I'd be suprised if a manufacturer recommended one method over another. Vertical boreholes is technically the best method. Even at 5' deep the ground temperature does change a little from summer to winter. To compensate for this more pipe is installed compared to a vertical borehole. This just means a little more pumping power is required to move the fluid. That being said horizontal loops is a perfectly acceptable method. Depending on the space available and the local work force horizontal loops are often cheaper.
Special equipment is not really needed but experience is needed.

How much trench you'll need depends on what you put in it, how many loops per trench, slinky, linear, etc.

SR

The ClimateMaster Homeowner's Guide To Geothermal Loops says "where space permits these (horizontal) loops are considered desirable".
That's where I felt like they meant the most prefered. It seems like the horizontal would be less expensive, maybe easier to service, replace?
At any rate, I'm trying to watch out for the installer that says "these trenches should run you 3-4 grand" when a good backhoe operator could dig them out in 2-3 days for around a grand.

I may sound cheap, but this economic environment should mean more room for negotiation than in the past.

cs

The loop field approach should take the soil type and geographic location into consideration. Then you have to factor in space requirements and any set backs - but it sounds like room is not any issue for you. It isn't a good idea to generalize one loop system over another.
There are many ways to make a horizontal loop field and if you have enough room and the right soil, they might not have to dig a large pit - just make trenches big enough for the loop pipes. There are many trades on the type of loop - slinky coils vs straight pipes vs spacing and depth - all of which effect the length, depth and number of trenches needed. Your GT designer should have software that allows them to model exactly what you need and explain it thoroughly. If not - find a designer who can.

I have a horizontal loop field (large pit) and it cost roughly $1700 per ton of HVAC cooling. The reason it cost so much was a) rocks and b) space. I had just enough room for the loop field BUT when they excavated it, they had to move all the dirt from point A to point B and then back again, and when they back filled they pulled out medium and large rocks. My pit is 120' x 50' x 6' - and that is a lot of dirt. If you went with a pit, yours should not be this large - maybe 1/3rd to 1/2 the size depending on house design. I also had them put in a 1 foot bed of stone dust at the bottom to surround and protect the loops. If I had room for the pit plus room to put the dirt around it, then it would have cost less (fewer machine hours to move dirt around).

I am not sure about the horizontal loop costing less to repair or replace. This is actually one of my fears - springing a leak. I took a lot of pictures when they were building the field with reference points so I know where the loop field and main manifold is - but how they would find out which of the 12 slinky runs had the leak would require some work. They would probably have to dig up where the manifold is and then pressure test each loop. Once the bad loop was identified, then i guess that one section of the field could be dug up and replaced. I don't know if that would be cheaper than replacing one section of a vertical loop (one well). Either way - take a load of pictures and maybe put some metal markers in the ground so you can find the loop field later on if it does need repair.

When I started down the GT path, I did not ask as many questions as I should have . Here are some things that I should have asked:

a) what is the BTU load for heating and cooling for the house. Show me the Manual J calculations and all assumptions. Tell me what, if any, conservative fudge factors were applied.

b) what is the recommended sizing of the GT system compared to a) above. Why were these units sized the way they were (check assumptions). Make ure they are not over or under sizing the system. Have the assumptions double checked. What are the options for backup heat (or second stage heat)? I have electric backup heaters - I wish I had thought about LP heaters.

c) what is the normal expected on and off times per hour for the heat pumps during the year for a typical degree day in winter and summer.

d) What type of loop field is required and what is the size. How much excess capacity does the loop field have just in case assumptions above are not correct.

e) what kind of pumping and manifold system will be used. Will each heat pump have it's own loop pump or will it be a shared field (multiple heat pumps use common loops). will the loop pumps only turn on when there is a demand for heating and cooling?

f) how will I know that the system is working as designed? will there be a monitoring system that tells me if the flow rate, delta T's for air and anti-freeze, CFM of the blower , and loop pressure are correct. if not - how do I know when the system is not working as efficiently as it is supposed to?

