High pressure cut out switch for Aquavar Solo2?

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Scooterbugg

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I have an Aquavar Solo2 driven constant volume system. I'm thinking about adding a high pressure cut out switch and setting it above system pressure but below pressure relief setting. Has anyone done this or can anyone recommend a good switch? The supplier of my system was well versed in the particulars of this system and said it is not necessary, but I prefer to err on the side of safety.
 

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I have an Aquavar Solo2 driven constant volume system. I'm thinking about adding a high pressure cut out switch and setting it above system pressure but below pressure relief setting. Has anyone done this or can anyone recommend a good switch? The supplier of my system was well versed in the particulars of this system and said it is not necessary, but I prefer to err on the side of safety.

Your pressure relief valve is the most dependable part of your pump system. It will pop off when the VFD fails to shut off the pump. The PRV will protect your pump from a deadhead condition, which will burn up your pump. Nothing will protect your pump from having to start for every drop of water used. The 2 gallon tanks hold about 1/4 gallon of water, which can't even be used unless the pressure drops before the pump starts, and the pressure climbs 20 PSI before the pump is shut off. Usually these little VFD systems do not have a pressure bandwidth like that, so the pump has to start for every drip out of the faucet.

I watched the video
http://residential.goulds.com/constant-pressure/

And while it makes the variable speed system sound inviting, it is incorrect about several things. First they claim the VFD system will eliminate water hammer when a faucet is suddenly closed, and it CANNOT do that. They also say the pump has less stress when it gradually ramps up the speed, which is not correct. The thrust bearing in a submersible motor needs to be up to at least 50% speed in less than 1 second, or it will not get the lubrication it needs and will quickly be destroyed. And they fail to mention that the RF interference produced by those units can cause problems with other electrical devices in and around the house.

But since you fell for the hype, you are now stuck with a 3 phase motor, and cannot easily change to a more reliable system. As long as you have the 3 phase motor down the well you are stuck using a VFD to convert your normal single phase house power into 3 phase that the motor needs. That way they usually get to sell you 2 or 3 of those expensive controllers before you starts looking for a reliable alternative and switch back to a normal single phase motor.

I did find the video interesting when it discussed all the problems with the old "traditional pressure tank only system". These problems are true, and is the reason these companies are trying there best to find an alternative to the old pressure tank/pressure switch system. But they want to find an alternative that cost a lot and doesn't last very long, which is where the VFD like the Aquavar comes in.

What they don't want you to know is that you could have added a simple, inexpensive Cycle Stop Valve to the standard pressure tank/pressure switch system and solved all your problems. The CSV would have worked with a regular single phase motor. It would deliver the same constant pressure as the Aquavar VFD. But the CSV would not have cost much, and would have made you pump system last several times longer than normal, and they don't like that.

If the Aquavar has a connection for a switch to start and stop the system, you can use a regular 40/60 pressure switch, which will shut the pump off on high pressure (60) like you are asking. And then the switch would start the pump again at 40 PSI when needed. But if the Aquavar runs on a pressure transducer as I am sure it does, you would have to use a relay for the switch to be able to shut power off to the Aquavar.

It is probably best to just leave it the way it is and see how long it last. In the meantime you can be saving money to replace the three phase motor and researching some more reliable ways of getting the constant pressure you want, which is a good thing as long as you don't use a variable speed type unit to get it.
 

Scooterbugg

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Your pressure relief valve is the most dependable part of your pump system. It will pop off when the VFD fails to shut off the pump. The PRV will protect your pump from a deadhead condition, which will burn up your pump. Nothing will protect your pump from having to start for every drop of water used. The 2 gallon tanks hold about 1/4 gallon of water, which can't even be used unless the pressure drops before the pump starts, and the pressure climbs 20 PSI before the pump is shut off. Usually these little VFD systems do not have a pressure bandwidth like that, so the pump has to start for every drip out of the faucet.

