On Mon, 18 Jan 2010 12:26:06 -0500
AK <00@case.edu> wrote:

> Correct, residential customers are only billed for real power used,
> regardless of power factor so this capacitor would never pay for
> itself.

Well, just to be complete, there are a few things to take into account:

1) Though I don't think they account for the numbers mentioned in the
ad, there are losses in your house that increase if the power factor is
bad. If the current increases, your house wiring and any
transformers _will_ heat up more (for which you _will_ pay), the fuses
_can_ trip faster (as they don't measure the current's angle), and other
secondary effects.

2) There is a tendency for utility companies to start checking the power
factor of residential users (in EU they already do), and impose limits.
Utily companies are interested that everyone use a power factor near
ideal, because else they would have to increase the section of their
cables to avoid overload (=investment...).

So, overall, a reasonable power correction is the green thing to do. I
wouldn't qualify this product as pure snake oil. Though I have my doubts
about the "6% or more" savings announced, but then I don't have a 10 HP
compressor A/C...

John

Note: If you don't compensate the power factor _at_ the motor (as
opposed to installing the unit at the house entry point), the internal
lines will still heat/lose power.
-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist