Well modifications for Geothermal

[Bill Arden]

It's strange how much cooling you need for only 90F outdoor temperatures.

It's examples like this that shows how much the local climate makes a big difference.

FYI: Here in MN the ground temp is around 65F and the outdoor temp ranges from -40F to +100F

Some thoughts
1. Valveman: Why would a "jet pump" be needed when the water is already at the surface and thus a regular "centrifugal pump" would work for the booster pump?

2. With such a low static water level, mild warm climate, and high water temperature you might be better off with "air source".

Closed loop would be better, but is probably too expensive until cheaper drilling is available.
(Vertical Ground source wells are getting cheaper. I'm guessing half price per decade?)

3. How is the Day/Night temps? A nighttime "ice making" system might be cheaper to run.

4. insulation R-Values, Radiation shields, Solar shading?

 

[iamjcl]

Thanks for the suggestions -

I'd say its often more than 90 degrees, but not that often is it much above 95.

That said, the house is fairly large, has high ceilings, has air infiltration levels higher than I'd like (working on that), and is less-insulated than I'd like.

No doubt that what you mention and other factors could improve the overall power-use situation, but streamlining the AC / well power use will help no matter what other improvements are made to go with it, and I was focusing on that in this forum since I haven't really found someone in my area who seems to know a whole lot about this type of thing.

Nightime ice-making sounds like a promising (albeit overly-complicated for residential) possibility, except for the fact that the power company offers no timed rate plan at this time. I asked about it recently.

Air source would probably (as my math seems to illustrate) be about as good with less fuss, but I've just put 3 new H20 units in, and have a 4th still working OK, and don't really have a good place to physically put the outside units. Also have grown fond of the "no noise" factor when I'm on a porch or in the yard.

 

[Sponsor]

 

[Valveman]

Pumping up to 60 PSI is the same as lifting an additional 138'. This more than doubles the horse power required to do the job. The heat pump does not need any pressure, just flow. You only need to develop enough pressure to overcome the friction loss of the heat pump coils and the piping going to them, which is probably less than 10 PSI.

You don't need a Cycle Stop Valve. The electric valves at each heat pump should have a flow control knob, or you need a ball valve with the electric valve. Then you regulate flow to each heat pump as needed with the manual valve. The flow rate of the pump will be determined by running either 1,2,3, or 4 heat pumps at a time. When running only 1 heat pump by itself, the flow will be lower and the 1 HP pump will only be using about ½ HP worth of power. When running 4 heat pumps , the pump will be pulling a 1 HP load. This will get you the lowest electric bill possible for pumping the water to the heat pump.

Then if you use the discharge water from the heat to irrigate with, not only are you not wasting this water but, you are using the same water twice, which makes it more energy efficient. A jet pump is a centrifugal pump, it just has a venturi nozzle to help increase the pressure. A standard centrifugal pump may need to have multiple stages or impellers to produce the same pressure as a jet pump but, either one will work as long as it builds the pressure you need. The jet pump will pick up the water at maybe 5 PSI and boost it to 50 PSI. If you do this before a heat pump, you will be boosting cool water. Then the heat pump coil will have 50 PSI when you are irrigating, instead of only 5 PSI when only the heat pump is running.

I know this is a new 2 HP pump, and changing to a 1 HP pump with a 3/4 HP jet pump added for irrigation, may cost more than the energy you would save. However, you should consider that cycling the 2 HP pump the way you are now, it will probably have to be replaced every couple of years. How much extra energy can you afford to pay for, to keep from having to replace that pump every 2 years? In other words, how much is it going to cost you per month, to replace that pump every 2 years, compared to having that pump last 20 years?

This is where the Cycle Stop Valve comes in. It will actually cost a little more in energy to use a CSV on that 2 HP pump, instead of letting it cycle as it is now. However, the CSV will make that pump last many times longer than letting it cycles as is. So without changing out the pump, how much will it save you to make the pump last let's say even 10 years, as compared to having to replace it every 3 years?

Anyway you do it, it is going to be hard to make this system less expensive to run, because you have 11 tons of AC. It is the 11 tons of AC that is expensive. Especially when compared to a smaller system like mine that only uses 3 tons. I still think the best way to save money in your situation, is to make which ever pump you use, last as long as possible.