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#41
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Alan, I picked up a little 2 gallon pressure tank for $20 and mounted
it right on the pump, kinda like you recommended. It took care of the inital surge of pressure and cured my problem. Now when the pump kicks on at 40psi, the pressure doesn't jump up at all. Before the pressure would jump up 20+ pounds causing the on off on off pressure switch problem. The air chamber / snubber cured it completely. Before trying the snubber, I changed out the 1" pipe I had on the end of the line going to my pressure tank with 1 1/4" pipe. That didn't make any difference. |
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#42
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Dear nomad:
"nomad" wrote in message oups.com... Alan, I picked up a little 2 gallon pressure tank for $20 and mounted it right on the pump, kinda like you recommended. It took care of the inital surge of pressure and cured my problem. Now when the pump kicks on at 40psi, the pressure doesn't jump up at all. Before the pressure would jump up 20+ pounds causing the on off on off pressure switch problem. The air chamber / snubber cured it completely. Before trying the snubber, I changed out the 1" pipe I had on the end of the line going to my pressure tank with 1 1/4" pipe. That didn't make any difference. Be prepared to bleed water out/force air into the tank. Over time this air precharge will bleed off. Additonally, since this tank is not kept wetted, there will be corrosion at the air-water interface (assuming either steel or stainless steel tank). You applied a bandaid, and one that will "become infected" if not replaced. A timer will work, as will moving the pressure switch or the tank. It is your house, your budget, and your time. You get to choose when and how you spend it. Good luck! David A. Smith |
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#43
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"N:dlzc D:aol T:com (dlzc)" wrote: You applied a bandaid, and one that will "become infected" if not replaced. A timer will work, as will moving the pressure switch or the tank. No he cured the problem your solutions would only mask the problem which is the the pressure surge on start and stop of the pump. If the 20 gallon tank is designed for what he's using it for (i.e. has a rubber bladder inside) none of your dire predictions apply. It is your house, your budget, and your time. You get to choose when and how you spend it. Yeah, don't listen to this guy. -jim ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
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#44
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jim wrote: "N:dlzc D:aol T:com (dlzc)" wrote: You applied a bandaid, and one that will "become infected" if not replaced. A timer will work, as will moving the pressure switch or the tank. No he cured the problem your solutions would only mask the problem which is the the pressure surge on start and stop of the pump. If the 20 gallon tank is designed for what he's using it for (i.e. has a rubber bladder inside) none of your dire predictions apply. It is your house, your budget, and your time. You get to choose when and how you spend it. Yeah, don't listen to this guy. -jim ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- "that guy" happens to be right. The fix -is- a bandaid approach to a non-problem if the system is installed correctly. Your concern about water hammer is unwarranted or there would be pipes breaking all over this land of ours. I have never seen a surge tank installed at the well head and I have seen a lot of systems. Harry K |
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#45
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Dear jim:
"jim" wrote in message ... "N:dlzc D:aol T:com (dlzc)" wrote: You applied a bandaid, and one that will "become infected" if not replaced. A timer will work, as will moving the pressure switch or the tank. No he cured the problem your solutions would only mask the problem which is the the pressure surge And your tank doesn't mask the problem? on start and stop of the pump. If the 20 gallon tank is designed for what he's using it for (i.e. has a rubber bladder inside) none of your dire predictions apply. It is 2 gallon "pressure tank". Have you *ever* seen this size for water service? I have seen them for compressed air service. It is your house, your budget, and your time. You get to choose when and how you spend it. Yeah, don't listen to this guy. You are entitled to your opinion. Fortunately, I don't have to hear it. plonk David A. Smith |
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#46
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Harry K wrote: jim wrote: "N:dlzc D:aol T:com (dlzc)" wrote: You applied a bandaid, and one that will "become infected" if not replaced. A timer will work, as will moving the pressure switch or the tank. No he cured the problem your solutions would only mask the problem which is the the pressure surge on start and stop of the pump. If the 20 gallon tank is designed for what he's using it for (i.e. has a rubber bladder inside) none of your dire predictions apply. It is your house, your budget, and your time. You get to choose when and how you spend it. Yeah, don't listen to this guy. -jim ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- "that guy" happens to be right. The fix -is- a bandaid approach to a non-problem if the system is installed correctly. Your concern about water hammer is unwarranted or there would be pipes breaking all over this land of ours. Well all pipes will eventually fail. He said he eliminated the pressure surge and that was the only reported problem. Simply moving the pressure switch to where the pressure surge doesn't exist wouldn't get rid of it. And no, the pressure surge won't cause his new pipes to fail immediately, but in 20 or 40 years when the system becomes brittle it will make a difference. What about this system do you think is not installed correctly? The surge is caused by the long run from pump to the holding tank. Moving the holding tank would also eliminate the surge. But putting a surge tank by the pump also works. That's why plumbing supply stores sell them in all different sizes. -jim I have never seen a surge tank installed at the well head and I have seen a lot of systems. Harry K ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
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#47
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Dear Harry K:
"Harry K" wrote in message oups.com... jim wrote: "N:dlzc D:aol T:com (dlzc)" wrote: You applied a bandaid, and one that will "become infected" if not replaced. A timer will work, as will moving the pressure switch or the tank. No he cured the problem your solutions would only mask the problem which is the the pressure surge on start and stop of the pump. If the 20 gallon tank is designed for what he's using it for (i.e. has a rubber bladder inside) none of your dire predictions apply. It is your house, your budget, and your time. You get to choose when and how you spend it. Yeah, don't listen to this guy. "that guy" happens to be right. The fix -is- a bandaid approach to a non-problem if the system is installed correctly. Your concern about water hammer is unwarranted or there would be pipes breaking all over this land of ours. I have never seen a surge tank installed at the well head and I have seen a lot of systems. Do you have any experience/history with soft starts being used with jet pumps? Since the problem is brought about by the "starting torque" of the motor, if you slowed the startup, the "cause" of the problem disappears (and it might even pay for itself in reduced starting currents). I just don't know how effective (long lasting) they are for high rpm motors... Something like the Telemechanique (Square D) Altistart ATS01, or something of its ilk... (McMaster Carr only has three phase soft starters available). Thoughts? David A. Smith |
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#48
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Air dissolves into water pretty fast -- a few weeks for two gallons of
air. That was the other reason for bladder tanks besides smaller size. Bret Cahill |
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#49
