Most Efficient Open Loop Geo System

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Valveman

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A customer has a 45' deep well with a water level at 15'. The Geo system requires 8-15 GPM at 20 PSI. The house requires about 5 GPM at 50 PSI. Using the smallest pump that will deliver the flow required is the most efficient system. Also using a submersible with a good drop in horsepower at low flow rates will help with efficiency. A Grundfos 16S05-5 is a 1/2HP that can deliver 20 GPM at 20 PSI from a depth of 24' using a CSV set at 20 PSI and a 10/30 pressure switch setting. And when restricted with a CSV to supply the 8 GPM heat pump zone that pump will only be drawing about 1/3HP load. This would be the smallest pump using the least amount of energy possible for the Geo system.

When the house needs water an additional 1/2HP jet pump can draw from the same line as the heat pump. The jet pump will pick up the 20 PSI delivered by the well pump and boost the pressure to 50 PSI for the house. So both pumps will run when the house needs water, but the little well pump will be running by itself when only the heat pump is being used. The house will only use water maybe 30 minutes per day, which is the only time both pump will be running. The heat pump could run for many hours per day while the little 1/2HP will be easing along at a 1/3HP load.

This two pump system allows the heat pump to work at 20 PSI and use the smallest and most efficient pump, while the extra pump comes on to boost the pressure when the house needs water. See the following drawing.
DUAL PUMP_HEAT PUMP-HOUSE SUPPLY.jpg
 

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In the example above the well pump needs to be able to supply 20 GPM, as the heat pump needs 15 GPM and the house needs an additional 5 GPM. In this example we can supply the heat pump and the house with a 15 GPM pump. All the water goes through the heat pump before going to the house, so the demand needed for the house doesn't add to the amount the heat pump needs. The water coming to the house will be a few degrees colder or warmer than when coming straight from the well pump, but this will let you use a smaller well pump and save the most energy.

Now we can do this 15 GPM heat pump and a 5 GPM house demand at the same time with a 15 GPM pump. Instead of a 1/2HP well pump to supply 15 to the heat pump and 5 to the house as in the above example, now a 1/3HP, 15 GPM pump is all that is needed. Since the heat pump could run many hours a day or even 24/7, it is most efficient to have the smallest well pump that can do the job.

1/3HP well pumps have become as "rare as hen's teeth". I am not able to find a 1/3HP that will do 15 GPM at 70' of head. So when using a 1/2HP in this case it won't make any difference if you tee off to the house before or after the heat pump. However, in most cases teeing off to the house after the heat pump allows the use of one size smaller well pump than if you tee to the house before the heat pump. The deeper the water in the supply well, the more difference this example makes. See this following drawing of how this is plumbed.
DUAL PUMP_HEAT PUMP-HOUSE SUPPLY from heat pump.jpg

Solenoid valve #1 must open when heat pump #1 is on, and it must also stay open and be able to dump the combined flow of all heat pumps when heat pumps 2,3, and 4 are all on. So the pressure sustain valve will be set to 20 PSI, which will hold back as much water as needed to feed the booster pump when the house is using water.
 
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MichaelSK

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In the example above the well pump needs to be able to supply 20 GPM, as the heat pump needs 15 GPM and the house needs an additional 5 GPM. In this example we can supply the heat pump and the house with a 15 GPM pump. All the water goes through the heat pump before going to the house, so the demand needed for the house doesn't add to the amount the heat pump needs. The water coming to the house will be a few degrees colder or warmer than when coming straight from the well pump, but this will let you use a smaller well pump and save the most energy.

Now we can do this 15 GPM heat pump and a 5 GPM house demand at the same time with a 15 GPM pump. Instead of a 1/2HP well pump to supply 15 to the heat pump and 5 to the house as in the above example, now a 1/3HP, 15 GPM pump is all that is needed. Since the heat pump could run many hours a day or even 24/7, it is most efficient to have the smallest well pump that can do the job.

1/3HP well pumps have become as "rare as hen's teeth". I am not able to find a 1/3HP that will do 15 GPM at 70' of head. So when using a 1/2HP in this case it won't make any difference if you tee off to the house before or after the heat pump. However, in most cases teeing off to the house after the heat pump allows the use of one size smaller well pump than if you tee to the house before the heat pump. The deeper the water in the supply well, the more difference this example makes. See this following drawing of how this is plumbed.
View attachment 36362
Solenoid valve #1 must open when heat pump #1 is on, and it must also stay open and be able to dump the combined flow of all heat pumps when heat pumps 2,3, and 4 are all on. So the pressure sustain valve will be set to 20 PSI, which will hold back as much water as needed to feed the booster pump when the house is using water.

That's very interesting. Very interesting indeed.

On my heat pump the thermostat sends a signal that tells the heat pump to open a solenoid valve on the discharge side. I control the flow with a suitable orifice. One would have to create a feedback system whereby a flow sensor would balance the "house demand" with a discharge pipe (sorry, I am not a plumber or engineer so the nomenclature is off - sorry). The flow sensor would be responsible for, in my case, delivering a steady 7 gpm when the heatpump is on to the house, irrigation, or pond discharge. Does that make sense?

