Virginia 2nd winter of hydronic radiant geo

Discussion in 'Geothermal Heat Pump Testimonials' started by frankz, May 2, 2017.

  1. frankz

    frankz New Member

    For sure last week was the last heating day of the season, so I’m happy to report a 2nd winter of completely trouble-free geo (see Total cost was on a par with last year, about 2940 kWh for the season, or $320 at 11 cents/kWh. In October I topped up the flow center with about a quart of water and flipped on the breaker, that was it. I find I don’t even have to bleed the radiators anymore because with the lower geo temperatures, air doesn’t accumulate there.

    This year we had a couple of consecutive 5°F nights, and we still didn’t need backup heat, although the system did run for 3 hours straight, so that is probably about the limit of cold it will handle. The radiators were topping out at about 118°, with LLT at 125°, which is the recommended max for the unit. HeatingSystem.png WaterTemps.png

    One big change was addition of 15 more solar panels in the backyard last June, for a total of 32. The tilt can be adjusted seasonally, using a crank. Fortunately, here in Virginia we can still get straight net metering. We basically break even over summer and fall and go into deficit in the winter, but build up a small surplus in the spring. Overall, we use about 10,000 kWh a year while the panels generate about 7,000 kWh. That includes about 1500 kWh for an electric car and another 1500 kWh for air conditioning with an old 10 SEER air-source unit. I plan to retire next year so driving should be cut by half at least, and planned conversion of the A/C to geo should cut that by at least half as well. So with a little more insulating maybe I can get to zero net usage. 000_0780.JPG

    But never mind the cost, we love our radiant geo heat. My wife finds the purr of the compressor very soothing, especially compared to the periodic ka-boom of the old oil burner.

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    Deuce likes this.
  2. Dinnerbellmel

    Dinnerbellmel New Member

    That's great frankz...another happy Geo user!

    It looks like the trees are shading some of your solar panels. Time to get out that chain saw!?
  3. frankz

    frankz New Member

    The shading actually isn't as bad as it looks, the contractor estimated 27%, and about half of that is basically untouched mature forest in the neighbor's yard that shades it after 4 PM. We did quite a bit of clearing and trimming to put in the array. We could do more, but a lot of expense (mature oaks and maples, so I can't do it myself) for a little more power.
  4. ChrisJ

    ChrisJ Active Member Forum Leader

    Is your Water to water HP warm water only? Doesn't reverse for chilled water?

    You mention a split HP for a/c. Cold water to an air handler from the same HP would be less work, I would think.
  5. frankz

    frankz New Member

    Yes the heat pump is reversible and I did consider using it as a chiller for A/C. But from the numbers I looked at there is a significant loss of efficiency in using water as intermediate vs. a straight split configuration. Plus if used as a chiller I would probably want to add anti-freeze in the load loop just because it's a part-DYI system and the consequences of a freeze in the exchanger could be catastrophic. So then anti-freeze would inevitably get into the radiator system with each switchover, increasing viscosity and decreasing efficiency. Unless I drained the heat exchanger each time, which could get pretty messy. The 2nd geo unit was only $2K, and since I had to replace the air handler anyway, it wasn't really that much more work or expense. Anyway, the work is now almost complete and might be ready for a test today. As noted, the contractor is sealing and insulating all the ductwork as well as eliminating some hard right angles to improve flow, so I am hoping for a pretty substantial increase in efficiency.

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