To get this item going, I have pulled the following drift from the Summer
1998 Agora Item:

#11 of 19: by C. Keesan (keesan) on Tue, Sep 15, 1998 (16:51):
 We have the refrigerator plugged into something that claims to regulate the
 voltage and save on power usage.

#12 of 19: by Big Snauf (lilmo) on Tue, Sep 15, 1998 (19:54):
 Re #11:  What is it?  If it would both save on power usage and even out the
 voltage, that sounds like someting that would be good for both our computers,
 and our budget!!

#13 of 19: by C. Keesan (keesan) on Tue, Sep 15, 1998 (20:36):
 electronic energy saver, it says, it reshapes the sine waves and changes the
 voltage depending on the load, the voltage drops when there is no load.
 Computers may not draw more power when starting, like refrigerators do.

#14 of 19: by Rane Curl (rcurl) on Tue, Sep 15, 1998 (23:40):
 You better be careful. Motors hate running at reduced voltage. In any
 case, if there is no load, why does it matter what the voltage is (short
 of doing damage)? What is it called? Sounds like a scam to me.

#15 of 19: by Klaus (n8nxf) on Wed, Sep 16, 1998 (06:30):
 It's a power factor controller.  It's a device that looks at when the
 voltage is at its peak and when the current is at its peak.  If the times
 coincide, the motor is running most efficiently.  If not, the device either
 increases or decreases the voltage, using a triac, to keep the two in phase.
 They are effective because most induction motors are designed to run in
 low voltage situations without burning out.  Especially in constant load
 situations like refrigerators and freezers.  When these motors are run
 above this minimum voltage, the power is wasted as heat.  These devices
 are very effective in situations where an induction motor spends a lot of
 time running at no load.  They also work pretty well on old refrigerators
 and freezers, even though they always run under full load, because these
 motors were over built to survive significant declines in line voltage.

#16 of 19: by Rane Curl (rcurl) on Wed, Sep 16, 1998 (13:10):
 Interesting. I don't know what the relation between the power factor
 (I/E phase) and the load is for induction motors, but it seems to me
 that you want them as out of phase as possible for proper operation
 as that is when the power factor is least and the least power is being
 consumed at that voltage.

#17 of 19: by C. Keesan (keesan) on Wed, Sep 16, 1998 (16:37):
 Why do old refrigerators always run at full load?  And how does the 'soft
 start' advertised for a central vacuum cleaner work?  It said something about
 gradually increasing the voltage, I think.  Why?

#18 of 19: by Scott Helmke (scott) on Wed, Sep 16, 1998 (17:21):
 This might be  a better discussion for the hardware conf, I thinks...

#19 of 19: by C. Keesan (keesan) on Wed, Sep 16, 1998 (17:26):
 Could someone who knows how copy the last few items to another conference
-
 I thought hardware was mostly computers, so maybe a refrigerator item in
 dwellings?

DONE!

18 responses total.

Induction motors are the most efficient when they look resistive to the
line.  If run under constant voltage conditions their inductive component
will decrease as the motors load increases.  The power consumed by an
induction motor is slightly less under a light load, probably due the
larger power factor, but one can reduce the power consumed much more by
reducing the voltage to the point where the motor can't handle the load.
This is the same point where the I & E phases are the same.

All refrigerators run under full load.  They are basically compressors
that are constantly compressing refrigerant.  They a re turned off when
no more cooling is required.  Something like a grinder, on the other hand,
may spend a lot of time just spinning the grinding wheel with someone 
occasionally loading it down by grinding something on the wheel.  A grinder
does not usually run under a constant load.

Yep, soft start is noting more than a circuit that gradually applies more
and more voltage to the motor to bring it up to speed.  It's a friendly 
way to start a brush type motor.  (Vacuum cleaners do not use induction
motors since induction motors can not spin the required 15,000 to 30,000
RPM.  Instead they use a universal (AC or DC) brush type motor.  The
speed of a induction motor is determined by the frequency of their power
source while the speed of a universal motor is determined by the voltage,
the load it's under and how it is built.