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jim wrote: Harry K wrote: jim wrote: "N:dlzc D:aol T:com (dlzc)" wrote: You applied a bandaid, and one that will "become infected" if not replaced. A timer will work, as will moving the pressure switch or the tank. No he cured the problem your solutions would only mask the problem which is the the pressure surge on start and stop of the pump. If the 20 gallon tank is designed for what he's using it for (i.e. has a rubber bladder inside) none of your dire predictions apply. It is your house, your budget, and your time. You get to choose when and how you spend it. Yeah, don't listen to this guy. -jim ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- "that guy" happens to be right. The fix -is- a bandaid approach to a non-problem if the system is installed correctly. Your concern about water hammer is unwarranted or there would be pipes breaking all over this land of ours. Well all pipes will eventually fail. He said he eliminated the pressure surge and that was the only reported problem. Simply moving the pressure switch to where the pressure surge doesn't exist wouldn't get rid of it. And no, the pressure surge won't cause his new pipes to fail immediately, but in 20 or 40 years when the system becomes brittle it will make a difference. What about this system do you think is not installed correctly? The surge is caused by the long run from pump to the holding tank. Moving the holding tank would also eliminate the surge. But putting a surge tank by the pump also works. That's why plumbing supply stores sell them in all different sizes. -jim No, he did -not- say that he eliminated the surge. The surge is still there but being absorbed by the surge tank, just as it was by the tank, just as it is in all systems. There will always be a surge at startup given any pipe at all between pump and tank. "move to where....surge doesn't exist"??? This is a hydraulic system. The surge will affect all parts of it. The surge will NOT (how many times do I have to say it?) affect the pipes. You are confusing a surge with a water hammer - two different things. It is a water hammer that causes damage. Again, adding something at the well head without doing anything else is a band aid approach to fix a problem that wouldn't exist if it was correctly installed. Curing the problem by adding unnecessary equipment is a band-aid approach and poor mechanical work. Were it my well I might do it but not on any other well I work on (of course had I installed it, the switch would have been on the tank). There is a right and wrong way to go about fixing things. Harry K |
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#50
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N:dlzc D:aol T:com (dlzc) wrote: Dear Harry K: "Harry K" wrote in message oups.com... jim wrote: "N:dlzc D:aol T:com (dlzc)" wrote: You applied a bandaid, and one that will "become infected" if not replaced. A timer will work, as will moving the pressure switch or the tank. No he cured the problem your solutions would only mask the problem which is the the pressure surge on start and stop of the pump. If the 20 gallon tank is designed for what he's using it for (i.e. has a rubber bladder inside) none of your dire predictions apply. It is your house, your budget, and your time. You get to choose when and how you spend it. Yeah, don't listen to this guy. "that guy" happens to be right. The fix -is- a bandaid approach to a non-problem if the system is installed correctly. Your concern about water hammer is unwarranted or there would be pipes breaking all over this land of ours. I have never seen a surge tank installed at the well head and I have seen a lot of systems. Do you have any experience/history with soft starts being used with jet pumps? Since the problem is brought about by the "starting torque" of the motor, if you slowed the startup, the "cause" of the problem disappears (and it might even pay for itself in reduced starting currents). I just don't know how effective (long lasting) they are for high rpm motors... Something like the Telemechanique (Square D) Altistart ATS01, or something of its ilk... (McMaster Carr only has three phase soft starters available). Thoughts? David A. Smith No, afraid not. I see no reason it won't work and should fix the problem. It doesn't add more equipment to the system as several others in the thread want to do. Harry K |
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#51
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There is an assumption that those who are reading posts in an engineering
newsgroup have sufficient knowledge to understand enough of the thread so as to be able to ask for clarification of a post, and to not make stupid comments until they do. you know, Dougie, if you have little experience or background in the subject matter as you appear to have, and your reading skills are as poor as yours, you should let the engineers who do this regularly, speak. Especially engineers with decades of experience in the particular subject and who have several well pumps of their own (two shallow installed 1981 and 1984 and one deep 1978 at the lake places, one jet 1970 at the lodge - still running with no problems, precharged to 30 psi.) see below for cites refuting specific neophyte comments "Doug Miller" wrote in message ... In article , "--" wrote: IMHE, the bladder is pressurized too high for efficiency, AND too close to shut-off. The air bladder should be lower than the low switch setting. I would first set the bladder charge to 25 psi. Not if the pump is set to come at at 40. Tank precharge should be approximately 2psi below pump cut-in pressure. Who says? For what purpose? One can select a precharge for the parameter one desires to maximize: for max usable volume, then precharge closer to low set point, and for max damping of pump-ripple in the water in order to minimize parts wear or to get maximum control stability, precharge at a lower setting-- or one can precharge somewhere between, as a compromise. There are four reasons that 38 psi precharge with a lower set of 40 psi is narrowly considered and the recommendation is poor engineering. And I don't care WHICH junior engineer made that recommendation. First, few people have a water pressure gauge that has better hysterisis than 2psi, let alone accounting for the system hysterisis, so calling for 38 psi precharge for a 40psi switch setting is total BS from an execution standpoint. Second, a precharge of 38 psi on a 40 psi start? So you can have pump ripple cycle all your control parts? A precharge set above 60% of upper pump setting would only be made by a pump salesman or switch salesman looking to sell more repair parts. 38 psi precharge on a pump starting atr 40 psi is BS from a basic design reliability standpoint. Third, set for 38 psi so you can have how much water stored under pressure at 40 psi? Enough to keep the pump from running except on draws above the rule-of-thumb of a gallon? A five gallon tank gives a gallon reserve at 25 psi precharge 40-60 psi, and the same five gallon tank gives a gallon and a half reserve at 38 psi precharge 40-60 psi. Try the old P1*V1=P2*V2 equation, using the differential from 40 psi and 60 psi. (Ppchg*Vtank^1.1)/Ppres = Vair-vol^1.1 and then use (Vair-vol 60)-(Vair-vol 40) to find water stored in the operating range for a given tank V between 60psi and 40 psi, V usable =[(Ppc/40) -(Ppc/60)] Vtank Fourth, experienced engineers avoid control settings near system spring constants unless the controls have dampers or they latch. 38 psi in an air bag is close enough to the switch setting of 40 psi such that oscillations in the 38 psi air volume from the moved-water momentum changes can adversely affect a non-latching switch. And they do. I also refer you to the Fluid Power Engineers Handbook, Parker Hannifin, page a-3. The pump in this thread is closer to isothermal operation, and so I quote " pre-charge..to about 1/3 to 1/2 system pressure. " I have gone to a higher precharge than 1/2 for specific design applications, and I knowingly accepted the loss in the other parameters. Next, since if the pump is not securely mounted and the switch is on the pump, the switch will move as the pump moves and the pump motion then moves the switch back. I would move the switch/secure the pump and the pump stand. If one of these does not work, you might need a 90 degree turn in the water line just before the securely mounted switch, but not a 90 turn supported by the switch. one of those should do it. ------------------------- background--- 1) - as incompressible water fills the accumulator tank with a bladder charged to 20 psi, the compressible air will stay at 20 psi until the water pressure rises above 20 psi. Complete nonsense. As water enters the tank, the volume of air decreases, and its pressure necessarily increases immediately. What, in your world P1*V1 = P2*V2 does not apply? 20psi air pressure*Volume air before water = 20psi air pressure* Volume after water means volume of air is constant. Same volume means no water can displace air. Apparently in your world, you can compress 20 psi air with 10 psi water and change its volume without changing its pressure. Patent it , quick. Neat trick in your mind, but not possible in the real world. "As water enters the tank, the volume decreases". That "water enter the tank" cannot happen below the 20 psi of my example, as I said. perhaps I should have written "tries to fill" rather than "fills" If the pump isn't developing more than 20psi, _no_ water will enter the tank whatsoever. Gee, that is EXACTLY what I said. "The compressible air will stay at 20 psi until the water pressure rises above 20 psi" If the pump is developing more than 20psi, water begins to enter the tank immediately, and the air pressure also begins to increase immediately. Which is what I said. [snip] Basically, #1 - if you have the bladder pressure set at the lower setting, the switch vibrates as part of a spring-mass-spring rigid-water-mass/pump with the switch spring set at 40 psi fighting the 40 psi air spring of the bladder. Setting the bladder to 25 psi should cure that. More nonsense. You really should not be posting to engineering newsgroups other than to ask a question. Read carefully again the comment by one who has done this for decades. After the initial fill, as water is withdrawn from the tank, the pump will kick on when the pressure drops to the cut-in setting of the switch (40psi in this case), regardless of whether the precharge pressure was 25psi or 38 as it should be. The only difference is that, at the moment the pump kicks on at 40psi, there will be more water in the tank if it was precharged to 25psi than if it was precharged to 38. In spite of the fact that I was addressing force interactions and you are fixated on precharge and have wandered off the path, I will comment on your error. Contained air is a spring, with a spring constant. The higher the precharge, the higher the spring constant. All pump-fluid-control systems are spring -mass systems that interact. When pumps false start, it is a sign of unintended interaction, There is no discussion among engineers that changing a spring constant changes the interaction, only discussion as to what amount. Either way, the pump comes on at 40 and shuts off at 60. The precharge pressure does *not* affect that. apparently the original poster's comments refute your statement. His pump shut off after a second at what appeared to be 40 psi. Off at 40 psi. Not off at 60 only, as you claim. In the real world, precharge pressure can and does affect controls. -- Regards, Doug Miller (alphageek at milmac dot com) Nobody ever left footprints in the sands of time by sitting on his butt. And who wants to leave buttprints in the sands of time? |
