Geothermal DX Systems That Use Copper Tubing

[westes]

Can someone tell me which Geothermal heat pump systems use copper tubing instead of polyethelene? The key requirement here is to greatly reduce the amount of trenching or well digging that needs to be done.

[inf_sys]

Check out http://www.earthtoair.com

[westes]

Check out http://www.earthtoair.com

I wonder couldn't you design a copper pipe system for a well that is shaped like a slinky, coiling the the tubing all the way down? That should let you fit about 1000 linear feet of piping into a single 100 foot well. If a non-copper tubing geothermal design requires 500 feet of tubing for each ton of cooling, a copper based one might need only about 200 feet. A five ton system that requires 200 feet of tubing for each ton could end up fitting all the tubing into a single 100 foot well.

That's still a chunk of change, but it starts to approach a level that a normal human being can consider.

[fsq4cw]

Can someone tell me which Geothermal heat pump systems use copper tubing instead of polyethelene? The key requirement here is to greatly reduce the amount of trenching or well digging that needs to be done.

http://www.nordicghp.com/mg/

Then click on 'Manuals' or 'Products', then 'DX'.

Best DX machines I ever seen...

SR

[RoBoTeq]

Isn't copper only used in direct expansion geothermal systems? With water loop systems, are we not committed to how much ground contact we have?

[beenthere]

Moved to residential geo forum.

[junkhound]

re: copper tubing instead of polyethelene

May have misread it, but the implication in the OP is that the better thermal conductivity of Cu vs. PE will allow shorter fields.

Not so. The pipe wall thermal impedance is trivial compared to film coefficients, earth contact, reynolds numbers, etc...

[westes]

re: copper tubing instead of polyethelene

May have misread it, but the implication in the OP is that the better thermal conductivity of Cu vs. PE will allow shorter fields.

Not so. The pipe wall thermal impedance is trivial compared to film coefficients, earth contact, reynolds numbers, etc...

You might be right, but what you are saying here directly contradicts pages on the web sites of almost every Geothermal DX product manufactured. For example, NORDIC makes this point:

" 'DX' systems can be installed in a more confined area than a conventional groundloop system, primarily because the heat exchanger coil is much more efficient at transferring heat to the refrigerant than a plastic earth exchanger. Normal loop lengths for a 'DX' machine are nominally 350’ per ton as opposed to 450’ to 500’ per ton for a plastic earth exchanger. Similarly, vertical systems require only a 3” bore hole to a normal depth of 120’ per ton."

You can find that on this page:

http://www.nordicghp.com/mg/nordicJul-25-04/DX_series.html

[Sleuth]

DX all copper,diagonal or horizontal:

http://www.earthlinked.com/

[jerryd_2008]

... If a non-copper tubing geothermal design requires 500 feet of tubing for each ton of cooling, a copper based one might need only about 200 feet. A five ton system that requires 200 feet of tubing for each ton could end up fitting all the tubing into a single 100 foot well.

...

Not an expert, but a geo contractor told me recently that the temp in the wells goes up into the 90's over the summer. Can one 100' well accept all of that heat and still have enough temp difference for the geo system to remain efficient for AC?:o

Same question for removing heat from the well during the heating season. I believe the contractor told me that the well temp can get quite low in the winter. Will there be enough heat in this small well to provide heating?

[Some Dude]

If you want to take the chance and dig it yourself then i would say go for it.
Otherwise even with an anode it would not be cost effective to have it installed.
Copper tubing is easily affected by electrolysis , imagine the headache of finding and repairing verses just replacing sections of loop verses replacing the loop again.
Just my opinion.
Let me put it this way, if i could be convinced on this forum it would work i would do it myself.

[Some Dude]

I just put a call in to them, i want to find out myself.

[westes]

Not an expert, but a geo contractor told me recently that the temp in the wells goes up into the 90's over the summer. Can one 100' well accept all of that heat and still have enough temp difference for the geo system to remain efficient for AC?:o

Same question for removing heat from the well during the heating season. I believe the contractor told me that the well temp can get quite low in the winter. Will there be enough heat in this small well to provide heating?

Probably you are right. The NORDIC system has an interesting feature that they start and stop different loops for just this reason. Their controller senses when a loop is too hot and switches over to use a different loop that is cooled down. Their approach has the additional advantage that when you are in heating mode they use a smaller number of loops and the unused loops become your storage for the refrigerant.

[westes]

I'm wondering if anyone makes a residential hybrid geothermal system that uses the approach of burying a chiller down six feet under the earth. The advantage of that approach is that you would have minimal cooling loss to environment so you would get maximum utilization from the chiller. And of course you avoid the need for a huge trenching or well digging project.

I'm sure this exists for large industrial applications, but just checking if someone has made an affordable one for residential.

[jdh]

Earthlinked DX systems.

Field required lengths, Copper tubing vs. HDPE
(First off, I'm not going down that road, one is better than the other. I like them both.)

In a water source system you are going for a sensible water temperature change, picking up or expelling of heat, transferring that to a refrigerant heat exchanger to deliver the BTU's needed.
As for the DX systems you add the latent change of the refrigerant being in direct contact with the earth temperature, the heat exchanger needed in the water source systems are taken out of the circuit, because the BTU's are being transfer directly into the copper caring refrigerant.

Systems are designed for the areas ground temperature. Pre-designed fields, with actual layout plans. So there is no short looping of fields.

Also, you can't pack 500' of copper tubing in a small space intended for one loop or one ton, and expect to run a 5 ton unit on it. The ground can only produce and regain only so much temperature, and still perform efficiently.

I like the Earthlinked DX system for some of the patented design features, as for the devices it uses, which could approve efficiency levels in standard AC units by 20%

And almost no printed circuit board, pretty much standard controls and common parts.


Check out earthlinked.com, I also checked out Nordic, but for me, I have a somewhat locate Dist.at heawarsaw.com I like. Other companies have come and gone, and then reopened up again. Earthlinked has been around for over 20 years

[junkhound]

westes: OK, I see what you are referring to now, direct refrigerant lines in the earth. Originally took it to mean a Cu water/glycol loop.

Basically, the film coefficient (part of the overall thermal conductivity heat transfer) on the refigerant side of a pipe wall is 1/50th or 1/100th that of even water to a pipe, and you are eliminating a probably 10C loss in having another loop.
The big disadvantage is that if you have a leak you lose a lot of refrigerant and $$$$, which aint cheap these days.

BTW, in a water source HP (e.g 1/2 gpm per ton flowing well water) a system only needs about 15 (yep just fifteen) feet of Cu line per ton.

Apples and oranges.