I'm a long time lurker and enjoy reading about problems and solutions from folks with far more experience and knowledge than me.  I'm a HVAC contractor relatively new to GHP's (3 years) with 10 successful and well performing installs.  My AO averages about 2500 HDD and 3500 CDD so I'm definitely cooling dominated but we have our share of cold weather in the winter.

From the very start, my supplier for Climatemaster was adamant that I only install vertical loops since horizontal loops will not work here in Texas.  From my studies, the IGSHPA book advises that any loop design will work as long as it is properly designed although some may not be practical due to loop length and excessive pumping requirements.  I'm pretty fluent in soil language as I also install On Site Sewage Facilities (septic systems) and for my license I had to be able to identify soils as far as clays, silts and sands. 

With customer money getting tighter every day, and drilling not getting any cheaper, last June (2011) I decided to experiment on myself and install a horizontal loop system in my shop and compare performance with my home system which has a vertical loop.  Last year was a record breaking drought with 45 days over 100 degrees.  For cost purposes, I just installed a 2-ton system.  My design and specifications, to keep power pumping requirements reasonable and the loop under 90 degrees required 2000 total feet of 1" pipe buried 7 feet deep.  I could have reduced the pipe length if I went down to 8 feet but I am in an area of huge rocks and I didn't want to break the excavator on a "free" project.  The system uses only one -99 pump.

All but the last foot of soil was dry and did not tamp well back into the ditch.  I started the system at the end of June and ran it pretty hard all summer (about 10-12 hrs/day) and my loop temp peaked at 96 in late August.  This spring we finally got some decent rain and the trench settled up to two feet in some areas so I know that the soil was not originally consolidated well around the loop piping.  This year, I am running a very consistent loop temp of 86-87 on the horizonal and 78-79 on the vertical so even though the horizontal is not as efficient, it appears that it is transferring heat better.  We also have not had rain for about 45 days and temps over 100 for the past 2 weeks.

I'd like to offer customers the option for horizontal loops due to 1) Less upfront cost with slightly less efficiency, 2) Since I already have the equipment, no third party drilling company and we make the money off the excavation and can control the schedule.  I'm considering installing a WEL once I find a way to uplink the results to my wireless since the shop is far from the house to validate my results to potential customers.

The photos show my current EWT on the horizontal loop, dry and dusty conditions here, the single pump and the loop field after I graded it.

Does anyone have any words of wisdom and sage advise for the newcomer.  I want to offer a good product to the customer and do not want to install something for a customer that does not work as advertised.

I would say you are on the right track.z

As I recall, there is evidence that some vertical loops suffer more from long term temperature drift. Would be nice to consolidate the soil within a foot or two of the loop immediately vs waiting a year. And/or address the susceptibility to drought. If you are free to grade it as you want, maybe a slight V shape to increase moisture around the loop.

Posted By Dig_texas on 04 Aug 2012 10:04 PM

....From the very start, my supplier for Climatemaster was adamant that I only install vertical loops since horizontal loops will not work here in Texas..... 
....Does anyone have any words of wisdom and sage advise for the newcomer.  .....

I would say that you have shown horizontal is viable in your area.

Definitely play to your strengths. If you can hold EWT to sub 90 in a climate whose air temperature is routinely 95-100 you have something to offer. Your experience supports the common experience that horizontals need time and rain to properly consolidate. I wonder if heavily watering the first foot or two of backfill would improve initial performance.

I'm in Jax, FL and have never attempted a horizontal loop. Our fear is that our sandy soil will fail miserably to transfer heat during drought conditions. What soil types do you have?

Our summer outdoor design temperatures are in the low 90s, not as high as most of Texas and the southwest, but our latent loads are higher. Our heating season is minimal, <1500 HDD so geo's winter advantage is less. It takes a lot of bore to hold EWT much sub 90, and if EWT approaches 90, the efficiency advantage over air source is slight if any.

Open loops (EWT 71-74) work if water quality and quantity permits (I have one in my own home), and I'm in the midst of commissioning another.

Geo for us is a niche product whose primary advantage shows up at the beach where air source units die an early death from sand and salt inhalation.

Welcome aboard!

It would be interesting to know what the ground temp is at 7' down come the end of August.

Thanks for the input. I do believe that horizontal is viable...at least in N Central TX. Its been a busy week since my post due to 100+ temps. My shop geo has been on about 16 hrs/day and the temps are still steady. Referencing the temp lag from Geodean, I plan on digging some test holes down to 10 ft. at the end of Aug to measure the temps. My current calcs indicate I should see 83-84 degree temps at 8 ft. I should have no problem with heat this winter!

Posted By Dig_texas on 04 Aug 2012 10:04 PM

... Does anyone have any words of wisdom and sage advise for the newcomer?  I want to offer a good product to the customer and do not want to install something for a customer that does not work as advertised.

I do, courtesy of Dwayne Dean ('geodean,' regular contributor).  Years ago, he posted something like this:

1.) Heat pumps work efficiently with entering water temps from 30° (F) in the winter to 90° in the summer.

