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Anyone have a geothermal heat pump system?

Post in 'The Green Room' started by BIGDADDY, Oct 6, 2012.

  1. schlot

    schlot Minister of Fire

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    I'm very surprised at this, but perhaps where you are, the average winter time temps are not so extreme. I had a air heat pump and with the colder nights, the heat strips were used extensively, which is a major cash drain. Air systems are best suited for moderate temps.

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  2. begreen

    begreen Mooderator Staff Member

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    You have to run the numbers. In our area a modern, 2 stage, high HSPF air to air heatpump made sense due to a milder climate and long shoulder seasons in the 40's. In other areas geothermal may pencil out a lot better. It's also worthwhile to explore the possibility of installing super-efficient mini-splits HPs when comparing pricing. Some units are amazing performers functioning without the heat strips down to about 0F.
  3. schlot

    schlot Minister of Fire

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    As said above, the air systems can be very competitive in moderate temps.

    A well insulated house is great no matter what heat source.
  4. begreen

    begreen Mooderator Staff Member

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    +1!
  5. schlot

    schlot Minister of Fire

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    Do you know why they decided to put the second pipe 9' below the top pipe?
  6. DickRussell

    DickRussell Member

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    central NH
    I have a two-ton, two-stage Climatemaster water to air heat pump. The gross square footage of the house is nearly 4,000 sq.ft, in central NH. But this house is superinsulated, so the heat load is very low in the first place. The heat load spreadsheet I built for the house seems to be on the conservative side. Although last winter wasn't particularly severe, with only a few nights getting below zero and something like 17% fewer heating degree days for the heating season, the heat pump never had to go to second stage to keep the house at 70. As best as I can figure, by backing out shoulder season electric bills from the heating season total bills, it appears that the whole season cost me around $500 last year. I may have better numbers over the upcoming season, as I have since installed an hour meter on the heat pump.

    The installation is SCW (Standing Column Well), which uses well water as a heat source; the slightly cooled water is returned to the well to regain heat from the rock around the borehole. I knew that the heat load would be small, and the house would have a new well drilled anyway for a water supply, so going geo made sense for us. We really didn't have to drill any deeper than needed to get added water supply for the house, and once they got to that point, at a depth that would support a three-ton system, I told them to stop at the end of that length of drilling pipe. So my ground connection actually will support more heat load than required. In general, for a SCW system, around 80 feet of water column is needed per ton of heat load.

    Ground water in the northeast usually is plentiful and of good quality, so that for a new house in this region, which ought to be built to be very tight and well insulated, a "geothermal" (ground source heat pump) system can make a lot of sense in a rural area if a water well is needed anyway. If the drilling is an extra, or if the house isn't particulary energy efficient, then geothermal is a harder sell. In any case, designing a geothermal system must be done carefully. With a conventional system, oversizing doesn't cost much more. With Geothermal, every extra ton of capacity costs quite a bit. One could argue that for an existing house, the money might be better spent on improving the outer shell, to reduce the load, rather than look for a cheaper source of energy to waste.
    sloeffle likes this.
  7. johnny1720

    johnny1720 Member

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    Because the area was not wide enough and they were worried about encroaching on the right of way for the town road. Had we known the highway superintendent had resigned the night before we could have chanced it. They had done entire systems like this before with good results.
  8. sloeffle

    sloeffle Member

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    I got around a 9k quote to install a Trane heat pump and propane furnace. The geo ended up costing me a little bit more than the Trane unit after government, electric coop rebates and selling my propane tank. I did pay for my own ( no HVAC contractor markup ) excavation. I also paid for the system in green backs which helped with the price. ;) A lot of folks are getting their outside AC units stolen so it is nice to also know that I am not going to come home from work and have a missing heat pump unit.

    If I remember the correctly the cost difference would be made up in a few years. I added in hot water generation into my figure also. I do have a wood burning furnace also so I usually run that when it is <25F out which helps with electric usage and keeping my loop temps up.

    Scott
  9. begreen

    begreen Mooderator Staff Member

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    ;ex:eek::oops::mad: I don't like that neighborhood.
  10. daveswoodhauler

    daveswoodhauler Minister of Fire

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    Interesting post. For those folks that have a geothermal unit installed, can you give us an idea of the following:

    Size of House?
    Climate?
    Average KW useage/year? (Pre/post useage would be helpful)

    Would be good to get some real time data from other Hearth members that have these systems installed.

