Standing Column Help Needed

Discussion in 'Standing Column Well (SCW)' started by thackery, Jan 3, 2009.

  1. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    Switch

    Isn't the switch just the breaker on the panel? You should have two breakers to a heat pump with electric supplemental. One services the unit, the other services the plenum heater. For my personal unit, I just leave the breaker servicing the electric plenum heater off until it is required - you'll be able to tell when:).

    FYI, Code locally for us, is a cutoff switch is required if the electrical panel is not in the same room as the unit.
     
  2. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    On some heat pumps the fan is on the same breaker as the aux heat. Mine is this way.
     
  3. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    Thanks

    Thought there must be an obvious reason.

    Do these electrical units have to be factory installed then due to the wiring?
     
  4. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    That is right.

    The aux heaters that come installed from the factory are wired into the unit.

    The field installed aux heaters can be wired and switched separately.
     
  5. Waukman

    Waukman Member

    My breaker panel for the geo system is right next to the geo system. I have two breakers. I was expecting to have one breaker for the 'geo' side and one for the electric heat side. But I also have the zone unit and it seems to derive power from the line that also feeds the aux heat modules. I have purchased my switch and one of these days I will get around to hooking it up.
     
  6. Rumplestiltskin

    Rumplestiltskin New Member

    I am trying to figure out why my FHP/standing column system won't work for more than about an hour. I have two FHP 3 ton units which use a single standing column well installation. The well is 580 ft deep and the pump is mounted at approx. 110ft(with no dip tube/porter shroud). The injection branch of the system returns water to the bottom of the well. The pump is a 1.5 hp submersable 20gpm unit. At system startup, everything works just as it should, but after awhile(generally about 30-45 minutes) the pressure in the water supply begins to degrade and within 10 minutes or so the water is really not moving anymore even though the pump is running(pipe vibrates, volts and amps are where they should be). If left on, the pump will eventually shut itself down, presumablly on thermal overload. The water level in the well never goes below 65ft.

    A representative of the pump manufacturer and the manufacturer of the pumps motor have suggested that the pump could be experiencing air lock from air driven into the bottom of the well at system startup and eventually reaching the pump. Although this seems unlikely to me, I am willing to accept it as a possibility. I need to find a way to test this theory and if it is indeed the case, a way to remedy it. The manufacturers rep suggested using an air release valve at the high point of the return line, which in my case is right at the top of the well because we do not use a pitless adapter. My concern about this solution is that it seems to me that the types of air release valves that I have found so far could be held open by the suction created by the water flowing through the pipe back into the well - therefore introducing even more air into the system.

    Has anyone here experienced a similar situation or feel comfortable offering any input on figuring out if this is my problem and how to fix it? Thanks in advance for your help.
     
  7. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    Hi and welcome,
    Some of the scw pros will chime in soon, but untill then I will shoot. Air locking a submersible pump is far easier than you think. The introduction of any air below the pump in the water colunm has a potential for trouble. The impellars on your sub are a lot smaller than you imagine. If the motor rep has been out and verified the run amps and the resistance to be on target you are left with the air lock theory.
    What is the hp and manufacturer of your pumping equipment? Diameter of well? Diameter of pump installed?
     
  8. GeoXNE

    GeoXNE Guest

    I am not going to pretend I know what is going on here.

    Is it possible there is an air leak in the injection drop pipe before it goes underwater, with air getting sucked into the well? Enough bubbles could cavitate the pump.
     
  9. arkieoscar

    arkieoscar Member

    I'm no expert on SCW but where would the air come from? In my understanding, the loop should not have any way for air to enter it with both ends in the well.
     
  10. GeoXNE

    GeoXNE Guest

    It could leak at any joint, pitless adapter or elbow down the well or bad pipe.
     
  11. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    Wouldn't the amps fall off if the pump get airlocked?

    Could ice be forming somwehere, reducing flow? I'd think air would manifest itself earlier...

