Texas desuperheater pump is not recirculating water into buffer tank

Discussion in 'Maintenance and Troubleshooting' started by KJW, Jan 15, 2015.

  1. KJW

    KJW Member

    Hello guys:

    I have an issue with my desuperheater pump not putting water into my marathon tank. I do believe it is plumbed correctly but the vacuum valve was left on the cold water input side of the marathon tank.

    System is a Bosch SM60. Plumbed into a marathon 105 gallon tank from the desuperheater into the drain. On top, I have cold water with a T coming into the tank and to the input side of the desuperheater. The marathon output side (hot) is plumbed to my condensing on demand Navien 240A. The tank appears to not be circlulating water from to the desuperheater. Could the vacuum breaker on the tank supply side be the issue? I will add pictures on the next post...

    Thanks...
     
  2. KJW

    KJW Member

  3. KJW

    KJW Member

  4. KJW

    KJW Member

    20150114_231238.jpg

    See vacuum valve?
     
    Last edited: Jan 15, 2015
  5. KJW

    KJW Member

  6. KJW

    KJW Member

    Does it matter if the tank water in goes into the tank and T's off to the desuperheater input as shown above? Or is it not dra wing water out of the tank first in this scenario and related pictures above?
     
  7. TheDude

    TheDude The Dude Abides

    Its hard to tell exactly whats going on from these pics.

    First thing is, you do need the vacuum valve.

    Second thing is, you do not show the return from the Desuperheater, It should be feeding the bottom of the tank. Do you have this?

    Third is that it needs to be configured in a way that you can use the domestic water pressure to initially purge the coil in the heat pump. So basically there needs to be a ball valve in between the tank and the tee. I don't see it , but it could be hiding behind that joist that is above the tank.

    If you have a valve there? you can shut it off, then open a hot water faucet or two. This will make all the water pass through the heat pumps coil and purge any air that might be in there.

    Finally, the SM units have a on/off switch located on the outside of the unit. After you confirm that the unit has been purged properly, check to make sure this is switched the on position.
     
  8. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    Could you give us a plumbing schematic to better understand how it's piped?
     
  9. KJW

    KJW Member

    Thanks. The desuperheater is plumbed to the bottom of the marathon drain valve. He has a ball valve on the line going to the drain valve and he has a ball valve on the downstream side of the T on the supply side (maybe this is wrong). It is configured so that you can turn off water to the desuperheater supply but fill the tank.... does that make sense...? See attached. Red line is coming to water tank and T is above it with valve going to desuperheater. 20150115_094624.jpg
     
  10. TheDude

    TheDude The Dude Abides

    Its fine to have valves isolating the Desuperheater, but typically there would be a valve placed somewhere on the red line running from the tee to the tank.


    Without that valve I am not sure how he could have purged it properly.
     
  11. KJW

    KJW Member

  12. TheDude

    TheDude The Dude Abides

  13. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    If I had to guess you have a check valve on the cold water inlet of the tank. I also want to caution you: the ball valves on the DSH line are considered isolation for a source of heat and what would become a sealed vessel. If you ever shut them off for anything, you must empty the lines and the heat exchanger (DSH). It always heats. Turning it off simply stops the circulator.
    j
     
  14. KJW

    KJW Member


    The dude,

    Please explain to me why I need the vacuum valve...? Confirming that I do indeed need to leave this?
     
  15. KJW

    KJW Member


    Interesting, as this vacuum breaker is allowing warm water to be drawn out of the top now... I think that we might have had a vapor lock in the system yesterday, as it is working now...????? not sure... anyone... ?
     
  16. TheDude

    TheDude The Dude Abides

    Marathon tanks need the vacuum breaker due to there makeup (Plastic, not Steel) The tank could destroy itself while being drained if the vacuum breaker wasn't present. Removing it would void the warranty.

    Air may slowly trickle out of the coil and start to heat the water. That doesn't mean that it is purged of all its air. It could purge itself of all the air over time, but it will be hard to confirm it.
     
  17. KJW

    KJW Member

    Awesome. You have been a real help. Thanks again...
     
  18. orchards

    orchards New Member

    I am not sure what is going on but I have had a couple of problems since I live on top of a mountain. If they service the water below me, the water will back flow out of the storage tanks and create an air pocket. Until that is cleared there will not be flow between the DSH and storage tanks. I had to flush while opening and closing the valves on the system to clear it. I wish I had installed a back flow valve to prevent this. The water line coming from the DSH got extremely hot to indicate this was going on. Once it was cleared, everything went back to normal.
     
  19. dgbair

    dgbair Just a hobby Forum Leader

    It's never too late to add one...
     

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