fact or fiction??

[Stewart Corman]

Yesterday I was attending an Earth week fest that had many exhibiters and organizations.

I had recently gotten a Kill-a-watt meter and noted the "power factor" reading, but didn't know of what use to make of it. Basically, a resistance load is 100% pf, while a motor that has inductance is something less.

One vendor was promoting a device called a "power conditioning unit" model PV-1200....it was rated at 220v/7amps. The claim is that it can "save up to 25%" on your electric bill .....IMHO, 2% is "up to 25%" also!

A demo setup showed it simply connected to a dedicated circuit breaker, so effectively it is placing capacitor across the two single phases of a grid supply at the main circuit box. The claim was that it would save $$$ ...question I have is how to quantify what the savings would really be if any?

As a particular example, my hot air circulation fan uses a 1/3hp blower motor rated at 5 amps = 575watts ( I haven't checked to see how much actual juice is being used and I suspect it to be far less). This runs for a great percentage of the 24/7 at a time while I am heating with wood burning. Other obvious lower pf devices would be room airconditioners, freezer and frig.

Found this link which explains in great detail:

http://powersave1200.gilchrist-electric.com/Power-Save_study.pdf

they claim that motors exhibit lower operating temp (= lower juice consumption??)

can't find prices on this unit or ABET-2201 ...but if it is only some large caps, it is trivial to implement .... if anyone is already doing this, can you post some cap specs?

Either need AC caps rated at 460v or DC caps wired back to back ...what sort of uF are we talking about, other than bigger is better?
Wouldn't it have to be hand tailored to 60Hz and know the specific inductance load each diff motor provides??

I saw one thread that claimed that it needs to be installed at each source, not connected to entire house wiring OR is it simply we want to have the meter at highest pf and don't care about each device?

This whole thing seems too good to be true and or if it really saved $, everyone would be installing them!

Stew Corman from sunny Endicott

[Rob Beckers]

Hi Stew,

IMO this falls for the most part under the "dubious" category as far as its usefulness goes. For a number of reasons: The average household presents a mostly resistive load. The motors (inductive loads) that are present usually only run for relatively short times, and are a relatively small load compared to all the other loads (lights etc., which are resistive). Your electricity meter already corrects for reactive loads (inductive or capacitive), meaning, you only pay for the actual kWh's used, not for the inductive component. Adding capacitors does indeed pull an inductive load towards being more resistive, it does not however change the nature of that inductive load. So, that motor is still just as inductive, and uses just as much power. All the capacitors will do is cycle energy between them and the inductive load, so to the outside the load looks more resistive. Don't know what the rules are here, I know that in the Netherlands the utility company requires industry, with large motors/inductive loads, to install capacitor banks to keep the power factor up to a minimum standard. This has to do with line losses incurred by the utility since reactive loads draw larger currents to create the same amount of energy. There's no such requirement for household loads, as mentioned they are mostly resistive anyway.

On a separate note, the "amps" of a motor have little to do with its energy consumption. That depends on the load you put on that motor. "Amp" ratings are just the maximum or continuous load the motor can handle without burning up (no clear standard when it comes to consumer motor ratings, advertising is all over the place with those "Amp" numbers to make it look good).

-RoB-

[Stewart Corman]

Rob,
You were on the money!
After posting on Otherpower and getting similar responses, the vendor sent me some files incl one from the US Dept of Energy:

"Some of the benefits of improving your power factor are as follows:
* Your utility bill will be smaller. Low power factor requires an increase in the electric utility's generation and transmission capacity to handle the reactive power component caused by inductive loads. Utilities usually charge a penalty fee to customers with power factors less than 0.95. You can avoid this additional fee by increasing your power factor."

Soooo, this confirms what you and everyone has said so far ...the utility saves money, not the consumer. In this respect, the vendor is disingenuous in claiming the consumer saves at his meter by buying his product!

this subject is over

Stew Corman from sunny Endicott

[Mark Parsons]

Hi Stew and Rob,

A friend of mine came to me about a year ago with a opportunity. He was looking for work and was exploring options. This opportunity was the 'install our magic box (capacitors) to your home electrical panel and save up to 25% on your electrical utility bills'.

All investigation I could find showed that utility meters only measure the true power and ignore reactive. To prove this I talked to a local power company worker. He came and installed one of the new smart meters on my house the next day with an instantaneous use display. I installed various capacitors across line to neutral and line to line in my main panel and turned on and off various appliances. Some - like my old freezer have a very poor PF. The utility meter very closely matched the Kill-A-Watt true power reading.

To make a long story short - your house meter only measures true power. Your house PF doesn't matter at all in your electrical bill. Power companies do not charge consumers for poor PF. PF correction for your house sold under auspices to save money on your electrical bill is a scam.:mad:

Regards,
Mark

[Dave Turpin]

I have seen this work firsthand. Remember that AC power is a triangle with the sides being Watts, Volt-Amps, and Volt-Amps-Reactive. Since ALL wire has inductance, there is always a reactive load. This can be cancelled out with a capacitor to eliminate the reactive load. If your PF is really bad (like 0.8 or so), you can definately save money by eliminating the reactive load. (the ACOS of PF is the angle between the VA and VAR legs of the triangle.. . Thus a PF of 1.0 eliminates the VAR leg and makes W = VA)

Here's the problem. You are talking about a BIG capacitor bank. On the scale of 10 or more Farad. A 10 Farad capacitor at 110volts would be enough energy not only to kill you, but to turn you cajun. That's why it's illegal. At least in most places.

I work in a nuke plant. We can actually control the PF by changing the excitation voltage on the generators. But you can never get it close to 1.0.

[Rob Beckers]

Hi Dave,

Since Mark won't be responding (he passed away a year or two ago) I'll do so instead. Your comment of "I've seen this work", does that refer to the devices that supposedly save you money by correcting the power factor? If so, I beg to differ, for the reasons written in my previous replies to this thread.

I agree that capacitors will correct an inductive PF, and are used for that purpose in industry, but the devices sold (to "save money") won't do squad. Even if they did, your house meter only records actual power (ie. P = V * I * cos(phase) ), not just V*A. So there is no financial benefit for a home owner to correct their power factor.

-RoB-

[Dave Turpin]

Well, no, I wasn't saying the little device did anything. It would have to be a huge capacitor bank to work.