RPC cuts power bill?

[strantor]

I'm watching a thread on a machinist's forum where several people are claiming that when they run large (15+HP) Rotary Phase Converters in their home shops, it actually cuts their power bill. Some even claim that it makes their power meter run in reverse!

Q1.A. Assuming an old-style rotating disk meter, is this really possible? I understand the difference between real and apparent power, and why a large inductive load might appear lesser than it really is, but given an already present constant load from the house, would adding a RPC possibly decrease the power bill for the whole house/system?

Q1.B. What about for smart meter? Do those have PF correction built in?

Q2. If this is confirmed, how much of this can you "get away with" at a residential address before the power company starts to take notice?

 

[ronsimpson]

I have a good idea of what will happen to my electric bill if I ran a 15 hp motor.

My neighbor has a crystal sitting on his meter and claims it helps.

There is much talk on the internet about putting magnets on the meter.

I have a hard time thinking there is a "free lunch" in any of this.

 

[schmitt trigger]

Think a little bit about it, from an engineering point of view.

Lowering your electric bill (measured in Kilowatt-hours) means that you either reduced the (REAL, not reactive) power consumption or reduced the time you used it.

Assuming that you have used it for the exact same time then:
A rotary converter, like any motor has losses. Mechanical losses, magnetizing losses, copper losses. The first losses are always fully there, even when the motor is not supplying any power at all.
Those losses consume real power.

I benchmarked many electrical motors in the past, and a regular 15 HP motor (NOT the premium high efficiency type) is about 85% efficient.
I never measured it, but in a RPC application its efficiency must be lower because of the phase unbalance.
So, as an engineer, I find it extremely difficult to believe that you can lower your electricity bill with an RPC, unless someone benchmarks it in controlled conditions.

 

[Externet]

There is a couple of ways to stop a power meter without even touching it nor even looking at it; but never learned of RPC being one. And none is with crystals nor magnets.

Not paying for power used is not ethical either. And electrical engineers at the power company are not idiots. For hands-off methods of stopping power meters, the power company can only replace a meter suspected as defective and make sure there has been no bypassing or tampering.

Unsure if a 'smart' meter would be different to trick/stop.

 

[BobW]

The old electromechanical watt-hour meters will run backwards if power is sent backwards into the utility distribution system. So, it is remotely possible that if the load connected to the RPC decelerates, dynamic braking could occur, sending power back into the lines, and causing the meter to slow down or reverse for a very brief period. But, I can't think of any way that it could occur continuously.

 

[MrAl]

Hi,

This is actually true. I run a 1500 horsepower electric motor off of a single AA size 1.5v alkaline battery that costs less than a dollar at Home Depot and use that to generate power for the whole neighborhood. We havent paid for electricity here for over 275 years now.

If something sounds too good to be true, it either isn't good or isn't true, or both.

 

[tcmtech]

I have been working with RPC systems since my teens and have tried every combination of circuits and whatnot I have ever heard of, and many more that I made up myself, and I have yet to ever get a common utility wattmeter to run backwards without putting power into the utility system.

Maybe there is a rare set of conditions where the utility has a very high inductive loading and poor PF correction in place on their end and a large grossly over compensated RPC unit (running massive positive PF) could make up for some of their local losses thus fooling the wattmeter into running backwards but I have yet to ever be able purposely replicate such an event.

As for machinists and electricity, I have yet to meet many that were as knowledgeable in how electricity worked as they were in how to make high precision paperweights.

Now as for the"I worked with a guy who knew a guy who did such and such" to be honest I have actually traced a few of those stories full circle to only find that the guy that someone knew did something supposedly near impossible was in fact me myself and the story was taken out of context or twisted around by someone who didn't have a solid grasp of what it was I was working on.

 

[bountyhunter]

I went to school with guys who worked at the local power company. What they said is:

For home (consumer) use, they only measure real power not VARs. So correcting power factor using a RPC does nothing. The typical home PF was about 0.85. If it got really low (like under 0.7) they would sometimes install a VAR meter and charge for that.