Currently, what I have done here in Florida is use the 7 gpm heatpump discharge to irrigate the yard, garden etc.

Currently there are two adults in this house. What do you figure for adults water use per day - maybe 60 gals? That would be, lets fudge a little - 150 gals/day. That's roughly 22 minutes of heatpump discharge. My system runs much more than that, moreover the water usage may not correspond with the heatpump running, i.e the flow sensor balancing system would shunt the discharge out of the house potable water.

I think it still comes down to either using your CSV or a large pressure tank. There is not a substantial change in head between the "needs." It's mainly a difference in flow demands. My problem is I don't know anything about pump efficiency and designs to make the choice of a pump. That is to say: would it be better to employ a pump with more stages (e.g. all pumps using a 3/4hp motor, but #1 a 12 stage nominal 10 gpm with a flow range of 5-14; or #2 a 8 stage nominal 16 gpm with a flow range of 10-20 gpm?)
 

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You don't need a flow switch. The modulating pressure sustain valve controls the flow. After your solenoid valve the pressure sustain is set to the pressure that makes your pump produce 7 GPM. So when the heat pump is running by itself, the solenoid opens and the pressure sustain maintains 20 PSI of back pressure, which should make the pump produce 7 GPM.

Using a low head, high volume well pump will change the head requirement quite a bit. This pump only needs to produce about 20 PSI at 12-15 GPM. When the heat pump is on by itself the well pump only produces 7 GPM. But when the house and/or irrigation is using water, it is coming through the additional booster pump that picks it up at 20 PSI and boost to 50 PSI. If the house is only using 5 GPM, then there is 2 GPM being discharged from the pressure sustain valve. If the house and/or irrigation is using more than 7 GPM, the pressure sustain valve will close and all the water will be coming through the heat pump, to the booster pump, and on to the house and/or irrigation. Anytime the house and/or irrigation is using water, it will be coming through the heat pump no matter if the heat pump is on or not. And when the house and/or irrigation is using more than 7 GPM, there will be more than 7 GPM going through the heat pump. If/when the heat pump is being used, this extra flow will not hurt anything and will actually make the heat pump more efficient.

Depth of pumping level makes a lot of difference in the size of well pump you can use?
 

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You don't need a flow switch. The modulating pressure sustain valve controls the flow. After your solenoid valve the pressure sustain is set to the pressure that makes your pump produce 7 GPM. So when the heat pump is running by itself, the solenoid opens and the pressure sustain maintains 20 PSI of back pressure, which should make the pump produce 7 GPM.

Using a low head, high volume well pump will change the head requirement quite a bit. This pump only needs to produce about 20 PSI at 12-15 GPM. When the heat pump is on by itself the well pump only produces 7 GPM. But when the house and/or irrigation is using water, it is coming through the additional booster pump that picks it up at 20 PSI and boost to 50 PSI. If the house is only using 5 GPM, then there is 2 GPM being discharged from the pressure sustain valve. If the house and/or irrigation is using more than 7 GPM, the pressure sustain valve will close and all the water will be coming through the heat pump, to the booster pump, and on to the house and/or irrigation. Anytime the house and/or irrigation is using water, it will be coming through the heat pump no matter if the heat pump is on or not. And when the house and/or irrigation is using more than 7 GPM, there will be more than 7 GPM going through the heat pump. If/when the heat pump is being used, this extra flow will not hurt anything and will actually make the heat pump more efficient.

Depth of pumping level makes a lot of difference in the size of well pump you can use?

Very interesting concept...

It's very interesting how you control flow with the modulating pressure sustain valve. Really, very cool.
Changes in well dynamics (e.g. static water level [head], pump motor electrical efficiency [electrical & mechanical], pump end efficiency [wear and tear...], etc.) are compensated for by the PSV?

Currently the heat pump logic controls the solenoid valve on the discharge side of the heat pump. One would disable that function entirely.

RE: the pump design (number of stages) - my static water level is usually around 30 feet, perhaps as deep as 45 feet. With your CSV design, can you opine as to the two pump choices.?

(I am a nurse....used to work with pumps too...lol)
As an aside, you better than most folks, can understand why it's so important to maintain one's blood pressure within optimal "design" parameters. In part because it puts a lot of wear on the pump and other plumbing. Too bad our pump is not a centrifugal design...lol
 

MichaelSK

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Very interesting concept...

It's very interesting how you control flow with the modulating pressure sustain valve. Really, very cool.
Changes in well dynamics (e.g. static water level [head], pump motor electrical efficiency [electrical & mechanical], pump end efficiency [wear and tear...], etc.) are compensated for by the PSV?

Currently the heat pump logic controls the solenoid valve on the discharge side of the heat pump. One would disable that function entirely.

RE: the pump design (number of stages) - my static water level is usually around 30 feet, perhaps as deep as 45 feet. With your CSV design, can you opine as to the two pump choices.?

