Add Heat Pump to boiler heated indirect

Discussion in 'Water Heater Forum, Tanks' started by drboom, Jan 24, 2016.

  1. drboom

    drboom New Member

    Joined:
    Jan 24, 2016
    Location:
    Londonderry, New Hampshire
    I apologize if this has been covered before, I searched and read quite a bit before posting this but please point me to a thread if I've missed it.

    We're in the northeast (NH) and have a buderus G215 oil fired boiler that heats our hot water via a SuperStor Ultra 60 gallon indirect tank. This works fine but obviously means that we have the boiler running in the summer with all of the negatives that go with it. I'm considering installing a heat pump water heater in series (before) the indirect tank and have a few questions.

    Is using an add-on heat pump like the Nyle Geyser-RO a better solution than adding a full hybrid hot water heater? If this is a good approach, any recommendations on which add-on heat pump to buy?

    If I install a hybrid heat pump hot water heater in series but leave it in heat pump only mode all of the time, will that make a meaningful difference in extending the life of the hybrid's tank?

    If I install a hybrid in series with the indirect tank, is it worth it and is there a good way to create a recirculation loop between the tanks to effectively create a larger tank?

    Thanks for your help.
    Jon
     
  2. drboom

    drboom New Member

    Joined:
    Jan 24, 2016
    Location:
    Londonderry, New Hampshire
    Bumping my old question. I'm still looking for ways to use the boiler less during the non-heating season. Are there any good ways to add a heat pump to my indirect hot water system? The goal is cost savings as the existing system keeps up just fine.

    Thanks, Jon
     
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  4. phog

    phog Active Member

    Joined:
    Jul 29, 2017
    Location:
    Rochester NY
    There used to be a standalone unit that would have been similar to what you're looking for, the Nyle Geyser-R heat pump. I don't know if they make it anymore. Sorry i can't be of more help than that.
     
  5. drboom

    drboom New Member

    Joined:
    Jan 24, 2016
    Location:
    Londonderry, New Hampshire
    What about adding a hybrid water heater in series before the superstor? Given electric costs in NH, I could leave the hybrid in heat pump only mode and lower the set point on the indirect hot water from the boiler to deal with any shortfalls.
    Thanks, Jon
     
  6. fitter30

    fitter30 Active Member

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    Feb 2, 2020
    Occupation:
    Retired service tech
    Location:
    Peace valley missouri
    If the hybrid was left in hybrid and piped in series and knowing that the high temp would be 120*. Check, valve in cw line going to hybrid with expansion tank, pump from hw line indirect to hybrid cold with a thermostat mounted on pump piping set at 115* 5* differential. If the hybrid could produce 135*-140* water the boiler could be set down to 110*-115* but it can't so the boiler would want to run. With a processor, temp sensors and code might make the boiler possible. Heres some info to look at
    [PDF] Field Performance of Heat Pump Water Heaters in the Northeast - NREL
    https://www.nrel.gov › docs
     
  7. drboom

    drboom New Member

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    Jan 24, 2016
    Location:
    Londonderry, New Hampshire
    I was thinking of putting the hybrid as a preheat before the indirect. I use about 200 gallons of heating oil during the non-heating season for hot water so it seems like I have a substantial potential savings. It seems that Nyle doesn't make that unit anymore and I'm not finding any substitutes.

    Thanks for your help.
     
  8. fitter30

    fitter30 Active Member

    Joined:
    Feb 2, 2020
    Occupation:
    Retired service tech
    Location:
    Peace valley missouri
    Using the hybrid for preheat only could short cycle the boiler because instead of razing the temp of incoming 50*
    your using 120* plus you wanted more capacity.
     
  9. phog

    phog Active Member

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    Jul 29, 2017
    Location:
    Rochester NY
    If you are OK with buying a full hybrid heat pump water heater, why not just have a couple hand valves to switch back and forth between the hybrid vs. the indirect based on the season. Instead of trying to make up some homebrew combined system that probably won't work well, just switch the valves and turn on whichever system is appropriate for summer vs. winter.
     
  10. drboom

    drboom New Member

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    Jan 24, 2016
    Location:
    Londonderry, New Hampshire
    I was originally hoping for something that would take advantage of the indirect tank with all of the associated benefits. Since that doesn't seem to exist, you are probably correct about the best alternative.
     
  11. phog

    phog Active Member

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    Jul 29, 2017
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    Rochester NY
    The associated benefit being quick recovery after a hot water drawdown?
     
  12. drboom

    drboom New Member

    Joined:
    Jan 24, 2016
    Location:
    Londonderry, New Hampshire
    My understanding is that the superstor indirect tanks essentially last forever as opposed to a typical hot water heater that will fail in a decade give or take depending on how effective the anode (w/replacement) is. I use ~200 gallons of oil during the non-heating season in NH even with a drain water heat recovery system.
     
  13. phog

    phog Active Member

    Joined:
    Jul 29, 2017
    Location:
    Rochester NY
    Ahh I see. Well if you're adding a second hot water tank to the system, then you are adding a component with a 10yr lifespan right there. Cross-connecting that tank with the indirect, or not, it will still need to be replaced in that timeframe.

    Now if you're proposing to somehow remove the heat pump from the hybrid system and discard the tank, to mate it with the indirect tank -- well in theory that could probably be done. In the same way that in theory you can install a Chevrolet big block V8 engine and transmission into a Toyota Prius. Is it worth your time and effort? That's not for me to decide and I have no idea how involved that could get.

    Doing that properly would involve not just a customp physical mating, it would also need a custom control system (so that the indirect doesn't automatically fire up and do the bulk heating after every hot water draw, defeating the purpose of having a heat pump). As others mentioned above, you could maybe play with temperature setpoints to see if you can find a workable configuration.

    If that seems like too much work, yes it sounds like you'd get benefit from having a heat pump hybrid tank and doing a manual valve switch seasonally as appropriate. One thing to pay attention to there is having a dead volume. You can get microbial growth such as legionnaire's disease if you're not careful.
     
  14. drboom

    drboom New Member

    Joined:
    Jan 24, 2016
    Location:
    Londonderry, New Hampshire
    Thasnk phog. I have no intention of dismembering a hybrid system. It seems that perhaps there isn't a good option now that the Nyle unit is discontinued. If I find a great deal on a large tank hybrid to run in parallel (valve off the indirect in the summer), then perhaps that would be worth it.
     
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