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#52
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FWIW - you have put a second air spring in parallel with the original air
bladder, and by 1/total spring=1/spring1 + 1/spring2, you lowered the total system spring constant (and in so doing, you reduced the peak force the system now sees from the moving water) Adding a second air chamber in parallel to the first air chamber had the same effect on the system as lowering the first tank's precharge in order to lower the system spring constant. "nomad" wrote in message oups.com... Alan, I picked up a little 2 gallon pressure tank for $20 and mounted it right on the pump, kinda like you recommended. It took care of the inital surge of pressure and cured my problem. Now when the pump kicks on at 40psi, the pressure doesn't jump up at all. Before the pressure would jump up 20+ pounds causing the on off on off pressure switch problem. The air chamber / snubber cured it completely. Before trying the snubber, I changed out the 1" pipe I had on the end of the line going to my pressure tank with 1 1/4" pipe. That didn't make any difference. |
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#53
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In article , "--" wrote:
"Doug Miller" wrote in message m... In article , "--" wrote: IMHE, the bladder is pressurized too high for efficiency, AND too close to shut-off. The air bladder should be lower than the low switch setting. I would first set the bladder charge to 25 psi. Not if the pump is set to come at at 40. Tank precharge should be approximately 2psi below pump cut-in pressure. Who says? For what purpose? That's a typical recommendation by manufacturers of well pumps and pressure tanks. [snip] Second, a precharge of 38 psi on a 40 psi start? So you can have pump ripple cycle all your control parts? A precharge set above 60% of upper pump setting would only be made by a pump salesman or switch salesman looking to sell more repair parts. 38 psi precharge on a pump starting atr 40 psi is BS from a basic design reliability standpoint. Obviously your experience with the reliability of residential well systems is purely theoretical. Third, set for 38 psi so you can have how much water stored under pressure at 40 psi? Enough to keep the pump from running except on draws above the rule-of-thumb of a gallon? A five gallon tank gives a gallon reserve at 25 psi precharge 40-60 psi, and the same five gallon tank gives a gallon and a half reserve at 38 psi precharge 40-60 psi. Try the old P1*V1=P2*V2 equation, using the differential from 40 psi and 60 psi. If you think that 40 and 60 are the right numbers to use, you don't know as much as you think you do. Hint: pressure guages read -zero- at an actual pressure of 14.7 psi. [snippola] background--- 1) - as incompressible water fills the accumulator tank with a bladder charged to 20 psi, the compressible air will stay at 20 psi until the water pressure rises above 20 psi. Complete nonsense. As water enters the tank, the volume of air decreases, and its pressure necessarily increases immediately. What, in your world P1*V1 = P2*V2 does not apply? I think I pretty clearly said that it does. 20psi air pressure*Volume air before water = 20psi air pressure* Volume after water means volume of air is constant. Same volume means no water can displace air. Apparently in your world, you can compress 20 psi air with 10 psi water and change its volume without changing its pressure. Patent it , quick. Neat trick in your mind, but not possible in the real world. "As water enters the tank, the volume decreases". That "water enter the tank" cannot happen below the 20 psi of my example, as I said. Read what I wrote. perhaps I should have written "tries to fill" rather than "fills" Ya know, I'm not a mind reader. If you don't say what you mean, then you should expect to be misunderstood. If the pump isn't developing more than 20psi, _no_ water will enter the tank whatsoever. Gee, that is EXACTLY what I said. "The compressible air will stay at 20 psi until the water pressure rises above 20 psi" fine... If the pump is developing more than 20psi, water begins to enter the tank immediately, and the air pressure also begins to increase immediately. Which is what I said. No, that's not what you said. But there's not much point in arguing about it. [snip] Basically, #1 - if you have the bladder pressure set at the lower setting, the switch vibrates as part of a spring-mass-spring rigid-water-mass/pump with the switch spring set at 40 psi fighting the 40 psi air spring of the bladder. Setting the bladder to 25 psi should cure that. More nonsense. You really should not be posting to engineering newsgroups other than to ask a question. Read carefully again the comment by one who has done this for decades. After the initial fill, as water is withdrawn from the tank, the pump will kick on when the pressure drops to the cut-in setting of the switch (40psi in this case), regardless of whether the precharge pressure was 25psi or 38 as it should be. The only difference is that, at the moment the pump kicks on at 40psi, there will be more water in the tank if it was precharged to 25psi than if it was precharged to 38. In spite of the fact that I was addressing force interactions and you are fixated on precharge and have wandered off the path, I will comment on your error. Contained air is a spring, with a spring constant. The higher the precharge, the higher the spring constant. All pump-fluid-control systems are spring -mass systems that interact. When pumps false start, it is a sign of unintended interaction, There is no discussion among engineers that changing a spring constant changes the interaction, only discussion as to what amount. So whose pump is false-starting? The OP's problem is that it *stops* when it should not. Either way, the pump comes on at 40 and shuts off at 60. The precharge pressure does *not* affect that. apparently the original poster's comments refute your statement. His pump shut off after a second at what appeared to be 40 psi. Off at 40 psi. Not off at 60 only, as you claim. Obviously not, if you've read the entire thread. The pump was shutting off _at_60_ due to pressure surge, not at 40 as it _appeared_ to be. In the real world, precharge pressure can and does affect controls. The OP's problem was not the precharge pressure; as noted by others in this thread, his problem is an improperly installed system. As you would know if you had any _real_world_ experience with residential well systems. -- Regards, Doug Miller (alphageek at milmac dot com) Nobody ever left footprints in the sands of time by sitting on his butt. And who wants to leave buttprints in the sands of time? |
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#54
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"--" wrote in message
... FWIW - you have put a second air spring in parallel with the original air bladder, and by 1/total spring=1/spring1 + 1/spring2, you lowered the total system spring constant (and in so doing, you reduced the peak force the system now sees from the moving water) Adding a second air chamber in parallel to the first air chamber had the same effect on the system as lowering the first tank's precharge in order to lower the system spring constant. No one here thinks that the problem is caused by the mass of water that needs to be accelerated when the pump starts? That the initial surge of torque in the pump needs to get the mass of water between the pump and the tank in the house moving, thus the reason for the higher pressure (seen at the tank) at switch-on? That moving the pressure switch to the tank end would definately solve the problem, but that adding a snubber (the OP chose to use a 2 gallon tank) before the mass of water would cure the problem too, and the OP didn't have to dig a trench that he didn't want to? If the air in the tank is going to be absorbed into the water so fast, what keeps normal snubbers (vertical bits of pipe in your house that stop hammering when you shut off the taps) from filling up with water? Al... |
