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  1. #1
    Join Date
    Feb 2007
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    999

    Power factor converter

    It has been suggested by my contractor (they don't install them) that a PFC would save on energy costs associated with heating/air conditioning systems and other household, motor driven appliances.

    Information on the web is highly technical so I couldn't get too good of a grasp on their workings.

    Basically, as I understood it, PFCs tend to deal with the reactive component of current, rather than the resistive part.

    Other than that, I'm kind of in the dark.

    Hoping the PROs can address this in terms of savings, effect on startup vs continuous run, and degree of surge protection (if any).

    Thanks.

    AM

  2. #2
    Join Date
    Jul 2008
    Posts
    53
    I've been reading up on your PFC question. As far as savings go, it would depend on what the power factor of your electrical service is. The lower your power factor the less efficient the electricity usage. The PF is rated between 0 and 1. Electrical companies want to see a PF of .95 or better.

    It seems that the biggest usage is in industrial complexes. For a homeowner, I'm not sure that there would be huge savings. But, it does seem that it would help reduce electrical "noise" that affects electronics. Also, the motors in your home would be more efficient. It will also help control voltage spikes from the transmission lines.

    Hope this helps, and if I've made any errors, someone will correct me.

  3. #3
    Join Date
    Jun 2006
    Posts
    294
    The "savings" to you would be infinitesimal; it only the reduces heating loss in the house wires leading to the unit, called the "I squared R " loss. So your benefit would be almost zero since the wiring resistance is negligible to begin with and decreasng the current by, say 15% would decrease this tiny loss a fraction.

    The only one to benefit would be the power company who has to drag that current over great distances.

    So bottom line DON"T DO IT unless you have stock in the power company and/or want to further enrich them.
    Last edited by sskzekeman; 08-02-2008 at 10:30 AM.

  4. #4
    Join Date
    Apr 2005
    Location
    NE PA
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    The only real savings is if you power company charges you for power factor, which I believe is not done anywhere for residential customers.

    paul

  5. #5
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    Jul 2008
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    Am I off on the electrical "noise" that can affect electronics? This is definitely a new subject for me.

  6. #6
    Join Date
    Feb 2007
    Posts
    999
    Thanks everyone for your replies. Bottom line is---I forgot about it.

    I remember studying Ohm's Law in Physics class and all of the conversions including I^2 * R, but can't remember the specific reference.

    That being said, since we are dealing with AC rather than DC, Ohm's law per se doesn't apply; rather, inductive or capacitive reactance is substituted for pure R (resistance).

    So going back to my original post, can anyone explain what if any relationship exists between power factor and circuit reactance?

    Thanks.

    AM

  7. #7
    Join Date
    Aug 2007
    Location
    Atlanta, Ga
    Posts
    213
    We had one installed where I work...All I can say is I'm glad it has a money back guarantee......

  8. #8
    Join Date
    Feb 2003
    Location
    Huntsville,AL
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    4,125
    since the power factor for a motor depends upon its load, how do you propose that the motor mfgr determine this?

    thousands of dollars for them to send a tech to measure for one!!!!
    harvest rainwater,make SHADE,R75/50/30= roof/wall/floor, use HVAC mastic,caulk all wall seams!

  9. #9
    Join Date
    Jun 2005
    Location
    SW Wisconsin
    Posts
    4,857

    The Power Factor would be listed at a specific nominal load

    Quote Originally Posted by cem-bsee View Post
    since the power factor for a motor depends upon its load, how do you propose that the motor mfgr determine this?

    thousands of dollars for them to send a tech to measure for one!!!!
    The Power Factor would be listed at a specific nominal load. There would be a ratio from the rating in relationship to the actual load.

    A lot of ratings that are listed depend on a specific load condition: SEER; BTUH; amp draw; EER; RLA; FLA; Service Factor, & more.

    It would be of value to me to know what the base PF is.

  10. #10
    Join Date
    Jul 2008
    Location
    Denver, CO
    Posts
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    I have heard of companies running motors without loads on them just to bring their PF down. But depending on if your PF is lagging or leading you may need a capacitive load rather than an inductive load to correct the PF.

  11. #11
    Join Date
    Apr 2005
    Location
    NE PA
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    698
    Quote Originally Posted by Tiger93rsl View Post
    I have heard of companies running motors without loads on them just to bring their PF down. But depending on if your PF is lagging or leading you may need a capacitive load rather than an inductive load to correct the PF.
    What you are referring to is called a "synchronous condenser" It is a synchronous motor with an overexcited field and no load. They improve power factor like a capacitor. They were used in large industrial settings to do power factor corrections to a large system. I remember down at Bethlehem Steel (when they existed in Bethlehem) they had several substations with synchronous condensers. Looked funny seeing a 10' high open frame motor with no shaft coming out of the bearing blocks. Very effective but large and relatively high maintainance (brushes and all).

    http://en.wikipedia.org/wiki/Synchronous_condenser

    paul

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