g) who is the GT heat pump manufacturer? What are the ratings of the equipment (COP and EER) compared to other GT heat pump manufacturers. What are the terms of the warranty and what will they not cover? If equipment failure due to power surges are not covered, make sure they install whole house surge protectors to protect your heat pumps.

h) what is the recommended way to operate the system - propper settings and use of the themrostats. My guys actually did do a good job exlaining this - but you need to know how to use the system properly or it can cause the system to work inefficiently. Ask them how to keep the backup heaters from coming on too frequenctly - the dreaded toaster mode, if you use electric as your backup heat source.

I love having the GT system, but I hate not knowing exactly how the system is performing and when I have an issue (except when I get my power bill which is not a good system at all). I am now in the process of adding the features needed to give me that information - but it should have been part of the system right from the start.

best of luck.

OK Sniffdog,
I'm thinking of printing out your list of ideas, then whipping it out to put the contractors on notice.
Will have to do some research and learning, first,though. They'd see thru me.

cs

Most of the info you need is here on this site. between the hvac and renewbale energy forums you can find out most of what you need. I am just a homeowner who wanted geothermal HVAC - but I wish I had studied up before I put my order in. I think my HVAC guys did an OK job - the system seems to be running fine and the electric bills are reasonable. But I should have asked them for the data before OKing the system. And once I install my monitoring system, then I will have the data I need.

I have a feeling that my system was oversized. Not by a lot - but I think I have more HVAC capacity than I need. They have to show you the required BTU's per hour during the summer and winter. Your system should be sized for the summer load because the heat can always be augmented a little (if you need a boost in oddly cold days) with the second stage heat. My house is very well insulated and sealed. I think that when the did the manual J (if they did it), the were too pesimistic on the insulation and window package assumed and then they added some fat just to make sure they had enough BTU/hr capacity.

Once you know the thermal load of the house, then they can design the GT system accordingly. All you have to do is ask a lot of questions and use the GW to get multiple second opinions.

The lack of performance monitoring really bothers me a lot. My system has nothing to tell me what the heck it is doing. Now that I understand how GT really works - reviewing simple thermal equations - i realize that with a little extra work it could have been added. Some GT heat pump manufacturers are catching a clue and adding performnace monitoring features to the heat pumps, but I still think it is far behind where it needs to be.

I just wanted to pass along my experience so you could avoid getting to the place where I am. Ask your HVAC people how you will know that what was installed is working as specified? And not just on the 1 day you show you - but any day you want to look and see. It should be unacceptable to wait until the end of the month when you get your electric bill to see that all is OK.

I would also ask them for what the expected annual heating & cooling bill should be with GT based on Heating & Cooling degree Days for your location. They should be able to determine the BTU/hr load for the house and give you an estimate. Otherwise when you get your bill - how do you know it is as low as it should be? You will have to calculate the other electric usage (lights, TV, etc) and add that to give you the expected bill, but you need something as a basline for comparison.

Good luck.

cs- I'm not sure where you are coming up with your numbers for a ground loop. You imply $3-$4k is a rip off. You didn't say what size system you are thinking about. For an average size house $3-$4k would be an awesome price assuming you are getting a properly sized ground loop. There's more involved than digging a hole and throwing pipe in the ground.

sniffdog- I'll reply to your questions. I design and install lots of commercial and residential geothermal systems so you can get a contractor's view.

a: good question
b: good question, I don't know how or why you would do something other than elec backup heat
c: I'm not sure how someone would answer this question
d: good question
e: good question, unless there are some strange situation there should be 1 ground loop connected to all the heat pumps. the pumps should only run when there is a call for heating or cooling
f: At startup the installer should check the water temperature drop or rise at the unit. If the number is in the manufacturer's temp range than the flow is good. If the house is warm or cool enough than everything is working properly :). To my knowledge there is no package monitoring system available.
g: good question
h: good question

