Geothermal heat pumps anyone?

[OZisKTB]

I have a LEED for Homes house, 3-years old, so it's well insulated and tight. 2400 sqft single story, and conditioned crawlspace same size. Situated near the top of a mountain (2600' is high for VA). When I sunk two 300' vertical wells for my geothermal (1.5 tons), I thought I would not need aux heat. My system kept locking up when it wanted aux and didn't get the boost in btus. Once locked, it would run fan, but not heat, until I recycled the breaker. Tried to use my sealed propane fireplace as aux, but couldn't activate with geothermal thermostat. Checked with a number of pros, they all said it was not a capacity problem, but that all geothermal units are more efficient with some secondary heating source. Mine was a problem in the programming, that I could not get around. Added electrical aux, and its run trouble free for a couple of years. Rarely pulls aux or emergency heat, no trouble heating the house or raising the temp when we've been away. Not as economical as I expected, but good enough. I like the low tonnage, I'm able to keep both living and crawl space very dry.

As the last guy on the power line inside a National Park, power outages are not uncommon. With 20KW propane generator, I can run the house, geothermal, and even heat my hot tub without circuit management. Would have preferred 15KW, but when I was purchasing Kohler dropped that capacity (14 or 20Kw) and I had to choose fuel efficiency over circuit management and I went for convenience.

I have a desuperheater circuit installed to preheat water for my on-demand Kohler water heater. Since I cool so rarely, I'm not sure how much this contributes. My plumber had no experience with this installation, and HVAC weren't much help. I think it works as advertised, but the EnergyStar inspector thought my 50gal resorvoir was too small to capture all of the heat that the pump was providing. Will sort out optimizing this one day.

 

[wngsprd]

We installed our geothermal system in 1998 when we enlarged our house - 3 horizontal loop trenches, and a hot water heater connection. With a larger house to heat/cool, I didn't have ability to compare to the old heat pump, but always felt the increase in electricity was small for the extra square feet.

I had to replace the unit in 2011, and went with a ClimateMasters two stage compressor, with aux heat. Electricity bill took a nice dive, since this newer system is more efficient. However, we had to have some duct work modified to fit this unit. It works great. We also heat with a woodstove, so having multiple zones, and the two stage compressor helps heat the rooms economically that are farthest from the central woodstove. The return vents are near the woodstove, so it also helps to recirculate the air from the room with the stove. Sometimes I just run the system on fan only.

I order filters from a website vendor that I'm very pleased with - FurnaceFilterWarehouse.com - the unit takes two 2 inch filters that are 20X20, so can't find them in the usual stores - I bought a "case" of a dozen recently to get a great price.

 

[techman]

I have a 2700 sq-ft home with 2 ClimateMaster hp's. A 2 ton for the first level and a 1.5 ton for the second floor. They are now 8+ years old. Great heating and cooling. I have backup elements, but neither have ever been on (2 ton unit does not have the control line hooked up to it). I also have a 1.5 ton air hp for a small addition, which was built after I installed the gshp units. I have a 10KW diesel backup genset and I can run all 3 units if the power fails. No problem. My ground loop is a 500' trench averaging 5' deep.

2+ years ago I added 9.2 KW of solar. Now, with 4 adults living there, my average electric bill is $ 1200/year. It is an all electric home with pool.

Paul

 

[rafski]

I have a 2000 sq-ft solid cedar post & beam home. I bought an old (1972) used backhoe and dug up over 400 ft, 3ft wide x 6ft deep Used the closed coiled method with a 3 ton water to water heat pump. At the same time I installed above the floor radiant heat tubing through out the house with new 3/8" hardwood flooring. I had oil base board heat and hated it. This system is 350% efficient quiet and with the radiant floors I have even heating with no drafts. My first winter heating cost was $300 to $400. Runs a lot at night when it gets below 10 degrees. Never used a backup for the 7 years I have had it. I usually keep it at 70 degrees and may loose a couple degrees on really cold nights, however it comes back in the morning. The geothermal coupled heat pumps are a perfect match for radiant flooring since you don't have to mix cold water with it like with a boiler to keep the floor temperature down below 120 degrees. Love the system! I am in upstate NY and I see you are in NC, you should have no problem that far south.
Rick

 

[LAFarm]

Have a 2.5 ton ClimateMaster 2 stage. It replaced a 20 yr old 2 ton single stage ClimateMaster earth coupled heat pump. Works great and highly recommend the earth coupled heat pump. Vertical loops take up less area, but in some cases are more expensive than horizontal trenching. Have worked over 20 years installing and maintaining over 3900 ClimateMaster units in housing units on a Military base. Proper ground loop sizing is extremely important. If you have any doubts about the load calculations, install additional ground loops. Even if you are confident of the calculations, install additional ground loop footage!! If ground loop is undersized, you will have performance and efficiency problems. Make sure you get the desuperheater option. This transfers waste heat to the water heater tank and saves energy there as well. Am very satisfied with my unit. Can't really tell how much difference the change from a 15 seer to a 22 seer made to my utility bill since we also have a 15 kw grid tied solar system and have excess kwh each month.

 

[techman]

Vertical loops take up less area, but in some cases are more expensive than horizontal trenching.

That's an understatement. Horizontal loops are always much cheaper, but usually the homeowner's lot size is the factor.

 

[MacLawn]

Thanks for this thread. I've been researching geothermal a long time. My current heat pump, a high $ carrier two stage is now 11 years old, śo when it goes out, I'm getting estimate. Probably a WaterFurnace.

 

[fordmantpw]

That's an understatement. Horizontal loops are always much cheaper, but usually the homeowner's lot size is the factor.

Vertical isn't as much higher as you think. I asked before putting ours in our new house. We have 48 acres with plenty open, so the spaces isn't an issue. The cost, to do it right, was only around $1k more to go vertical. That doesn't count re-seeding all the ground they tear up, waiting for it to settle, etc. Also, the vertical is more efficient (in our case) as it contacts water, and that is a much better heat transfer medium than just dirt.

 

[Country Geek]

Since I started this thread and it's now popped up I'll update that I've decided to do the Geothermal system. I'll be putting in a 5 ton Climatemaster Tranquility with a trenched ground loop (I have plenty of land for it .

One additional benefit that I hadn't figured on is that this unit is a single package, so it will all be under the house with no outdoor unit. I appreciate that especially now, sitting on my deck on a beautiful day typing this while my soon-to-be-replaced outdoor unit grinds noisily away.

 

[fordmantpw]

One additional benefit that I hadn't figured on is that this unit is a single package, so it will all be under the house with no outdoor unit. I appreciate that especially now, sitting on my deck on a beautiful day typing this while my soon-to-be-replaced outdoor unit grinds noisily away.

That's one of my favorite things about our GSHP. As I walk through the neighborhood in the morning, hearing the AC units kick in reminds me how much I don't miss that sound.