High Efficiency Air Source vs Ground Source - Considering Proposals

Discussion in 'General Discussions' started by GorgeFarmer, Aug 11, 2020.

  1. GorgeFarmer

    GorgeFarmer New Member

    I have been looking at upgrading my 20 year old propane furnace, I don't currently have cooling. I have 40 acres of fairly flat land without much landscaping in yet. So I was thinking a geo/groundsource heatpump might be a fit for me. I have a proposal for about $43,000 for a WF 5 NDV064J111CTLODA ground loop install, not including excavation.

    I have a quote for a 4 ton Trane XV19 for about 20K and a 5 ton variable speed air source from another installer that is private labled, I believe its the Daikon 21 Seer 10 HSPF.

    I'm looking for some help in evaluating these options? Geo seems to point to COP but the air source don't really list COP just SEER and HSPF. $25,000 is a big difference in upfront cost. How do I calculate on payback based on efficiency gains for geo?

    Thoughts on models and methodologies to determine if air source or geo makes more sense for me?

  2. SShaw

    SShaw Active Member Forum Leader

    Given an accurate heating and cooling load calculation for your house, there is software that can calculate your heating and cooling costs, based on historical temperature data for your location. Your WF dealer should be able to run a GeoLink report for you that compares the performance and operating costs of the GSHP and other options. Or, you can do one yourself using LoopLinkRLC. They are estimates, and may not be completely accurate, but they are useful for comparisons.

    People like to talk about payback, but if you consider time value of money, there may not be any "payback" over an ASHP in 20 years, especially if no propane is needed. An expensive repair on a high end system can wipe out the savings quickly too.

    I went with a WF 7 series. Comfort, performance, and other factors need to be considered. For me, I liked getting rid of the noisy outdoor unit, getting rid of the old/noisy/dangerous oil furnace inside, having a constant BTU output vs outdoor temp, not having a defrost cycle blowing cold air, and not needing to rely on backup heat when it gets cold. The GSHP is much quieter inside the house than the old system was also, which is nice.

    A more economical choice for me would probably have been going with a Bosch BOVA ASHP, which would have cost about 1/3rd up front and $550 more per year to operate.
    Noobie likes this.
  3. GorgeFarmer

    GorgeFarmer New Member

    Thanks for the response SShaw. I've never had any sort of heat pump previously so no first hand experience. Not having a noise maker out by my patio or deck has been a check in the geo column. It sounds like you had an air source prior to going with your 7 series? Is there a significant comfort advantage with geo in your experience? We have big dreams and plans for the property so I have a lot of things I can spend money on. I'm just struggling with pulling the trigger on something that may cost me more over the lifetime of the unit if I can't identify solid reasons/advantages to going that direction. I am worried about being on an air source that is in de-frost all the time and blowing cold when I need it most. The air source camp seems to be saying that is a thing of the past and these new high efficiency low temp heat pumps work and work efficiently down to 8 degrees.

    Does anyone here have direct experience with one of the newer high efficiency air source pumps?
  4. SShaw

    SShaw Active Member Forum Leader

    I had an old 3.5 ton 13 SEER York ASHP from 1994, an 80k BTU 80% oil furnace from 1989, and an outdoor wood boiler. The ASHP would work down to maybe 25 degrees or so. It would blow cold air on defrost, but it didn't bother me that much. The wood boiler circulated 160-deg water through a fan coil and pre-heated the hot water. The wood boiler was the most even and comfortable heat by far. The geo is a close second though. Most of the time it runs in low stages and the airflow and operating noise is hardly noticeable.

    Take a look at the Bosch BOVA2.0.
  5. Deuce

    Deuce Member

    The other consideration is that a geo system should last twice as long as an air source heat pump. 15 years vs 30 years.
  6. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    Looplink is very good for the loops, but does not represent the energy use and the associated operating costs very good. It overestimates the air source performance, and does not use the correct performance data for the 7 series. It uses the dual stage 5 series performance data to model the 7 series.
    Waterfurnace's Geolink software is spot on with the performance estimates, but is not very good with the loop design and calculations. Too few input criteria you can choose from. For example no grout data selection, which can double or cut the loop performance in half.

    Keep also in mind that you have a 26% federal tax credit for 2020. Not sure if Washington State has an additional discount.

    As mentioned above, this is not only about payback. I do admit a certain bias towards ground source, but the performance data for air source is usually greatly overstated.
    Real World performance is much less, since the rating system is biased und unrealistic. It is a rating game.
    Same for Ground Source, but not to that extend.

    In our climate zone, we monitor air source perform annually at about 60% of the efficiency of ground source. Peak performance is not even close. Ground Source does not know how hot or cold it is outside. Other things to consider are life expectancy, resilience,

    Trying to look up some performance parameter or data for the Trane XV19, but cannot find any detailed data. Which is typical for ASHPs.

    Can anyone here enlighten me?
  7. SShaw

    SShaw Active Member Forum Leader

    I could not find detailed data on the XV19 either, but I did find the attached FAQ which indicates it's not the best choice for heating at low outdoor temps. It was supposedly designed to be small and very quiet, specifically to work with Seattle's noise ordinances and closely-spaced homes. Seattle's minimum temp is 28-degrees.

    Regarding the modeling, the latest version of LoopLinkRLC online agrees very closely with GeoLink for both the 5 and 7 series, so they might have updated their models. As an example, here are the results for my 4T system and closed ground loop.

    Total Heating Cooling Hot Water
    WF5 $1,297.80 $845.60 $273.42 $178.78
    WF7 $1,062.60 $709.66 $174.44 $178.50

    Total Heating Cooling Hot Water
    WF5 $1,347.74 $871.55 $234.52 $241.67
    WF7 $1,118.11 $682.25 $193.68 $242.18

    Attached Files:

  8. GorgeFarmer

    GorgeFarmer New Member

    Does anyone have input on how good waterfurnace's geolink is at modeling costs of the current airforce heatpumps? I hear from a pro geo installer that it actually makes airforce look too good. From another guy that it underrepresented air source pumps. Anyone have any real world experience that can help? It early feels like I'm splitting hairs on these options.
  9. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    So if you go with 8x 600 ft loops, instead of 6 x 800 ft, your total system pressure drop with go up by 25%, usually meaning 25% higher pumping power.

    You loop field pressure drop will go from 8.3 to 18.4 ft/hd if you go with 6x800 instead of 8x600 loops.

    That is all with 17 gym flow with a 7 series 5 ton.

    Attached is my loop link version of your house, given that you have about 1800 galloons of propane use, you have at least 70,000 but/h heatloss. Thus a 5 ton would be recommended. I personally would also make you 100% of your hot water via geo, but that would be me. Keep in mind, the tax credits expand to the hot water system if geo is being used for domestic hot water.

    Attached Files:

  10. Noobie

    Noobie Member


    We are well rid of our oil burner. My wife exclaims over how smooth the heating and cooling are. After installation, we had to improve our ducts and dampers for the kitchen/bedroom, but it has allowed for effective zones. Geo will somewhat highlight deficiencies elsewhere in the system.

    We are in a rural setting. I can’t say often enough how much we appreciate the quiet HVAC.

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