how much coppper pipe will this need? What size? Are you gonna buy it by the roll? Is it to be soldered and will it hold up under the earth? (Copper is expensive). What is the heat transfer of air in and underground tube vs fluid? What is the heat transfer of copper in the ground? Just curious.

All good questions. If I were to attempt this I would try to size the copper loops based on an existing DX system of similar size. I know that copper is expensive and that it would take a lot of it but it has still got to be way cheaper than purchasing the whole geothermal unit. If I were to do it, yes all the connections would be soddered.

Bacsically it would be the ground loop of a DX system with the compressor/pump, reversing valve, wiring, etc of an air to air unit.

I'm not sure how much copper you would need, but I'm pricing out a DX system and am told it takes about 700' of copper per ton capacity.
Not sure what capacity you need, but you are talking about a fairly big trench or ditch to accommodate your plan.

Not sure if this would work, but why not try it with the HDPE pipe (geo tube) I've seen it charged and hold 100-115 psi. Should be cheaper and in rolls. Not sure if that is its intended use either.

It won't work.  You cannot run refridgerant through plastic pipe.

That seems awfully high. I looked at using a DX system in the house I'm building. The loop lengths were on the order of one 100' well per ton. I think the tube size was 1/4" going down and 1/2" coming up.

700' does seem pretty high when you consider that copper is an excelent conductor and it is in direct contact with the ground, and you are making the exchange directly to the refrigerant and not to water then to refrigerant. When you look at the existing coils in an air to air heat pump, there is not a whole lot of area and you are making the transfer with air blowing over it, so you wouldn't think it would take that many feet of pipe per ton.

I did call a rep for a DX system to get some more info on my ideas and he started talking over my head. Stuff about if the trench isn't perfictally level then the pressure drop in the line will cause the oil to seperate out of the refrigerant, settle in the low spots, and not make it back to the pump and burn it up. Has anyone ever heard anything about this. He said it is a big issue even with the current DX systems, not just with my crazy ideas.

Yes, I was told the same thing. It's not the pressure drop, it's the velocity of the refrigerant. If the refrigerent doesn't flow fast enough the oil, which is heavier than the refrigerent, drops out. I don't remember why this isn't near the issue with vertical loops. I asked about trenching with a 3' drop from end to end. Was told no way would it work.


If you were talking to ECR Technology it's understandable why he may have lost you. They have a unique system with their flooded Active Charge Control tank.

Your Right "velocity Drop" is what the guy said.

I just dont understand why every thing has to be so perfictally level. Do they do something different with there vertical systems that they dont with there horizontal to prevent the velocity drop.

If what the rep I talked to said is true about the velocity drop causing the oil to settle in the low spots, then you would think the same would happen in a vertical system resulting in all the oil in the in the bottom.

Apparently.



I don't know why one is OK and the other not. Since I wasn't going to be able to do horizontal I didn't pursue the differences issue. All I know for certain is they do both. I've since given up on going geosource for a couple of reasons. My heat load calculates out so low I don't think the pay back is there and the well cost was going to be north of $6000. I was going to do ceiling radiant for both heating and cooling and that was going to cost a few $$. I found a viable alternative, Daikin air-to-air split system heat pump. It'll put out heat down to 10F outdoor temp without using auxiliary heat. I'm doing sealed and conditioned crawl space and will use it for the supply plenum. That'll give me warm floors and save ducting cost.

My current air to air unit will put out good heat down to 17 degrees after that I got it set for the propane to take over, which isnt very often, but I still have to use it. Set at 17 degrees, when it gets close to that the heat pump does run a lot but it is still cheaper than propane. I think if I try to go any lower though, it would almost run continuously. But I want to do something so that I don't have to use any propane at all.

Since I first posted a couple of other Ideas have ran through my mind.

First, continue to use the outdoor evaporator and fan but plumb a ground loop in after the evaporator. That way the evaporator still heats the refrigerant as much as it normally would and then let the ground add to it. This would make the system require far less line to be burried in the ground. This would only benifit the heating though because in cooling mode, the refrigerant would go through the ground loop before the evaporator instead of after it. But I use the heating mode way more then the cooling.

A second Idea I have thought about would be to conver to a water based system. I would move the heat pump into my basement, and disconnect the evaporator and fan. Now all I need is a ground loop, circulating pump, and a heat exchanger(I think they call it the intermediate heat exchanger).

I would really like to try one of these Ideas this spring so I guess my question to you guys is which do you think has the best chance of working and which will be cheaper? I have never priced or even know where to get an intermediate heat exchanger?

I guess I started thinking about these Ideas because the rep for the DX system kinda scared me off when he started talking about the velocity and pressure drop an burning the pump up. I think the water based system would be the easiest to engineer because there is a lot of info on how big to make the ground loops, and how many GPM the pump needs to circulate, etc. It would be just moving the unit, burring the loops, and hooking everything back up.

First of all, what you are thinking about doing will void the listing [ UL , ETL, ARI ] on your current piece of equipment. If you were unfortunate, had a fire or damage as a result of your experiment, your homeowners would be void since you altered that piece of equipment. Not even licensed contractors can do that legally. If you alter the system, you are taking on a huge responsibility / liability.

There is much more to the design than burying copper in the ground. What distributors will you use? The distributor directs the refrigerant to each circuit buried in the ground. What orifice will you use? This regulates how much refrigerant is allowed to flow through the distributor. What metering device would you use, Thermostatic Expansion Valve [TXV] or pistons? Only one works well with this system. What will you do with the extra refrigerant in the system...where will you store it? What solder would you use? It can't be soldered, it must be brazed with a certain alloy or galvanic reactions will occur destroying the loop system.

Having installed a number of DX systems, I know the in's and out's of the system. It is not just "burying copper in the ground", but how is buried in the ground. There are tried and true methods to this type of system. There is allot of engineering envolved, designing, etc. The best system installed incorrectly is a problem at best and a bad investment. The system is one of the most simple heat pump designs on the market. But you really have to understand the workings.

I used to work on cargo ships that had refrigeration systems for the crews chill box and freezer as well as AC systems for the officers quarters.
The compressor units/resevoirs were in the engine room since they used sea water for cooling. The expansion units were way way above decks.
There was never any issue with oil, and now I am wondering why.
Bruce

Wow! I was expecting this thread to continue.
"The system is one of the most simple heat pump designs on the market. But you really have to understand the workings. "
Where can we get this info.

Most likely this thread didn't continue because people have realized that it's not a viable option.

I would agree with Dakers. This is not something you will want to try. There is a lot more to the system than running copper in the ground. If you were running Horizontal lines you would need to be pretty deep. Most DX Geo systems are around 100" deep lateral lines and utilize a grout around the copper. Assuming you have a heat pump with a mechanical TEV, you would need to adjust it for the required change in supper heat. The distribution device would be somewhat simple. Most use a venturi type and let the expansion valve do the work. In the best case you would use an electric valve and write the algorithm to adjust the supper heat based on the season. There is only one company I know that used deep well DX. It is very hard to manage the Oil and coolant in these systems as Gravity plays such a large role.

I also don’t think your current compressor would last long. The risk of liquid returning to the compressor is just two high.