Open Loop pumping, looking for improved efficiency

I have a 5-ton WF Envision Dual Unit coupled to an open loop supplied with water from my well pump (a 3/4hp 16gpm supplying both my domestic water, and water for my WF.)


One area where I think improvement may be found, is in the pumping. Since I only have 1 supply well, and it provides my domestic water as well as supplying my geo furnace as 12gpm. My current pump, like most water pumps, is horribly inefficient, at almost 1.5kw.

Does anyone know if it is possible to t-off from my current supply line and add a small pump to run the furnace, using the check valve at the bottom of the submersible as the check valve for the pump supply line?
When the domestic water calls for the submersible pump, there will be a positive pressure on the back of the furnace pump, but other than that I can't seem to see an issue. Any ideas?


Here are two drawings of my current and proposed systems

Hello Project x
Your proposed set up is very interesting. I have done this the other way around. That is with the high flow, low pressure pump in the well, and a booster for the house. Your idea should work, but I am seeing a couple of control problems. Been busy, so I need some time to think about it. It is a great idea. I can see where the right combination could cut your pumping cost to 1/3rd of present. I will look up some pump curves tomorrow.

OK, I found a 1/3 HP centrifugal pump that will deliver 12 GPM at about 60' or 25 PSI. The flow control for the heat pump will need to be opened up so you get 12 GPM at only 25 PSI. The depth to water will be critical. If it stays at 5', or at least does not fall below about 15', a Sta-Rite JHB pump should work. Now for the control issues...

This booster pump can be started and stopped by the heat pump controller. Heat pump comes on, discharge valve opens, pump comes on. Heat pump goes off, discharge valve closes, pump goes off. No problem. However, this kind of pump is designed for about 60 PSI max, so it should have a 75 or 100 PSI seal and gaskets. When the 3/4 HP, 16 GPM sub comes on, the back pressure on this booster could be as high as 104 PSI. I am afraid this alone will blow out the seal and gasket on the booster.

Now if we do not turn off the booster when the sub is running, the booster will add 25 PSI to the amount of pressure coming from the sub. When the house is using very low flow, the back pressure from the sub will be 82 PSI at 12 GPM. So the booster will be putting 107 PSI to the heat pump. This will dramatically increase the flow to the heat pump as the flow control is adjusted for 25 PSI. Even if we turn off the booster when the sub is running, the pressure on the heat pump will still be 82 PSI, and the flow will be too high.

Turning the booster off when the sub is running is another problem. The sub will turn on and off as the water is used, and then turned off in the house. This means the booster will have to cycle every time the well pump cycles. It would be better to let the booster pump continue to run. It is not going to make much difference in the pressure, which will be too high either way.

There is also an issue with drawing water from between two check valves on the well system. When everything is off, the booster line and heat pump will drain the pressure from between the check valves. When the well pump starts, this can cause water hammer, which will slam into the second check valve and also the booster pump. Water hammer multiplies the pressure by a factor of 10. So the 80 PSI coming from the well pump could be a 800 PSI thump on the booster pump. This will most certainly take out the seal and gasket.

The only way I can see this working is if the two pump systems were separated. Add a stinger pipe with a foot valve to the booster pump, and drop it in the well about 20' with the sub. Let the well pump supply the house, and the booster pump supply the heat pump. As long as the water level stays above 15', this will work. If the combined pumping of the two pumps pulls the water level lower than 15', the booster pump will run dry and burn up.

Later I will describe how to do this with a low pressure, high volume well pump, and a booster for the house.

valveman, thanks for your detailed information, I will review them this evening.

Another way to cut pumping cost which would be easier to control follows. I would use a 16S05-5 pump end, remove 2 impellers, and use a 1/3 HP motor. This pump would deliver 16 GPM at 50' of lift. Control this well pump with a 20 PSI Cycle Stop Valve, a small pressure tank, and a 10/30 pressure switch. After the pressure tank, one line tees off to the heat pump, another tees off to a booster pump for the house. Use about a 3/4 HP jet pump with it's own Cycle Stop Valve set at 50 PSI, and a 40/60 pressure switch.

When the heat pump alone is running, an electric discharge valve opens, the pressure tank drains to 10 PSI, and the pump starts. The 20 PSI CSV will vary the flow to match the 12 GPM usage and maintain 20 PSI. This should cut your pumping cost to 1/3 of what the 3/4 HP is doing now. When the heat pump shuts off, the electric discharge valve closes, and the CSV slowly fills the pressure tank to 30 PSI, and the well pump is shut off.

When the house alone is using water, the pressure will drop from 60 to 40 PSI and the 3/4 HP jet pump will start. The 50 PSI CSV will maintain 50 PSI to the house no mater the flow rate being used. This jet pump system is drawing water from the well pump system, so the pressure tank on the well pump system empties as the pressure drops from 30 to 10 PSI, and the well pump is started. The CSV on the well pump feeds exactly as much water to the jet pump booster as the house is using. Both pumps run as long as the house is using water. When the house stops using water, the CSV on the jet pump will slowly fill the pressure tank to 60 PSI, and the jet pump is shut off. Then the CSV on the well pump will slowly fill it's pressure tank to 30 PSI, and the well pump is shut off.

When the heat pump is running, the well pump/CSV is delivering 12 GPM at 20 PSI. If the house needs water at the same time, the jet booster pump comes on, and the CSV on the well pump opens up to supply both the heat pump and the jet booster pump. Depending on the water level, you should be able to get about 18 GPM total when the house and heat pump need water at the same time. When the house no longer needs water, the jet pump system will fill it's pressure tank to 60 PSI, and the jet pump is shut off. Then the CSV on the well pump reduces the flow to 12 GPM, matching the amount used by the heat pump. Again, when the heat pump is shut off, the well pump fills it's pressure tank to 30 PSI, and both pumps stay shut off until water is needed again.

If the water level in the well pulls down to more than 20' at high flow, you will have to stay with a ½ HP well pump and not remove impellers from the 16S05-5. Even this will cut your pumping cost to half of what they are now.

I have a couple of additional questions,


What if I put a 20psi CSV between the "T" and the furnace pump? This would limit the pressure on the supply side of the furnace pump.

scenario 1.
Furnace triggers a pump start relay on the furnace pump and supply's water pulled through the check on the sub.
Will the 20psi CSV work in this fashion (i.e. without a high pressure behind it)?

scenario 2.
Furnace pump is running, and sub is turned on, sub will supply water to the house @50psi, and @20psi to the furnace pump. (Two pumps running, but only for a short period)

scenario 3.
similar to 2. demand for domestic water turns on sub. Furnace triggers pump start relay and supplies the furnace.


From a control perspective this should be relatively simple, a pump start relay for the furnace pump and the current pressure tank./switch/ CSV for the sub.


I guess the issue is still the water hammer...
I'm sure that I am missing something,....

The CSV is designed to hold pressure but not a vacuum. It will actually let air in under a vacuum and the pump will lose prime. When the booster pump is not running, the CSV will still let the pressure equalize on both sides. This means the seal and gasket on the booster will still see high pressure from the back pressure of the submersible. I still think the simplest solution is to drop a 20' stinger with a foot valve in the well for the booster pump.

valveman said:

The CSV is designed to hold pressure but not a vacuum. It will actually let air in under a vacuum and the pump will lose prime. When the booster pump is not running, the CSV will still let the pressure equalize on both sides. This means the seal and gasket on the booster will still see high pressure from the back pressure of the submersible. I still think the simplest solution is to drop a 20' stinger with a foot valve in the well for the booster pump.

Click to expand...

I get it, I had also forgotten about the water hammer.