Ok, I have read past posts, but they seemed to turn into professional slinky vs 6 pipe wars. I have 10 acres, what would you recommend for a large system I do myself. I am a newbie, but to me, it would seem almost easiest to take a trencher and just make long ass loops, or zig zag them in all over. There is no frost line here, so I just figure as deep as you can easily trench ? I can use a backhoe also if needed as I will have to have one on my septic. It is just a matter of more hours on the rental.
slinky would work fine, or 2,4 or 6 pipe in one trench. I think the key is to go non-pressurized, and header inside, so you don't need outside fusion and a surge cart. Now Texas is a heating dominated climate....are you sure you don't want someone to put an air source heat pump in? what is your load? heating and cooling degree days? soil conditions?
Thank you so much for your reply. I agree to me non pressurized header seems easiest / most economical in my situation. An Air Source Heat Pump ? I that not just a conventional A/C system with a heat pump for the few days a year we need heat ? Description: Fahrenheit-based 5-year-average (2012 to 2016) cooling degree days for a base temperature of 65F CDD % Estimated Jan 24 1 Feb 39 0 Mar 92 0 Apr 193 3 May 301 0 Jun 503 2 Jul 578 0 Aug 606 0 Sep 449 1 Oct 251 0 Nov 70 7 Dec 39 0 Total 3145 1
Description: Fahrenheit-based 5-year-average (2012 to 2016) heating degree days for a base temperature of 65F Station: Granger, TX, US (97.43W,30.74N) Station ID: KTXGRANG4 HDD % Estimated Jan 507 1 Feb 369 0 Mar 229 0 Apr 79 3 May 28 0 Jun 1 2 Jul 0 0 Aug 0 0 Sep 6 1 Oct 62 0 Nov 259 7 Dec 428 0 Total 1968 1
I think what DJ was / is getting at is that your Texas climate is cooling-dominated, in other words, 80+ percent of the annual HVAC load is air conditioning. Nearby Austin TX 99% design temps are 28 winter 98 summer - very mild winter but long hot summer. My own area is Jax, FL. 99% design temps are 32 winter 93 summer. We have worked out that, absent direct oceanfront exposure, conventional air source heat pumps offer lower lifetime cost of ownership over water source, especially with the demise of the tax credit. Stated another way, the additional up front cost of geo will likely not be recovered via energy savings over the life of the system in many warm climates. The oceanfront exception has nothing to do with energy efficiency, but instead the short life expectancy of air source outdoor heat pumps exposed to salt air. Geo lifetime cost of ownership advantage comes from not having to replace system every 5-7 years as is the case with air source.
Thanks Curt. You hit the nail on the head....Loops will heat up quickly so no energy savings can be realized compared to air source heat pumps.
So in a cooling dominated climate what % would the loop field need to be increased to not heat up and affect the efficiency? Would a vertical loop be better in this case?
There is no easy answer to your question. The type of loop and the footage of pipe installed all comes down to economics. If it is cheaper to dig a lot of pipe in the ground than it is to drill then I would dig. If it is cheaper to drill than to dig, then drill. This is where a pro in your area can really help steer the design in the right direction. It all starts with a correct load and the feet of pipe needed to meet that load. Eric
Again, what is your heating load and cooling load? Weather data does not help, they are in a database. What is needed is the amount of heating and cooling your house needs. For example, if you have a lot of southern facing windows and not so good insulation, your cooling load is higher, meaning you will reject more heat into the ground loop, so you need a larger loop.
Gotta getta good Manual J! Our strategy for beachfront geos is to request the well sub to bore two wells into the Floridan Aquifer about 50 feet apart. Year round temp is 71 - 74. A dedicated variable speed pump with a pressure controller setting pump speed drives water from one well through the geo(s) to the other well where it is reinjected. If they want irrigation water, we ask that they pull it from the reinjection side using a pump dedicated to that purpose only.
Geothermal is fighting double issues to become popular in highly cooling dominated climates. (The deep South!) As mentioned before, we need almost double the loop ground contact as up north, and dealing with warmer ground temperatures to boot. Our loops actually grow in temperature for few years until it stabilizes. This means the ground loop installation becomes much more costly, and the cooling operating savings are not near as much as heating savings. Makes it a tougher sell, but most consumers are quote satisfied with the end result. The unhappy ones are usually ones that were sold a bad loop design that is overheating.
