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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Lee wrote:

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.
--
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
professorpaul 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?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
HeyBub wrote:

. 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--


Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.