The only way to determine the size needed is to do a man J. The man J will tell you what your btu needs are. If the basement is enclosed and not open to the outside, then it does not require as much conditioning. The problem becomes air changes per hour. If an airhandler is too small, it will never provide the air changes needed to keep the basement healthy. It may be comfortable, but have bad air. I smoker could die in hours, if the air is poor.

As to holes dept, this is variable with the geology conditions. I have heard of 150 ft holes per ton This would be 300 ft of pipe. My area requires 250 ft holes. this would be 500 ft of pipe. Not enough pipe and the system does not have enough to work to specifications. The system will run continuously and soon self destruct.

Hole cost is substantial. In 2000, when I bid my house, the retail cost was 2500 per hole in N. Texas. Some drillers wanted $4000 per hole. I found a driller who would do the job for $1200 per hole. I had to help him install his system. The WF equipment is expensive in comparison to standard HVAC equipment. I don't feel it is superiour, just more expensive. I found an AH that included a freon coil and a water coil, for less than $1700 retail last year. WF wants about $8k for thier AH.

There are 2 steps involved to size a geothermal system. One is to size the unit doing a heat loss calculation. The procedure is the same for any system. If you come up with 3 tons then that part is done. Next is to determine the amount of pipe needed. You didn't mention if you are talking about vertical bore holes of horizontal trenching. For your area a contractor should know how many feet is needed per ton.
If you have too little pipe you will not be able to transfer enough heat to/from the earth. Having too much pipe will only make the install cost higher.

>>The WF equipment is expensive in comparison to standard HVAC equipment.We haven't decided what we want yet. Just started looking into everything.

>>You didn't mention if you are talking about vertical bore holes of horizontal trenching. For your area a contractor should know how many feet is needed per ton.I did mention trenches in my post. Yes, the contractors should know but apparently they have differing opinions. I do know that they each used Waterfurnace's calculation software, so again, I don't know why the difference.

>>If you have too little pipe you will not be able to transfer enough heat to/from the earth.That is my concern. I don't understand how they can all come to such a big difference in pipe needed. I thought I would ask here before I talked to them so that I would have a better idea if they are BSing me or not.

>>Having too much pipe will only make the install cost higher.I know the initial cost will be higher, if we plan for the future, to have them install more pipe than needed now but will it cost even more to add the pipe later? Will it affect the performance now if we have them put in the extra pipe.

Someone did the math wrong. More pipe means more capacity. It also means more dollars. The only affect will be when you increase the btu load. The system will take longer to deliver.

I have a 2500 square home. Laid down 4000 feet of pipe for a 5 ton system. (pressureless horizontal closed loop)

I went with a MegaTek dual fuel HydroHeat unit (no electric banks for backup heat).

I too have a full basement which would double my home size. HVAC guy said I will be fine for 5 ton unit if I zone the basement and main level...also, no capacity left to heat my domestic hot water which I would have liked.

Talking to the HVAC guy, they have done a couple homes with 12000 feet of pipe and use 3 seperate systems.

The "exterior" cost for pipe and trenching was less than $5000 for my system.

The pipe was buried 9 feet deep and laid in five seperate trenches 150 feet long.

>>I have a 2500 square home. Laid down 4000 feet of pipe for a 5 ton system. (pressureless horizontal closed loop)This is the first time I have heard the term "pressureless". Could you tell me what this means? So your HVAC guy installed 800 ft of pipe per ton?

>>The "exterior" cost for pipe and trenching was less than $5000 for my system. The pipe was buried 9 feet deep and laid in five seperate trenches 150 feet long.That sounds really cheap especially since they went down 9 ft. Around here anything over 6 ft requires safety measures which costs more.

Did you use it this winter? Any comments (negative or positive) about it if you did? What temp did you set your house at? I am hoping for 73 with only backup kicking in on the coldest days. I think the contractors sized it for 70 though so it is something I need to bring up with them.

"Pressureless" simply means that when the pumps are not running, the fluid in the groundloop pipe is at zero pressure. My HVAC guy began doing it this way about a year ago. There is a small storage tank which the pumps are mounted to. I guess you could call it a closed loop that is not under pressure.

600 feet per ton is standard as well as 6-7 feet deep for the trench. My HVAC guy usually oversizes the groundloop because the extra cost is minimal. The manpower and equipment is already there.

The plastic pipe (very thick and very hard to bend) is cheap and a backhoe around here runs $85 an hour with the operator. I wasn't talking much more money and there are no codes (or "safety measures") used where I'm at.

Took about eight hours to install the 2 return and supply lines, hot melt the 5 loop headers, dirtwork, and dropping in the pipe. While the excavator was digging the trench, the 2 hvac guys were uncoiling the pipe and using zip ties to hold the pipe in a nice swirled pattern that was then just flipped into the approximately 4 foot wide trench.

My system will be fired up shortly. 2 people I know have the same system and are very happy. Geothermal systems have the highest customer satisfaction. Only bad comments I ever hear are the larger upfront costs.

BTW, I would price the cost to pipe it at 4 tons. If you ever add on or want to heat more space...you will be very limited.