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#55
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No one here thinks that the problem is
caused by the mass of water that needs to be accelerated when the pump starts? Most agreed to that near the beginning of the thread. I thought a check valve could let a little water through each cycle but I forgot, 1. the check valve in conventional systems is at the bottom of the well, and, 2. preloaded check valves are loaded shut, not open. .. . . If the air in the tank is going to be absorbed into the water so fast, what keeps normal snubbers (vertical bits of pipe in your house that stop hammering when you shut off the taps) from filling up with water? Here are some suspect theories: 1. Maybe the water doesn't flush through or exchange very much. 2. The water is already saturated with air. 3. Very little or zero air is necessary to stop hammer. You really only need to adjust the volume. I used a bladderless 40 gallon tank for 4 years and every 6 months I had to drain the water out because the air somehow escaped. The water was brought up 50' in turbulent two phase flow and should have been pretty well aerated for a vacuum. Bret Cahill |
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#56
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"Bret Cahill" wrote in message oups.com... I used a bladderless 40 gallon tank for 4 years and every 6 months I had to drain the water out because the air somehow escaped. The water was brought up 50' in turbulent two phase flow and should have been pretty well aerated for a vacuum. Perhaps you had microscopic leaks? Big enough to allow gas through, but too small for water... I've designed quite a bit of stuff for underwater and given enough time things can get through... Usually it's the welds, but once I had leakage past some hydraulic purge caps that were pressed into service as air bleeders... I got a couple cups of pure tasting water into several electronics pressure cases that were down ~50m for 2 years... and this was in the Bosporous.. salty water... The water was so pure we never had any corrosion or even electronics failures in the cases... Anyways, I'm guilty of applying my mind to the OP's problem, though I've never installed a well pump... And as this stuff isn't anything new, he really shouldn't have asked for help here.... He should have gone to the place where he bought the well equipment... But it is fun to think this stuff through and learn a thing or two. And perhaps he wanted to avoid "the right way" for reasons of his own, in which case this is exactly the right place to come and get ideas from... Al... |
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#57
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Doug Miller wrote: In article , "--" wrote: "Doug Miller" wrote in message m... In article , "--" wrote: IMHE, the bladder is pressurized too high for efficiency, AND too close to shut-off. The air bladder should be lower than the low switch setting. I would first set the bladder charge to 25 psi. Not if the pump is set to come at at 40. Tank precharge should be approximately 2psi below pump cut-in pressure. Who says? For what purpose? That's a typical recommendation by manufacturers of well pumps and pressure tanks. [snip] Second, a precharge of 38 psi on a 40 psi start? So you can have pump ripple cycle all your control parts? A precharge set above 60% of upper pump setting would only be made by a pump salesman or switch salesman looking to sell more repair parts. 38 psi precharge on a pump starting atr 40 psi is BS from a basic design reliability standpoint. Obviously your experience with the reliability of residential well systems is purely theoretical. Third, set for 38 psi so you can have how much water stored under pressure at 40 psi? Enough to keep the pump from running except on draws above the rule-of-thumb of a gallon? A five gallon tank gives a gallon reserve at 25 psi precharge 40-60 psi, and the same five gallon tank gives a gallon and a half reserve at 38 psi precharge 40-60 psi. Try the old P1*V1=P2*V2 equation, using the differential from 40 psi and 60 psi. If you think that 40 and 60 are the right numbers to use, you don't know as much as you think you do. Hint: pressure guages read -zero- at an actual pressure of 14.7 psi. [snippola] background--- 1) - as incompressible water fills the accumulator tank with a bladder charged to 20 psi, the compressible air will stay at 20 psi until the water pressure rises above 20 psi. Complete nonsense. As water enters the tank, the volume of air decreases, and its pressure necessarily increases immediately. What, in your world P1*V1 = P2*V2 does not apply? I think I pretty clearly said that it does. 20psi air pressure*Volume air before water = 20psi air pressure* Volume after water means volume of air is constant. Same volume means no water can displace air. Apparently in your world, you can compress 20 psi air with 10 psi water and change its volume without changing its pressure. Patent it , quick. Neat trick in your mind, but not possible in the real world. "As water enters the tank, the volume decreases". That "water enter the tank" cannot happen below the 20 psi of my example, as I said. Read what I wrote. perhaps I should have written "tries to fill" rather than "fills" Ya know, I'm not a mind reader. If you don't say what you mean, then you should expect to be misunderstood. If the pump isn't developing more than 20psi, _no_ water will enter the tank whatsoever. Gee, that is EXACTLY what I said. "The compressible air will stay at 20 psi until the water pressure rises above 20 psi" fine... If the pump is developing more than 20psi, water begins to enter the tank immediately, and the air pressure also begins to increase immediately. Which is what I said. No, that's not what you said. But there's not much point in arguing about it. [snip] Basically, #1 - if you have the bladder pressure set at the lower setting, the switch vibrates as part of a spring-mass-spring rigid-water-mass/pump with the switch spring set at 40 psi fighting the 40 psi air spring of the bladder. Setting the bladder to 25 psi should cure that. More nonsense. You really should not be posting to engineering newsgroups other than to ask a question. Read carefully again the comment by one who has done this for decades. After the initial fill, as water is withdrawn from the tank, the pump will kick on when the pressure drops to the cut-in setting of the switch (40psi in this case), regardless of whether the precharge pressure was 25psi or 38 as it should be. The only difference is that, at the moment the pump kicks on at 40psi, there will be more water in the tank if it was precharged to 25psi than if it was precharged to 38. In spite of the fact that I was addressing force interactions and you are fixated on precharge and have wandered off the path, I will comment on your error. Contained air is a spring, with a spring constant. The higher the precharge, the higher the spring constant. All pump-fluid-control systems are spring -mass systems that interact. When pumps false start, it is a sign of unintended interaction, There is no discussion among engineers that changing a spring constant changes the interaction, only discussion as to what amount. So whose pump is false-starting? The OP's problem is that it *stops* when it should not. Either way, the pump comes on at 40 and shuts off at 60. The precharge pressure does *not* affect that. apparently the original poster's comments refute your statement. His pump shut off after a second at what appeared to be 40 psi. Off at 40 psi. Not off at 60 only, as you claim. Obviously not, if you've read the entire thread. The pump was shutting off _at_60_ due to pressure surge, not at 40 as it _appeared_ to be. In the real world, precharge pressure can and does affect controls. The OP's problem was not the precharge pressure; as noted by others in this thread, his problem is an improperly installed system. As you would know if you had any _real_world_ experience with residential well systems. -- Regards, Doug Miller (alphageek at milmac dot com) Nobody ever left footprints in the sands of time by sitting on his butt. And who wants to leave buttprints in the sands of time? Well said! Mr -- apparently knows more than the engineers at the pump/tank manufacturing plants. Harry K |
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#58
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snip all but the below If the air in the tank is going to be absorbed into the water so fast, what keeps normal snubbers (vertical bits of pipe in your house that stop hammering when you shut off the taps) from filling up with water? Al... They do. It just takes longer than would one would expect. The water in the tube is pretty much captive and very little exchange is made. Given long enough the tube will water lock and need to be drained. Harry K |
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#59
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In article .com, "Bret Cahill" wrote:
I used a bladderless 40 gallon tank for 4 years and every 6 months I had to drain the water out because the air somehow escaped. The air didn't "somehow escape" - it dissolved in the water. -- Regards, Doug Miller (alphageek at milmac dot com) Nobody ever left footprints in the sands of time by sitting on his butt. And who wants to leave buttprints in the sands of time? |