2.) A loop that is designed with the idea to keep install costs low will approach 30° towards the end of the heating season in a heating dominate area and will approach 90° towards the end of the cooling season in a cooling dominate area (mine got as high as 85° last year during the record heat we had in Dallas; this year mine peaked at 84° and is already coming down).

3.) A closed loop that swings 20° above and below the undisturbed down deep earth temp (a 40° swing) is a properly designed loop.

4.) The cost of putting in enough pipe in the ground to keep EWTs within 5° of undisturbed down deep earth temp (a 10° swing) could be as much as 10 times more than letting the loop swing 40°.

5.) There would never be a pay back in a system installed to keep the EWTs within a 10° swing.

Just holler if there's anything I can be of assistance with.  Hope the above helps.

Best regards,

Bill

I agree with all that - a classic description of the operating parameters of a ship-shape geo system.

Consider a more nuanced approach. Geo often competes with air source options, conventional or ductless splits.

Geo competes well in climates with wide air temperature swings - 30*F EWT provides a heat pump compressor with much better source heat than 0*F outdoor air.

OTOH, 90 EWT compares badly with average outdoor air temps of 85-90, typical of the hot humid southeast.

OTOOH, 90 EWT compares quite well in desert climates with outdoor air temps routinely over 100.

So if a geo contractor can provide a waterside system capable of providing EWT well below average outdoor air temps in summer and well above in winter, then it is likely to offer significant cost savings over air source or fuel-fired systems.

Posted By engineer on 11 Aug 2012 08:02 AM

... 90 EWT compares quite well in desert climates with outdoor air temps routinely over 100.

So if a geo contractor can provide a waterside system capable of providing EWT well below average outdoor air temps in summer and well above in winter, then it is likely to offer significant cost savings over air source or fuel-fired systems.

You'll need to include the Dallas area as an area that has a climate very compatible with GSHPs.  See this chart , showing average hourly outside ambient air temperature and EWT, since Oct., 2008.

Here we see EWTs (blue lines) even up to 90° works well in the Dallas heat (red lines).

And not unexpectedly, for the cooling dominant climate we have here, 60 - 65°F EWTs at the end of the winter season are still so high that heating with geo in this location is not part of the design equation when sizing geo.

Best regards,

Bill

My loop temps are still holding below 90. I feel more confident now that a properly designed and installed loop should be able to withstand our temperature extremes and low precip. At my location I have only recorded .10" during the last 60 days and the temps have been above 100 for the past month.

Next week I will dig down and record the temperatures.

An interesting question would be how does the efficiency compare to running the system in reverse (air to water) at night (when ambient temps are ~85F) and then storing chilled water for use during the day. No loop needed (but you need a tank).

85*F is by no stretch of the imagination "chilled" water, and 85*F is well above ground temp, so I question the usefulness of such an arrangement.

There is renewed interest in ice thermal storage for big buildings - done right a building needs quite a bit less tonnage, and the hours of operation can be shifted deep into the night when (commercial) power is cheaper.

Chilled as in ~45F. By the heat pump running at night. Undisturbed ground temp is largely irrelevant, what matters is EWT (which the OP has at 85F-90F, higher than night air).

Of course the downside to any completely off hours system is that it needs to be over sized.

Ice storage requires cooler temperatures (less efficient) but certainly uses much less space than water.

As far as getting a WiFi signal to the workshop for data reporting, there are a number of range extenders that work well for wireless networks. I have seen various home made models as well work with an existing wireless router. If you search Pringles can antenna amplifier, you'll see some, or there are folks repurposing old direct TV dishes with wifi antennae. http://www.ampedwireless.com/products/sr600ex.html

You'd need the mother of all water tanks to store enough "cold" in liquid water. 36 ton-hours of cooling, roughly equivalent to a 3 ton system running 12 hours on a design day, and limiting water temperature rise to 10*F for reasonable efficiency and comfort, would require over 5000 gallons of chilled water. That's a big tank needing a bunch of insulation. I can't imagine it cost effective for the incremental efficiency gain.

I dimly recall reading of a system whose owner proposed to bury a railroad tank car as a water storage tank...

Posted By engineer on 15 Aug 2012 11:40 AM

I dimly recall reading of a system whose owner proposed to bury a railroad tank car as a water storage tank...

wouldn't it be fun it you could just do all of this kind of stuff just for the heck of to see how well it worked

> I can't imagine it cost effective for the incremental efficiency gain.

Large tanks, even with insulation, are cheaper than many geo loops. But then geo loops running at 85-90F probably aren't cost effective for cooling, so that may not be a good comparison.

I agree that off peak electric rates and reduced system size are benefits that may need to be included for active thermal storage to be cost effective. Or higher day/night temperature swings than most of Texas has (Lubbock looks better).

Thermal storage system work well to reduce peak demand on the loop, but there applications are very limited when you continously reject heat over 1 or 2 months. Then a chiller running only at night when temps are below 80F makes more sense.