I watched the video
http://residential.goulds.com/constant-pressure/

And while it makes the variable speed system sound inviting, it is incorrect about several things. First they claim the VFD system will eliminate water hammer when a faucet is suddenly closed, and it CANNOT do that. They also say the pump has less stress when it gradually ramps up the speed, which is not correct. The thrust bearing in a submersible motor needs to be up to at least 50% speed in less than 1 second, or it will not get the lubrication it needs and will quickly be destroyed. And they fail to mention that the RF interference produced by those units can cause problems with other electrical devices in and around the house.

But since you fell for the hype, you are now stuck with a 3 phase motor, and cannot easily change to a more reliable system. As long as you have the 3 phase motor down the well you are stuck using a VFD to convert your normal single phase house power into 3 phase that the motor needs. That way they usually get to sell you 2 or 3 of those expensive controllers before you starts looking for a reliable alternative and switch back to a normal single phase motor.

I did find the video interesting when it discussed all the problems with the old "traditional pressure tank only system". These problems are true, and is the reason these companies are trying there best to find an alternative to the old pressure tank/pressure switch system. But they want to find an alternative that cost a lot and doesn't last very long, which is where the VFD like the Aquavar comes in.

What they don't want you to know is that you could have added a simple, inexpensive Cycle Stop Valve to the standard pressure tank/pressure switch system and solved all your problems. The CSV would have worked with a regular single phase motor. It would deliver the same constant pressure as the Aquavar VFD. But the CSV would not have cost much, and would have made you pump system last several times longer than normal, and they don't like that.

If the Aquavar has a connection for a switch to start and stop the system, you can use a regular 40/60 pressure switch, which will shut the pump off on high pressure (60) like you are asking. And then the switch would start the pump again at 40 PSI when needed. But if the Aquavar runs on a pressure transducer as I am sure it does, you would have to use a relay for the switch to be able to shut power off to the Aquavar.

It is probably best to just leave it the way it is and see how long it last. In the meantime you can be saving money to replace the three phase motor and researching some more reliable ways of getting the constant pressure you want, which is a good thing as long as you don't use a variable speed type unit to get it.
Wow. Thanks for the bashing. And from a moderator no less.
I will just take a minute to correct your assumptions then I will leave this forum for good. No need to stay where I'm not wanted, where moderators make gross assumptions and treat members poorly and can't get off their high horse long enough to just answer the simple question that was asked. I was just asking for a switch recommendation.
I know how a PRV functions. But I like redundant systems. I know firsthand how valuable redundancy is.
I've also read all about cycle stop valves and am well aware of how effective they are and how much you like them from your posts in other threads on the forum. Obviously you know more about wells and pumps than me. That doesn't mean you have any right to be condescending and abrasive to me. I'm surprised that Terry would even let you moderate if you act like that. I wouldn't want someone acting like that on a website that is named after me.

You know nothing at all about me and come right out and say I bought into the "hype". I just bought this house as is. It was vacant for several months, the owner passed suddenly. I researched the system before powering it up and checking the plumbing and called the installer (control box had a label on it) who told me all about it. The system works well for now and so far you're the only really negative review I can find on it.

I work for a global auto manufacturer in Ohio. In the last 21 years I have spec'd out and installed VFDs on hundreds of motors in all kinds of installations. I can tell you from experience that there are multiple benefits to having VFD driven motors. Reduced power consumption is just one benefit that people commonly hear about. VFDs now cost about 20% of what they did just 15 years ago and are becoming commonplace. My cost on a Mitsubishi industrial VFD for this motor size (1.5 hp) is around $425 new. I can easily get them used for much less (read:dumpster dive) when we do our time based replacements at work. In the future please be more respectful of members. I will not be one of them.
 