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On Thu, 2 Jun 2005 21:13:27 -0700, "N:dlzc D:aol T:com \(dlzc\)" N:
dlzc1 D:cox wrote: Do you have any experience/history with soft starts being used with jet pumps? Since the problem is brought about by the "starting torque" of the motor, if you slowed the startup, the "cause" of the problem disappears (and it might even pay for itself in reduced starting currents). I just don't know how effective (long lasting) they are for high rpm motors... Something like the Telemechanique (Square D) Altistart ATS01, or something of its ilk... (McMaster Carr only has three phase soft starters available). Thoughts? David A. Smith This line of thought has merit, I reckon. A start current limiter would have something of the same effect. Though if it is contactor driven, it's as easy to get burned contacts as a malfunctioning bladder tank, I suppose. Then again, something like a light/motor dimmer/controller [cheap!] could readily be rigged, and the solid state, hands-off use might well be very reliable, barring lightning induced transients, or some such. Brian Whatcott Altus OK |
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#61
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from the original poster: My problem is that the pressure switch trips or cycles on off on off on off every second when the pressure reaches 40psi. I noticed when the pump is kicking on and off every second, the pressure gauge is jumping from 40 to 50 to 40 to 50. see below - "Alan Adrian" wrote in message ... "--" wrote in message ... FWIW - you have put a second air spring in parallel with the original air bladder, and by 1/total spring=1/spring1 + 1/spring2, you lowered the total system spring constant (and in so doing, you reduced the peak force the system now sees from the moving water) Adding a second air chamber in parallel to the first air chamber had the same effect on the system as lowering the first tank's precharge in order to lower the system spring constant. No one here thinks that the problem is caused by the mass of water that needs to be accelerated when the pump starts? What you note (accelerating a mass of water) would more likely cause a cavitation problem - what I addressed is the already moving water (being relatively incompressible, the water is already moving in under that one second at start-up, since its response time is much like a steel rod connected to the impeller) hitting the compressible air and rebounding, and that dynamic rebound energy being added to the static pressure energy, causing a force spike that the switch sees as misreads as static pressure- that interaction a fairly common problem in fluid power. That the initial surge of torque in the pump needs to get the mass of water between the pump and the tank in the house moving, thus the reason for the higher pressure (seen at the tank) at switch-on? No, there is always an initial surge of torque with a pump, even when unloaded ( due to the resistance of the rotor and/or water-mass accelerating). If the mass of water is too high for the pump, usually it will either cavitate (make noise and eat impellers) or run hot at start. I haven't seen an undersized or improperly designed pump cycle the start-up. That moving the pressure switch to the tank end would definately solve the problem, but that adding a snubber (the OP chose to use a 2 gallon tank) before the mass of water would cure the problem too, and the OP didn't have to dig a trench that he didn't want to? Yes, there are many physical ways to remove the symptom and stop the pump from cycling on start. Once a change is found that works at removing the symptom, then one should see what change in the scientific parameters the physcial change made, so as to check if the fix added a future problem. Occasionally a fix in one area creates a problem in another, and sometimes the fix could have been done more cheaply and the cost of that experience can be amortized over furture problems If the air in the tank is going to be absorbed into the water so fast, what keeps normal snubbers (vertical bits of pipe in your house that stop hammering when you shut off the taps) from filling up with water? I don't believe I ever claimed that air was entrained in water at residential pressures. The snubbers don't fill up with water at residential pressures. Al... |
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Some facts -
I wrote apparently the original poster's comments refute your statement. His pump shut off after a second at what appeared to be 40 psi. Off at 40 psi. Not off at 60 only, as you claim. Dougie wrote Obviously not, if you've read the entire thread. The pump was shutting off _at_60_ due to pressure surge, not at 40 as it _appeared_ to be. Original poster Nomad wrote My problem is that the pressure switch trips or cycles on off on off on off every second when the pressure reaches 40psi. I noticed when the pump is kicking on and off every second, the pressure gauge is jumping from 40 to 50 to 40 to 50. and later, Nomad said again I am able to get the system up to 60psi by holding the pressure switch contacts closed for the first few seconds of cut-in at 40psi, when the contacts are jumping open and closed over and over again. which explains why Dougie has problems with understanding the poster's problem nuff said......... "Doug Miller" wrote in message om... In article , "--" wrote: "Doug Miller" wrote in message m... In article , "--" wrote: IMHE, the bladder is pressurized too high for efficiency, AND too close to shut-off. The air bladder should be lower than the low switch setting. I would first set the bladder charge to 25 psi. Not if the pump is set to come at at 40. Tank precharge should be approximately 2psi below pump cut-in pressure. Who says? For what purpose? That's a typical recommendation by manufacturers of well pumps and pressure tanks. [snip] Second, a precharge of 38 psi on a 40 psi start? So you can have pump ripple cycle all your control parts? A precharge set above 60% of upper pump setting would only be made by a pump salesman or switch salesman looking to sell more repair parts. 38 psi precharge on a pump starting atr 40 psi is BS from a basic design reliability standpoint. Obviously your experience with the reliability of residential well systems is purely theoretical. Third, set for 38 psi so you can have how much water stored under pressure at 40 psi? Enough to keep the pump from running except on draws above the rule-of-thumb of a gallon? A five gallon tank gives a gallon reserve at 25 psi precharge 40-60 psi, and the same five gallon tank gives a gallon and a half reserve at 38 psi precharge 40-60 psi. Try the old P1*V1=P2*V2 equation, using the differential from 40 psi and 60 psi. If you think that 40 and 60 are the right numbers to use, you don't know as much as you think you do. Hint: pressure guages read -zero- at an actual pressure of 14.7 psi. [snippola] background--- 1) - as incompressible water fills the accumulator tank with a bladder charged to 20 psi, the compressible air will stay at 20 psi until the water pressure rises above 20 psi. Complete nonsense. As water enters the tank, the volume of air decreases, and its pressure necessarily increases immediately. What, in your world P1*V1 = P2*V2 does not apply? I think I pretty clearly said that it does. 20psi air pressure*Volume air before water = 20psi air pressure* Volume after water means volume of air is constant. Same volume means no water can displace air. Apparently in your world, you can compress 20 psi air with 10 psi water and change its volume without changing its pressure. Patent it , quick. Neat trick in your mind, but not possible in the real world. "As water enters the tank, the volume decreases". That "water enter the tank" cannot happen below the 20 psi of my example, as I said. Read what I wrote. perhaps I should have written "tries to fill" rather than "fills" Ya know, I'm not a mind reader. If you don't say what you mean, then you should expect to be misunderstood. If the pump isn't developing more than 20psi, _no_ water will enter the tank whatsoever. Gee, that is EXACTLY what I said. "The compressible air will stay at 20 psi until the water pressure rises above 20 psi" fine... If the pump is developing more than 20psi, water begins to enter the tank immediately, and the air pressure also begins to increase immediately. Which is what I said. No, that's not what you said. But there's not much point in arguing about it. [snip] Basically, #1 - if you have the bladder pressure set at the lower setting, the switch vibrates as part of a spring-mass-spring rigid-water-mass/pump with the switch spring set at 40 psi fighting the 40 psi air spring of the bladder. Setting the bladder to 25 psi should cure that. More nonsense. You really should not be posting to engineering newsgroups other than to ask a question. Read carefully again the comment by one who has done this for decades. After the initial fill, as water is withdrawn from the tank, the pump will kick on when the pressure drops to the cut-in setting of the switch (40psi in this case), regardless of whether the precharge pressure was 25psi or 38 as it should be. The only difference is that, at the moment the pump kicks on at 40psi, there will be more water in the tank if it was precharged to 25psi