My VFD motors can change the world !

[ritelec]

The "pool guy" asked me about upping from 120v to 240v for his vfd pool pumps he's installing ( as it was raining on me while I was screwing around with a HP rated switch and a plastic two gang cover).

He's wondering what it would take? Like a ~ 4 or 6 hundred dollar transformer to go from 120 to 240 so he could run this pump and potentially save his costumers hundreds of dollars a year.

Not always playing with the numbers, I sometimes question myself. So am I in the right frame of mind thinking ? That,
Besides the cost of a transformer and wiring,

The motors he is installing are 1.5 HP 10 amp (name plate) So at 240 volt that motor would be on a 20 or 25 amp circuit.
At 120 volt with a transformer, that 120 volt circuit should be 40 or 50 amps.

Is that right?

Thanks

 

[K8MHZ]

The "pool guy" asked me about upping from 120v to 240v for his vfd pool pumps he's installing ( as it was raining on me while I was screwing around with a HP rated switch and a plastic two gang cover).

He's wondering what it would take? Like a ~ 4 or 6 hundred dollar transformer to go from 120 to 240 so he could run this pump and potentially save his costumers hundreds of dollars a year.

Not always playing with the numbers, I sometimes question myself. So am I in the right frame of mind thinking ? That,
Besides the cost of a transformer and wiring,

The motors he is installing are 1.5 HP 10 amp (name plate) So at 240 volt that motor would be on a 20 or 25 amp circuit.
At 120 volt with a transformer, that 120 volt circuit should be 40 or 50 amps.

Is that right?

Thanks

I don't see where the savings would come from. Both configurations have the the same watts.

 

[texie]

I don't see where the savings would come from. Both configurations have the the same watts.

Yes, watts are watts, but I'm not sure the OP thinks they are not. I read it as he needs 240 volt so he can have a variable speed pump which would in turn save energy.
But I don't think stepping up the voltage with a transformer to do it is the way to go. Too much involved to make it compliant and you would have some losses in the process. I think better would be to just convert the circuit to 240 volt.

 

[__dan]

A pool filter does not seem like a VFD application. There is no short cycling or demand/load matching to see where a lower speed is called for. The VFD will have some through losses and higher maintenance, install costs.

I'm thinking the VFD will also output to a 3 phase motor. At 1.5 Hp they are adding a lot of cost, so it would have to be done by the numbers. They would have to show the 3 phase motor is overall saving money by efficiency gains compared to single phase. It's not clear they know what they are talking about.

If he wants to install single phase VFD's with 3 phase pump motors, 240 v is the way to go.

 

[Jraef]

A MAJOR fallacy in the VFD sales game is for people to say that a VFD will ALWAYS save energy. That is blatantly untrue (and yes, I an in the VFD business). A VFD can only save energy on centrifugal loads such as many pumps and fans, but more importantly, it only saves energy IF it is replacing some OTHER means of VARYING* the flow. If the flow never varies, then the VFD will actually INCREASE the losses in the system, thereby WASTING energy.

The reason for the success in REPLACING OTHER FLOW CONTROL METHODS is because of what is called the "Affinity Laws". One of those laws of physics dictates that the power needed by a centrifugal load varies as the cube of the change in speed. So for example if you run the pump at 50% speed to reduce the flow, the power required by the pump from the motor is going to be .5 x .5 x .5 or 12.5%, or rather at 1/2 speed, the pump only demands 1/8 of the power it did at full speed. So because the VFD can exactly match the motor output to the pump demand by changing the speed, the law follows through and reduces energy.

Changing flow by using a throttling valve ALSO reduces energy, but it is not by the cube, it is direct. So the energy savings in using the VFD is in the DIFFERENCE between using the motor speed to vary the flow, or some other less efficient means of varying the flow. However, again, if you do NOT vary the flow, there is NO savings.

* Notice that I use the term "vary", not "change". That's because they are different issues. Varying means constantly changing, but if you just want to PERMANENTLY change the flow in a pump, and it will always still run the SAME speed, then it is more efficient to just have the impellers trimmed. VFDs lose about 3% of the energy through them (as heat). If you gain more efficiency in the variation, that becomes irrelevant. But if you always run at the same speed, you have to compare that to trimming the impellers, and trimming wins. Also, NEVER add a VFD and then run it at full speed all the time because it will be a total waste of money, unless you have a machine with a motor that can ONLY be 3 phase, at which point the VFD represents less losses than any other type of phase converter.

