power savers are they real ?

[bmuss51]

i saw on tv news and searched the net for the things they call power savers. and from what i see is that they are suppose to cut down on the electric that you use by 10-35%. but from what i can understand is that they only save electric on running motors. but i have a heat pump which has 3 motors, a well pump and all my machinery in the shop plus other motors around the house.
so my ? is : do they work as good as advertised or is the thing a scam?

my cousin installs them for a business he works for and says that he is installing alot of them . but he does not know if they work as described or are just a spike eliminator. and i asked locally about the things to what i would say are proficient in electric knowledge and they say you might save 1% if that. but the adds show different in real time movies of the savings.

 

[ksouers]

TANSTAAFL

They don't work. Everything requires a certain amount of energy to run, can't change that.
If it needs 100 watts to run an electric motor to drive a pump, it will still require that same 100 watts no matter what magic black box you plug it into.

The only way to reduce the power consumption is to build (buy) a more efficient pump.

They used to sell diodes for light bulbs back during the 70's energy crunch. All that did was block one phase of the AC current. You did use less electricity, but the bulb was much dimmer. If you did that with a motor, it would run slower if it ran at all and draw more current on the one phase.

 

[Kermit]

I saw on tv news and searched the net for the things they call power savers. and from what I see is that they are suppose to cut down on the electric that you use by 10-35%. but from what I can understand is that they only save electric on running motors.

They refer to the 'power factor' the motor creates due to its capacitive/reactive loading of the mains line.

The device would save ordinary citizens money because our meters "supposedly" do not merely meter our electric useage, they also show empty power, or watts wasted in powering the capacitive/reactance of the load. Bottom line is the claim that we are paying for power we are not using, and the device can fix that.

The theory is correct, but it is doubtful you will save anything or even enough to notice it on your bill. Such an attempt without knowing your situation could even make your bill cost you more. Power factor can be corrected. It is done in a situation by situation, case by case, who? wants to pay for it sort of way. It is measured and then compensation is added and everything remeasured. It changes with load and would be like standing a ten foot long two by four on end, and keeping it balanced forever against the blowing of the wind. A very dynamic situation. It isn't cheap to do. If you do it right. Every motor switched on and off, every capacative load that appears and then disappears from the mains. All these things affect it.

If you think that is wrong, I'm sure I know a fella on Ebay who'd love to meet ya! ;D

Technology has come a long way, but some things in life will always stay the same. : : :

 

[Lew Hartswick]

P.T. Barnum said it very well a long time ago.
"there's one born every minute".
...lew...

 

[jack.39]

Some utilities, in my own personal experience, charge a "power factor penalty" for having to deliver what is often called "wattless power", but the only instances where I have seen this were commercial power users, manufacturing plants.

Such penalty is arrived at by use of a special electric meter which monitors power factor changes, as well as totalling the usage of actual power; these are called "power factor meters", and I have never heard of one installed at a residential use point.

As an example, the wallboard manufacturing plant where I was employed in the mid-70s, in Florence, Colorado, was billed a power factor penalty which amounted to several hundreds of dollars monthly. In Phoenix, Arizona, the plant I worked for was not billed similarly, which suggested the regular power rates were adjusted upwards to cover wattless power delivery.

By way of explanation, certain electrical devices, motors primarily, cause a difference or displacement in time, between the instant when voltage appears, and the flow of current begins. This current "lag" is reflected back onto the lines supplying the device, and also those coming from the power company. When the current flow begins at exactly the same time as voltage is applied, the "lag" is zero, and such a condition is assigned a Power Factor of 1. The penalty is applied typically whenever the factor drops below about 0.8 or 80% Power Factor.

Residential power usage consists mainly of devices exhibiting Power Factor of 1, such as light bulbs, toasters, water heaters, electric stoves, and the like. Appliances containing motors DO cause a drop in Power Factor, but evidently their amount of usage is a small part of the total, hence, the added cost of Power Factor monitoring is simply ignored by the power companies.

One of my jobs in the Plant was to evaluate the installation of devices called Capacitors, to balance the lagging power factor, and thereby minimize the penalties charged. This of course required consideration of initial cost for capacitors, installation, and pay-back time . Typically, most Plant changes or improvements involving a pay-back time of more than just a few years are usually declined by top management. jack

 

[bmuss51]

thanks guys ! this makes a total of 5 people that are telling me the same thing on this type of unit. so i guess i will not spend any money on them! but hey: it did not even hurt to ask !
next ? on the power saver. i saw that they are suppose to act as a surge suppressor, so is that part true?

 

[mu38&Bg#]

I bought a Killawatt not too long ago. It measures power factor. I was surprised to learn that my PC's run at ~0.7 PF. I happen to have a power hog of a PC that runs 350W with the monitor.

Anyhow, I thought the goal of these power saver devices was to move your power factor to closer to 0 so the meter doesn't correctly register power consumed. This assumes the meter the power company has on your house doesn't correct for power factor. The trouble is if you did manage to do this and the power company realized your consumption dropped by 50% or more, they might notice.

By identifying devices that consume a lot of power, and shutting them off you'll save more money. I was using an internet phone on a PC and leaving it on all the time. The electric bill got high and It turned out that the computer I was using was pulling 150W 24-7. Moving the net phone to a 28-35W laptop made a big difference, almost $10 per month. I thought the automatic bread maker used a lot of electricity, but it turns out it only takes 0.4kWh to bake a 2Lb loaf.

 

[Lew Hartswick]

The powerfactor on switch mode power supplies will be "leading" while that on motors
is "laging" so just put a motor on your computer and it should equalize the factor to
1 (NOT Zero) . It really is the cosine of the phase angle between the voltage and current. And we all know the cosine of 0 deg is 1 don't we???
...lew...

 

[Kermit]

The powerfactor on switch mode power supplies will be "leading" while that on motors
is "laging" so just put a motor on your computer and it should equalize the factor to
1 (NOT Zero) . It really is the cosine of the phase angle between the voltage and current. And we all know the cosine of 0 deg is 1 don't we???
...lew...

It appears that motors can be made to have a higher than 1 power factor (I've been reading books again). Of this, I was not aware. The builder must know what power factor is needed and then he can build it. It probably is not done anymore, since the book I was reading about motor and generator repair, rewinding, and modification was written around 1918. As a general rule, running a motor on lower voltage than designed for will improve(raise) its power factor, and running it on higher voltage than designed will make the power factor worse.

Books are better,
Kermit

 

[Lew Hartswick]

Power factor can not exceed 1. That is when the current and voltage are exactly in
phase.

 

[Steam4ian]

G'day all

There is a lot of snake oil about.

These "power saving devices" are generally power factor improvers which means that the volt amp product is closer to the watts drawn from the supply. Whilst improving the power factor, can't get better that 1 by definition, reduces the volt amp product the energy drawn is still the same. Your average consumer is billed on energy not volt amps so sees no difference at the meter.

In the 1980s NASA came up with a power saving device for electric motors. Most motors are oversized for the job most of the time. If the voltage to the motor is reduced some of the losses are also reduced, mainly the excitation loss. The idea was that the device lowered the voltage on the motor when the demand on the motor was reduced and raised it when the load was closer to the motor rating. Although developed by NASA I have never seen them used after 40 years in the EE industry.

Regards
Ian