For commercial buildings, some do have both Watt and VAR meters and so correcting PF does lower their total bill.

 

[bountyhunter]

I have been working with RPC systems since my teens and have tried every combination of circuits and whatnot I have ever heard of, and many more that I made up myself, and I have yet to ever get a common utility wattmeter to run backwards without putting power into the utility system.

Correct. You could theoretically get the meter to stop if you skewed the PF all the way to zero where everything was VARs and no Watts but that never happens.

 

[BobW]

VARs are immaterial. You could skew the power factor by adding an extremely reactive load, but the real power consumption never changes, and that's the only thing the meter reads. In other words, the real power consumption will always prevent the power factor from going to zero. And even a zero power factor wouldn't make the meter run backwards.

 

[bountyhunter]

VAR's are not immaterial to the power company because they like to make money. They don't like you just pumping power back and forth to their correction caps on the lines, they want you burning what they can bill you for. As long as your PF isn't too far off unity, it's not worth their hassle of having both types of meter. But if it's enough VAR's they will put in a meter and charge you for it. If you are paying for VAR's, phase correction MIGHT be worth the cost but usually only for businesses where the savings are big enough to justify the expense of the machine.

 

[tcmtech]

Well, I hope those guys never find my Phase Converter thread on the RE section and find out they don't even need an RPC unit ahead of their big three phase motor driven equipment.

 

[BobW]

VAR's are not immaterial to the power company because they like to make money. They don't like you just pumping power back and forth to their correction caps on the lines, they want you burning what they can bill you for. As long as your PF isn't too far off unity, it's not worth their hassle of having both types of meter. But if it's enough VAR's they will put in a meter and charge you for it. If you are paying for VAR's, phase correction MIGHT be worth the cost but usually only for businesses where the savings are big enough to justify the expense of the machine.

I agree that power companies don't like highly reactive loads, but my point was that no matter how high the reactive load is, it's never going to make the watthour meter run backwards.

 

[bountyhunter]

I agree that power companies don't like highly reactive loads, but my point was that no matter how high the reactive load is, it's never going to make the watthour meter run backwards.

True. I said the same thing. If you could get the PF to zero it would stop but it can't run backwards.

 

[gary350]

1982 the power company suspected me of stealing electricity. I noticed they replaced my house watt meter over and over many times in 6 months. One day I came home from work there was a box setting in the yard with wires going up to the power lines with a clamp device on the wires. A week later the box was gone. About 2 weeks later the power company called me, my power use had dropped 90% and they wanted to know why.

I built 30 flat plate solar hot water panels and put them on the roof of my house. I mounted a large radiator inside the house. When the sun came up every morning a thermostat inside 1 panel warmed up to 70 degrees it turned on the water pump. When the warm water reached the radiator in the house a thermostat on the radiator turned on the fan. The system ran all day while we were at work. In 15 degree weather I could get the temperature inside the house to 98 to 100 degrees every day and 90 degrees even on a cloudy day. Wife and I were young we stripped off our clothes and wore swim suit until bed time. We slept with no blankets until the temperature dropped then we used quilts and blankets to keep warm. Temperature inside the house never got below 55 about 8 am the solar heat came on and when we returned home it was 100 degrees in the house again. We never used the house heat system all winter. We had a clothes line in the back yard we used it all winter and all summer. The electric clothes dryer was 40% of our electric bill I bought my own watt meter to test every thing at home. The hot water heater was 12% of our electric bill it was on a timer it came on 30 minutes before bed time so we could take a warm shower then hot water heater shut off for 23 hours. Our electric bill all winter was never over $40 a month.

