Desuperheater Installation Question

Discussion in 'General Discussions' started by Teddyo1971, Jun 17, 2021.

  1. Teddyo1971

    Teddyo1971 New Member

    Dandelion Energy recently installed a 4Ton Bosch Split System in my home. The entire experience was great but I have some concerns with the desuperheater portion of the installtion. It is the beginning of summer and the AC doe not run that often so I don't expect much in the way of pre-heated water. But the concern I have is with the piping for the desuperheter to the storage tank. The configuration is as follows:

    Cold line in to Cold In of preheat tank is split to DSH In
    DSH Out to Hot Out of preheat tank and split to Cold In of Heat pump water heater

    Most of the diagrams I view online has the DSH Out to the drain of the preheat tank. I just want to make sure that this configuration is valid. And if it is what are the benefits of the DSH Out to drain over DSH Out to Hot Out of the storage tank.

    Thank you taking the time to review my question.

    Attached Files:

  2. SShaw

    SShaw Member Forum Leader

    There's a lot of discussion on this forum about how to plumb the DSH. Mostly it's talk between inlet on top/outlet on bottom, or vice versa.

    The consensus seems to be it doesn't make a lot of practical difference, as long as a buffer tank is used. Some experts say a buffer tank larger than 50 gallons doesn't work as well. I believe it's because there's usually not enough hot water production to get the larger tank to 130-deg.

    I don't think I've seen one with both DSH connections at the top, where the water inlet and outlet is, though. I have no data on it, but I'd be skeptical about that. Seems less likely to mix well in the buffer tank and more likely to draw water from the top of the buffer tank without utilizing the whole tank. However, maybe Dandelion has done some testing and figured out this is the best. You should ask them.

    I have a 50 gal buffer with the DSH output entering the bottom of the tank, and the DSH input coming from the cold water inlet feeding buffer tank. I have a temperature probe and it seems to work well, in Winter at least, always ending up at 130 degrees in the morning. I didn't have the probe last Summer, so I don't know yet how it will do. In the Summer, you won't see much hot water production until the loop EWT gets into the 70s. Mine's at 66 now and the buffer tank is only 85 degrees.
    Last edited: Jun 18, 2021
  3. Teddyo1971

    Teddyo1971 New Member

    Thank you for the rely. I did open a case with Dandelion and they assured be that this configuration is viable and will meet my needs. I also watched the "This Old House" episode that featured a Dandelion Geothermal installation with a desuperheater and noticed that the storage tank was also not utilizing the drain connection. They have performed 100's of installations and I guess this configuration is their standard. I will have to wait until the winter to get a consistent idea of how well it works. Overall I am very happy with the installation and look forward to no longer transferring 4 Tons wood pellets into my basement or using oil.
  4. SShaw

    SShaw Member Forum Leader

    Interesting. You could put a couple temperature sensors on the tank and monitor the performance. I have one sensor on mine under the insulation where the top heating element is located. One on each element would be better.

    For this, I'm using a wireless sensor from Monnit that reports to the Internet every ten minutes.
  5. Teddyo1971

    Teddyo1971 New Member

    I would like to use the sensors. How well do you think it would work with the Rheem Marathon Water Heater? Especially with the "super" thick insulation.
  6. SShaw

    SShaw Member Forum Leader

    I'm not sure about the Marathon. On mine, you can open the access panel, pull back the insulation, and tuck the metal sensor probe under the insulation against the side of the tank. Should be similar with the Marathon.

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