Geothermal heat pump

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smackre

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New to the forum but joined to see if I could pick up some ideas for my Geothermal.

I have a brand new 6 ton 2 stage geothermal heat pump. Kinda a diy project I have been working on for a year. I had a well drilled to supply water to it and also my domestic water. 1HP pump that pumps about 25GPM. My goethermal pump requires 8gpm on first stage and then 4 additional gpm on the second stage for a total of 12gpm. I have normal water needs for domestic water. I have 32 gallon well tank with around I think 10 gallon draw down.

I was wondering about CSV valves. Is that the way to go on a open loop geo setup with domestic water tied in with it.

Also my pump right now is running at 40/60 pressure and that is way to much for my heat pump. Do people generally run 40-60 pressure thru there geothermal?

Which valves do you guys suggest. I was looking at this for my shutoff valves:
http://www.supplyhouse.com/Taco-Z075T2-2-3-4-Zone-Sentry-Valve-Normally-Closed-Threaded

And this for my flow regulators:
http://www.build.com/watts-0856738/...81159&ef_id=VVDEeAAAAf1i73c0:20150511152203:s

I saw on another forum someone using the discharge on there geothermal for there domestic water and that seemed like a good idea. It would make weird temperature water sometimes but it should make hot water heater and desuperheater not do a lot in the summer.

If you have any advise let me know.

Thanks
 

valveman

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A heat pump only needs about 20 PSI to cover the 10 PSI loss across the heat exchanger. You could use a 3/4HP, 25 GPM pump to do that lower pressure. Then you would need a 1/2HP jet pump to boost the pressure to the house to 50 PSI. But the extra booster pump won’t run 30 minutes a day. So the 3/4HP would be running at about 1/2HP load when restricted to 8-12 GPM. This would save some energy over the 1HP running at a 3/4HP load all the time for the heat pump, and up to 1HP when the house also needs water.

I am experimenting with using the discharge from my heat pump to supply my house. In this way you won’t need 12 GPM for the heat pump and another 6-8 GPM for the house, requiring a 20+ GPM pump. The 12 GPM coming through the heat pump would then go to the house as needed, making a 12 GPM pump all you would need. At 20 PSI and using a jet pump to boost the house pressure when needed, this would reduce the required well pump size to 1/2HP. And it would be using less than 1/2HP much of the time. This offers a great deal of energy savings on the heat pump use, and the water to the house is only 10 degrees warmer or colder than normal, depending on the season.

Some people told me that it might no be safe to drink water that has run through the heat pump coils. But I had it tested for copper, nickel, and a host of other things, which came out clean. I have been using my heat pump this way for 8 years now and love it. I did learn that I need to use a very small tank with the CSV for my well pump, so there is enough flow through the heat pump at all times. I found out with a larger pressure tank that my heat pump was starving for water when the pressure tank was refilling. I switched it out to a 4.5 gallon size than and have not had any problems.
 

smackre

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I really like that idea. Any chance I can get a diagram where you put your valves. I'm not sure how you got domestic water when the geothermal is off. Did you put in a backup way for when the valves are closed on the Geo. Do you have two CSV values or just one? Also what values did you use and flow regulators?
 

valveman

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I just teed the house into the discharge of the heat pump before the electric zone valve. After the electric valve I have a pressure sustain/pressure relief valve. The pressure sustain is set to hold back 50 PSI to the house. When the heat pump is not running, the water still flows through the heat pump on the way to the house. When the heat pump is working the electric valve is open. Then the pressure sustain valve holds back 50 PSI to the house. If the house is using 3 GPM, the pressure sustain is dumping 5 GPM. If the house is not using any water, the pressure sustain dumps 8 GPM. If the house is using 8 GPM, the pressure sustain valve closes and doesn’t let any go to the dump well.

Your second 3 GPM electric zone valve would just need to tie into the dump line, as the house will be served through the heat pump before the 8 GPM zone valve. If the house is using more than 8 GPM, it will just flow more than 8 GPM through that zone, which actually makes the HP more efficient.

An open loop heat pump is only as efficient as your pumping cost. So it pays to use as small a pump as possible, and this is a good way to make that happen.

I just have one CSV on the well pump and it will make the well pump supply from 1 GPM to 11 GPM, depending on how much water the house and the heat pump is using.
 

smackre

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Valveman what are you using for flow regulators and shutoff valves?

What pressure sustain/pressure relief valve are you using?
 

valveman

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This is the electric valve I use. It is inexpensive and has a flow control knob on top.
http://www.irritrol.com/valves_205.aspx

This is the pressure relief valve I use. The ¾” is only good to about 6-8 GPM. You may need one a little larger. These are not cheap valves, but they work very well for small flow like mine at 3-5 GPM. You maybe able to find a larger and less expensive one. All you need is a modulating pressure relief/pressure sustain valve good for about 8 GPM.
http://www.cla-val.com/documents/pdfs2/ECRL_55F.pdf
 

smackre

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I really like your idea of using a smaller pump. And I will go down that road later on. Right now I want to get the heat pump running off the pump I got. I can see how that would cost me money pumping. I'm going to get two of those plastic valves and wire up the heat pump and see how it acts. But I like that CSV over the large pressure tank.
 
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