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Wow. Thanks for the bashing. And from a moderator no less.
I will just take a minute to correct your assumptions then I will leave this forum for good. No need to stay where I'm not wanted, where moderators make gross assumptions and treat members poorly and can't get off their high horse long enough to just answer the simple question that was asked. I was just asking for a switch recommendation.
I know how a PRV functions. But I like redundant systems. I know firsthand how valuable redundancy is.
I've also read all about cycle stop valves and am well aware of how effective they are and how much you like them from your posts in other threads on the forum. Obviously you know more about wells and pumps than me. That doesn't mean you have any right to be condescending and abrasive to me. I'm surprised that Terry would even let you moderate if you act like that. I wouldn't want someone acting like that on a website that is named after me.

You know nothing at all about me and come right out and say I bought into the "hype". I just bought this house as is. It was vacant for several months, the owner passed suddenly. I researched the system before powering it up and checking the plumbing and called the installer (control box had a label on it) who told me all about it. The system works well for now and so far you're the only really negative review I can find on it.

I work for a global auto manufacturer in Ohio. In the last 21 years I have spec'd out and installed VFDs on hundreds of motors in all kinds of installations. I can tell you from experience that there are multiple benefits to having VFD driven motors. Reduced power consumption is just one benefit that people commonly hear about. VFDs now cost about 20% of what they did just 15 years ago and are becoming commonplace. My cost on a Mitsubishi industrial VFD for this motor size (1.5 hp) is around $425 new. I can easily get them used for much less (read:dumpster dive) when we do our time based replacements at work. In the future please be more respectful of members. I will not be one of them.

Well so it was the previous owner who fell for the hype, not you. I apologize if I offended you in anyway. But after re-reading what I wrote, I do not think any of it was directed at you. That is unless you are the VFD manufacturer. All of my comments were directed at VFD's, not you. I did not mean to be, nor do I think I was being "condescending or abrasive" to you at all.

I have been doing this a long time. And what I find is that people do not like being corrected. Some people think I am being "condescending and abrasive", when all I was doing was correcting their incorrect assumptions. The only thing I said about you was that you fell for the hype. And I apologize since it wasn't you, but the previous owner who fell for the hype. But since you still think a VFD can save energy, you have still fallen for the hype. VFD's do not save energy on pumping applications. If you are running a conveyor belt or auger, they might save energy, but not on pumps. Of course I am the only negative review you can find on VFD's, everyone else is trying to sell you the hype.

It is much easier to sell the hype than to explain the truth. People like to have the wind blown up their skirt more than they like to face the ugly facts.
 

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If the Aquavar has a connection for a switch to start and stop the system, you can use a regular 40/60 pressure switch, which will shut the pump off on high pressure (60) like you are asking. And then the switch would start the pump again at 40 PSI when needed. But if the Aquavar runs on a pressure transducer as I am sure it does, you would have to use a relay for the switch to be able to shut power off to the Aquavar.

And I did answer your question. But if you have installed hundreds of these over the years, you should have already know all of this.
 

Scooterbugg

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And I did answer your question. But if you have installed hundreds of these over the years, you should have already know all of this.
My system runs a transducer. I was looking for a clean option, not a dual purpose switch and wasn't looking to use the switch to turn pump on, only to protect from over pressure. Again you attack with silly comments like "you should have known this" and imply I don't know what I'm talking about when it comes to drives. And I still haven't bought the hype. I listen to facts and make my own judgements. I'm have decades of experience with frequency drives. Most are with drop lifts, injection molding machines, conveyors and such but a few cooling tower applications as well. My point is that they are so cheap now and prices are still falling. It's my opinion that they are not a terrible option.
 

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I'm thinking about adding a high pressure cut out switch and setting it above system pressure but below pressure relief setting. Has anyone done this or can anyone recommend a good switch?
It seems odd that that is not a commonly offered product -- a cutoff pressure switch for potable water. The unit could latch power off, or just be momentary.

Maybe you could have a regular Pumptrol mechanical pressure switch set for 50-70 PSI (or whatever) in series with the power to the whole system.

Another idea would be to route the pressure relief water to a bucket. The bucket would contain a float switch that would cut the power when the float floats.
 

