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  1. #1
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    Air to Water heat pump install

    I am doing something completely different for my own personal use. I am install a 30kw air to water heat pump and wanting to use a forced air hydronic furnace for living space on 2nd floor and radiant heat in concrete on first floor garage/shop. Need help in choosing air handler. Need heating and cooling for 2nd floor and finding a air handler with “chiller” and heating is quite difficult. Do I need different coils for each use?

  2. #2
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    A 4-pipe (dual coil) air handler will allow you to perform dehumidification as required, otherwise you can do it with a single coil 2-pipe AH as long as you take care of the switching between heat and cool externally. You may need to consider coil size and FPI to determine whether you will have enough surface area to work effectively in both heat and cool modes if you go with the 2-pipe setup. Often the coils are sized differently for each mode because of the difference in delta-T between the air and the coolant in each mode.

    A good common brand for this application is First Company (http://www.firstco.com/#/). Is your heat pump reversible so that it can produce cooling as well? Do you plan to have any thermal storage of either cool or warm water? Keep in mind that air handler heat must be a lot hotter than floor heat, so you will need to have them on separate temperature zones. If you want simultaneous heating and cooling, consider using a water-to-water heat pump and adding on a water-to-air heat exchanger outside the building.

    The last 3-4 issues of PM Engineer magazine have had an excellent series of articles by John Seigenthaler that help with this sort of hydronic design scenario.

  3. #3
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    Thread Starter
    The heat pump is reversible, also the heat pump only produces max of 120 degree water so temp will be the same in floor as the air handler. It is similar temp as water to water geothermal system. I looked up firstco air handler First Co 12VMB-277 looks like the perfect unit.
    I bought one of John Seigenthaler books on hydronic heating and there is a lot of great information. One other question is selecting the circulation pump. I know what size based off the head and gpm required, but I’m looking at the loadmatch pump by taco. Is that a good fit to my system? Wanting one main pump and zone valves on each zone.

    I am installing a buffer tank for thermal storage and dwh, not sure on how many gallon yet.

    Look forward to reading your reply.

  4. #4
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    I'm not an expert, but 120 degrees seems too hot for floor heat to me, unless you have inch thick carpet or something.

  5. #5
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    Thread Starter
    It’s 4” slab of concrete, and max temp is 120 min temp is 108 degrees. I’m not a expert either but I’ve read that I just shouldn’t go above 140?

  6. #6
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  7. #7
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    In order to do that effectively without complication you will want to select a hydronic heating coil which will produce all the heat the space will require - At The Same Water Temperature that the floor radiant will be using.

    So if the floor loops and lengths were designed for 105º water - you will want to select a heating coil sufficient to heat the second floor with 105º water in it.

    Do you have the heat loss / heat gains calculations done already?
    If so; what are they?
    If not; how were you expecting to select equipment? <g>

    BTW: Why do you want to do it this way? Why take heat out of air, put it into water, and then put it back into air again?

    Have you considered Unico equipment? It comes in snap-together modules. Including hydronic heating coils.

    PHM
    ----------



    Quote Originally Posted by Jbeard9 View Post
    I am doing something completely different for my own personal use. I am install a 30kw air to water heat pump and wanting to use a forced air hydronic furnace for living space on 2nd floor and radiant heat in concrete on first floor garage/shop. Need help in choosing air handler. Need heating and cooling for 2nd floor and finding a air handler with “chiller” and heating is quite difficult. Do I need different coils for each use?
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  8. #8
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    Sep 2018
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    Thread Starter
    Heat loss gain-
    25k in living space (2nd floor)
    36k shop (radiant heat 4” concrete slab)
    21k garage (radiant heat 4” concrete slab)

    I want to do it this way b/c a water to water geo system is pricey to install bc of the ground loops and A air to water heat pump is the next best thing for efficiency. I want to take air to the living space so I can cool the area, wound like in floor radiant heat in 2nd floor but it’s not economical to install bc I would still need to run air in the summer time.

    I got a price quote for First Co hydronic air handler that works with the water temp and heat/cooling load for the second floor living space.

    Just not sure how to zone everything? Use different pumps or zone valves?

  9. #9
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    Sep 2002
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    Sorry about that; that's not exactly what I meant.

    Which portions of the space are going to be cooled / air conditioned?

    What are the cooling requirements for each of the 'to be air conditioned' spaces?

    Are the shop and garage to be only heated - or cooled as well?

    We can come back to zoning after the above gets laid out.

    PHM
    -----------


    Quote Originally Posted by Jbeard9 View Post
    Heat loss gain-
    25k in living space (2nd floor)
    36k shop (radiant heat 4” concrete slab)
    21k garage (radiant heat 4” concrete slab)

    I want to do it this way b/c a water to water geo system is pricey to install bc of the ground loops and A air to water heat pump is the next best thing for efficiency. I want to take air to the living space so I can cool the area, wound like in floor radiant heat in 2nd floor but it’s not economical to install bc I would still need to run air in the summer time.

    I got a price quote for First Co hydronic air handler that works with the water temp and heat/cooling load for the second floor living space.

    Just not sure how to zone everything? Use different pumps or zone valves?
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  10. #10
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    Sep 2018
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    Thread Starter
    Cooling load:
    2nd floor 12kbtu
    Shop 24kbtu
    Garage 11k btu

    I want to eventually cool my shop and garage but right now it isn’t a priority. For now I only want to cool the 2nd floor.

  11. #11
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    Is there an existing heating system for the 2nd floor?

    Are the 2nd floor air ducts already installed?

    PHM
    --------

    Quote Originally Posted by Jbeard9 View Post
    Cooling load:
    2nd floor 12kbtu
    Shop 24kbtu
    Garage 11k btu

    I want to eventually cool my shop and garage but right now it isn’t a priority. For now I only want to cool the 2nd floor.
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  12. #12
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    Thread Starter
    Nothing existing right now except for pex in concrete slab on first floor

  13. #13
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    Then I suggest a Unico System 1218 air handler and air ducts for the second floor. Have the installers put a water heating coil in the return air duct with about a 175K-200K BTU capacity. (this rating would be at 180º water - your system will have closer to 100-105º - making that coil about right for your needs)

    Have the installing contractor properly install the matching heat pump condensing unit of your choice to go with the above.

    Have a three ton air-to-water heat pump installed for the first floor PEX. This will also provide heating water for the 2nd floor system's water coil.

    Water flow rates must be constant for the air-to-water heat pump. So: have them install a 60-80 gallon electric water heater. Pipe the WH, the circulator pump, and the air-to-water heat pump in series. The air-to-water heat pump will heat this water heater tank.

    Have the installers pipe all the output zones - I would use a separate pump for each zone - each From the water heater.

    Have them wire the water heater with a manual switch. During cold weather it will switched on to provide an additional 15.3K BTU's. And a real HVAC mechanic can arrange for it to provide 30.6K BTU's if needed. This can also be done automatically by a thermometer sensing the outdoor ambient.

    When you get on to cooling the shop and garage it can be accomplished with air handlers with chilled water coils.

    PHM
    ----------



    Quote Originally Posted by Jbeard9 View Post
    Nothing existing right now except for pex in concrete slab on first floor
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

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