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Kill A Watt
Topic Started: Jul 25 2005, 11:57 AM (406 Views)
Jolly
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Geaux Tigers!
I'm going to have to get one of these...

http://www.supermediastore.com/kilwateldet...awatt&WT.srch=1
The main obstacle to a stable and just world order is the United States.- George Soros
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LadyElton
Fulla-Carp
My parents could use one of those. The electric bill has been sky high recently. I think it's due to running the central air, computers and ceiling fans so much.
Hilary aka LadyElton
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big al
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Bull-Carp
I bought one of those last year. I didn't get any enormous revelations but it is interesting to determine where some of the money is going (Is that fridge in the garage for the beer worth the cost?, etc.). Be aware that it is built to be plugged in so you can only use it for 120V appliances, table lamps, etc., not hard-wired loads like central air conditioning, fixed lighting, dishwashers, electric hot water heaters and such. Also, no 230V loads like electric clothes dryers and some window air conditioners.

Mother's old advice about turning things off along with sensible measures like looking at energy usage labels, using compact flourescent light bulbs where suitable, and adding insulation are about the best things to do.

Big Al
Location: Western PA

"jesu, der simcha fun der man's farlangen."
-bachophile
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Jolly
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Geaux Tigers!
Where this device really appeals to me, is in the monitoring of vampire electronics and appliances.

Like when the TV is off, but it really isn't...
The main obstacle to a stable and just world order is the United States.- George Soros
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iainhp
Middle Aged Carp
You can do similar investigations using the power utility meter if you have the patience. You can time the revolutions of the wheel going round, then try unplugging something and retime the wheel again. The meters are all a bit different and mine is locked up somewhere in a condo utility room so I can't go check, but I think there may be something written on the meter to tell you what 1 rev of the disc measures. Otherwise you could time the difference between before and after of turning on a 100W light bulb.
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JBryan
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I am the grey one
Big Al points out a serious deficiency in this device in that it does not connect to the loads with the worst power factor. The big inductive loads like the AC or anything with a motor. The only way you are going to minimize your costs aside from, as he says, turning off the lights, etc. is by increasing the power factor to as close to unity as possible. However, aside from the TV which is becoming ever more efficient with switching power supplies and whatnot, most of the heavy inductive loads run on 220V or are hard wired.
"Any man who would make an X rated movie should be forced to take his daughter to see it". - John Wayne


There is a line we cross when we go from "I will believe it when I see it" to "I will see it when I believe it".


Henry II: I marvel at you after all these years. Still like a democratic drawbridge: going down for everybody.

Eleanor: At my age there's not much traffic anymore.

From The Lion in Winter.
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AlbertaCrude
Bull-Carp
JB I have left my Bryston amp on since I bought it almost 20 years ago. The dealer said they were designed to be left turned on. Is this true for some types of electronics? Or is it a myth perpetrated by sales weasels?
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JBryan
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I am the grey one
It has lasted twenty years hasn't it?

There is a lot of truth to the concept of longer life through continuous operation as opposed to repeated startup and shut down for many electronic devices. However, in your case I would have to say nothing works like success.
"Any man who would make an X rated movie should be forced to take his daughter to see it". - John Wayne


There is a line we cross when we go from "I will believe it when I see it" to "I will see it when I believe it".


Henry II: I marvel at you after all these years. Still like a democratic drawbridge: going down for everybody.

Eleanor: At my age there's not much traffic anymore.

From The Lion in Winter.
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Larry
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Mmmmmmm, pie!
I've never tried it, but I've had several people tell me that if you hang a big magnet next to the meter it will slow it down and cause it to read a lower power usage.

Truth, or fiction?
Of the Pokatwat Tribe

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The 89th Key
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Depends on how big the magnet is I guess... :P

Posted Image
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big al
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Bull-Carp
JBryan
Jul 25 2005, 07:55 PM
Big Al points out a serious deficiency in this device in that it does not connect to the loads with the worst power factor. The big inductive loads like the AC or anything with a motor. The only way you are going to minimize your costs aside from, as he says, turning off the lights, etc. is by increasing the power factor to as close to unity as possible. However, aside from the TV which is becoming ever more efficient with switching power supplies and whatnot, most of the heavy inductive loads run on 220V or are hard wired.

This is only partially true. Large users are penalized for low power factor and therefore have an incentive to improve it. I am not aware of a residential tariff that has this penalty. Residential rates usually are solely energy charges plus a fixed monthly service charge so you only pay for actual watts used. Unless you have a demand charge for peak kVA drawn or something similar, low power factor will not cost you anything except a tiny increment for additional losses.

As to putting a magnet near the meter, this could in theory work if you still have a conventional disc type meter, not a newer solid state meter. The meter in fact has a magnet to provide retarding torque to the disc and so an additional magnet could possible amplify this effect if it could be located appropriately. It could also do the opposite. In any event , don't get caught doing it, because fraud is, aside from being criminal, also usually grounds for discontinuing supply.

