geothermal chiller

[Cuby2k]

<a href=showthread.php?s=&postid=7337802#post7337802 target=_blank>Originally posted</a> by chicken
Does anyone have any recommendations for pumps to run a geothermal setup? I have 250' of 1" copper pipe already burried and just picked up a titanium heat exchanger. All I need now to start testing is a pump. Any ideas?

You have 250' of copper buried!!!! Dude, that is very good. WOO HOOO, this house is clean, thank you Jesus. Do I hear an amen?

sorry, I lost my head. I do that sometimes.

The pump you want depends on the load (BTUH) you have. But as a minimum you want 6 GPM. Assuming a pressure drop of 1.9 PSI/100 feet your head, well your pressure drop IN feet of head, will be 11 feet plus 5 feet for misc valves, your indoor piping, fittings etc. So, total expected PD is 16 feet of head.

So pick a pump that has high head capabilities. It is likely the pump you select will also have a much higher flow rate than that required which is ok because as the flow increases so does the pressure loss and the pump will ride the curve to the system head.

I would use something like a Grundfoss UPS15-58F, 1/25 HP for less than $100. This can only be used in a closed loop system because it has a cast iron impeller. Be sure to include an expansion tank and make sure the system is filled with a positive pressure to ensure NPSH at the pump inlet.

Cool, please keep us posted.

 

[salty joe]

What is NPSH?

 

[Cuby2k]

<a href=showthread.php?s=&postid=7339983#post7339983 target=_blank>Originally posted</a> by salty joe
What is NPSH?

It's the desired and required positive pressure at the inlet side of the pump to prevent cavitation . Net Positive Suction Head is the wording for the acronym as I recall.

 

[salty joe]

Thanks. Does that mean that the pump has to be lower than the rest of the closed loop?

 

[Cuby2k]

<a href=showthread.php?s=&postid=7340426#post7340426 target=_blank>Originally posted</a> by salty joe
Thanks. Does that mean that the pump has to be lower than the rest of the closed loop?

Well, that's the beauty of a true closed loop system. Because the system is not open to the atmosphere at any point it can be and in fact should be put under a positive static pressure.

When that is done the pump can be placed anywhere in the system and does not have to be below the water line.

looky here . . .

http://reefcentral.com/gallery/data/500/119502CLOSED_LOOP_2.jpg

 

[Marco67]

Do you guys think the advantages of copper outweighs the risks here?
what about the life of copper in soil/ sand?

 

[Cuby2k]

<a href=showthread.php?s=&postid=7341640#post7341640 target=_blank>Originally posted</a> by Marco67
Do you guys think the advantages of copper outweighs the risks here?
what about the life of copper in soil/ sand?

Sorry, I don't mean to be a hog on this thread, I am just psyched about the issues and the potential of this type of cooling.

The advantage of the copper IMO are the rapid heat transfer and the stability of the metal when buried and wet. It is probably the perfect solution to this problem other than cost.

As far as the disadvantages, again cost is the only one I see. Assuming:
1. You are NOT using it in a sump as the heat exchanger.
2. You are not running tank water through it.
3. You insulate all piping above grade.

There may be more catches but that is all I can think of right now.

AH! One more thing I forgot to mention above is that with the closed loop systemyou NEED to provide an airvent to let the oxygen out so the cast iron impeller doesn't corrode.

 

[Marco67]

The biggest disadvantage/risk is that no matter what the design it will always have the risk of exposure to tank water (leak)

 

[douggiestyle]

<a href=showthread.php?s=&postid=7341817#post7341817 target=_blank>Originally posted</a> by Marco67
The biggest disadvantage/risk is that no matter what the design it will always have the risk of exposure to tank water (leak)

is that a complaint about this sytem or a compliment?

 

[Marco67]

Just a concern, something to be aware of
I love the idea of the heat transfer advantage, but darn a leak would cause very serious issues.

 

[douggiestyle]

<a href=showthread.php?s=&postid=7342508#post7342508 target=_blank>Originally posted</a> by Marco67
Just a concern, something to be aware of
I love the idea of the heat transfer advantage, but darn a leak would cause very serious issues.

some fresh water sitting in some copper pipe should cause little problems. if it all dumped into the tank there maybe something. but, there are a lot of people out there using tap water. if someone was to use some sort of antifreeze and a leak occured i would be very concerned. i dont know what antifreeze would do to a reef tank. i dont think it would be good. i would be more concerned with a comercial chiller leaking into my tank. im not worried, just if i had to pick a worst leak scenario that would be the one.
i have not tested any of these therories. im only using logic and known truths.

marco im not being critical, just trying to enlighten. this is such a great idea/system, i dont want anyone to be scarred away.

 

[salty joe]

Hey Cuby2k,
I looked at that link, the entire closed loop is under pressure caused by the pump, do I have it right?

