Been wanting a geothermal heatpump for a few years and finally see the light so I''m getting down to more design questions. I have two wells on my 1.2 acres. One's an old brick hand dug ground water well that's 36 feet deep and 30" in diameter. At rest it's got about 30 feet of water in it. I'm in the process of revitalizing it by keeping the water level down about 20' or so. Between it and my other well, a much deeper traditional 8" well that hits a different water table much further down (don't know how deep but it's got a lot of sulfur that this old ground water well doesn't. Anyway, if the deeper well can pump at least 5-10 gpm I know I can go open loop but was wondering if it would work to put a slinky closed loop down into the 30" well and let it take the heat/cool directly from the water. What I don't know is would there be enough water in it to act much like a pond. I figure I could hook up a thermostat controlled pump that would pump out some water if it got too warm or too cold... What I don't know is how much heat would be transferred into or out of the well through the bricks. Would it be enough to keep the water temp stable enough to support a closed loop? Is there a formula for computing such a thing. I PS: I'm in southern Michigan so it gets pretty warm.. in the summer and cold.. but not MN cold in the winter. I'm thinking about 3 - 3.5 Tons would do the job for my 1892 farmhouse... 1850 sq feet.. with double pane windows and good attic insulation and insulated fiberglass siding. PS: In really cold times, I have 170k BTU worth of coal stoker stoves and a propane FA system. Any input on the best way to approach these wells and whether you think my closed loop idea might work would be appreciated.
Hi and welcome! You have a lot of questions and a rabid curiosity so I will try and help. Lets start with your old house. I live in a old house with geo and they can be problematic. The load of your house is the key to this puzzle in front of everything else. Call a pro and get a blower door test done on your home. This will determine the load your house requires, represented in tons. With that info you can size a system to meet this load. After you get the results of you blower door test, keep in mind that the best money you can spend on any home is on the envelope. That means spending money to tighten up and improve on your insulation prior to spending money on tonnage. Short answer is the less the load the cheaper it is to heat or cool. Geo or conventional methods. if you have x to spend and your envelope leaks, fix your envelope first. Hope this helps Eric
Good advice and something I've been doing in the few years I've owned this place. Owning one, you know it's a journey more than a one and done. When I got the place it was all single pane windows and not good ones at that... with limited insulation in the attic. First winter (polar vortex) the FA system died and we'd only gotten half the windows done. Anyway, since then I have invested in lowering my heating costs by taking these initial steps. 1. I purchased the existing leased 500 gal propane tank from my supplier so I could shop around and buy cheaper propane. then I bought a second tank (500 gal). I also bought two 85k BTU coal stoker stoves.. one for the basement and one in the living room. This filled both tanks in August when propane was only $1.09 and bought 3 tons of coal. Made it through the winter and have enough propane to wait for the right price this summer. With two heat sources (propane and coal) I can use which ever is cheapest per BTU as either system is capable of heating the house independent of the other. I've also added about 9 inches of blown in insulation into the attics and finished installing new double pane windows throughout. Still got more to do to really seal up the place but, as I said, it's a journey. I bought a geothermal hot water heater (they're awesome and really save vs electric only) and this summer I'm going to install a heat exchanger on my basement coal stove and a pre-water heater holding tank which I'll pre-heat with the coal stoker which is on all winter. Will have almost endless hot water at almost no cost... and in the summer, I can heat the holding tank from the geo unit once it's installed. So, I am working on the envelope and will continue to improve it over time. Right now I'm trying to imagine the possibilities of how best to install whatever unit I decide on and the question of how to best create the heat exchanger is what I'm working on right now. At first I just assumed I'd do the traditional 6' ditch method but the more I think about these wells as possible assets, the more I'm leaning in that direction. Seems to represent a considerable savings if they can be used affordably. Any thoughts on the well situation?
Your wells will have a capacity, your house will have a load. If those two numbers agree with one another it is feasible. Eric
Does your 8" well have a pump in it and does it supply the water to your home? If not, you might consider dropping a couple of "U" bend loop pipes down it. Depending on depth, that might be worth a ton or more of capacity. That along with a couple of custom made coils to drop down your dug well might get you close to 3 tons of closed loop capacity. Maybe add a small (1/6 HP) submersible sump pump to your dug well if it has good ground water makeup. Have the pump kick on based on water temperature to dump a few gpm of the cold water out of the well and allow fresh ground water to flow in.