    Thanks.
  11. woodgeek

    woodgeek Minister of Fire

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    Ideally folks would know their seasonal BTU loads, and kWh usage for the geo to compute a COP. A recent study found that many geos were giving COPs that were way below spec because of installation issues.....like 2.5-3 rather than 4-5. OF course, many badly installed ASHPs are giving COP~1.5 instead of 2.5-3.
  12. johnny1720

    johnny1720 Member

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    Size of house, 2500 Square Foot built in 1856, I have been gutting and insulating room by room. I am over 1/2 done. I have also installed all new windows and spent considerable money and time caulking and sealing.
    Normally 7300 heating degree days, according to the manual j that was performed i need about 48k btus per day. I have seen it as cold as -20 in January for days on end. I have seen it as warm as 90 for days on end in July.
    I have only had the system for 9 months and I can give you totals of KW usage for the last 4 years from January to October.
    2009 January to October KW Usage 10075 $1,353.78
    2010 January to October KW usage 10230 $1,365.67
    2011 January to October KW usage 8692 $1,217.62
    2012 January to October KW usage
    10816 $1,296.91

    Remember these figures represent 100% of my homes electric usage. Now I dont have to purchase pellets or fuel oil ever again. I installed this unit in February of 2012, I will have better numbers when I run through an entire normal winter.

    For the difference in energy usage each month I could not buy a ton of pellets @ $200. And a ton of Pellets will heat about 1/2 of my house to 75 degrees and leave the rest of the house at 65 degrees. This unit now keeps the entire house at 72 degrees.

    I have seen case studies of homes in my area that were purchasing 1500 gallons of fuel oil @ market price of $3.50 = $5250. They installed geothermal and only seen increases in electric usage of about $1200 per year. So each year they are saving $4000. I just checked the cost of fuel oil today and it was $4.06 per gallon. So it makes that persons savings this year $4890.
  13. semipro

    semipro Minister of Fire

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    One thing I really like about our ground-source heat pump...there's no outside condenser units making noise in the summer or winter.
    Our last house in a neighborhood was situated so that from our rear deck we could hear the outside units running from our house and both our adjoining neighbors.
    schlot and sloeffle like this.
  14. sloeffle

    sloeffle Member

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    1400 sq ft modular with a crawl space. 2x6 exterior walls with decent insulation and windows
    768 sq addition - full basement with R10 insulation, 2x6 exterior walls with spray foam, R50 in the attic, low E argon filled windows

    Climate Zone 5A

    usage.jpeg
    Our house is all electric. We got the geo unit in September of 2011, so that is why you see the big spike. The electric bill over this past summer was cheaper with 2100 sq ft of space and the geo unit vs 1400 sq ft along with a 10 SEER AC Unit. Unfortunately I cannot get the graph from the electric company to show all of 2011's usage.

    Scott
  15. begreen

    begreen Mooderator Staff Member

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    Is the Caddy used to heat the house? If so, how much in the winter?
  16. sloeffle

    sloeffle Member

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    Yeah, we used the Caddy last year to heat the house when temps were below 25 - 32F to help keep the loops temps up on the geo. Last year was pretty mild so I only burned about 1.5 cords. I have 25 acres of woods and hate to see it go to all of the dead ash trees go to waste.

    The Caddy is also nice for when the power goes out in the winter since it only has a 120v 1/3 HP blower motor. The geo unit uses a 50 amp x 240 volt circuit so you would need a pretty healthy ( 15k watts ) generator to run it. Luckily most of the current is drawn at start up. It only uses about 20 amps while running but it uses around 32 amps on start up.
  17. jdp1152

    jdp1152 Minister of Fire

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    Apologies for the delayed response. I came back and typed up a reply, but figure I navigated away before I hit the post reply button.

    A variety of reasons to give here. My house is older and we are remodeling both interior and exterior. Where it is now, most certainly will not be where it is next year or the following year. It's a room by room process of upgrading insulation and decreasing leakage (and modernizing). The only reason we are moving this year on the geothermal system is the 25k loan from Mass Save is not guaranteed in subsequent years and that isn't a risk I'm willing to take. 7 years and interest free on that sum of money is too good to pass up....plus other efficiency upgrade supplements from mass save per year in following years.

    Using typical winters for my area, the supplement will only really be needed 10-30 days a year without improvements. We also have a solar array that provides some of that supplement, though the sooner it is out of the yard the better (trees prevent any rooftop array so the previous owner put one right in the front yard...an eyesore to say the least). This doesn't even take into account I've got about 6 cords of wood from clearing trees away from the house and probably another 3-4 from clearing a place where the drilling rig will put the wells, and probably another 6 from clearing some additional yard (yard is full of huge Ash, Maple, and Oak trees). I have another 2800 sq feet of basement that will eventually be finished and only heated through wood or pellet supplement when usage requires it (have a huge woodstove down there that ties into the hot water baseboards, but would prefer not use a non EPA stove). I do a fair amount of financial modeling for work and put together a slew of monte carlo simulations (using @Risk software and an optimizer add in to Excel) to cover my bases on cost of electricity/temperature/and a few other variables and it just doesn't make sense for me to pay considerably more up front when models factoring uncertainty into the mix say otherwise.

