Most Efficient DSH Setup For New Construction

Discussion in 'Geothermal Heat Pump Applications' started by csementuh, May 24, 2016.

  1. csementuh

    csementuh Member


    Running a Carrier (Bosch) unit that is brand new in a new construction house. HVAC sub wanted wayyy to much money to install desuperheater and tank, but the geo unit has the stuff so I plan to do my own dual tank setup.

    Looking to maximize my investment here: I have a 'free' new 50 gallon electric Bradford White tank that I can either use as the main tank or the preheat tank depending on what is best.

    Do I:

    1. Buy the Lowes/Home Depot el-cheaper 50 gallon electric tank to use as a pre-heat tank and then keep the Bradford tank as the finish tank? This will cost about $600 or less for tank and plumbing.

    2. Buy a higher end electric tank for the finish tank and use the Bradford tank for the pre-heat? Cost ??? depending on the finish tank.

    3. Buy a hybrid heat pump 50 gallong heater for the finish tank and use the Bradform tank for the pre-heat? This would cost about $1000 for the heat pump tank, plus the plumping parts. But! With a Lowes 10% coupon, a $300 local power company rebate and a federal tax credit, this options isn't very expensive in the long run!

    Does a desuperheater work good or OK with a hybrid type heat pump water heater for the finish tank? If so I'm starting to lean that way...

    I've seen lots of DSH plumbing diagrams online. What is the best way to do things? Do you need ball valves, check valves and air vents in places (where?) to do it best?

    Since this is new construction and we aren't even in the house, I want to do it best and 'right' the first time!

    Thank you!
  2. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    Hello and welcome.

    Owning a geothermal heat pump is like the Army; Be all you can be.

    You paid for the ability so go ahead and use it.

    1. Wholesale supply houses still, this week, beats big box pricing. You are close on pricing, and if you go to plastic do it to code.

    2. Not needed.

    3. I have done both and everyone was happy except Doc. Do the math and run the cost of fuel for the finishing tank. Electric is what it is.

    Heat pump is a better value than resistance water tank elements as a fuel.

    The best, industry standard piping diagram is offered here by Bergy and others. You need the buffering tank. The heat pump makes a small lift in delta T easier than a big lift. Too many check valves and ball valves can never be. Air eliminator is the first faucet with an H.

    I just sold my travel trailers, so the geo-gypsies are no longer in business or I would offer to bring my plumber and I to lend a hand.

    Find your diagram and if you need clarification call me.

  3. Stickman

    Stickman Active Member Forum Leader

    Figured I'd try to build up my stats and go for an assist on the Bergy diagram hunt. :D

    I believe the heat pump HWH does pull some heat from the surrounding area, which may be a problem during heating season.

    Attached Files:

  4. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader


    You are good on stats with me.

  5. csementuh

    csementuh Member

    Thank you gentlemen!

    Mark, can you please elaborate what you mean by "Too many check valves and ball valves can never be. Air eliminator is the first faucet with an H." I don't follow that at all. Do you need check valves, if so, where and what kind? The Bergy diagram doesn't seem to label anything like that.

    I have two scenarios I'm thinking of:

    1. Do a normal 50 gallon tank for pre-heat and be happy with basic DSH function! Keep it simple and install tanks right next to geo unit.

    2. Get all crazy and move the hot water tanks to the front basement utility room and use a hybrid HP heater for the finish tank. This area will be a smallish room that has a server rack (computers and network equipment) in it that gives off quite a bit of heat. In my crazy mind that equates to an even more efficient HPWH with 'free' heat in the room (even in the dead of winter)! No? The water entrance to the house is also right in that area as well as the power panel. That will require moving the HW tanks about 20-30 pipe feet away from the geo unit's DSH and about 15-20 pipe feet away from the main trunk of the house hot water line. Will I see adverse conditions with this longer run for hot water? Too long at the faucet? Too much heat loss in this system? I can annotate a house plan picture if it would be helpful.

    Really just trying to get my best bang for buck here. With option 2:

    -Keeps my servers cooler, in a place where cooling would have maybe been a problem
    -Gives me back wasted space next to geo unit, this is central space where I planned to build an office beside. Now I can make the HW wasted space into a large closet.
    - Take up more space in the front utility area that was previously just empty wasted space.

    -Longer HW pipe runs may have an impact on readily available HW and also efficiency due to loss


    Thanks again!
  6. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    Pittsburg is pretty much heat dominated, meaning that you have about 60% of your hot water (depending on your hot water usage) coming from the DSH. So the return is diminishing on a heat pump hot water heater, which takes the heat out of the air anyway, which you have to heat up now with your geo heat pump.
    Certainly different with Florida climate. Now you throw a server room in the mix, and you might want to have a way to take the heat from that area 24/7.
    In that scenario you want to keep your buffer tank close to your heat pump, but your final tank can be closer to the server room. You will loose some heat through longer lines....but likely more than compensate for it with warmer source air.

    Mark, as always, I have trouble comprehending your comments.
  7. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    I have done both, used cheapest fuel finishing tanks and air to water DWH heat pumps all worked we.
  8. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader


    Unless you think like Dan Holohan, and can "see" where the water is going to go, mortals add check valves pointing in the direction that they think the water should go.

    Everything in a hydronic system is going to need service or replacement. I like service isolation valves on both ends of a serviceable component. Why? Money savings on time and water quality.

    The first hot water faucet past your install is your air bleeder valve.

    If you want to move the DHW system to the back yard go for it. Insulate the de-superheater water lines coming and going. You can add a timed DWH re-circ pump to the delivery system.
  9. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    The most important variable in evaluating domestic water heating alternatives is demand, and that is driven mostly by number of permanent residents and a bit more by their hot water usage habits.

    I like a dedicated desuper-fed buffer tank feeding a heat pump water heater finishing tank, but that's pricey and may never get paid back for a small household in a heating-dominated climate.

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