So back to the pool filter pumps. I rarely see a pool filter system with a servo controlled proportional valve that changes the flow, but it happens on larger commercial systems like municipal pools or big hotels. I have NEVER seen that on a residential pool, which by virtue of the 115V and HP size you mention, means tht is what is being discussed here. The only thing I have seen is two speed pumps where the low speed is used most of the time to just run the filter, then once or twice a day they connect a cleaner that uses the high speed. If THAT is what he wants to replace, there may be some merit to it, but it depends on the type of 2 speed motor he uses. If it is a Variable Torque 2 speed motor, probably not going to save energy. How you tell is by looking at the nameplate. If the low speed shows a lower HP, and the HP is lower by more than the speed difference, that is a variable torque version. If it says 2 speeds but only shows one HP, then the VFD will save him energy.

 

[ritelec]

thank you

 

[Jraef]

thank you

A VFD for that would be a total waste, unless, like I said, he has a controllable valve on the system someplace that can be removed. But given the size and type of pump here, I would bet a paycheck that valve is non-existent.

By the way, people also often think that a 3 phase motor is "more efficient" than a single phase motor, so that's why they think they want to do that. Also a fallacy. Watts = watts and motor efficiency is whatever the motor says it is, has nothing to do with being single or 3 phase. But if you only have single phase available and you add the VFD just to be able to use a 3 phase motor thinking it will be more efficient, you are not only wasting the money on the VFD and new 3phase motor, but again, you have added the losses in the VFD that you didn't have before. Lose lose.

 

[just the cowboy]

Single phase motor

Single phase motor

That is a single phase motor. Maybe they want to use one of these, single phase output for speed control. http://www.anaconsystems.com/text/eagle1.html 1 1/2 hp 10.5 amps are $500.

 

[StarCat]

JRAEF your information is always eloquently stated.
I have one pump system in particular that a VFD saved us on and it is just as "J " has stated with respect to reducing flow.
I had a Utah pool operators certification at one time, not that I really wanted it. As other things it was a learning experience.
The filter systems I ran required a static GPM range to work correctly.
Most pool jet pump motors are dual voltage 115V-208.

 

[Fulthrotl]

A MAJOR fallacy in the VFD sales game......

So back to the pool filter pumps. I rarely see a pool filter system with a servo controlled proportional valve that changes the flow, but it happens on larger commercial systems like municipal pools or big hotels. I have NEVER seen that on a residential pool, which by virtue of the 115V and HP size you mention, means tht is what is being discussed here. The only thing I have seen is two speed pumps where the low speed is used most of the time to just run the filter, then once or twice a day they connect a cleaner that uses the high speed. If THAT is what he wants to replace, there may be some merit to it, but it depends on the type of 2 speed motor he uses. If it is a Variable Torque 2 speed motor, probably not going to save energy. How you tell is by looking at the nameplate. If the low speed shows a lower HP, and the HP is lower by more than the speed difference, that is a variable torque version. If it says 2 speeds but only shows one HP, then the VFD will save him energy.

pentiar makes a vfd controlled pool pump, which is probably what is being offered by the pool guy.

http://www.pentairpool.com/products/pumps-inground-intelliflo-vs-svrs-variable-speed-pumps-76.htm

my question is that if you have a pressure transducer in the pump to prevent overdriving the
pump, that would allow you to maintain a constant output pressure, and not waste power by
running at synchronous speed, yes?

so that way when you were heating the pool as opposed to filtering you'd have different flow rates,
and the pump would automatically adjust for that.

in your experience, is that true, or not?

 

[DTLight]

The Pentair VS pumps only run at preset speeds, they don't compensate for pressure. The VF pumps are preset for flow rate, and the pump controller adjusts the RPM to achieve the desired flow rate. They are both three phase motors, driven from the integrated 240V single phase VFD. I have a VF pump, and am saving around $50 a month in electric costs. The VF pumps don't have a vacuum anti entrapment features like the VS pumps do, so the pool plumbing would have to have to be compliant with the Virginia Graeme Baker Pool and Spa Safety Act to install a VF pump. Either pump can be set up with 4 programmed speeds/flow rates inside the VFD, or for more options if the pump is networked to an automation controller. I presume that Jandy has similar capabilities for their pumps.


The two speed non VFD pumps are about half the price, and about 80% of the savings.

 

[Jraef]

pentiar makes a vfd controlled pool pump, which is probably what is being offered by the pool guy.

http://www.pentairpool.com/products/pumps-inground-intelliflo-vs-svrs-variable-speed-pumps-76.htm

my question is that if you have a pressure transducer in the pump to prevent overdriving the
pump, that would allow you to maintain a constant output pressure, and not waste power by
running at synchronous speed, yes?

so that way when you were heating the pool as opposed to filtering you'd have different flow rates,
and the pump would automatically adjust for that.

in your experience, is that true, or not?