than if it was precharged to 38. In spite of the fact that I was addressing force interactions and you are fixated on precharge and have wandered off the path, I will comment on your error. Contained air is a spring, with a spring constant. The higher the precharge, the higher the spring constant. All pump-fluid-control systems are spring -mass systems that interact. When pumps false start, it is a sign of unintended interaction, There is no discussion among engineers that changing a spring constant changes the interaction, only discussion as to what amount. So whose pump is false-starting? The OP's problem is that it *stops* when it should not. Either way, the pump comes on at 40 and shuts off at 60. The precharge pressure does *not* affect that. apparently the original poster's comments refute your statement. His pump shut off after a second at what appeared to be 40 psi. Off at 40 psi. Not off at 60 only, as you claim. Obviously not, if you've read the entire thread. The pump was shutting off _at_60_ due to pressure surge, not at 40 as it _appeared_ to be. In the real world, precharge pressure can and does affect controls. The OP's problem was not the precharge pressure; as noted by others in this thread, his problem is an improperly installed system. As you would know if you had any _real_world_ experience with residential well systems. -- Regards, Doug Miller (alphageek at milmac dot com) Nobody ever left footprints in the sands of time by sitting on his butt. And who wants to leave buttprints in the sands of time? |
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#63
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Harry, I have no problem challenging engineers on the breadth and scope of
their recommendations. My questions have on several occasions caused industry "rules-of-thumb" to be flat-out changed. As a chief engineer and principal engineer for almost 30 years, I am not cowed by an engineer because an engineer was hired by a firm or because he works there. To increase the firm's engineering team's outlook and experience and knowledge is often part of my job. Ironically, if the engineer always does their job right, they never have any problems nor any non-book feedback to learn from. Almost all work I do for a firm is done at the firm's request, done when a firm's engineering teams are unable to solve their company's technical problems. And often as not, they missed fundamentals and relied on their own misinterpreted experience. Engineers are human. Like all humans, they give their best guess based on their knowledge and experience, and like all humans, their knowledge and experience may be misapplied or it may be inadequate or through poor management they may have misinterpreted their own experience. The better engineers ask, so as to interact and expand their understanding. Others......... "Harry K" wrote in message ups.com... Doug Miller wrote: In article , "--" wrote: "Doug Miller" wrote in message m... In article , "--" wrote: IMHE, the bladder is pressurized too high for efficiency, AND too close to shut-off. The air bladder should be lower than the low switch setting. I would first set the bladder charge to 25 psi. Not if the pump is set to come at at 40. Tank precharge should be approximately 2psi below pump cut-in pressure. Who says? For what purpose? That's a typical recommendation by manufacturers of well pumps and pressure tanks. [snip] Second, a precharge of 38 psi on a 40 psi start? So you can have pump ripple cycle all your control parts? A precharge set above 60% of upper pump setting would only be made by a pump salesman or switch salesman looking to sell more repair parts. 38 psi precharge on a pump starting atr 40 psi is BS from a basic design reliability standpoint. Obviously your experience with the reliability of residential well systems is purely theoretical. Third, set for 38 psi so you can have how much water stored under pressure at 40 psi? Enough to keep the pump from running except on draws above the rule-of-thumb of a gallon? A five gallon tank gives a gallon reserve at 25 psi precharge 40-60 psi, and the same five gallon tank gives a gallon and a half reserve at 38 psi precharge 40-60 psi. Try the old P1*V1=P2*V2 equation, using the differential from 40 psi and 60 psi. If you think that 40 and 60 are the right numbers to use, you don't know as much as you think you do. Hint: pressure guages read -zero- at an actual pressure of 14.7 psi. [snippola] background--- 1) - as incompressible water fills the accumulator tank with a bladder charged to 20 psi, the compressible air will stay at 20 psi until the water pressure rises above 20 psi. Complete nonsense. As water enters the tank, the volume of air decreases, and its pressure necessarily increases immediately. What, in your world P1*V1 = P2*V2 does not apply? I think I pretty clearly said that it does. 20psi air pressure*Volume air before water = 20psi air pressure* Volume after water means volume of air is constant. Same volume means no water can displace air. Apparently in your world, you can compress 20 psi air with 10 psi water and change its volume without changing its pressure. Patent it , quick. Neat trick in your mind, but not possible in the real world. "As water enters the tank, the volume decreases". That "water enter the tank" cannot happen below the 20 psi of my example, as I said. Read what I wrote. perhaps I should have written "tries to fill" rather than "fills" Ya know, I'm not a mind reader. If you don't say what you mean, then you should expect to be misunderstood. If the pump isn't developing more than 20psi, _no_ water will enter the tank whatsoever. Gee, that is EXACTLY what I said. "The compressible air will stay at 20 psi until the water pressure rises above 20 psi" fine... If the pump is developing more than 20psi, water begins to enter the tank immediately, and the air pressure also begins to increase immediately. Which is what I said. No, that's not what you said. But there's not much point in arguing about it. [snip] Basically, #1 - if you have the bladder pressure set at the lower setting, the switch vibrates as part of a spring-mass-spring rigid-water-mass/pump with the switch spring set at 40 psi fighting the 40 psi air spring of the bladder. Setting the bladder to 25 psi should cure that. More nonsense. You really should not be posting to engineering newsgroups other than to ask a question. Read carefully again the comment by one who has done this for decades. After the initial fill, as water is withdrawn from the tank, the pump will kick on when the pressure drops to the cut-in setting of the switch (40psi in this case), regardless of whether the precharge pressure was 25psi or 38 as it should be. The only difference is that, at the moment the pump kicks on at 40psi, there will be more water in the tank if it was precharged to 25psi than if it was precharged to 38. In spite of the fact that I was addressing force interactions and you are fixated on precharge and have wandered off the path, I will comment on your error. Contained air is a spring, with a spring constant. The higher the precharge, the higher the spring constant. All pump-fluid-control systems are spring -mass systems that interact. When pumps false start, it is a sign of unintended interaction, There is no discussion among engineers that changing a spring constant changes the interaction, only discussion as to what amount. So whose pump is false-starting? The OP's problem is that it *stops* when it should not. Either way, the pump comes on at 40 and shuts off at 60. The precharge pressure does *not* affect that. apparently the original poster's comments refute your statement. His pump shut off after a second at what appeared to be 40 psi. Off at 40 psi. Not off at 60 only, as you claim. Obviously not, if you've read the entire thread. The pump was shutting off _at_60_ due to pressure surge, not at 40 as it _appeared_ to be. In the real world, precharge pressure can and does affect controls. The OP's problem was not the precharge pressure; as noted by others in this thread, his problem is an improperly installed system. As you would know if you had any _real_world_ experience with residential well systems. -- Regards, Doug Miller (alphageek at milmac dot com) Nobody ever left footprints in the sands of time by sitting on his butt. And who wants to leave buttprints in the sands of time? Well said! Mr -- apparently knows more than the engineers at the pump/tank manufacturing plants. Harry K |
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snip Well said! Mr -- apparently knows more than the engineers at the pump/tank manufacturing plants. Harry K You are obviously well qualified in your field. Your field very obviously is not in practical applications, at least not from what I have read. Well systems have been in use since before recorded history. Insisting that changing an industry standard that has stood the test of time is not 'practical application'. The '2psi below cut-in' is the standard and for very good reasons. One is that it minimizes pump cycle times, i.e., max water delivered between cycles. That at least is what I was taught. Since it works in practice I see no need to get a masters in theoretical physics or calculus. There is fun in trying various things to see if something can be made to work better but there comes a point in development (well systems for example) where further tinkering is a dead end. The guy has a problem with a pressure wave spike going over 60psi at start-up. He band-aided it. It is not now a problem and would never have been a problem if the switch had been at the tank to begin with. That is the simple cut and dried version. All your theoreticals isn't going to change it. Harry K |
