Hello, I am new to this site. My ranch style home is ~1400 square feet. I am located in Alburgh, Vt. The heating/cooling requirements are 48,000 BTU's or 4 tons. My current source of heat is a warm air, LP gas fired furnace. All duct work is in place, although it is un-insulated (I know I need to insulate). I have a drilled 6" diameter well that is 420' deep. The well has a 6" casing for the first 20', the soil to a depth of 12' is clay. The remaining depth of the well (408') is shale. The well is used for a back-up of our domestic water supply. there is a 3/4 HP pump and a 1" diameter plastic line in the well. The head of the well is under my house accessible from a crawl space and an access hole for pulling the pump. My main source of water is Lake Champlain located ~225 pipe' across the road. Several years ago I purchased a 4 ton Carrier Genesis horizontal water source heat pump. My initial thought was to pull the pump and drop 1 3/4" u-bend loop into the well with the existing pump and pipe. My question is, what would the length and diameter of the u-bend tubing need to be to allow proper exchange for a 4 ton system? Would one loop be be enough? Brian
Brian: You live in and on rocks, big deep rocks. Rocks like geothermal heat transfer. A 4-ton heat pump is worth 48,000 btuh. If you buy a big enough pump a single 3/4" loop might work. I have been to VT.
There was recent post talking about Twister loops... http://www.agreenability.com/index-3.html That may get you closer... but I'm guessing not close enough.
A 4 ton heatpump is rated 48,000 BTUs for cooling, but usually has a heating capacity of less than 40,000 Btus/h, and usually extracts less than 30,000 BTUs/h from the loop. The whole thing depends on the energy requirements of the house, how much energy do you take out of the borehole. How much LP did you use last year over a 12 month period. A 4 ton heatpump needs 12 gpm water flow, or 9 gpm at a minimum. 840' of 3/4" pipes with 30% glycol would have 294 ft hd of pressure drop with 12 gpm. At a minimum of 9 gpm you are at 174 ft of hd. Both numbers are way out of the range of a geothermal design which serves a customer well. Sure, you can get a big expensive pump on the back of a truck and try to push that much water through a pipe, but having that pump then be there permanently and pay for the pumping power when the run time is 3,000 hours per year is giving really bad advise to people here. You had issue with understanding of flow requirements and pressure drop issues before, you really need to read up on the physics. Brian, running the twister loops in parallel will get you there from a flow requirement, but capacity is up to your house load. I also don't by the claim of 50% lesser borehole with the twister. The shorter ground simply is unable to transfer heat to the borehole.
I have been in contact with the twister designer for quite some time now. He has been persuading me to try the loops in my area. I am willing to try it, but it needs to be in the right circumstance and with the approval of my customer too. I am hesitant to try it until I do a test install at my own property or a willing customer jobsite. I don't think he is claiming 50% less bore ( at least not with me). He has sold a few 400' twisters to a local HVAC contractor in my area, which I will get a chance to see being installed shortly. reviews to follow.
I met him too. I would not question that the borehole resistance is improved, and in the first days or weeks it works well, but it will deplete the ground around the borehole quicker, due to more heat being extracted from lesser ground. Then what?
It's not that I resist new technology... I have just been around long enough to see a lot of really good on paper ideas fail down the road. With the low cost of hdpe pipe and the cost per foot of drilling going down, it is going to be a hard sell. Eric
You nailed it right on the head Eric. Southern NJ mud rotary drilling per ft. Price makes it hard to justify compared to air rotary per ft. Prices in the northern end of NJ, PA, and NY areas. Another other down side I see is a lot more trench work. 10 fusion joints compared to 2 conventionally.
Dan, Eric, correct me if I am wrong but once you have a drill positioned and mobilized to the job site, and in my case cased down to bedrock, simply drilling deeper is usually not that much more effort.
I am not a air rotary driller. We do not encounter bedrock here. Our drilled holes are not cased at all. Drilling in unconsolidated formations with mud rotary is a bit different from air rotary drilling in rock or overburden cased holes. It's not a huge deal to drill deeper but the longer a borehole stays open with mud rotary, the higher the risk of it collapsing in on itself. In our area, and Eric's area I believe are mostly all sandy soils.
Process, people, profit. I love that line! Mud rotary drilling is wildly unstable by nature. The larger the diameter and depth of the hole, the risks go up, production goes down. We need to get in and out of the hole quickly and efficiently. Increase depth and diameter and the cost per foot goes up. Eric
