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  1. #1

    Water Cooled Unit Piping

    Had a service call the other day, customer was complaining they had 2 units that had been tripping on high head periodically over the past few months.
    I checked the head pressures on the units. 225psi and 330 psi for R-22 and 410a respectively. Entering water temperature was 42F, water reg. valve was in good shape.
    I see that the 3-ton unit calls for a 3/4" water connection but had been bushed down to 1/2". The 6-ton had the proper sized 1" line.
    Here is a photo of the piping arrangement...

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    Not sure what the supply water pressure is, there was no gauge in the line. Should they be able to achieve the proper flow with this line size? If so, what pressure is required?
    Seems to me like the water main should be larger. The 3 ton unit was a new addition about a year ago.
    The gpm's were taken from the manufacturer's literature for the given water temperatures. 45F and 65F for winter and summer.
    Worst case scenario they would require 10.5 GPM in the summer if both units were running full out.

  2. #2
    Join Date
    Apr 2007
    Location
    Central PA
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    51
    1 in will flow 16 gpm with less than 20 psi and 1/2 will flow 7 gpm I would check for obstructions in the pressure reg valve. They should have strainers on them if they don't they will plug up very easily. The gpm based on what I could find for PVC pipe not sure what the units are pipes with. Also it would depend on the length.

  3. #3
    Join Date
    Dec 2011
    Location
    Fort Worth, TX
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    What is high pressure cut out pressure set at?

  4. #4
    High pressure cut out is 350 for the R-22 Unit. Not sure of the 410a unit, it's a bullet style switch.
    trykonxlgold75... The main supply is stainless steel, the branch for the 3-ton is copper and 10-12' long. The main supply is probably over 100', not sure where the source is.
    Maybe they are having intermittent water pressure drops? I could install a water pressure switch if that is the case.

  5. #5
    Join Date
    Dec 2011
    Location
    Fort Worth, TX
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    80
    Quote Originally Posted by FrostGiant View Post
    High pressure cut out is 350 for the R-22 Unit. Not sure of the 410a unit, it's a bullet style switch.
    trykonxlgold75... The main supply is stainless steel, the branch for the 3-ton is copper and 10-12' long. The main supply is probably over 100', not sure where the source is.
    Maybe they are having intermittent water pressure drops? I could install a water pressure switch if that is the case.
    If time and money permitted I would put my yellow jacket analyzer on it and chart it. You would then be able to have a recordable chart it high and low pressure.

  6. #6
    Join Date
    Jul 2011
    Location
    Croatia
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    do you have balancing valves on branches? without them, you can hardly achieve desired water flows and too small branch diameter can add to trouble.

    balancing valves also have measuring nipples that allow flow measurement, it is flow data what you need, one-spot pressure measuring is not useful in close loop system.

  7. #7
    Quote Originally Posted by Drazen View Post
    do you have balancing valves on branches? without them, you can hardly achieve desired water flows and too small branch diameter can add to trouble.

    balancing valves also have measuring nipples that allow flow measurement, it is flow data what you need, one-spot pressure measuring is not useful in close loop system.
    This is an open loop, waste-water system.

  8. #8
    Join Date
    Jul 2000
    Location
    Dallas,Texas
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    45 and 65 are pretty cold for condenser water. That is why your flow rates are less than half of standard design rates. If the water is warmer than rated you are in for problems. The 'least trouble' way is to put on an automatic head pressure valve. Like something in the
    Johnson V246GB1 line. Let it control water flow based on head pressure.

  9. #9
    Join Date
    Jan 2009
    Location
    Keokuk, IA
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    We have dozens of pump and dump systems... they all get head pressure controls valves standard.



    Sent from my SGPT12 using Tapatalk 2

  10. #10
    Join Date
    Apr 2007
    Location
    Central PA
    Posts
    51
    Did you check temp rise? It will give you a real good idea if you have enough flow. An yes you need something to control flow. What are you call water reg valves. Are they static like globe valve or dynamic pressure control valves. If they are static then you need to make sure they are set with both units running this will make them less efficient when only one unit running but should ensure enough flow when both units running.

  11. #11
    They are Johnson water regulating valves, as wolfdog had mentioned in the previous reply. Not sure what the temp. rise is off the top of my head. I'll be going back to the site later on this week, will have a closer look.

  12. #12
    Join Date
    Jul 2011
    Location
    Croatia
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    yes, for open loop most of the previously mentioned comments apply as well.

    pressure drop over line gives you data about flow, while measuring temperature can possible give useful information as well.

    there can be either too low water flow in lines or too high entering temperature - the relevant water entering temperature is the one measured at time of tripping, so you need some data about possible entering temperature fluctuations.

  13. #13
    Join Date
    Jan 2009
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    Keokuk, IA
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    Sometimes you have to jsutstart tracing piping to see all that located on each branch. Could be as simple as whenever 2 commerical toilets are flushed at the same time while all the units are running, the flow dorps enough to cause issues.

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