The power factor controller work was done by Frank Nola at the NASA Marshall
Space Flight Center and was patented by NASA in 1984.  Power Efficiency Corp.
licensed the technology and, one of several Co's that sell real devices is
Preformance Controls here in Ann Arbor.

Besides drills and vacuums, what other things use brush-type motors?
The central vac will flash a light at us to tell us when to have it serviced
(or replace the brushes before they wear down and damage other parts).
Klaus, can you explain how the two types of motors work?  I assume other
nontechnical types are reading this item.

I'd rather not.  Check into your local library if you want more info.

Many, many appliances use brush-type (universal) motors.  Electric mixers,
weed-wackers, leaf blowers, sewing machines, slot cars to mention only a
few.  I wonder how the vacuum knows that it's brushes need replacing?
Some sort of timer?

Every fifteen hours it tells you to clean out the dirt container, and I
presume it also counts hours of use between brush replacements.
Do fans use brushes?

As in window fans?  No.  Those use minor variants of the induction motor.

attic fans.  Ours has a large motor, about 5" diameter, looks not unlike the
one in the shop vac to me, which someone said was brush type.
Should we start a fan item?

Naw, it's an induction motor.  Induction motors run either 1725 RPM for
two sets of poles or 3450 RPM for on set of poles.  Brush motors run a
lot faster than that.

That sounds fortunate, no brushes to wear out.  Jim says it should be
installed vertically to prevent the bearings from wearing out, so we are
building a little compartment for it, one side of which will be insulated and
will swing down to insulate the hole in the winter.

I ran mine with the shaft vertical.  It was 4 years before I pulled it
apart and replaced the thrust washers.  I wanted to use ball bearings
but didn't have one that would fit and didn't want to take the time to
make one.

Actually putting the fan vertical lets us use the hole in the ceiling to clim
through and makes it easier to insulate in the winter.  Should this be moved
to an attic fan item or are we done with the subject?
Our newest refrigerator, which was used in a basement apartment, also has a
lot of rust in the bottom and may have the same condensation problem.  We will
try fixing a dehumidifier to reduce humidity, and hope that the cost of
running the dehumidifier is balanced by the reduced power usage of the freezer
that is currently acting as a dehu;midifier.  Should we worry about the water
heater rusting out at the bottom before the tank goes bad?
I assume it is foam insulated, the freezer and refrigerator are fiberglass.
Maybe we should switch to a newer freezer with foam insulation.  Anyone
have a chest freezer no more than 24" in the narrowest dimension, so it can
get down the steps?

Why should external rust on a hot water heater be a problem?  They should
run on the warm side and thereby not condense water on or in their jackets.

Good point, thanks.  But we have it propped off the floor until it is actually
installed.

I got a nifty power meter and attached it to our circa 1987, large sized,
refrigerator a couple of days ago.  The compressor draws about 170 watts.
It draws about 500W when the self-defroster kicks on.  I programed the
power meter that our electrical cost is 10 cent / KWh and it has calculated
our monthly energy cost for the fridge at about $5.90.  No too bad.  I
was surprised at how little power the compressor used and how much the
the defrost heater used.

How much power would a large circa 1970 refrigerator use?  A friend had two
of them running, we rearranged his stuff into half of the one.  His electric
bills are $50/month in summer, $70/winter (hot-water heat gets pumped). He
has an electric stove that is little used, washer and dryer (twice a week),
well pump, and not much else.  TV half hour a day.  Bill seemed pretty high.
Large self-defrosting freezers on both, maybe 20 cu ft?

It does seem rather high.  I no longer know what ours is since my wife takes
care of them, however, she did mention that we were paying < $40 a month since
we started spending so much time at the project house.  I recall it being
around $50 years ago.

That seems rather high.  My bill for small refrigerator, electric stove,
computer, washer, lights, is about $10/month.  Jim's house with almost no
cooking but a refrigerator (not self-defrosting) and two dehumidifiers is
about $20.  Plus the $7 we donate to solar research.  Mine has been as low
as $7 spring and fall (no heat or fans).

I'm probably getting bills confused.  $50 is too high.

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