Electrical question - "power save" gadget
 

Rec'd an email from an electrician I'd contacted for an estimate a while
back. He was advertising some sort of power saver
(http://www.power-save1200.com/). I don't know enough about electricity
to know if this is legit. Something about saving electricity from
motors? Just curious, because with just having bought a new house, I've
moved out of the area he services anyhow, but if this is something that
actually works, I may eventually look into it.

Electrical question - "power save" gadget
 

Lee wrote:
Rec'd an email from an electrician I'd contacted for an estimate a while
back. He was advertising some sort of power saver
(http://www.power-save1200.com/). I don't know enough about electricity
to know if this is legit. Something about saving electricity from
motors? Just curious, because with just having bought a new house, I've
moved out of the area he services anyhow, but if this is something that
actually works, I may eventually look into it.

While theoretically true, for typical household motors are not the
significant fraction of overall load--resistive loads are. In this
case, difference would be small. Not zero, but unlikely to be a major
difference.

The reference in the link to the DOE information is to a brochure on the
large motor efficiency initiative wherein the example is for a single
100 kW motor load--not exactly the dishwasher or furnace fan.

--

Electrical question - "power save" gadget
 

On Mar 9, 10:12*am, Lee wrote:
Rec'd an email from an electrician I'd contacted for an estimate a while
back. He was advertising some sort of power saver
(http://www.power-save1200.com/). I don't know enough about electricity
to know if this is legit. Something about saving electricity from
motors? Just curious, because with just having bought a new house, I've
moved out of the area he services anyhow, but if this is something that
actually works, I may eventually look into it.

Appears to be a power factor correction capacitor and if your system
power factor is indeed rather low, it could help out your electric
bill. Power factor tends to get out of whack the further from the
generating source you get. That's why you see those mysterious groups
of pole mounted boxes with twin insulators hooked up to the medium
voltage power lines way out in the country. Without them the power
company would lose money shoving more current through the wires.
In some areas the power company will measure a customers power factor
on request. This would help you judge whether any device would be
beneficial.
Some high line welding equipment can be supplied with capacitors
already installed to calm down the current draw and there likely other
examples in the market. Bottom line, if you are in a new subdivision
at the end of miles of power lines with no PF correction this device
could be useful. OTOH, there may be similar less pricey ways of adding
capacitance to your system. Maybe some of the EE's in this NG can
comment better on the topic. HTH

Joe

Electrical question - "power save" gadget
 

This issue is power factor.(EE, long ago and far away). As one other
poster points out, it is only an issue with pretty large motors -- 10
HP or better. Stuff you have in your house isn't going to make a
difference. The power factor correction capacitors the power company
has takes care of the problem on their side, especially for large
industrial loads.

Electrical question - "power save" gadget
 

professorpaul wrote:
This issue is power factor.(EE, long ago and far away). As one other
poster points out, it is only an issue with pretty large motors -- 10
HP or better. Stuff you have in your house isn't going to make a
difference. The power factor correction capacitors the power company
has takes care of the problem on their side, especially for large
industrial loads.

(Probably even longer ago and farther away) But can't a suitable capacitor
change the phase on a motor such that the reactive load is out of phase with
the resistive load thereby fooling a KWH meter into thinking the motor (say
on an AC unit) is all reactive and therefore not measured?

Electrical question - "power save" gadget
 

HeyBub wrote:

(Probably even longer ago and farther away) But can't a suitable capacitor
change the phase on a motor such that the reactive load is out of phase with
the resistive load thereby fooling a KWH meter into thinking the motor (say
on an AC unit) is all reactive and therefore not measured?
..
The electric meter will in all cases read the real power used. You can't
fool it with caps. High capacitive loads don't fool the meter any more
than high inductive loads.

----------
To the OP:
For residential customers the powersave 1200 is a scam. For others it is
probably a scam.

Power factor is an issue with most industrial and some commercial users
because the utility measures 'reactive' power (separate VAR meter) and
adds a penalty to the utility bill. The utility does not measure
'reactive' power for residential users.

The utility meter measures the actual power you are using. It does not
measure the higher current that results from low power factor as some
literature implies.

In a residence, low power factor results in the current being a little
higher so the I squared R (heat) losses in the wire are slightly higher.
The powersave only helps in the losses in the wire from the meter to the
point where the powersave is connected - negligible. And the amount of
correction must be adjusted as the power factor in the house changes.
Does the powersave do that?

There were 2 threads at alt.electrical.engineering recently on the
powersave1200:
ttp://tinyurl.com/39de4q

http://tinyurl.com/36w67f
(entire thread)

--
bud--

Electrical question - "power save" gadget
 

"HeyBub" writes:

(Probably even longer ago and farther away) But can't a suitable capacitor
change the phase on a motor such that the reactive load is out of phase with
the resistive load thereby fooling a KWH meter into thinking the motor (say
on an AC unit) is all reactive and therefore not measured?

No. In theory, a pure capacitive load is all reactive, and the current
drawn by that load will not show up on a normal watt-hour meter - but
that current can't do any useful work either. It's just some
electrons that slosh back and forth between the capacitor and the
utility. Put a resistance or an inductance in the circuit and you can
extract useful work - but the current phase will shift back towards the
voltage phase, and the meter will measure the actual power being
delivered.

Most motors are inductive on their own, and by adding capacitors to them
you can correct the phase angle back towards zero degrees. This gives
the same power output with less current, which reduces losses in the
wiring, so it's an advantage in some circumstances. But it doesn't
reduce the power recorded by the meter. And if you add too much
capacitance, current starts leading voltage, making things worse rather
than better.

Dave