After talking to the power company they sent the theft inspector to our house. I had fun talking to the theft inspector and showing him what I was doing. The theft inspector told me about all the people they catch trying to steal electricity. The big red flag is sudden drop in the typically power use that they keep on record for every customer. Some people cut holes in the walls to try and rewire the wires on the back side of the watt meter box. People try magnets and all kinds of things but there is 1 thing that really did work in those days. Get a large magnifying glass project a 5000 degree hot spot through the watt meter glass, use the hot spot to distort the turning device inside so it locks up. If the meter locks up it will not read power use but the power company will notice that next time they read the meter and will replace the bad meter. If the power company has to replace a bad meter over and over they know your doing something to the meter. You can not cheat the power company and get away with it for very long. The theft inspector said, if people would only cheat us out of 5% power we would probably never catch them.

The new digital meters these days are high tech. I don't know if they can be defeated. Maybe a 5000 degree hot spot will destroy the circuit board.

When I was in college we were told voltage is out of phase with the current on a large 100 hp electric motor and a watt meter will not read the true power used. You could use the motor to run a generator to power your house. But the biggest problem with that is do the math, idle current with no load attached on a 100 hp motor is about 20 hp all the time, current for a 20 hp motor will be 4 times more than running the AC unit or the Electric dryer none stop all the time. Just because voltage is out of phase with current does not mean you save big money the phase shift is only about 3% that is very little on a sine wave. Draw a sine wave on paper as the wave goes peak to peak 3% less it still about 99.8% full power. The largest electric motor we had at work was 60 hp the power company told me they test every ones power shift from time to time so they can make adjustments to the bill for power factor loss, we pay for it anyway.

 

[strantor]

Now as for the"I worked with a guy who knew a guy who did such and such"

I didn't see any of that in the thread. 4 people came forward and claimed first hand experience slowing the power meter with a RPC. That's the only reason I posted this.

Their stories contradict what I believe to be possible, but there were enough of them to make me question my understanding. Gauging by the other replies in this thread I was probably stupid to have doubted myself.

 

[tcmtech]

No, I understand that. My electric bill has been dropping by ~$10 every month since my divorce and my getting the Ex moved out.

Coincidence? Maybe, but I'm not going to question the plausibility of the connection too far. I mean the cost behind everything else about living here has dropped drastically as well, so....? Could it be?

 

[ronsimpson]

My electric bill has been dropping by ~$10 every month since my divorce

Divorcing takes much energy.

 

[MrAl]

1982 the power company suspected me of stealing electricity. I noticed they replaced my house watt meter over and over many times in 6 months. One day I came home from work there was a box setting in the yard with wires going up to the power lines with a clamp device on the wires. A week later the box was gone. About 2 weeks later the power company called me, my power use had dropped 90% and they wanted to know why.

I built 30 flat plate solar hot water panels and put them on the roof of my house. I mounted a large radiator inside the house. When the sun came up every morning a thermostat inside 1 panel warmed up to 70 degrees it turned on the water pump. When the warm water reached the radiator in the house a thermostat on the radiator turned on the fan. The system ran all day while we were at work. In 15 degree weather I could get the temperature inside the house to 98 to 100 degrees every day and 90 degrees even on a cloudy day. Wife and I were young we stripped off our clothes and wore swim suit until bed time. We slept with no blankets until the temperature dropped then we used quilts and blankets to keep warm. Temperature inside the house never got below 55 about 8 am the solar heat came on and when we returned home it was 100 degrees in the house again. We never used the house heat system all winter. We had a clothes line in the back yard we used it all winter and all summer. The electric clothes dryer was 40% of our electric bill I bought my own watt meter to test every thing at home. The hot water heater was 12% of our electric bill it was on a timer it came on 30 minutes before bed time so we could take a warm shower then hot water heater shut off for 23 hours. Our electric bill all winter was never over $40 a month.

