DIYbanter - View Single Post

wrote:
I would look into power factor correction first.

There are companies marketing power factor correcting boxes to
homeowners. They are just boxes with a bunch of capacitors in them and
instructions on how to connect up the "right" number of capacitors to
your incoming power conductors to try and bring your home's average
power factor closer to unity. I think the guys promoting them are just
"Sharp cookies selling Girl Scouts." G

AFAIK none of those boxes do an automatic correction when the overall
power factor of the loads being used changes as different appliances get
turned on and off.

Also, the big joke is that very few utilities install meters which can
measure power factor at peoples homes so nearly all the residential
meters in use now measure only the "real power" consumed anyway.

So, using one of those power factor correction boxes won't do much to
directly reduce your electric bill. It will however help reduce the
power company's losses on THEIR lines, which in a perfect world could
allow them to pass those savings back to their customers about the same
time as pigs start flying.

Installing power factor correction capacitors directly at the larger AC
motors used home appliances would reduce by a tiny amount the power
"wasted" in heating wiring within your house, but I wouldn't expect the
resultant savings to be worth the effort.

A bit more effective is the addition of capacitors arcoss the starting
winding switches on induction motors to make them work in a "capacitor
run" mode. That was shown by some US Navy researcher back in the 70s
(IIRC) to improve the efficiency of those kind of motors by about 10%.
AFAIK nothing much ever came of that, but maybe the skyrocketing cost of
fuels will bring that idea to the fore again.

Jeff

--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"Truth exists; only falsehood has to be invented."