(I am a nurse....used to work with pumps too...lol)
As an aside, you better than most folks, can understand why it's so important to maintain one's blood pressure within optimal "design" parameters. In part because it puts a lot of wear on the pump and other plumbing. Too bad our pump is not a centrifugal design...lol

That must be a BIG house with four heat pumps. I designed and built my house circ. 1990. It's about 2100 ft2. My electric bill is now about 80 - 90 dollars/month (and I keep it cool in the summer 70F).
 

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You want to continue letting the heat pump control the solenoid valve to discharge water. But after the solenoid valve will be the modulating pressure sustain/relief valve. Even when the solenoid valve is open to discharge, the pressure sustain will only let it dump water if needed. If the house is using 7+ GPM, the pressure sustain valve will be closed and no water will be discharged. If the house is using 3 GPM, the pressure sustain will be dumping the extra 4 GPM the heat pump is using.

I would use a 10S05-9, 1/2HP in the well with a PK1A set to 20 PSI with a 10/30 pressure switch. Then I would use an additional 1/2 or 3/4HP jet pump as a booster for the house. The booster will increase the pressure from 20 to 50 PSI when the house needs water. All other times the well pump will be supplying 7 GPM at 20 PSI directly to the heat pump.
 

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That must be a BIG house with four heat pumps. I designed and built my house circ. 1990. It's about 2100 ft2. My electric bill is now about 80 - 90 dollars/month (and I keep it cool in the summer 70F).

The drawing is for a system with 4 heat pumps. The OP has a single stage heat pump that uses 7 GPM.
 

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You want to continue letting the heat pump control the solenoid valve to discharge water. But after the solenoid valve will be the modulating pressure sustain/relief valve. Even when the solenoid valve is open to discharge, the pressure sustain will only let it dump water if needed. If the house is using 7+ GPM, the pressure sustain valve will be closed and no water will be discharged. If the house is using 3 GPM, the pressure sustain will be dumping the extra 4 GPM the heat pump is using.

I would use a 10S05-9, 1/2HP in the well with a PK1A set to 20 PSI with a 10/30 pressure switch. Then I would use an additional 1/2 or 3/4HP jet pump as a booster for the house. The booster will increase the pressure from 20 to 50 PSI when the house needs water. All other times the well pump will be supplying 7 GPM at 20 PSI directly to the heat pump.
Thanks
 

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Valveman, would you post a schematic. Since my head injury (TBI), I need to see drawings....I cannot visualize anything in my head anymore. I can't do any work standing now - I have to concentrate on visual clues to have any clue where my body is in 3D space (huge vestibular defect now)....sigh
I just completely redid all the plumbing in my house (all PEX home-runs to a Manabloc manifold). It took me a long time. I am very pleased with the results. Remodeled the kitchen, bathrooms, porch...all part of therapy (I couldn't walk, had difficulty speaking, hallucinations,etc. It was interesting being a patient in the neuro unit....)

I will try to post a photo that shows the PEX manifold in the new wet wall that I built, on the right is the heat pump hotwater heater mounted on a dolly so that I can easily disconnect the unit and roll it into the great room where it is easily worked on.
IMG_5444.jpg
 

MichaelSK

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You want to continue letting the heat pump control the solenoid valve to discharge water. But after the solenoid valve will be the modulating pressure sustain/relief valve. Even when the solenoid valve is open to discharge, the pressure sustain will only let it dump water if needed. If the house is using 7+ GPM, the pressure sustain valve will be closed and no water will be discharged. If the house is using 3 GPM, the pressure sustain will be dumping the extra 4 GPM the heat pump is using.

I would use a 10S05-9, 1/2HP in the well with a PK1A set to 20 PSI with a 10/30 pressure switch. Then I would use an additional 1/2 or 3/4HP jet pump as a booster for the house. The booster will increase the pressure from 20 to 50 PSI when the house needs water. All other times the well pump will be supplying 7 GPM at 20 PSI directly to the heat pump.


I forgot to ask: irrigation for about 13,000 ft2 garden/yard?
 

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Your heat pump only needs 7 GPM, and since the house and irrigation will use the water coming out of the heat pump, there is no additional demand for the well pump. So the irrigation is actually what determines the size of pump you need. The 10S05-9 I suggested will only give you about 12 GPM for the irrigation. If you want to be able to run the irrigation at times when the house would also be using water, I would suggest adding 5 GPM for the house to the demand needed for irrigation. Also the booster pump will need to be large enough to run the house and irrigation at the same time.

The drawing will be the same as the second one above, except you will only have one heat pump instead of four.
 

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Valveman, is it possible to "over-drive" (sorry don't know the proper 'pump-terms') the little 10S05-9 pump? For example: the heat pump is running (7 gpm), irrigation (sized to 12 gpm), house (5 gpm) = approximately 17 gpm flow with the booster pump.....? Does operating outside the little 10S05-9 parameters endanger the submersible?

Is it just problematic trying to irrigate with the smaller pump?
 

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Irrigating with a smaller pump just means it takes longer to get things watered. What you can do with 12 GPM in 3 hours would take 6 hours at 6 GPM.

I doubt that you can even draw more than 17 GPM from a 10S05-9. If you can it will certainly put the sub in an upthrust condition. But it probably won't hurt a little pump like that very much.
 
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