars per timeperiode How long will it take you to stop to lose money: x/y.

http://www.abb-control.com/documentation/docucatalog.htm

 

[leitmotif]

I completely agree. But at the present and last place I worked they did not even have the brains to turn off 50 HP air compressors over the weekend or off shift - they spent money on the power to compress air to chase their leaks.

We (we my foot -- THEY) are building up new plant - all energy conservation measures went out window to keep construction costs to minimum.

Dan Bentler