Yes, that could be true, IF the system design allows for it, which is my point. Just putting in the VFD alone will not save energy, there has to be a REASON to use the VFD, which must mean that you have a way to decrease the LOSSES in a system. So if the system is designed with a single speed pump, and that pump runs at full speed no matter whether it is filtering or heating, then if one part of the process COULD take advantage of having less flow, and the VFD can be made to detect that and adjust to it, then yes, it would save energy compared to NOT doing it. But... if the heater system was designed to have full flow through it, because that is what they EXPECTED when designing it, and you artificially REDUCE that flow, there may be other consequences to that, not all of them good. So it is not quite that simple, you have to consider the entire SYSTEM design. If you read that Pentair information, they make the same point.

The Pentair VS pumps only run at preset speeds, they don't compensate for pressure. The VF pumps are preset for flow rate, and the pump controller adjusts the RPM to achieve the desired flow rate. They are both three phase motors, driven from the integrated 240V single phase VFD. I have a VF pump, and am saving around $50 a month in electric costs. The VF pumps don't have a vacuum anti entrapment features like the VS pumps do, so the pool plumbing would have to have to be compliant with the Virginia Graeme Baker Pool and Spa Safety Act to install a VF pump. Either pump can be set up with 4 programmed speeds/flow rates inside the VFD, or for more options if the pump is networked to an automation controller. I presume that Jandy has similar capabilities for their pumps.


The two speed non VFD pumps are about half the price, and about 80% of the savings.

Just for the benefit of those unaware of this new issue brought up by the rather wild energy savings claims from that Pentair salesy piece, here is what it behind it (although I'm not buying it all).

There is a new trend happening in the OEM industry right now that is making it possible to save significantly more energy than JUST by having the VFD for flow control; Permanent Magnet AC motors. These are different from standard induction motors where the stator induces current flow in the rotor to produce magnetic fields that make it spin. In the new motors, they use rare-earth magnets in either the stator or the rotor, so there is no slip. The rotor spins simply because it is interacting with the FIXED magnetic fields in one half of the motor. That SIGNIFICANTLY reduces the losses inherent in the motor design, allowing for efficiencies of greater than 95% in many cases. In addition, they allow for higher speeds, which if designed into a system correctly, can further increase efficiencies. The down side of them is that they MUST have a VFD to control them, they do NOT work without one, that VFD must be very specially capable of controlling that type of motor (very few are and they are the more expensive varieties), and the motor itself, because of it having rare-earth magnets, is significantly more expensive. So that explains, by the way, why the 2 speed standard induction motor will provide some energy savings, but at a much lower price.

They claim savings of 90% in that website, I find that hard to swallow. You CANNOT save anything that is not wasted. So in order to "save" 90%, that means that the system must have been designed to only be no better than 10% efficient, and the new system will now be 100% efficient at that 10% level. I find that all hard to imagine.

 

[Besoeker]

Yes, that could be true, IF the system design allows for it, which is my point. Just putting in the VFD alone will not save energy, there has to be a REASON to use the VFD, which must mean that you have a way to decrease the LOSSES in a system. So if the system is designed with a single speed pump, and that pump runs at full speed no matter whether it is filtering or heating, then if one part of the process COULD take advantage of having less flow, and the VFD can be made to detect that and adjust to it, then yes, it would save energy compared to NOT doing it. But... if the heater system was designed to have full flow through it, because that is what they EXPECTED when designing it, and you artificially REDUCE that flow, there may be other consequences to that, not all of them good. So it is not quite that simple, you have to consider the entire SYSTEM design. If you read that Pentair information, they make the same point.



Just for the benefit of those unaware of this new issue brought up by the rather wild energy savings claims from that Pentair salesy piece, here is what it behind it (although I'm not buying it all).

There is a new trend happening in the OEM industry right now that is making it possible to save significantly more energy than JUST by having the VFD for flow control; Permanent Magnet AC motors. These are different from standard induction motors where the stator induces current flow in the rotor to produce magnetic fields that make it spin. In the new motors, they use rare-earth magnets in either the stator or the rotor, so there is no slip. The rotor spins simply because it is interacting with the FIXED magnetic fields in one half of the motor. That SIGNIFICANTLY reduces the losses inherent in the motor design, allowing for efficiencies of greater than 95% in many cases. In addition, they allow for higher speeds, which if designed into a system correctly, can further increase efficiencies. The down side of them is that they MUST have a VFD to control them, they do NOT work without one, that VFD must be very specially capable of controlling that type of motor (very few are and they are the more expensive varieties), and the motor itself, because of it having rare-earth magnets, is significantly more expensive. So that explains, by the way, why the 2 speed standard induction motor will provide some energy savings, but at a much lower price.

They claim savings of 90% in that website, I find that hard to swallow. You CANNOT save anything that is not wasted. So in order to "save" 90%, that means that the system must have been designed to only be no better than 10% efficient, and the new system will now be 100% efficient at that 10% level. I find that all hard to imagine.

