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Old 10-01-08, 07:04 PM   #1
roflwaffle
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Default KVAR Energy Controllers

I've seen these advertised at a semi local energy fair and was wondering what exactly it did. For owners who are billed a KVA demand charge according to the power factor of their equipment, power factor correction may be useful. For residential users, the only advantage in terms of energy consumption would be via line losses.
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As the demand for power runs through your home, there is non-productive current (heat) that strains your home appliances and wiring. This heat is wasted energy that you are paying for. The KEC optimizes the power that comes into your home, allowing your appliances and equipment motors to operate more efficiently. This reduces heat (wasted electricity), which in turn lowers your electric bill
These line losses are proportional to the the current draw of a device (squared), it's power correction factor, and the resistance of the home's wiring. For example, an electric air conditioner motor rated at 1000W would only use ~600W according to a killawatt or similar and has a PFC of about .6. The penalty of the additional power draw of ~400W measured in VA is excess line losses, which are the current squared times the resistance. In this case, 400W over 120V AC would result in 6.6bar amps of current, and assuming we had roughly a quarter of a km of 14 AWG wire at 8ohms/km, lines losses would account for around 23-23W, or 25W for the sake of simplicity. This is roughly 2.5% of the power draw, and assuming the device was on constantly for eight hours a day six months out of the year, would result in an extra 36kWh saved.

Given an entire household full of items with PFCs of .6, something like this could save upwards of 150kWh/year. Which at the average rate in the U.S. is around $15/year. The only problem with this is the price of the unit... Assuming the owner installs the device themselves, it would only take a mere 25 years to recoup it's initial cost, and on the other side of the spectrum, for those of us who aren't electricians, want to keep the warranty, and don't have many devices w/ a low PFC, well... a payback period of more than a century may be possible. This is a bit puzzling considering that the site states the device has an...
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Investment return (36 months or less)
But I suppose the company could be assuming household electricity consumption of seven or eight times the national average.

In short, given the high cost and low potential savings, even for a residential home with nothing but low PFC items, these cannot amortize their costs anywhere near the claimed time interval. That being said, it looks that a circuit for passive power factor correction can be put together on the cheap, so even if the mentioned product isn't the best this isn't an idea w/o merit.


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Old 10-02-08, 07:11 AM   #2
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Very odd, I've never heard of a system like that. I'm guessing, like you mentioned, it wouldn't save much electricity especially if your house is properly wired.
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Old 10-02-08, 08:48 AM   #3
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Too funny : Saving Energy
You can't send your electricity back. If you could, the counter counts only in one way.

I have been told that you are paying the kWh, not the kVAh, where kWh = kVAh x cos(phi).

All systems with motors, transformers... have cos(phi) != 1.

My kill-a-watt shows the cos(phi).
iirc my computer has a cos(phi) of 0.8-0.9.
I remember on a notebook with LCD off the cos(phi) was going down a lot (0.5 iirc) and then the VA was higher than when LCD was on. On the same time the kWh was lower when the LCD was off than when it was on.

I don't think this thing is something else than a placebo, but I'm OK if someone shows me I'm wrong.

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Old 10-02-08, 12:20 PM   #4
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Almost surely a placebo, at least at that price/described effect since utility meters measure watts, although an individual DIY circuit to correct the power factor may be worthwhile due to line losses. I guess someone (deliberately?) forgot to use a RMS multimeter or actual electricity meter to measure energy consumption.

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Old 07-16-10, 02:52 PM   #5
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I work in the Brandeis University High Energy Physics Lab. We did a study on the KVAR Energy Controller. We found that the KEC is nothing more than a capacitor in a box. In order to save money and energy, power correction must be done at the device, not at the breaker panel. That means that in all but very strange and specific situations, different KECs would have to be applied at each load whose power factor you want corrected. Here is a link to our report:

alignment.hep.brandeis.edu/Lab/KVAR/
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Old 07-16-10, 05:55 PM   #6
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Default KVARs are money makers. If you are selling them..

I like this one.. KVAR Power Factor Correction in the Home is a Scam

I can't believe that people are still buying these capacitors (for outlandish prices)
after all the information that's available on the web about them..


The line loss calculations for a washing machine at 0.11 Ohms made me laugh,
a lot of Digital VOM meters have leads that show 0.2 or 0.3 Ohms!!
Not like in the old days, when you could Zero your meter..

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