    Long winded answer to say that I've put a lot of thought into this, talked it over with 6 contractors by phone, 3 contractors in person (all of which I am soliciting drilling separately to get another 3 opinions) and with all things accounted for, it doesn't make sense.
  18. jdp1152

    jdp1152 Minister of Fire

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    Where do you live in the Northeast and who did your install?
  19. woodgeek

    woodgeek Minister of Fire

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    I hear ya. When I switched from oil to an AHSP in 2008, I made the sizing call on the new unit.....going for a 4 ton single speed conventional split (cheap). AS in your case, I was in the process of dropping the heating load. On install, the unit only carried my 2400 sq ft down to a disappointing ~29°F (with help from ~4000 BTU/h standby loss from the old boiler). That figure is currently down to ~21°F (w/ the boiler scrapped), after a few years of DIY insulating and airsealing. Our average january high temps are 32°F, lows are 25°F. In my own experience, sizing to january average lows (or a tad under) is pretty optimal---there is conflicting advice out there that says otherwise.
  20. Bad Wolf

    Bad Wolf Minister of Fire

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    Dick, why do you "backout" the shoulder season costs in order to get your heating costs? Can you translate your cost to KW?
    Also what is the current draw and how much would it run on the cold days? i.e. how many kilowatts/day
  21. johnny1720

    johnny1720 Member

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    I live in Allegany, NY in Western New York South of Buffalo, NY.

    My installer was Jim Snyder, Domestic Energy Systems in Salamanca, NY
    http://www.domesticenergyresources.com/
  22. DickRussell

    DickRussell Member

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    I don't have separate metering on the heat pump, or the well pump for that matter. Having an hour meter running now, tied to the compressor contactor, will be better, although I'll have to rely on the mfg tables on how much power the unit draws under my conditions, and I'll still be guessing at power draw of the well pump. OK, that's an educated guess, based on that mfg's pump curves and an estimated pump efficiency. Until now, what I actually did was look at the KWH numbers on the electric bill. The NHEC bill gives KWH usage by month over the prior 12 months. Then I multiply by $0.14/KWH, which I got by subtracting the fixed account charges from the bill and dividing by KWH for that bill, to get $ for each additional KWH.

    I don't know what the startup or continuous current draw is for either the heat pump or the well pump. The well pump is VFD, so is supposed to be a "soft start." The breaker for the heat pump is 20 amps, but then it's only a two-ton unit. There is a separate 40 amp breaker for the emergency electric strips, 1 and 5 KW.

    I don't know how many hours it runs on a cold day, but now with the hour meter installed I could look to see over a day or month's time this coming winter. I do know that the heat pump doesn't run continuously on cold days, at least not the coldest we had last winter. It just runs longer each cycle as the weather gets colder. So far, it has been keeping the house warm running part time, and I haven't seen it go to second stage to do that. I imagine in a more normal winter, when we do get some nights at -10 to -15 F, with following days only in the + single numbers, then maybe it will need second stage to keep up with the heat loss, but that's what it is designed for.
  23. sesmith

    sesmith Member

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    home_elec_usage.jpg
    Here's a link to mine with some pics:

    http://www.hearth.com/talk/threads/new-geothermal-install.75486/

    Here's also a chart showing our electrical usage 2010-2012. The geo system went in 10 / 2011. In the previous years we went through around 6 full cords of firewood and around 50 gal of fuel oil. In years that we heated with fuel oil we used to use 700-800 gallons. Last winter we used the geo system only. FWIW, the last 2 months of this year, where our electrical use climbed a little, was due to the fact that our son was living with us...nothing to do with ac load or geo system running. I figured the geo system upped our electric bill around $300 last heating season.

    One other note. The high usage in Jan 2010 was common back then. By Feb of that year I had chased down excessive usage with a killawatt meter. I was able to cut back our usage by 1/3, mainly by replacing an ineffective dehumidifier and super-insulating our horse stock tank, which drastically reduced electrical use of the stock tank heater. So basically, we're able to heat our house now with the amount of electricity I used to waste.
  24. Mr A

    Mr A Minister of Fire

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    With this sort of thing, there should be absolutely no questions. American taxpayers have already contributed trillions of dollars to get this type of alternative energy going, to reduce dependence on foreign energy,.From what I have researched myself, the constant temperature underground in the mid to high 60's is optimal to pump refrigerant through, to run a heat exchanger much like an electric heat pump, that can also provide air conditioning in the summer. I have a larger than average corner suburban lot. Trenching is not an option. Vertical? Maybe, but drilling costs are prohibitive. there are do it yourself kits available. You still need to drill or trench. Expensive because hauling and operating the machinery required is not cheap. Then there is this guy. I like his simple and innovative approach to solving problems. Once in place,. you wouldn't need much wood to burn if any, to keep warm in winter.

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