Need comments on a big project.

Discussion in 'General Discussions' started by bILL wILT, Nov 19, 2020.

  1. bILL wILT

    bILL wILT New Member

    Would anyone be willing to put their 2 cents in on the following?

    Not ready yet to deal with contractors who will inevitable pester me to sway this way or that. I want to figure out my best options from other’s experience first at my own pace.

    I'm planning a 6,000 sq. ft. roughly half slab half second story house with radiant floor heat, limited (hydronic?) ductless AC, with a 17,000 gal indoor pool in a walkout half basement (with southern exposure, full passive solar, and cover when not in use). In Colorado at roughly 7,500 feet. And then 6 people in the house.

    I'm an amateur architect since I was 13 so I know space planning and CADD well enough to get a working design for the house but this is still just a dream at this point.

    From what I've gleaned so far from Google searches (and without a degree in thermodynamics), I'm thinking a 8-9 ton pump for the house and 2-ton pump for the pool (and area) with DSH's for both for DHW. An 80 gal preheat storage tank for the DSH's, with an 80 gal HPWH. Storage tank shouldn’t need heat. Pool will be heated 24/7/365. House will be super insulated and not many big windows except floor to ceiling in 20’ high (20' x 30') west facing living room with wood burning fireplace and 13’6 ceiling in pool area (36' x 30'). It’s going to have to be a vertical loop system with probable rock at about 4-6’.

    I think the house pump is smaller than recommended but I'm hoping to get away with that because I only need warm, not hot water with radiant floor heat(?). Pool pump too may be smaller than recommended but it will have full passive solar and plenty of sunshine in the Colorado winters.

    I realize it's hard to give recommendations on a system this big without very specific requirements but you may at least help me not make a complete idiot out of myself when I try to pursue this.

    Any comments/questions/recommendations would be greatly appreciated.
  2. gsmith22

    gsmith22 Member

    if you have your heart set on radiant floor heat, waterfurnace makes a synergy 3D unit (that someone else highlighted a week or so ago on another thread) that can do radiant heat, ducted air heating, or ducted air cooling all from the same unit (but not all at once). not sure if other heat pump manufacturers sell something similar. It would allow radiant heat and ducted a/c from the same unit and eliminate separate equipment for non ducted a/c and radiant heat. indoor pools are probably well suited for heating from geo with water-to-water units but don't know the details of how to do that. big west facing windows tend to create need for cooling load because of the heat gain - may need a/c in that room during late afternoon in the fall or spring for instance when other areas of the house need heat. obviously shades can help but west facing windows can create individual room mismatches for hvac. In terms of overall size of equipment, i think you need some sort of plan with orientation and window layout to do a general calc on the heat loss (I recommend coolcalc). really hard otherwise and rules of thumb can be way off with unique conditions (like big west facing windows or use of passive solar gains). wood burning anything tends not to work well with super tight houses so careful with that - combustion air would have to come from outside, be ducted directly to unit, and then out chimney. I don't know the details but super insulated/super air tight homes pretty much never have wood burning anything (or combustion of anything for that matter).
  3. wing

    wing Member

    My two cents worth - you get what you pay for of course !

    Huge project, couple of million and years of construction time, you will want to hire a design professional to run manual J and hydronic layouts. No need to guess here on how big a heat pump you need, leave that for design results.

    Hydronic floors add a lot of cost and complexity to a house build. On an equivalent size build, I’ve got an extra $60k cost for radiant associated with gypcrete slabs, distribution network and labor. Also your planning needs to be precise as any floor attachments - internal walls, stair landings, built ins , ect need to have sleepers embedded into the floor slab before you pour. It’s very nice, the feeling of a warm floor on your tootsies early in the morning - but you’ll pay dearly for the privilege.

    it’s no problem to run one or more hydronic air handlers (Vara Therm) off a bare bones water to water heat pump via the distribution panel and personally I would stay away from the complexity of a combination system like the synergy 3D. Some on this board don’t like this setup because ideally an air handler would perform more efficiently with water hotter than what you would produce for in floor heating. But it’s good enough as the heating base load is carried by the in floor heating system, you’ll probably be needing it mostly for cooling and air handlers also have electric heating elements that can be activated on the rare nights temperatures go below zero or for emergency purposes in case the heat pump fails.

    Desuperheaters add very little in a heating dominated climate like Colorado and I wouldn’t bother with hooking them up. Again, you can heat water just by hanging off a dedicated pump that circulates heat pump water through coils inside a suitable hot water heater.

    Big west facing windows are problematic and you might consider adding powered shades to better control solar gain during the afternoon and radiant loss during the night.

    Are you considering heat recovery ventilation in a house with low air exchange ?

    You are a brave man to plan an inside swimming pool. DW wanted this feature in our build, I had to be the grinch as I saw a lot of problems with sealing the pool area from the rest of the house in the interests of humidity control.

