South Dakota Geocomfort Compass XT review

Discussion in 'Geothermal Heat Pump Testimonials' started by wyatt, Oct 27, 2020.

  1. wyatt

    wyatt New Member

    I installed a 4 ton GeoComfort Compass XT (water to air, package) in September 2019, so after a year with it, here is my evaluation.

    The system replaced a 3.5 ton Carrier ASHP with a 4 ton LP backup furnace. That system was good to keep my house (3800 finished sq ft, 2003 construction) heated down to around 10-15 degrees on electricity. But, the heat pump was 16 years old, nearing the end of it's life, and the furnace needed some work to make it through another winter.

    The new system was installed with a directional bore loop field. There were 2 main reasons for this. 1) due to the location of the existing furnace, deck, patio, drainfield, directional bore was the only reasonable way to connect the loops with the indoor unit without some major post installation repairs. As long as you have the machine there, might as well do the rest with it. 2) The water table in the ideal loopfield location was/is, barring a major drought, very high. At the time of installation, it was probably 3-4 feet below the surface. 8 ft trenches might have been a problem.

    The loopfield is performing reasonably as far as I can tell. Deep temperature is 47 degrees here according to the maps, and, high/low temps on the loop are 27/67, for a +/- 20 degree range from the mid point. Note, those temps are on the worst days of the year, when the system has been running continuously for hours in stage 2. Loop temp is less a function of what time of year it is, and more a function of the overall load for the day.

    I did a lot of analysis comparing my previous system with a replacement system prior to making the decision to make sure I could justify the upfront expense. Having had the system for a year, I think it will come out at a wash vs the previous system. Of course, in the end, that will all come down to where interest rates, LP prices, & electricity prices stay over the next 10-20 years. Where I messed up in my calculation was neglecting pumping costs. The spec sheets say that the power drawn does not include pumping costs, but I missed seeing that. So, where the spec sheet says it should draw 3.05-3.10 KW, I see the full system is actually drawing closer to 3.8KW. It might not all be pumping costs, the spec sheet allows that the system might run +/- 15% from the specs, so, combined with the pumping costs, that would cover the difference. It's not a lot, but it's enough to make the difference between profitable change vs break even.

    There are two saving graces that I believe are keeping me either at a wash or slightly profitable. 1) With an all-in-one electric, the fan runs of the same 240v circuit as the compressor. With an ASHP + furnace, the fan runs on a separate 120v circuit. The effect of that is, I pay the reduced heating rate for the fan's electricity in the new system. That's a $.03/kWh savings on fan electicity. That adds up. 2) The desuperheater is thankfully producing a lot of hot water. More importantly, it's producing it with that reduced heating rate electricity, which ends up making it even cheaper (that rate would not be available with an electric water heater). If I didn't have the desuperheater, there's no way this system would justify it's installation cost.

    Other, non-dollar related differences.

    The different arrangement of an all-electric vs HP + gas has caused some problems. In the all electric, it's coil then fan, with gas, it's fan then coil. I'm convinced not having the coil after the fan to "smooth" things out has created more/different turbulence in the main duct. That ended up translating into additional register noise. The solution, at least for the worst of it, was to replace a single register's duct with flex duct. Ideally, there'd be a say 1 foot chuck of flex duct in line where each branch comes off the trunk to isolate the trunk vibrations from the register. Of course, ideally they wouldn't have put a 90 degree bend in the main trunk only 6 foot away from the furnace when they built the house, but I can't (afford to) do anything about that now.

    The old ASHP had a lot of ice build up underneath it in the right/wrong winters. Not having to watch that or do the once-a-year ice melting operation in February is nice.

    Propane consumption, being only for hot water (partial) anymore is much more predictable. Not having to watch the propane tank (and remembering to do that) during the annual cold snap(s) in January is nice.

    Gas furnaces (at least the high efficiency kind) have a lot of sensors and stuff to keep from filling your house up with combustion gases and killing everyone inside. Those sensors/systems seemed to be a frequent source of problems in the old system. It remains to be seen if the new system will be more reliable over the long run. Over the short run, it is, but any brand new system should be reliable.

    With a soft-start kit installed, I can run this system of my backup generator. Before, heating was fine (LP furnace), but cooling was a no go if the power was out. Of course, if the power is out around here for an extended time, it usually means "ice storm" and you worry about heat, not cool.

    In short, it's a mixed bag. I can justify it to myself based on the break even costs and some of the non-dollar advantages, but I'm not sure with perfect foresight if I would have went the geo route again.
  2. Deuce

    Deuce Member

    Remember that the Geo system should have a longer service life.
  3. wyatt

    wyatt New Member

    I know, I've used that to rationalize the purchase myself. But given the large standard deviation (variability) in service life on both ASHP & GSHP systems, and the relatively small sample size (my personal remaining service life is around 40 years), I'm hesitant to put much weight behind that advantage.

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