The following is typical of what many pump installers believe after listening to the manufactures. I hope this helps clear up some of the misinformation that is causing some people to fall for a Constant Pressure Pump. The principle is so technical that even the pump installers do not understand. I am sure they think they are selling you the best technology available. You should study the facts before making that decision. Doing what the pump manufacturers recommend is not usually what is best for the end user, just for the manufacturer.
Junior Member Join Date: Jul 2008
"Constant pressure pumps work great, we have sold hundreds of them. They aren't a new concept they have been out for 15+ years going back to the old Hays Pumps days." Driller
You are right, variable speed pumps are an old concept going back about 30 years. The "old Hays Pump Days" were only about 10 years ago, and none of them are still working.
Then came the Grundfos SQE. These pumps are still on the market after 9 years but, there have been so many upgrades to that system that I can no longer count them. The latest upgrade makes the pump cycle on and off like a standard pump for 1000 cycles, to see if it can again regain communication with the motor before faulting out. This is probably the best of the variable speed pumps available. However, only a tiny fraction have lasted 9 years, and the average life is less than 4 years. BTW, none of the upgraded stuff works with the older stuff so, if you have a problem, the whole thing has to be replaced.
Then came Franklins CP Water, which had water running through the electric controller to try and keep it cool. These were only 7 years ago and everybody in the industry knows these didn't last very long. Next was the Frankin Sub Drive in the black box about 5 years ago. Apparently the black colored box was the reason these units were getting hot and failing so quickly, so after a year or so they started painting these boxes white. This change about 3 years ago was supposed to keep the controllers from overheating. Reports from the field show that the white boxes quickly turn black and even discolor the wall they are mounted on.
In the last 3 to 5 years there have been many other brands of these variable speed controllers come and go on the market. Problems with cooling, low flow, communication, voltage spikes, and many other things have made these type systems unreliable.
Since you agree that variable speed pumps are "not a new concept", you should be aware that the Cycle Stop Valve has been replacing these variable speed pumps for about 15 years now. This makes the Cycle Stop Valve the most advanced technology available. Since 1993, when Cycle Stop Valves first started replacing variable speed pumps, every time a VFD system is discontinued, it has been replaced with a CSV.
"Read this press release from 15 years ago that I found on this website called xxxx this proves that constant pressure (CP) has come along way." Driller
I don't see anything about constant pressure on this web page except for the ConstaBoost for centrifugal pumps, they make no mention of the Sub Drive or Mono Drive. Maybe this company has already learned their lesson about constant pressure pumps.
"The CP controller converts your 1-phase power to three-phase (which three-phase is cheaper to run on) It is variable speed and ramps up and down depending on your demand."Constantpressure
A 3 phase motor is a little more efficient than a 1 phase motor but, the heat losses of the VFD itself, the loss of motor efficiency running on current with harmonic content, and the 40 watts of power used by the VFD when the pump is not even running, more than add back any energy saving that could have been available from varying the speed.
"A standard pump just kicks on full blast until it can shut off. The standard pump when it kicks on runs twice the amperage and slams the pump, motor, pipe, & wire against the well casing when it torques on." Driller
Actually starting a standard pump against a Cycle Stop Valve delivers the same reduced amp soft start as when ramping up the speed slowly with a VFD.
I have heard a lot more problems with rubbing holes in the pump, motor, and wire, from the two million switches on and off per month, that happen when the system is controlled by the Franklin Drive, because it has a small bandwidth pressure switch instead of a pressure transducer.
"Constant pressure pumps require a much smaller tank which saves you money.
CP pumps because they run on three-phase you are able to use smaller wire which can be a huge savings." Driller
A CSV uses the same small tank as a CP pump. However, all the water in this small tank can be utilized with the CSV, while the CP pump has such a small pressure bandwidth, that it does not allow any of the water in the tank to be used. This means that a CP pump must start for every glass of water or even to fill the ice maker. It also means that any water in that tank gets stale and contaminated, and this does not happen with the CSV. Using a three phase motor so you can reduce the wire size, only helps a little with the extra cost of the VFD controller.
"They save power, you could say they are more "Green" than a standard pump." Driller
A CP pump DOES NOT save energy, compared to the energy reduction of a standard pump being controlled by a valve. To say that CP pumps are more "green" is incorrect. Actually the energy used to manufacture these computerized controllers exceeds any energy savings that might have been saved by there use.
"The only problem ever had with the constant pressure pumps were the check valve they put in the head of the pump. The checkvalve was cheap and the water coming out so fast and spinning right out of the pump would ruin that spring." Driller
I am sorry but, spinning is not what is wearing out the check valves. The switching on and off of the pump by the "pressure sensor" of the Sub drive, which can happen about two million times per month, is also opening and closing the check valve two million times per month, which equals check valves not lasting very long.
"Don't get me wrong constant pressure pumps aren't ideal for every situation I just wanted to clear some things up because ALOT of people want to knock the pump systems with little or no knowledge of them and without ever installing or owning one." Driller
I am knocking the "Constant Pressure" pumps because I have A LOT OF EXPERIENCE with them. I was building and installing them about 20 years ago, and can go back 40 years if you want a real history lesson. We have had so many problems with Variable Speed Pumps, that we devised the Cycle Stop Valve to replace them about 15 years ago. Ever wonder when the "old Hays Pumps" failed, what was used to replace them. We have been replacing every brand of variable speed pump or controller with Cycle Stop Valves for 15 years now. Everyday we use Cycle Stop Valves to replace SQE's, Sub Drives, Mono Drives, Balance Flows, Aquavars, ABB's, Toshiba's, Allen Bradley's, AC Tech's, and countless other brands of Variable Speed Pumps and controllers.
The people who use Cycle Stop Valves everyday, are those who have already been through a dozen different VFD pumps, with the promise that the newest model will solve all the problems of the previous models. They finally realize that VFD's are just "hype" designed to increase profits for the manufacturer, and reduce the life expectancy of the equipment (planned obsolescence). They soon realize that the Cycle Stop Valve is the newest and most beneficial technology available to deliver "Constant Pressure" dependably, and at an affordable price.
I would be happy to discuss any of these or other questions you might have, either here on the forum or personally.