Snake oil, smoke, and mirrors are obviously the currency of such technology.......

 

[Jraef]

Snake oil, smoke, and mirrors are obviously the currency of such technology.......

Sad, but all too true. The sad thing is that the technology is real, and it really does save some energy. But then the marketing people get hold of the basic kernel of truth and somehow not only make it look like a whole corn cob, they often take it to become an entire corn CROP, which in reality then makes it into crap, not crop...

 

[GoldDigger]

My, you are waxing eloquent today!
Must have hit a sensitive spot.

 

[Jraef]

My, you are waxing eloquent today!
Must have hit a sensitive spot.

We just lost a big turnkey project to some pump dealer who is selling a broken-out packaged deal of pumps and drives (no install), and their proposal was spewing this kind of crap profusely so the user went for it. I can still bid on the install, but I'm not interested in becoming the scapegoat when all the lies come to the forefront. I feel sorry for the guy who gets that part though. He will have bid on it with no margin on the materials, so any mistakes have no "fudge factor" to protect him and when he gets dragged into the mess that will take place when all the FM fails to materialize, even though it will not have been his fault, he will lose his ass on the project just from the process of defending himself.

 

[DTLight]

My local electric utility estimates a 70% reduction in pump operating costs with a variable speed pump, and the pool pump is often the largest electrical power user in a residential home.

http://savewithsrp.com/RD/poolpump.aspx



For what it's worth my AC is 10 years old, presumably the AC is the largest power user in the three hottest months of summer in Arizona. I could have achieved similar savings by adding a 1/4 HP pump for filtering (if one was available) and leaving the existing 2HP pump for vacuuming and other times that higher water flow was required. The old pump used drew 8 amps and the new variable speed one about 2 amps pumping water through the filter.

 

[mbrooke]

The "pool guy" asked me about upping from 120v to 240v for his vfd pool pumps he's installing ( as it was raining on me while I was screwing around with a HP rated switch and a plastic two gang cover).

He's wondering what it would take? Like a ~ 4 or 6 hundred dollar transformer to go from 120 to 240 so he could run this pump and potentially save his costumers hundreds of dollars a year.

Not always playing with the numbers, I sometimes question myself. So am I in the right frame of mind thinking ? That,
Besides the cost of a transformer and wiring,

The motors he is installing are 1.5 HP 10 amp (name plate) So at 240 volt that motor would be on a 20 or 25 amp circuit.
At 120 volt with a transformer, that 120 volt circuit should be 40 or 50 amps.

Is that right?

Thanks

You will have savings, but only pennies maybe at most a few dollars per year from voltage drop on the wire.


A 1/2 HP 120 volt motor pulls about 9.8amps full load, will round it to 10amps. If the same motor is configured to 240 volts it will pull 5 amps. Assuming 14 gauge with both voltages at 240 volts you will improve efficiency on the wire. As for the motor itself, watts are watts. 240x5=1200 watts, 120x10=1200 watts. I assumed unity power factor but watts hold true for any power factor.



So in total factoring everything together on a 200ft run of 14 guage wire:


120 volts: 1205 watts, at 240 1202 watts.

 

[kwired]

My local electric utility estimates a 70% reduction in pump operating costs with a variable speed pump, and the pool pump is often the largest electrical power user in a residential home.

http://savewithsrp.com/RD/poolpump.aspx

View attachment 10402

For what it's worth my AC is 10 years old, presumably the AC is the largest power user in the three hottest months of summer in Arizona. I could have achieved similar savings by adding a 1/4 HP pump for filtering (if one was available) and leaving the existing 2HP pump for vacuuming and other times that higher water flow was required. The old pump used drew 8 amps and the new variable speed one about 2 amps pumping water through the filter.

Again, it will only save if the pump can have reduced speed. If the pump never needs to run at the higher speed it would cost less to go with a different pump design, as the first one was designed for more flow then was needed. It could also cost less if only two speeds are necessary and you used a two speed motor instead of the VFD.

Don't take too much meaning from "amps" drawn. You don't buy amps you buy energy (kilowatt hours).

Also remember if you are reading direct motor amps and the first one was 8 amps @ 120 volts (aren't most single phase pool pumps 120 volts?) you would be drawing 960 VA and would need to know power factor and efficiency to figure out just what the watts are, but could easily be in the 800 -900 watt range.

Now most VFD are going to be outputting 3 phase (and likely @ 240 volts), so if you had 2 amps @ 240 volts you have about 830 VA, not quite as amusing of a number going from 960 to 830 as it is to go from 8 to 2 is it? You need to know what it is that you are comparing.

Not saying you are wrong, just saying make sure you are right.

 

[DTLight]

Both readings were at 240V, although the first reading on the old pump was not with a true RMS meter, and the second reading is off the VFD display.