After talking to the power company they sent the theft inspector to our house. I had fun talking to the theft inspector and showing him what I was doing. The theft inspector told me about all the people they catch trying to steal electricity. The big red flag is sudden drop in the typically power use that they keep on record for every customer. Some people cut holes in the walls to try and rewire the wires on the back side of the watt meter box. People try magnets and all kinds of things but there is 1 thing that really did work in those days. Get a large magnifying glass project a 5000 degree hot spot through the watt meter glass, use the hot spot to distort the turning device inside so it locks up. If the meter locks up it will not read power use but the power company will notice that next time they read the meter and will replace the bad meter. If the power company has to replace a bad meter over and over they know your doing something to the meter. You can not cheat the power company and get away with it for very long. The theft inspector said, if people would only cheat us out of 5% power we would probably never catch them.

The new digital meters these days are high tech. I don't know if they can be defeated. Maybe a 5000 degree hot spot will destroy the circuit board.

When I was in college we were told voltage is out of phase with the current on a large 100 hp electric motor and a watt meter will not read the true power used. You could use the motor to run a generator to power your house. But the biggest problem with that is do the math, idle current with no load attached on a 100 hp motor is about 20 hp all the time, current for a 20 hp motor will be 4 times more than running the AC unit or the Electric dryer none stop all the time. Just because voltage is out of phase with current does not mean you save big money the phase shift is only about 3% that is very little on a sine wave. Draw a sine wave on paper as the wave goes peak to peak 3% less it still about 99.8% full power. The largest electric motor we had at work was 60 hp the power company told me they test every ones power shift from time to time so they can make adjustments to the bill for power factor loss, we pay for it anyway.

Hi,

Very interesting story. I worked on a house years ago that had a large solar heating system. It was a house built to study the effects of having solar energy for both electric and hot water heating. The tanks for the heat system were large and insulated and i think they had rocks inside to hold the heat from the daylight hours.

The facts about motors and energy usage though is pretty well understood. If a motor draws power with a current phase angle of 60 degrees (just for this example) then the power is E*I*cos(60) which is E*I/2, so that is half the E*I product. That's half the power. Now let's say that it is driving a generator and the generator is putting out some power to some devices like light bulbs, and the phase angle again is 60 degrees. Now with 120vac and say the current measurement is 10 amps, with that same phase angle we get 120*10*0.5=600 watts going into the motor. What that means is that the maximum power that we could ever get out of the generator is 600 watts, and that would only happen if it was 100 percent efficient, which BTW no typical generator is. But even if it was, we are seeing 600 watts go in and 600 watts come out, and that's it. We'll never see 600 watts go in and 601 watts come out, that's physics for ya. So we drive 600 watts worth of bulbs but still have to pay for energy use of 600 watts times whatever time it was on for. In reality though the motor and generator would use some power too, so if we see 600 watts on the output we might see 650 or even 700 watts on the input depending on how good the motor and generator were made.

In all likelihood what would happen is once we connect the load the power factor would go down, because then we'd be using more real power, but in the end the real power in (the stuff we pay for) will always be more than the power we get out (the stuff we use). That's a basic law of physics.

So in short, the phase angle can be anything it wants to be we pay for the real power which is E*I*cos(phaseangle) no matter how it is converted and reconverted.

As a side note, some things can be made more efficient with better design, but nothing goes over 100 percent and most things do not get too close to that either. An example would be the LED which we all know and love. The efficiency can be raised by converting the heat from the device back into electrical energy which then helps run the device. That's fine, but there is never more heat than the energy we put into it that made that heat so we never get better than 100 percent, in fact, still much lower because the energy conversion devices are never that good either.

 

[schmitt trigger]

A contractor once told me: "You want to save energy at home? Put extra insulation! That is the easiest, lowest maintenance and cheapest in the long run."

Sage words.
When I built my new home 3 years ago I followed his advice. I added about $2600 in extra insulation and better windows, which in the total cost of a new home, is nothing. People spend more than that in bathroom fixtures.

Nowadays, although this new home is about 40% larger than my older one, my energy consumption is about 5% lower.

Another one, but this is a long time investment: trees. Two or three strategically located shade trees can do wonders during summertime in our south Texas weather.