1923mack,

Your profile shows you to be an architect/engineer. As such, you should know the importance of having the system properly designed...

Do it once, do it right.

Bergy

You could also use HDPE and stab it with a knife every foot or so. Unlike near the surface, where you have evaporation, air flow, roots, etc, not much water is needed to keep deep soil moist.

I agree that it should only take a minimal amount of water to keep the soil moist in the area of the HDPE pipe.  The more acurate and precise data and ideas we can get for the system 
the better the final design.  Moist soil has a better Thermal Conductivity than dry soil so the engineering numbers for it are greater.  We are willing to actively manage the total system so will use zoning, watering and whatever other ideas are developed to get a good system at a reasonable cost.  Am trying to determine if it is cost effective in Southern California to install an GSHP system.  From a preliminary and relatively quick design I can price out a final cost.  We intend to stay at this house for may years so can do a total cost analysis.  Install plus annual energy costs plus maintenance over a 30 year or so period. If the cost estimate shows total cost for conventional or some hybrid system is a lot cheaper than we will install that other system.  If a GSHP system looks close to a conventional system I really would like to do it.  Willing to pay a few extra thousand and be a guiney pig for the area. 

Again you will still be limited by the conductivity of the surrounding soil. What you describe will work, but not as you envision. It will work more as a passive open loop system.
Since you have all this water available in southern CA, why not just go with an open loop system.
The only contributer that likes your idea has no geo experience, he simply researches and theorizes. Not sure you want that endorsement.
Do it right.
J

jonr,

Have you ever tried to "stab" a piece of HDPE ? I think you would stab yourself several times before you really even nicked the HDPE.

Bergy

I am not sure why one would say we have "all this water available in Southern California".  We are in the middle of a 3 year drought.  May areas are on rations.  With the groundwater at 73 degrees I agree the open loop does sound tempting.  Well has not been run since we have been here (23 years) so not sure of its capacity.  10 gpm over 24 hours uses 108,000 gallons per day.  We would be using a lot of water.  Pumping and recharging that amount is problematic.  That and the fact that in Califoria red tape to do anything different is huge. I doubt I could get a groundwater  permit to do an open loop system.  Design wise the open loop would be nice though.

Pumping and returning 10 gpm from 64' in sand is easy and is no net "use". But no idea if your state would approve it.

Unfortunately there do not appear to be any installers with local experience in GEO.  There are drillers, and there are HVAC professionals, but I have been unable to locate anyone with GSHP experience.  A designer theoretically would not have to be local.  Calculations are calculations.  But like you say, local experience is prefered.  Local rep for ClimateMaster will not even return my calls, and he is not really that local.  Will keep calling.  The more information we get the better.

Generally, drillers will work with more than 1 hvac guy. Poll the drillers you find on who they work with.
j

We have been having an extended hot period here in Southern California.  Not an unusuall thing.  Air temps in the low 100's to high 90's for two weeks plus.  My temp probe at 6' deep has increased from 80 degrees to 84 degrees.  The one at 3.5 feet deep is at 89 degrees, and the one 4" down read 109 degrees when the air temp was 86 degrees.  Horizontal loops looking worse and worse.  May take suggestion and find out what red tape is required to do open loop.  Take the 73 degree water and then do a leash field to recharge it.  Leach field would be cheaper than drilling to recharge the water.  California says it wants to be green so maybe we can get this to work.  The basin we live in is heavily regulated (Water Master, recharge rules, pump tax, recharge credits, no wells, jet fuel polution, PCB's,  etcetera), which is why my original response was negative. Getting information can rarely hurt.

You might ask your designer about a standing column well with no bleed - all of the water is put back into the same source well.

Putting the used water back in to the original well would be a nice cost saver.  Since my well is not real deep, 26' of water in a 90 foot deep well, I am thinking that we would be putting to much heat back into the area.  Out EWT might quickly increase over long periods of continuous use. 

True, not deep enough to be useful for a SCW.

As mentioned before you might have to go vertical in your area. You mentioned a willingness to spend a few extra bucks, are you trying to avoid vertical loops?
The temps you've found, may be why you can't find anyone to do horizontal fields in your area.
I was also not convinced that we have properly sized equipment in mind. If you can't find a local guy, you should probably consider conventional before you try to pioneer something on your own.
High end airsource equipment gets much closer in energy usage (to geo) in cooling dominated climates.
You need someone who can help you determine if geo is a good fit for you.
Good Luck,
J

Joe/Just a Mechanic;

     I think you have nailed the issues.  Common sence says to go to a conventional high seer HVAC system (Carrier Infinity comes to mind).  I do not require a 100% assurance that a HSHP system will work reasonably well, but after spending this kind of money would like a semi functional system.  Got two designers within 1000 miles of my area.  Will see what develops from them.  Checking with groundwater rules to see if that can pan out.

    

I'm concerned about the long term here... You are thinking about watering the loop field now, what about 10 years from now? 25? What effect might that have, what cost of water, and where would it come from? After all, that loop field should ideally be functional for at LEAST 50 years, if not hundreds. I agree with the others that said design properly first, don't try to "fix" it with watering.

I do not think that adding water to a dry hot soil is necessarily a bad design.  Does adding a supercharger to a engine make it a bad engine?  The supercharger enhanses the performance of the engine.  It provides more power.  Keeping the soil moist to increase thermal properties would appear to be a good design.  We have a well on the property, so we would be recycling the water back to the goound.  No net water useage, just pumping costs.  I would not shorten the amount of pipe required for the system when using water on the soil, but just use it to have the system perform better.

Not a good analogy... The engine is very capable of moving the vehicle around without the supercharger.

If your loop design can not provide the required heat of extraction/rejection a different design is needed. What happens if the well runs dry?(not like that's ever happened before)

Bergy

The best suggestion by far in this string is hire someone that knows how to design a geo system for So. CA. Here's a link to try http://www.buildbydesign.com and there are many others if you'll look. I'm surprised there's not a single entry related to grout and its importance in a GSHP system, particularly in an area with the extreme vadose zone you describe. Using the correct grout for your conditions may be the best and least expensive solution to compliment competent design assistance.