Determining head pressure by GPM?

You might want to turn that pressure relief valve toward the wall on the wood stove loop - those loops boil quick when some circulating element fails. Here we have to take it outside and turn it downward.

Why not put the return flow to the well through 3 or 500 feet of poly pipe laid in a pit or trench to gain or lose heat before that dump back into the well?

Sorry for delayed response, I have been working. You are going to need to make a few changes from your drawing. Pressure tank needs to be on the incoming line from well. Otherwise when your Taco valve opens, the water from your pressure tank will be dumped down the well before the pump will come on. During this time there is no flow to the Heat Pump.

Also need to do away with the anti-syphon valve.

I would run the return pipe close to 450' deep, and keep the pump as shallow as possible.

Anytime you use water in the house it will draw in fresh water into the well and help with the heat exchange. If your heat pump runs a long time without having used any water in the house, it is possible to heat up or cool down all the water in the well, especially if there is no flow in the aquifer. You could use a thermostat in the incoming line that operates a sprinkler or solenoid valve. This valve will dump water through a sprinkler or just outside the house, which will draw fresh water into the well and cool or heat it up as needed.

Give me a few days and I will see if I can help with a new drawing. In the meantime you can call me during regular working hours if you have more questions.

Cary Austin
800-652-0207

Also, my picture was taken before I completely finished. The pressure relief valves have since been plumbed to a drain.

valveman
Don't apologize, I don't expect any responses unless at your convenience.

Due to my inexperience at this, I think I misled you with my novice drawing.

If my pressure tank wants to discharge to my return line it has two choices...
1) go the 'wrong way' thru the back-flow preventer
2) push it's way thru a back-pressure valve at over 50-60 psi.
Let me know if you still think it's a problem.

I created that little loop to the domestic water line, so I can reduce pressure when the heat pump is the only thing calling, increasing flow and reducing pump strain.

Anti-syphon valve will be eliminated (it was an artifact left over from a design with a 10% bleed circuit).

Please don't spend much time on me (making a new drawing), you (and others) have already given me more time than I was hoping to take.

Thanks valveman

FYI to anyone, a G.C. friend of mine just told me to use a bronze insert male adapter on my poly to pvc connection, he said it's a much thinner wall than the nylon ones, and will help with flow.

I don't understand the rationale for Valveman's suggestion of putting the return to 450 ft and the pump as shallow as possible. Since the well is about 450 ft deep that appears to mean that he would put the pump near the top of the water level in the well. I don't see the thermodynamic advantage of it but perhaps Valveman can provide the heat and mass balance analysis that supports his suggestion.

Without any irrigation you will probably use about 250 gallons per day over about 16 hours. At a 20 degree F difference that will contribute only about 2500 BTUs per hour which is a very small part of the heat pump load. In one hour you will pump 25 to 30 times as much water for the heat pump as you will for domestic use.

Since most of the energy comes from heat transfer between the well wall and the earth, the pump and return should be as far apart as possible, but the pump should be located where it will get the most reliable source of water. I would be reluctant to place it high because of the risk that it would run out of water at large drawdowns.

Your well has a static of 1'. After 2 hours of 5 GPM the pumping level is 107'. Without any irrigation, I would think that the house use will never pull the water level down to 107'. Therefore, I would set the pump at maybe 120'. To keep the pump and discharge pipe as far away from each other as possible, I would set the discharge pipe close to the bottom of the well. Also, if the pump is already set close to the bottom of the well, you should set the discharge pipe at about 120'.

If there is any flow in the aquifer, the well water will not heat up. Heat and mass balance analysis all depends on this. Some wells do not have this type of flowing aquifer and will not allow in fresh water until you displace water from the well. Then I would install a purge valve connected to a thermostat. When the well water heats up, the purge valve will dump water outside or to a sprinkler until the water temp drops. Opposite for heating conditions.

Without drawing a picture, I would put things in this order. Pump, pressure tank, pressure switch, heat pump, tee with one side to house, and other side of tee to Taco Valve, back pressure valve, and then to discharge in well at 450'. The only back flow preventer you need is the check valve on the sub pump itself.

You really need to hold about 50 PSI back pressure on this pump when discharging back to the well. Otherwise the siphon effect and no back pressure will cause the pump to go into upthrust and destroy itself. Difference in power consumption for this pump between 0 PSI discharge pressure and 50 PSI discharge is minimal.

The back pressure valve in your drawing, set at 50 PSI, will not let the tank drain below 50 PSI, so the tank will not empty to 40 and the pump will never start. Also you would only have one tank of water for the house. When the tank is empty the house would have no water. With a back pressure valve in the right place, you will have the same pressure in the house as is held by the back pressure valve. Install the back pressure valve as the last thing before the discharge pipe. Set it to 50 PSI and turn your pressure switch up to 52/72. I use a Cla-Val CRL 20-200 pressure relief valve for this purpose. It is not a cheap valve but, very accurate and reliable. I can help you with this if needed.

The flow required for the heat pump can be controlled by the pressure setting of the back pressure valve. It will also determine the house pressure. When you use water in the house, the back pressure valve will reduce the amount being dumped back down the well but, the flow through the heat pump will still be the same or slightly more as the system pressure decreases.