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My system runs a transducer. I was looking for a clean option, not a dual purpose switch and wasn't looking to use the switch to turn pump on, only to protect from over pressure. Again you attack with silly comments like "you should have known this" and imply I don't know what I'm talking about when it comes to drives. And I still haven't bought the hype. I listen to facts and make my own judgements. I'm have decades of experience with frequency drives. Most are with drop lifts, injection molding machines, conveyors and such but a few cooling tower applications as well. My point is that they are so cheap now and prices are still falling. It's my opinion that they are not a terrible option.

You can use a relay as a latch for a regular 40/60 type switch, where you have to punch a button to re-engage the power. But this will have to be installed prior to the drive, and will shut power off to everything. You can't put the switch on the 3 phase side of the drive.

They also make high pressure kill switches for pivot sprinkler systems. These type switches just latch off at high pressure, and you have to manually restart them. But I doubt they would handle the amperage needed, so the latching relay idea works the same with a high amperage switch.

I also have decades of experience with frequency drives. I have some on injection molding machines. And other than having to keep an air conditioner dedicated to each one to keep them from tripping, they do a fantastic job compared to my hydraulic machines. But when you apply the affinity law for centrifugal pumps to the reduction of speed from a VFD you see that pumps are not good applications for VFD's. Lose of head by the square of the speed is a real deal breaker for VFD's when you are dealing with a pump system that requires a constant amount of head, lift or pressure.

You are right, VFD pump systems are not a terrible option. They do work on the principle of maintaining a constant pressure by varying the pumps flow, and work with a very small pressure tank. These are all good things, but even more so if you can accomplish it without the problems that go with VFD's.

Sorry about the "you should have known" comment. But there is no difference here than a drive on an injection modeling machine. You either have to connect a switch to an on/off contact on the VFD, or shut the power off to the VFD with a relay or a switch.
 

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I don't know about the Aquavar, but I've seen Subdrives installed with a pressure switch wired in between the transducer and controler. Why? Because if the transducer gets a little sediment in it, it hangs up and blows off the PRV.
 

Scooterbugg

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I don't know about the Aquavar, but I've seen Subdrives installed with a pressure switch wired in between the transducer and controler. Why? Because if the transducer gets a little sediment in it, it hangs up and blows off the PRV.
Thank you. That's exactly what I was looking for. The drive has an enabling input that is jumpered from the factory. I prefer to use an over pressure switch in place of the jumper and set below the level of the relief valve to prevent the mess in the first place. Since my well was unused for months you can imagine the amount of crud that came out when I fired it up. I've cleaned and checked the transducer since the initial flush and all is ok for now. I emailed my Asco supplier and they have several options.
 

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I don't know about the Aquavar, but I've seen Subdrives installed with a pressure switch wired in between the transducer and controler. Why? Because if the transducer gets a little sediment in it, it hangs up and blows off the PRV.

Subdrives use a switch with 1 PSI differential, not a transducer like the Aquavar. You can use a regular 40/60 switch on the subdrive instead of the 1 PSI differential switch. But you can't use a switch to cut off the 4-20 ma signal from a transducer or the VFD goes to full speed. You can tie a switch into the enabling input in the drive, and it is not high amperage, so any switch will work. But the switch needs to latch off at high pressure and not let the pump come back on at low pressure.

And if a PRV is plumbed to the outside or to a drain it doesn't cause a mess.
 

Craigpump

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Actually, I'm kinda on the fence about PRV's having female threads, I've seen too many that have plugs put in them because they dripped. People just don't understand what it's for and what can happen to the tank.
 

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Actually, I'm kinda on the fence about PRV's having female threads, I've seen too many that have plugs put in them because they dripped. People just don't understand what it's for and what can happen to the tank.

And you wouldn't see a PRV on a water heater plugged and not plumbed to a drain or outside. It is usually leaking for a reason. Plug the PRV and they usually find out what that reason was after the catastrophe.
 
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