    Totally shooting from the hip here...
     
  12. I have had some experience with SCW, Most SCW of the depth you described are constructed with the pump 10 ft
    off the bottom of the well, and the return 10 ft below the static level of the well, this way any air that is in the system will bleed off and quickly rise up to the surface, additionally re-injecting at the top will also induce aquifer advection, thereby increasing the energy transfer to the water in the borehole.

    My guess is that the problem that you are having is caused by the extreme weight of water in the return line
    to the bottom 580ft = -238 PSi vac. (if my math is correct) is drawing air in and the water is pushing all this air to the bottom of the well, where it will rise up to, and air locking the pump.

    When a SCW is constructed with the pump at the top, as in a deep SCW installation, a porter shroud ( 4" PVC with aprox 120 Quarter sized holes drilled in the bottom 20 feet) is placed from the bottom of the well up to just below the pitless adapter, return water is then injected into the space between the borehole wall, and the PVC shroud, where it will vent any air, travel to the bottom, enter the shroud, and make its way back up to the pump location.

    The only operating cost difference with the pump at the bottom is the friction losses in the drop pipe, as the pumping level is the static level of the well.

    Generally SCW over 500 ft are constructed with a porter shroud, however a 580 ft well is not cost effective (the cost of 1.25 SCH 80 Drop Pipe vs 4 in PVC sch 40 well casing) to construct as a deep SCW.

    The best way to correct this is to install the pump at the bottom of the well, unless liner/casing/screen is needed for some geological reason.

    Mark
     
  13. Rumplestiltskin

    Rumplestiltskin New Member

    This post was accidentlly posted twice so I deleted this version, the real post is two or three down from here. Sorry for any confusion.
     
  14. GeoXNE

    GeoXNE Guest

    Mark

    Thanks for jumping in here. What you are saying makes a lot of sense.

    My uneducated theory? - Just as you calculate the head you are pumping from the water level in the well (not depth to pump), in the case of a return drop pipe, wouldn't you calculate the turn to negative pressure from water level in the well also (in this case some where between 30 & 65 feet down)???

    Just trying to wrap my head around this.

    I also understand it is not that simple. This point of turn to negative pressure would change depending on whether the pump was on or off and maybe a little by temp difference of water in the drop pipe.

    My only point is-
    If I am correct, Rumplestiltskin could maybe calculate where his "suspected air leak" is.
    If I am wrong and he is dealing with over -200psi, I would also be concerned about pipe collapse or failure.
     
  15. Sorry about that, my numbers reflected an empty casing,which is not the case, in any event, unless he is using all fusion joints, most common plumbing supplies (ie Barbed fittings, or PVC) are not designed to handle vacuum at any level, with his installation
    at some point vacuum will occur, causing air induction,
    I dont think locating leaks would help, because all SCW
    designs have air vent-off provisions at or near the static water level, that in this case cant be done, unless he wants to install the porter shroud/liner down to the bottom of the well, as I mentioned in the earlier post, the cost of drop-pipe, and cable would be less than the shroud/liner.

    Im using a SCW for my personal home, with similar load and depth, my pump is at 10 feet from the well bottom, with re-injection at the top, and Im using electric valves at the heat pumps, and small (2 gal) pressure tank with a VFD pump, to keep the entire system pressurized at all times, I use a seperate
    well for domestic purposes, and Ive havent had any issues with air, water, or the pump, I did have some problems programing the VFD pump, but that was solved with rated flow restricters on each heat pump.