If air getting to the pump is bad, then placing the pump in a lower position would be advantagious, wouldn't it?

Would a sight pipe at the top of the closed loop to keep an eye on the water level be worthwhile?

Would the expansion tank be filled with air? If so, would the air be under the same pressure as the water? Is this an expensive component?

I love the idea of geothermal, just trying to understand the basics.

Thanks,

Joe

 

[H20ENG]

Salty,
The loop should have a few psi even when its off. The expansion tank is there to deal with the expansion of the water at different temperatures.
You can get them at the Depot for $50. An air vent is another $25 or so.

 

[douggiestyle]

i think cubys more worried about heat expansion. i would think something like a home made water hammer arrester would work. or a store bought expansion tank. just like radiant heat, in the begining you would have to bleed it every now and then.

 

[chicken]

What are your guys thoughts of using an open loop setup? I wanted to use a 200g reservoir of water so I could deal with spikes in cooling demand? On top of that I am trying to use the geothermal setup for two different tanks of mine. One is a 200g reef (about 350g system capacity) and a 600g aggressive (about 1700g system capacity). I was thinking of using 3 different pumps. One between the 200g reservoir and the actual copper geothermal loop. Then I would use two other pumps, one each for my two tanks, between the reservoir and a titanium heat exchanger. Thoughts??

 

[H20ENG]

I can see you using 3 pumps. One for the chilled loop and the 2 others for "injection" pumps (just like zoned hydronics). When either setup calls for cooling ti will trigger that sytems injection pump AND the loop pump.
You would obviously have to have enough capacity for both systems.

 

[skeeter_ca]

This thread is great. Alot of useful ideas and genius thinking. But the threat of contamination is very real with any kind of cooling system. I knew a guy (urban myth type situation here)that had his chiller leak into the tank water. Wiped everything out in hours. If your using copper pipe in a closed system the water in the pipe will develop a high concentration of copper. What does copper do in a reef tank. Can you spell WIPE-OUT. The only way to make it the safest is to use total inert material, which won't be as efficient. Use sterile water, as most all water has organics and will decompose in a closed enviroment. Thats one reason i used an open system with tankwater flowing through it and all pvc. FWIW.

 

[Cuby2k]

<a href=showthread.php?s=&postid=7343475#post7343475 target=_blank>Originally posted</a> by H20ENG
Salty,
The loop should have a few psi even when its off. The expansion tank is there to deal with the expansion of the water at different temperatures.
You can get them at the Depot for $50. An air vent is another $25 or so.

Salty, I agree with what H20ENG has said. The idea is that if the system is at a positive pressure at rest, the pump won't need to worry about getting water to start. The neat thing about the little (5 gallon or so) tanks at the Depot is they have a fill valve that you can add pressure to the system as needed.

Also, Doug mentioned the issue of expansion due to temperature swings and the expansion tank takes care of that. It has a rubber type of bladder in there that moves with the pressure variations.

You know you could put a small manual ball valve at the high point of the system and it could act as an air vent. Just run a 1/2" PEX (or whatever) line to a high point in your house and put the valve there. The air in the system will tend to gravitate to that high point where you can vent it.

I almost hate to mention this, but it would be nice to put a pressure reducing valve on a domestic water fill line that is connected to the system. This could be dialed in to a minimum and then when air is vented, it would be replaced by city water.

But don't let that get in your way of moving ahead.

You probably should add thermometers on the supply and return so you could document the temperature differences.

ARGH! I want to try this now. At this rate I am going to have a very cool system setup but with ZERO livestock. I guess this is what attracted me to this hobby in the first place. I can't wait until I know enough to ask questions about water testing and feeding and all that.

 

[Cuby2k]

I have a question concerning the two tank setup that chicken asked about. Isn't it good to keep the water systems separated when using multiple tanks?

Also, aquadw, I agree that if you had a leak from a closed loop system bleed into your tank water it could be (it WOULD be)disastrous. But if the piping were properly installed the chance of that happening are really pretty small. I would put it on the same scale as a kid in the neighborhood shooting a pellet gun through the kitchen window and right through the front wall of your tank.

Could it happen, sure.
Has it happened? It wouldn't surprise me.
But will it happen again? I would bet you could buy a home owners policy amendment for cheap saying that it won't happen.

I am not making light of your concern, it is valid, but man there are so many things that could go wrong . . . . I guess I am saying that the benefits of the copper pipe in the earth far out way the risks.

As I think about it, a closed loop system soon becomes void of oxygen so corrosion is lessened. But I know that ANY closed loop system gets pretty rank after a while. That's just another point that system failure, in the heat exchanger, is pretty rare.

If anyone does this I hope you document it and share the results. I promise that I will when I get around to it.

 

[chicken]

Cuby2k I am going to have two titanium heat exchangers, one for each of my tanks. Those in turn will have a circulation pump from the 200g reservoir that gets kicked on as needed.