I haven't gotten far enough along to know what size system the house will need, but it will be a single story 2151 sq ft house. Still 8 months out from starting. I just used that $3000-4000 as a fictional example.
I do,however, know a good backhoe operator that charges $45 an hour. Last year he dug me a 4 ft waterline trench 120 ft long for $200. I feel he could dig whatever trenches necessary for well under $3000, then let the HVAC contractor do his thing. Maybe that's not the way things work, I don't know.
Just trying to make my mistakes here, rather than when it comes down to dealing with installers.

cs,

I am not sure how your HVAC contractors wok down there, but I receieved a bid from my HVAC company and it included everything except excavation. They told the excavator what to dig and the excavator dug the pit. One thing I liked it is that they bid the job with 2 options - one with High efficiency heat pumps and the second with GT heat pumps and extra's needed like the loop pumps & plumbing. So it was easy for me to see the true delta cost of going with GT. For a 12 ton system (way more than you will need) - the delta cost was 15 thousand excluding excavation.

My excavator looked at the material coming out of the hole - boulders and some good sized rocks. So he brought this to my attention and recommended that he a) sift the big rocks out and b) use the stone dust base - both of which cost more but was worth the price. The HVAC guy agreed - but it was my excavator who knew that digging and then backfilling without precautions could lead to future leaks.

So you need to be a little careful. You may think that it is just a hole but you have to remember that you are putting a bunch of poly pipe under a gazzilion tons of dirt. If the guy has never done it before, someone needs to provide supervision of what he digs and most importantly, how it is back filled. The 45 per hour sounds like a good deal.

funny - my guys did do the initial check out of delta T and flow. BUT - they did it in early December before it got really cold. I ran into a problem in Jan when they had to come in, add some additional anti-freze, and balance the loop manifold valves so that the two 3 ton heat pumps did not extract as much heat from the loop field (they were over supplied with flow) and have more flow to my 6 ton unit which was starved for flow. That was when I realized I needed a monitoring system.

It is true that they do not make a packaged system yet to do this, but I have found process control system suppliers that make sensors and instruments that might make it easier for me to do it.

You've figured it out, the big downside to the vertical wells is cost. Those holes cost me a lot more than a few days of excavator operation.

In addition, NC seems to be hosed up with regard to geothermal. While the county managed to inspect, permit, and sign off on my water well in a few days, the state took months to approve the well holes for the closed loop system. Further, I have to keep going back every five years to get an operating permit. This I don't understand. The waterwells that are open forever they don't sweat, the boreholes that were immediately grouted up and have no communciation with the surface I have to deal with bureaucracy over. And they wonder why nobody builds green in this darn state.

Excellent points about filtering rocks, monitoring systems,etc. That's what I like about this forum, I can let my stupidity show here, without costing me anything but embarrassment.

I'm trying to do a good job, without spending unnecessarily, is a polite way to put it. I'm retiring from my job, then building this house. Like alot of people, my retirement funds have taken a hit, so I have to watch where every dollar goes.

One side question: can you zone your ductwork with geothermal systems? Had thought of putting in a damper to zone off part of the house, but don't know if these systems can handle that.

I have a GT forced air system, and my second floor (guest rooms) are zoned so that each bedroom has their own tstat - so yes it can be done. There are a lot of posts on this forum about zoning do's and don'ts so you should search on that topic to get more specifics.

ron - I am surprised that NC has those rules on the wells for vertical loops - is the concern they have about the anti-freeze possibly leaking into aquifers? Why such red tape? Do they also have the same restrictions with horizontal loop systems?