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In article , "--" wrote:
Some facts - I wrote apparently the original poster's comments refute your statement. His pump shut off after a second at what appeared to be 40 psi. Off at 40 psi. Not off at 60 only, as you claim. Dougie wrote Obviously not, if you've read the entire thread. The pump was shutting off _at_60_ due to pressure surge, not at 40 as it _appeared_ to be. Original poster Nomad wrote My problem is that the pressure switch trips or cycles on off on off on off every second when the pressure reaches 40psi. I noticed when the pump is kicking on and off every second, the pressure gauge is jumping from 40 to 50 to 40 to 50. and later, Nomad said again I am able to get the system up to 60psi by holding the pressure switch contacts closed for the first few seconds of cut-in at 40psi, when the contacts are jumping open and closed over and over again. which explains why Dougie has problems with understanding the poster's problem Quite the contrary - I've grasped one essential point that has obviously eluded you, with your purely theoretical understanding of residential water wells, namely that the surge hits 60psi (shutting off the switch) and drops back to 40psi, faster than the gauge can react. The apparent pressure shown by the gauge is not the actual pressure. -- Regards, Doug Miller (alphageek at milmac dot com) Nobody ever left footprints in the sands of time by sitting on his butt. And who wants to leave buttprints in the sands of time? |
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Doug Miller wrote: Quite the contrary - I've grasped one essential point that has obviously eluded you, with your purely theoretical understanding of residential water wells, namely that the surge hits 60psi (shutting off the switch) and drops back to 40psi, faster than the gauge can react. That would be a guess. Another guess would be that he simply failed to observe the brief flutter in the needle. -jim ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
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There is fun in trying various things to see if
something can be made to work better but there comes a point in development (well systems for example) where further tinkering is a dead end. True in many situations but you'ld be surprised at how often you can find alternatives in "mature" fields using decades old technology. I was hooked up to city water that, at times, when the alge mixed with the chlorine, made it undrinkable. I didn't like hauling water back from the store, but there was an old deep well out back that hadn't been used for years. Wells clog up over several decades and a well driller suggested I first check the flow rate by pouring water into the well. This is supposed to be a good indicator of the possible flow rate out. It was only about a few quarts/ minute under a few feet of head which is probably why the pump system was removed in the first place. No common off the shelf system will work at such a low flow rate. I didn't need a continuous high flow rate so I used a small 1/3 hp shallow well pump to pump water out of the bottom of a water softener tank and used the resulting vacuum to bring the water up 50' in a two phase flow. Pin holes above the water line allowed in enough air to develop slug flow. The shallow well pump only saw 25' of liquid, but it was being used as a deep well pump. A float switch in the tank cut the pump, opened a solenoid valve and restarted the cycle when the water got low. It paid for itself in a few months and was a lot of fun. I calculated the efficiency which compared to conventional systems. I used it for four years before I moved. Two phase flow is common in materials handling. Plastic pellets, for example, are discharged with a similar vacuum/separation tank system The need will probably never appear in real life but you can always get a bucket of water from any depth with just 1/4" tubing for capillary slug flow and a shop vac. Bret Cahill |
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Harry K wrote: There is fun in trying various things to see if something can be made to work better but there comes a point in development (well systems for example) where further tinkering is a dead end. The guy has a problem with a pressure wave spike going over 60psi at start-up. He band-aided it. It is not now a problem and would never have been a problem if the switch had been at the tank to begin with. What evidence do you have thatyou keep insisting that your solution is better than the one Nomad used. The fact is that the pressure spike on a long run of pipe on start-up (and quite likely on shut-down also) is not good for the system and will when the pipes get old and rusty (and they will eventually) lead to an earlier failure of the system. Chances are good, there is something about the capacity of the pump and the length of pipe to the house that creates a resonant condition that amplified the startup pressure pulse. Anyway, it's not good to just ignore the pressure spike and let it continue. And sure there is still a pressure pulse in the short length of pipe from pump to surge tank but that doesn't involve a long column of water being cracked like a whip (i.e. at a rate faster than the needle moves on the pressure gauge). And maybe it isn't of the magnitude where the water column separates and crashes back together but it still isn't good and he did well to get rid of it. After he solved the problem there is no benefit to moving the sensor and incurring the additional cost, work and maintenance that would involve. -jim ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
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Dear --:
"--" wrote in message ... .... What you note (accelerating a mass of water) would more likely cause a cavitation problem - Only on the suction side of the pump. Not where the pressure switch is reported to have been. what I addressed is the already moving water (being relatively incompressible, the water is already moving in under that one second at start-up, since its response time is much like a steel rod connected to the impeller) And how did this "steel rod" of water become already moving, since it has distributed inertia? Did it perhaps require *pressure* and *time* to accelerate? The pressure spike had nothing to do with: hitting the compressible air and rebounding, Acceleration of mass requires force. In the case of a fluid, this is usually a gradient in pressure, and the line pressure stays pretty close to tank pressure, even at startup. Note that the OP indicated that changing to 1.25" line did not have any effect, where with your "model" it should have had an effect. David A. Smith |
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jim wrote: Harry K wrote: There is fun in trying various things to see if something can be made to work better but there comes a point in development (well systems for example) where further tinkering is a dead end. The guy has a problem with a pressure wave spike going over 60psi at start-up. He band-aided it. It is not now a problem and would never have been a problem if the switch had been at the tank to begin with. What evidence do you have thatyou keep insisting that your solution is better than the one Nomad used. The fact is that the pressure spike on a long run of pipe on start-up (and quite likely on shut-down also) is not good for the system and will when the pipes get old and rusty (and they will eventually) lead to an earlier failure of the system. Chances are good, there is something about the capacity of the pump and the length of pipe to the house that creates a resonant condition that amplified the startup pressure pulse. Anyway, it's not good to just ignore the pressure spike and let it continue. And sure there is still a pressure pulse in the short length of pipe from pump to surge tank but that doesn't involve a long column of water being cracked like a whip (i.e. at a rate faster than the needle moves on the pressure gauge). And maybe it isn't of the magnitude where the water column separates and crashes back together but it still isn't good and he did well to get rid of it. After he solved the problem there is no benefit to moving the sensor and incurring the additional cost, work and maintenance that would involve. -jim What evidence?? 80 years at least of these systems operating in the field without the dreaded fatigue and pipe failure you are referring to. There are systems out there with runs of over 1/4 mile from the pump to the tank with the switch at the tank. Again: A pressure pulse is NOT a water hammer. The pressure pulse damps out at the first opportunity - the tank before he did it, the surge tank after he installed it. A "long water column being cracked like a whip"???. You push on one end of the colume, pressure builds on that end and propagates along the colume. Just where is this dreaded 'crack like a whip'?? As to the benefit of moving the switch after he put the surge tank in. Correct, very little except for the occasional maintenance of having to air up the surge tank. It still comes down to a band-aid approach to a non-problem if done correctly to begin with. Harry K |