    Good luck with your geo journey.
  4. gsmith22

    gsmith22 Member

    agree with all except the desuperheater part. At least with my units (WF 7 series), superheat is produced at all incoming water temps during heating operation (natural ground temp here is 55 likely colder in CO). For my units, superheat is not produced in cooling use until you get incoming water temps at like 60 degrees or more. Being in a heating dominated climate and the heat pumps and ground loops sized for 100% of the heating load, units and loop are way oversized for cooling. So my ground loop temp doesn't rise all that much in the summer ( I think it got into the mid 60s but I didn't stalk it). Given this paradigm, my hot water heater runs alot in the summer but barely runs in the fall, winter, and spring because the geo units output so much extra heat and keep the buffer tank near 120 all the time. In fact if I look through the unit error messages via Symphony, I get constant messages about the desuperheaters turning off because the upper limit of water temp is met. I have an 80gallon heat pump hot water heater and 50 gallon unpowered buffer tank. Were I to do it again, I would probably make the buffer tank larger to capture all the excess heat. I can't imagine my situation being terribly different from most heating dominated climates but maybe there is an aspect I am missing here?
  5. bILL wILT

    bILL wILT New Member

    I guess I need a better understanding of how DSH's work within the system. My thinking was when the pump was on, the DSH was doing what needed to (could) be done for HW and the buffer tank. Didn't know there was any other threshold to cross before operation.
    Last edited: Nov 22, 2020
  6. wing

    wing Member

    @gsmith22 is using what he has to produce hot water, nothing wrong with the strategy.

    He has a high tech WF 7 heat pump, which is a water to air system without capability for hydronic in floor heating. As there is no hot water output, the desuperheater has been plumbed into the DWH system. Ergo, 5 to 10% of the heat pump BTU nameplate capacity created as heat by product during the compression cycle is directed towards DHW. If there is no zone demand for hot air, the heat pump does not operate and there is no DHW heating. If there is a big demand for DHW, the desuperheater cannot deliver enough BTU’s to keep up and the electric backup switches on.

    Per the testimonial this is good enough and @gsmith22 is happy with the setup.

    @bILL wILT will employ a water to water heat pump due to desire to implement in floor hydronic heating in his new build. Therefore he has an alternate , and in my opinion superior, DHW strategy by directing 100% of the heat pump output towards DHW via a dedicated pump off the distribution panel and priority override logic. DHW will be on demand and not dependent on whatever calls the heating system may or may not be activated.

    The heat created during the compression cycle will be dumped into the mechanical room, which is presumably inside the heating envelope and not wasted.

    There is an inefficiency created by not utilizing the desuperheater as compression cycle heat will not be utilized during cooling cycles. My guess is at 7500 feet in Colorado, there are not many cooling calls. Thus the comment I wouldn’t recommend @bILL wILT bother with the added complexity of a desuperheater for his application.

    Good luck to all on your different paths on the geo journey.
    Last edited: Nov 22, 2020
  7. bILL wILT

    bILL wILT New Member

    So am I to understand a DSH doesn't work at all in cooling mode?

    Also thinking water to air (vs w-w) might be a better choice (as much as I really prefer the comfort of radiant floors) because of the wild temperature swings, especially in the spring and fall, and the fact that radiant heat is slow to adjust. I wouldn't want to put my system into "panic" mode trying to keep up with varying demands in the house.
    Last edited: Nov 22, 2020
  8. gsmith22

    gsmith22 Member

    No, a desuperheater works in both heating and cooling. The amount of the desuperheater output depends on the incoming water temp to the heat pump.

    Wing is suggesting a different setup not using a desuperheater but rather using (i think) the main output of the water to water heat pump for both in floor radiant as well as domestic hot water with flow to one or both of these. I'm not clear on the details of how to do that but that would only be possible due to the water to water setup. I can't do that because I have water to air heat pump so a desuperheater is my only option. Anyone could always have a dedicated water to water heat pump specifically for domestic hot water ( presumably done if the demands are great enough). I think Wing's suggestion is to mimic a dedicated water to water heat pump for domestic hot water in an "equipment efficient" manner by sharing with the radiant. Wing, correct me if I have this wrong.
    Last edited: Nov 22, 2020
  9. bILL wILT

    bILL wILT New Member

    So warmer loop means less compression means less hot gas the DSH has to work with to make hot water?
    But in heating dominated climate such as mine, wouldn't the loop be relatively cool most of the time? Or am I missing something else?
  10. gsmith22

    gsmith22 Member

    • No you got it and I can confirm that is how my system has worked too using a desuperheater. Wing is suggesting that if you already have a water to water heat pump ( because of the radiant floors) it would be more efficient to use that also for domestic hot water rather than a desuperheater.
  11. bILL wILT

    bILL wILT New Member

    Ok, so the DSH for the house pump would be overkill.
    Now with a full-time heated pool, I should still be able to utilize a DSH with the (separate) pool pump all year round, no matter what the loop temp is correct?
  12. gsmith22

    gsmith22 Member

    I'm not sure "overkill" is the right word. there are different methods to achieve the same thing. I'm going to let wing jump in here because these are systems I don't have and I don't want to give you bad advice. I would point out that your heated pool would also be a water to water heat pump so I presume he would have the same opinion of not using a DSH. His belief above seemed to be that a DSH makes sense when you have a water to air heat pump only. Wing I think has a build thread on here with some pretty sophisticated systems/diagrams. might be to your benefit to search that out on the forum. I found this one that might be of interest :

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