Delaware High pressure drop

Discussion in 'Maintenance and Troubleshooting' started by Kastenusa, Feb 26, 2015.

  1. Kastenusa

    Kastenusa New Member

    I have a Climatemaster 5 ton unit with one single flow pump. (5 loops 200ft deep), return closed header. My pressure drop across the coil is 7 psi. In manual specs say my pressure drop should be around 4.8 psi with 15gpm. I recently contact Climatemaster support with this question. Here is what they say:
    "If your water was 50° and is a closed pressurized loop then the pressure drop of 7 is too high. You most likely would be moving in excess of 5 gpm which could over a long period of time cause erosion damage to the coaxial heat exchanger. If this is so, and there are some type of valves on the system, the water should be slowed down to the appropriate pressure drop based on the incoming water temperature."

    I don't have any valves installed. My question is it ok to restrict the flow or i need new pump? Please give me your thoughts.

    Thanks!
     
  2. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    You could throttle the flow easily enough. A smaller or multi-speed pump would be the better answer, but it is difficult to gauge the ROI for replacement.

    Whoever spec'd the oversized pump is due a dope slap.
     
  3. Kastenusa

    Kastenusa New Member

    I just got second email from CM.
    They talking about using 3-way to slow the flow. What do you think about this? Is it gonna do some damage to the pump?

    "You should reduce it to around 4.5 psi differential. If you have an external flow center you can utilize the 3-way valves on each side of it to slow water down. Having a flow restrictor or full port ball valves in line is the preferred way, but since everything is installed I would use it so you don’t have to have the loop reflushed. "
     
  4. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    I would not use the 3 way valves for throttling. How old is your system? What does the OEM installer have to say about it? How accurate is your psi measuring device? What model flow center do you have?
    Eric
     
  5. Kastenusa

    Kastenusa New Member

    It's a new system installed in October. PSI device is brand new, i bought it on ebay 75$. Flow center products BGM 136, PL36 230 VAC 1.1 A Cast Iron.
     

    Attached Files:

  6. TheDude

    TheDude The Dude Abides

    Do you know what size the loop piping is? type of antifreeze and % ?
    I would call the installer explaining your conversation with CM and kindly ask him to swap out the pump for an appropriate model.
    I would also stay away from using the 3 ways to throttle down
     
  7. Kastenusa

    Kastenusa New Member

    My loops are 3/4 . 20% Methanol. I just talk to installer. Hi said that this is the smallest pump they make. His gonna put valve to restrict the flow to manufactures specs. Instsller also said that I'm gonna lose output BTUs by slowing down the flow. And it's gonna make some nose too.
     
  8. TheDude

    TheDude The Dude Abides

    its not the smallest pump they make
     
  9. TurboTom

    TurboTom New Member

    Recheck your pressure readings or get a new gauge that pump with 3/4" loops is not capable of pushing water through loops and HP at over 15 GPM
     
  10. Kastenusa

    Kastenusa New Member

    I just double checked my pressure readings before I called installer. It's the same 31psi in 24 psi back. I'll compare my reading with installer reading when hi is gonna stop by next week.
     
  11. TurboTom

    TurboTom New Member

    At 15 GPM your loops would have about 11 feet head add the 7PSI 0r 16 feet of head through the HP and your at 27 feet and the pump curve shows it is at about 14 GPM. So there may be a restriction in the heat exchanger giving you that differential but its not the pump giving you too much flow.
     
  12. TheDude

    TheDude The Dude Abides

    What is your temperature differential?
     
  13. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    A lot of stabs at a problem, but still not enough data to reach a prognosis. A simple reality check would be to run through the math for flow rates and feet of head, then compare to the pump curve of the bgm 236. The oem installer should have provided a throttling valve at the time of initial install. On the matter of your pressure gauge. Measuring instruments need to be calibrated, even if new. with such a small difference in psi pressure drop, making such a big flow chane, your data collection needs to be rock solid.
    Eric
     
  14. Kastenusa

    Kastenusa New Member

    My delta-T 6f. Ewt 37f Lwt 31f. The other thing is when unit goes in second stage ewt drop very fast.
     
  15. TheDude

    TheDude The Dude Abides

    Is that 6 delta in first or second stage?
     
  16. Kastenusa

    Kastenusa New Member

    First stage.
     
  17. TheDude

    TheDude The Dude Abides

    Your delta T suggests that your flow is good. I would confirm the pressure drop with another gauge before making any changes
     
  18. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    A 5 ton CM in first stage has about 28,000 BTU/h heat extraction in 1st stage.

    Flow = 28,000/(6 (degree delta T) x 485) = 9.62 gpm

    This suggests your pressure gage is way off, and you are under powered.
    Another possibility is that your methanol level is not high enough, and in combination with such a low flow, there are ice rings forming inside your heat exchanger.
    Thus the flow restriction would cause a high pressure drop and suggest a high flow when in reality your flow is too low.

    A PL-36 is to small to provide 15 gpm at your system pressure drop, if anything it is underpowered.

    The fact that there are not shut off valves suggests that your installer is not very fond in geo. How long are your loops (loops, not boreholes), how big is the pipe coming in and out of your house out to the loop field. How far away is the loop field?
     
    Palace GeoThermal likes this.
  19. Kastenusa

    Kastenusa New Member

    I think CM 27 has around 37500 btu in first stage heating. So Flow would be around =12.8 gpm . My loops are total = 940 feet to header . From header to pump is probably 25 feet. From pump to HP 14 feet. My unit located in mechanical room up in the attic. Not sure about % of methanol in the system. It should be around 20%.
    Installer stop by today his gage shows only 5 psi pressure drop. My gage still shows the same 7 psi. Hi is not sure where to put valve. I kinda want it close to the unit, so if it's gonna make some noise it will be upstairs. Not in the garage aria. Hi said to install it upstairs hi is going to need to install two more pt ports.
    Not sure about valve now , I think Docjenser is right , it's probably just not enough flow, plus I don't have AUX heat. I think it makes my system run no stop in the coldest days. This way loops don't have enough time to recover.
     
  20. pfer10

    pfer10 Member

    Kasten the 37.5k is the heat output. Doc is talking about the heat of extraction or the heat removed from the water. The rest is from the compressor energy that gets converted to heat that it takes to move that heat from the water to the air. When I first did the measurements on my system I was impressed I was only heating my house on 24k. I was then informed I didn't add in the compressor energy. :)

    See below for 14GPM and 1650CFM you will be at 29.3k HE at 40EWT. The output of the unit is 38.5k. You will be a little lower than that since your EWT is 37F.

    Screenshot_2015-03-03-15-45-17~2.jpg
     

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