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On Sat, 04 Jun 2005 02:42:03 GMT, Brian Whatcott
wrote: On Thu, 2 Jun 2005 21:13:27 -0700, "N:dlzc D:aol T:com \(dlzc\)" N: dlzc1 D:cox wrote: Do you have any experience/history with soft starts being used with jet pumps? Since the problem is brought about by the "starting torque" of the motor, if you slowed the startup, the "cause" of the problem disappears (and it might even pay for itself in reduced starting currents). I just don't know how effective (long lasting) they are for high rpm motors... Something like the Telemechanique (Square D) Altistart ATS01, or something of its ilk... (McMaster Carr only has three phase soft starters available). Thoughts? David A. Smith This line of thought has merit, I reckon. A start current limiter would have something of the same effect. Though if it is contactor driven, it's as easy to get burned contacts as a malfunctioning bladder tank, I suppose. Then again, something like a light/motor dimmer/controller [cheap!] could readily be rigged, and the solid state, hands-off use might well be very reliable, barring lightning induced transients, or some such. Brian Whatcott Altus OK Here's a more radical thought. The thread seems to have converged on a pressure pulse occuring at motor on. Why an over pressure pulse. One way to explain it is to use the transmission line electrical analogy. Put a voltage step onto a transmission line (like a co ax) and the pulse travels to the far end - and stops there if the end is matched to the line. If the line is open circuit at the far end, the pulse gets to the far end and bounces back at double height. If the line is shorted at the far end, the pulse bounces back as a negative image of the incident pulse. In this case, because the start pulse seems to come back twice as high - assume that the far end is terminated in a high impedence. So the far end pipework narrows or the far end bladder is too stiff. THERE's a new insight! Brian W |
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Dear Brian Whatcott:
"Brian Whatcott" wrote in message ... On Sat, 04 Jun 2005 02:42:03 GMT, Brian Whatcott wrote: On Thu, 2 Jun 2005 21:13:27 -0700, "N:dlzc D:aol T:com \(dlzc\)" N: dlzc1 D:cox wrote: Do you have any experience/history with soft starts being used with jet pumps? Since the problem is brought about by the "starting torque" of the motor, if you slowed the startup, the "cause" of the problem disappears (and it might even pay for itself in reduced starting currents). I just don't know how effective (long lasting) they are for high rpm motors... Something like the Telemechanique (Square D) Altistart ATS01, or something of its ilk... (McMaster Carr only has three phase soft starters available). Thoughts? This line of thought has merit, I reckon. A start current limiter would have something of the same effect. Though if it is contactor driven, it's as easy to get burned contacts as a malfunctioning bladder tank, I suppose. Then again, something like a light/motor dimmer/controller [cheap!] could readily be rigged, and the solid state, hands-off use might well be very reliable, barring lightning induced transients, or some such. Here's a more radical thought. The thread seems to have converged on a pressure pulse occuring at motor on. Actually it seems like it turned into a shouting match... Why an over pressure pulse. One way to explain it is to use the transmission line electrical analogy. Put a voltage step onto a transmission line (like a co ax) and the pulse travels to the far end - and stops there if the end is matched to the line. If the line is open circuit at the far end, the pulse gets to the far end and bounces back at double height. Only if you continue to add power in resonance. If the line is shorted at the far end, the pulse bounces back as a negative image of the incident pulse. That doesn't sound right. this case, because the start pulse seems to come back twice as high - assume that the far end is terminated in a high impedence. So the far end pipework narrows or the far end bladder is too stiff. Narrowing has been eliminated to no effect. Bladder is about 1/10th of a second away at the speed of sound in water. Resonance is contraindicated, since the phenomenon stops after a short time. THERE's a new insight! You are bored! David A. Smith |
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On Sun, 5 Jun 2005 21:42:56 -0700, "N:dlzc D:aol T:com \(dlzc\)" N:
dlzc1 D:cox wrote: Dear Brian Whatcott: "Brian Whatcott" wrote in message .. . On Sat, 04 Jun 2005 02:42:03 GMT, Brian Whatcott wrote: On Thu, 2 Jun 2005 21:13:27 -0700, "N:dlzc D:aol T:com \(dlzc\)" N: dlzc1 D:cox wrote: Do you have any experience/history with soft starts being used with jet pumps? Since the problem is brought about by the "starting torque" of the motor, if you slowed the startup, the "cause" of the problem disappears (and it might even pay for itself in reduced starting currents). I just don't know how effective (long lasting) they are for high rpm motors... Something like the Telemechanique (Square D) Altistart ATS01, or something of its ilk... (McMaster Carr only has three phase soft starters available). Thoughts? This line of thought has merit, I reckon. A start current limiter would have something of the same effect. Though if it is contactor driven, it's as easy to get burned contacts as a malfunctioning bladder tank, I suppose. Then again, something like a light/motor dimmer/controller [cheap!] could readily be rigged, and the solid state, hands-off use might well be very reliable, barring lightning induced transients, or some such. Here's a more radical thought. The thread seems to have converged on a pressure pulse occuring at motor on. Actually it seems like it turned into a shouting match... Why an over pressure pulse. One way to explain it is to use the transmission line electrical analogy. Put a voltage step onto a transmission line (like a co ax) and the pulse travels to the far end - and stops there if the end is matched to the line. If the line is open circuit at the far end, the pulse gets to the far end and bounces back at double height. Only if you continue to add power in resonance. If the line is shorted at the far end, the pulse bounces back as a negative image of the incident pulse. That doesn't sound right. this case, because the start pulse seems to come back twice as high - assume that the far end is terminated in a high impedence. So the far end pipework narrows or the far end bladder is too stiff. Narrowing has been eliminated to no effect. Bladder is about 1/10th of a second away at the speed of sound in water. Resonance is contraindicated, since the phenomenon stops after a short time. THERE's a new insight! You are bored! David A. Smith Hehe....maybe - but transmission line mismatch is not a resonance effect. You can easily demonstrate the effect (even the one that doesn't sound right to you), with 50 ft of coax, a relay, a battery and of course, a scope! Brian W |
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On Mon, 06 Jun 2005 03:47:44 GMT, Brian Whatcott wrote:
In this case, because the start pulse seems to come back twice as high - assume that the far end is terminated in a high impedence. So the far end pipework narrows or the far end bladder is too stiff. THERE's a new insight! Only looks that way. Perhaps because you appear to have skipped much of the thread... The far end pipe does narrow, but changing it may no appreciable difference. The far end bladder is not too stiff, because then the pressure would only increase, not be a spike. The pressure spike it high, not because of a bounce back, but because water is incompressible, water has mass hence inertia, and pipes have friction. The pump starts, wants to move water, water does not start to move instantly, so the pressure seen near to the pump has a high spike that rapidly reduces as the water starts to move. Not rocket science, well understood in well pump systems for many years. That is why the proper installation puts the pressure switch near the pressure tank. (My system, for example, has 150-200ft between pump and tank, and less than 3ft between tank and pressure switch.) sdb -- Wanted: Omnibook 800 & accessories, cheap, working or not sdbuse1 on mailhost bigfoot.com |
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I would assume the pump power comes from the house? Why not put the
pressure switch in the house next to the tank and break the power there? go from the breaker panel to the pressure switch, to the pump house. Put a disconnect switch in the pump house so you can service the pump and wire from there to the pump. You can use the existing wire from the house to the pump, so it should be easy to do. The voltage drop in the existing wiring should not change, as the wire length is no different than before. You have just changed the location of the switch, so everything should work just fine. Of corse if the power feeds the pump house from somewhere else, forget I said anything. BTW, Every shallow well and booster pump I have ever worked on or installed, said set air precharge to 2 PSI below switch cut-in setting in the instructions. It gives you the biggest draw down on the bladder tank. Stretch |
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