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Geothermal vs. air-source heat pump

Dean Sandbo | Posted in General Questions on

I have researching and getting quotes on hvac for a while now.. It is getting to crunch time.
Well insulated, tight house.

All three quotes include:
3 units, 3 air handlers, each zoned 3 times. Rigid Trunks and short flex runs.

option A. Carrier 18seer 25vna08… 5 stage. ( I don’t like the potential harmonics problems of their greenspeed)

option B. Lennox x25 top of their line variable.

option c. Waterfurnace 7 series geothermal units. horizontally drilled ground loop.

Just received Waterfurnace quote today, and with the tax credit, it is actually cheaper than option a and b. Very reputable company… I never researched geothermal, because I thought it would be so much more. But with the tax credit it is coming in cheaper than the other two companies.

Is there any reason why I wouldn’t choose the geothermal? These three companies all have amazing reputations, and come highly recommended…

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  1. GBA Editor
    Martin Holladay | | #1

    This is a very telegraphic post. For other GBA readers, as well as myself, I'll begin to fill in the missing information.

    The Carrier Infinity 18VS 25VNA8 is an air-source heat pump. More info here: Carrier Infinity 18VS 25VNA8.

    The Lennox XC25 appears to be a split-system air conditioner, but perhaps Lennox also makes an air-source heat pump with the same designation. More information here: Lennox XC25.

    P.S. OK, I found another piece of equipment, the Lennox XC25 heat pump (air-source). Here is the link: Lennox XC25 heat pump.

  2. GBA Editor
    Martin Holladay | | #2

    My only hesitation is that you are planning a system with 3 air handlers and 3 zones. [Correction: 9 zones.] That may be necessary -- or it may be overkill. It may also be an indication that you have a poorly insulated house.

    Assuming that your house has a good thermal envelope, and that someone you trust has performed an accurate Manual J calculation, and you are satisfied of the logic behind the decision to install three air handlers, the most important element of your decision comes down to the reputation of your contractors. If all three companies are trustworthy, there's no reason not to install the ground-source heat pump.

  3. Dean Sandbo | | #3

    manual j by energy vanguard.
    reasonably tight
    pretty well insulated
    4 foot overhangs...
    good glass

    actually 3 units 9 zones...
    I am just so surprised that the net cost of geo is lower than the quotes I am getting for traditional...

    Geo is using a directional drilling of horizontal pipe runs.... crazy technology..

  4. Expert Member
    Dana Dorsett | | #4

    The costs of GSHP vary quite a bit by region/location, but I too find it odd that it's competitive on upfront cost!

    Since the 30% tax credit extension that got pushed out for solar and wind did not apply to GSHP, the installers may be sharpening their pencils already. It has to be installed before 31 December 2016 to be able to get in on that subsidy.

  5. Charlie Sullivan | | #5

    That's great that the geomthermal is coming in at a good price. The horizontal drilling is an interesting option for geothermal. Once you are 10 to 20 feet deep, the ground temperature is constant over the year (aside from what happens when the heat pump pulls heat out and puts it back in). Drilling deeper is only to get enough length, so horizontal is just as good, assuming most of it is at least 10 to 20 feet deep. I'd been unsure what the costs for horizontal would be, but apparently they are not bad. One of the advantages, at least in some cases, is that you can drill in multiple directions from a single starting point, reducing costs associated with trenching between well heads. And multiple short wells, plumbed in parallel, can reduced pumping costs compared one ore a few long or deep wells, especially with an efficient pump.

    I don't have direct experience with the waterfurnace 7 series but they look like terrific systems with substantially better features and performance than what used to be available.

  6. Dean Sandbo | | #6

    chiltrix doesn't work for the same reason mitsubishi multi splits didn't work..
    domestic hot water is already ordered and planned for with a heat pump water heater... made that decision before geo came in the picture.. Starting to get excited about geo, no units outside, apparently long life of equipment... (10 year parts and labor on the contract helps)... and I believe my most efficient option.... getting it done by december 31st is going to really push me to get this project done... that is the only part that scares me a little.

  7. Richard McGrath | | #7

    Don't forget to ask for system COP numbers or estimates from these bidders . It makes one wonder if a series 5 water furnace and 3 AHUs would not be a better option .

    Again , with that zoning a Chiltrix might be a real nice fit without the need for any ductwork except for DOAS .

    What will make your DHW ?

  8. Reid Baldwin | | #8

    What was the reason that Mitsubishi multi-splits don't work (maybe you mentioned that is a different thread)?

  9. Richard McGrath | | #9

    Would a water to water option similar to the Chiltrix system be something you might be interested in ? The water furnace series 5 can do both heating and cooling using HTP Ultra thin fan coil units ( same as chiltrix) terminal units without the need for glycol , better efficiency since water gains and releases BTUs more readily . Zoning would be much less of an issue if an issue at all while again removing ductwork from the equation . Still qualifies for the incentives less work , better overall efficiency , room by room control and comfort control . Probably less expensive also .

  10. Dean Sandbo | | #10

    Smallest ductless were oversized for many of the applications... Mitsubishi rep said they are really hoping to come up with a 3k head... this would really help.. Really wasn't crazy about having a bunch of ducted low static pressure units around either.. Really looking for simplicity and efficiency , combined with an experienced installer...

  11. Reid Baldwin | | #11

    If minimum head capacity was the problem, I am surprised that you say Chilltrix would have the same problem. They have fan coil units with around 2Kbtu/hr capacity (with 95 degree water). How do the air handlers you have in mind solve this problem?

  12. Brian W | | #12

    Richard - how would this Waterfurnace / HTP Ultrathin system work? Do you still need a ground loop? Sorry to jump in on your discussion, but it peaked my interest, along with the Chilltrix system. We are currently evaluating a Mitsubishi mini split system and are in a similar predicament with the sizing of the units and worrisome costs of the system.

  13. Dean Sandbo | | #13

    ok... so this is all new to me, what I was planning on was three 3 ton water furnace 7 units. each one zoned 3 times....

    So, I would still need the water furnace units, but instead use the ultra thin units in each zone (or room) instead of ductwork? This is very interesting....

  14. Richard McGrath | | #14

    Brian ,

    Chiltrix is a nice system . It does require a glycol / water mix however which makes the fluid pick up heat less readily as well as distribute it less readily . Glycol mixtures are also more viscous requiring more power used by the circulators . On the W/W system circulating power is reduced along with a higher fluid Delta or reduced flow rates . Chiltrix uses a narrow Delta for their system fluid which is thicker thus why it requires more power . While the GSHP W/W system still requires Glycol on the source side there is no requirement for that HTF on the load side making the whole system efficiency much better .

    Dean ,

    3 , 3 ton units is kinda crazy for a house such as yours , I think . Zoning with ductwork also adds a level of expense and complications thus cost . 1 properly sized series 5 , a buffer tank and the appropriate number of heat / cool FCUs is a no brainer . Remember , one 3/4" tube can deliver the same BTUs as a 14 x 8 duct . Zoning is a non issue and ECM circs running on Delta T of the actual fluid is foolproof , damn near . As long as that loop field whether horizontal or vertical is properly sized .

  15. GBA Editor
    Martin Holladay | | #15

    Here is a link to an article with more information on the Chiltrix air-to-water heat pump: Air-to-Water Heat Pumps.

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