Big Al
Location: Western PA

"jesu, der simcha fun der man's farlangen."
-bachophile
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JBryan
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I am the grey one
big al
Jul 26 2005, 12:06 PM
This is only partially true. Large users are penalized for low power factor and therefore have an incentive to improve it. I am not aware of a residential tariff that has this penalty. Residential rates usually are solely energy charges plus a fixed monthly service charge so you only pay for actual watts used. Unless you have a demand charge for peak kVA drawn or something similar, low power factor will not cost you anything except a tiny increment for additional losses.


I stand corrected. Of course, since residential users are charged per kilowatt-hour, power factor is irrelevant to their electric bill. Not sure what I was drinking at the time I wrote this.
"Any man who would make an X rated movie should be forced to take his daughter to see it". - John Wayne


There is a line we cross when we go from "I will believe it when I see it" to "I will see it when I believe it".


Henry II: I marvel at you after all these years. Still like a democratic drawbridge: going down for everybody.

Eleanor: At my age there's not much traffic anymore.

From The Lion in Winter.
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iainhp
Middle Aged Carp
Electricity meters measure Watts. If the power factor is unity then the actual power = the real portion of the power (ie the KVAs = KWatts) as there is no imaginary component (KVars). SO increasing the power factor will make your electricity bill higher, as the meter only measures Watts. Reducing the power factor will reduce your electricity bill, but is illegal (and won't reduce the actual power consumed, just the real, or KWatts, portion of it). Or have I forgotten my engineering theory again?
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AlbertaCrude
Bull-Carp
iainhp
Jul 26 2005, 06:02 PM
as there is no imaginary component (KVars).

I have always thought of Vars as sort of electrical back pressure on a high voltage transmission line. Am I right?
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JBryan
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I am the grey one
iainhp
Jul 26 2005, 09:02 PM
Electricity meters measure Watts. If the power factor is unity then the actual power = the real portion of the power (ie the KVAs = KWatts) as there is no imaginary component (KVars). SO increasing the power factor will make your electricity bill higher, as the meter only measures Watts. Reducing the power factor will reduce your electricity bill, but is illegal (and won't reduce the actual power consumed, just the real, or KWatts, portion of it). Or have I forgotten my engineering theory again?

Actually, increasing the power factor will have no effect on the real power (Watts) component. The actual current would be reduced but since you are charged for power (watts) consumed and not current it has no effect on your electric bill.
"Any man who would make an X rated movie should be forced to take his daughter to see it". - John Wayne


There is a line we cross when we go from "I will believe it when I see it" to "I will see it when I believe it".


Henry II: I marvel at you after all these years. Still like a democratic drawbridge: going down for everybody.

Eleanor: At my age there's not much traffic anymore.

From The Lion in Winter.
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JBryan
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I am the grey one
AlbertaCrude
Jul 26 2005, 09:07 PM
iainhp
Jul 26 2005, 06:02 PM
as there is no imaginary component (KVars).

I have always thought of Vars as sort of electrical back pressure on a high voltage transmission line. Am I right?

VAR is equivalent to the additional current required due to reactive loads (capacitive or inductive). Since they are reactive loads no real power is consumed but the additional current above that you would obtain by dividing the real power (watts) by the voltage is present along with a phase difference between the voltage and current equal to the arcosine of the power factor.
"Any man who would make an X rated movie should be forced to take his daughter to see it". - John Wayne


There is a line we cross when we go from "I will believe it when I see it" to "I will see it when I believe it".


Henry II: I marvel at you after all these years. Still like a democratic drawbridge: going down for everybody.

Eleanor: At my age there's not much traffic anymore.

From The Lion in Winter.
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AlbertaCrude
Bull-Carp
Okay. :blink: So if I'm an operator in the central power grid control room and my SCADA tells me that the dedicated 110 KVA transmission line to a steel plant is feeding back VARS into the substation during an arc melt, what exactly is happening to my transmission grid?
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JBryan
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I am the grey one
Reactive loads are energy storage elements. Capacitive loads store electrical energy in the form of an electric field; Inductive loads in a magnetic field. Since we are talking about AC circuits here we are referring specifically to the extra current required to charge and discharge these loads over and above that which is delivering real power (or, equivalently, doing work) in the purely resistive loads. If I understand your question correctly, you are referring to an estreme case where an immensely inductive or cappacitive load creates a current surge in one direction or another (charge or discharge) at some point in time. AC inductive motors, for instance, have a tremendous inrush current at start up. You seem to be presenting an example of just the opposite. That is when an electrical storage device delivers its enrgy in a surge back to the grid. Aside from the technical aspect of handling the current involved it is really a wash to the provider. The only issue here is that the current delivered in storing this energy may have been less than that delivered back to the grid since the time involved in each my have been much different.
"Any man who would make an X rated movie should be forced to take his daughter to see it". - John Wayne


There is a line we cross when we go from "I will believe it when I see it" to "I will see it when I believe it".


Henry II: I marvel at you after all these years. Still like a democratic drawbridge: going down for everybody.

Eleanor: At my age there's not much traffic anymore.

From The Lion in Winter.
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AlbertaCrude
Bull-Carp
I think I get it now.
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