When they started digging my pit, after about 30 minutes of digging they hit a 5 ton boulder which the bull dozer could got pull out. The excavator got worried that the entire pit was full of these monsters and so we had to make a decision to either scrap the horizontal system and go with wells, bring in a bigger machine and keep digging and pray, or scrap GT altogether. That was one of the worst days in our build - massive headache. I did some quick calculations, looked at the land where they were able to dig, considered that our large foundation footprint was dug with very few rocks, and then decided to get the bigger machine and pray. That worked - we only had a few massive boulders - everything else was diggable with smaller machines. We did not hit any rock shelves which would have required a ram hoe (blasting is not allowed where I live) , and that is where it can get really pricey. I live on a mountain so rock shelves are common, and had we hit one of those I might have scrapped the GT altogether. This is the one big risk with GT - you just never know what is under ground until you start digging.

The problem I had with the wells was that on top of the 10 bucks per foot for drilling (now it is about 13 per foot) , you still have to excavate trenches to run the pipes to the house and between each well, and you need to fill up all well holes with the slurry mix. By the time I got done adding all that up, it was still a lot more expensive than bringing in the big track hoe and scooping out the huge boulders. I am sure there are cases where wells are the only way you can go - but if you have the space and good soil, a pit or trenches is hard to beat especially if you have someone who will excavate for $45 per hour.

With that said, you still need to have your GT designer work through a complete design. If they have been in the business for a while, they should have a good idea of what is typical in your location. The design has to tailored to your specific site and house design.

Luckily, there should be no problems with trenching. The soil isn't bad, has a little clay and sandstone, but digs easy enough with a backhoe. This guy I use is fantastic. He's been doing site prep, dozing, septics, etc for about 50 years, and still going strong.
Have traded emails with an installer that has around 20 years experience, and seems knowledgeable. Still not a bunch of installers around, plus this is a very rural area. I hope to find at least a couple to get bids from.

I don't know. I could understand it for the open loop systems (essentially where you pull water from one well and dump it in another), which they do similarly regulate. However, the closed loop system is, unlikely to fail, not particularly easy for them to detect, and to my knowledge they didn't send any inspector out. All they did is take my money and waste my time.

cs

That is the same in my area. There is really only 1 company that has been doing GT for a long time - something like 20 years. Everyone else - just a few - are newbies. And you have to factor all of that into your decision.

For the install, you could have a company travel from a distance to do the job. But what happens when things go wrong - if (when) you need service? I have had a contoller board and a fan relay fail on one unit within the first 12 months - both of which seem to be related to a power surge. But when heat is out, and it is cold outside, I want it fixed right away! And I mentioned it before - put whole house surge protectors in your main panel to protect your HVAC equipment (see www.smarthome.com, Panamax Whole House Surge Protectors).

Make sure you spend the money and get good equipment, read the warranty and post with the equipment recommendations to get second opinions. I also think that if your company is a distance away, having some guages on the system so you can trouble shoot with your HVAC guys over the phone will help. Some of the tools the HVAC guys use (like temperature probes) are not expensive, so you could do things like check loop input and ooutput temp, air input & output temp - the basic things they would do to trouble shoot a problem. Have them explain to you what to look for on the contoller board when there is an issue - and how to reset it if your compressor locks out. With mine (Econar GeoSource 2000) the lights on the board will tell you if the compressor is locked out or if there was a pressure alarm condition.

In my last home, I had gas heat and electric A/C. I found a great HVAC company and never worried about the system - knew very little about it. When it broke, I just called my guys. With my new home, I want to know everything about my GT system - not just because I find it inetersting, but because I know that if that one company who installed it goes belly up, there are very few people around here that know anything about GT or how to maintain the system I have.

I also recommend that you install some form of backup heat if you live in a cold place. I chose to install direct vent fireplaces that are rated as heaters. This decision has turned out to be one of the very best investments we made in the house. When power goes out - or the heat pumps break - I can fully heat the house with one wood burning fireplace and two gas fireplaces. All of the fireplace units units have blower fans and thermostats - so they can be set to operate just like a heating system. All fireplace electronics are connected to the backup generator. I can live without A/C on a hot day, but cannot live without heat on a very cold night.

Just some ideas to think about.