    Mark
     
  16. Rumplestiltskin

    Rumplestiltskin New Member

    WaterPiratre: The reps have said that it isn't that hard to airlock the pump, but the reason that I find the airlock theory dubious is that I have heard this pump in a truly airlocked state. It was originally installed at about 80 feet and over the course of an hour or so of run time it would begin to really pump alot of air with the water(making for a very loud system). The mechanical equipment distributor came out and listened to it and said that the pump was creating a vortex in the well and eventually going out on thermal overload. This problem developed about two weeks ago after we replaced a dead pump(our 2nd pump replacement in 7yrs - so now on my 3rd pump). In this original situation there was not really any period of reduced pressure to the Geo unit. The well pump ran and provided pressure until it could not any longer and then it shut off. Our solution to this problem was to lower the pump 40 more feet down the well and now we have the "new" problem described in my original posting.

    This "new" problem situation does not really include any meaningful amount of air noise in the pipes to and from the well and the pump water pressure seems to "step" down rather than drop quickly to nothing. The pump continues to run (though at slightly lower amps than normal operation). The pump will eventually cut itself off, but that can take some time and until then it runs but does not really move water(the pressure in the supply line drops to less than 10 psi where it would normally be 45 to 52psi).

    My pump is a 1.5 hp 20 gpm Dynaflo Duro 4" Submersable with a FE motor. It is currently set at about 110 ft down in a 6" well.

    Pine Mountain Energy:

    As I said, I am willing to be convinced that air lock is the problem, but I don;'t want to just keep trying things with the hope that eventually something will work. Your concern about the vacuum created by the return pipe is the reason that I am leary of trying the solution proposed by the pump manufacturer, which is to install an air release valve in the return line right before the drop down into the well(the highest point in the system). I am concerned that the vacuum will draw more air in to the system during operation. However, in calculating this vacuum does one use the entire disance to the bottom of the return pipe or just to the water level?(which has never been observed to be more than 64 ft and is usually more like 55ft) It seems to me(a layperson) that the return water won't really be "falling" once it passes the surface of the water in the well.

    Some of the people we have talked to have, in fact, suggested lowering the pump to the bottom of the well but because it is the most expensive solution we have heard, I really want to make sure that we are
    a)sure that the problem is air lock and
    b)sure that lowering the pump will solve the problem.

    Keep in mind, we already "solved" an airlock/cavitation problem once by lowering the pump. I really want to make sure that I am locked on the the right target before I waste another expensive bullet.(see above) Further, if air lock because of the relative location of the pump and return pipes is really the culprit, I have to wonder why it hasn't manifested itself at any other time since our original system installation in 2002. This problem never showed up before we recently replaced the pump. I would be interested to hear your opinion of the air release valve idea.

    Again, I am thankful for all of your help and I am anxious to be convinced of the root of the problem and the solution.
     
  17. Sorry I thought this was a newly installed system, so if it previously worked fine and the only change was the pump,(presumably) with the same HP, and GPM rating,and performance curve,
    Is there a posibility the drop tube (to bottom) was damaged by the pump installer,( what is this pipe material) or some other cause, do you have an automatic bleed ? ( to moderate water temp.) that could be stuck,thereby admitting air, what are you using for flow control?, are there any strainers, etc, that could have a bad gasket, did the new pump curve match the old one? you may not have enough back-pressure (head) to prevent the pump from cavitating, pumps will not work properly with-out the minimum of back-pressure, espescially larger motor pumps, can you hear air traveling through the HX, at your flow rates, it would be very noticeable,
    have you tried partially closing a valve on the loop, in an attempt to create more back-pressure on the pump.

    Just some ideas to try... let us know

    Mark
     
  18. Looby

    Looby Member Forum Leader

    That would really suck; but happily, in this situation, there is no
    such thing as "-200 psi"

    Atmospheric pressure is about 14.7 psi absolute; and thus, it's
    not possible for the pressure inside the pipe to be more than
    14.7 psi below ambient atmosphere.

    Looby
     
  19. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    So now knowing atm pressure, what is the longest straw one could use to drink with? :D

    (an old physics question)
     
  20. Looby

    Looby Member Forum Leader

    About 34 feet if you're drinkin' [yech!] water...

    ...or about 50 feet for Bacardi 181

    Looby
     

Share This Page