I know this is an old post, but for people still looking for the best answer, here it goes...

I've been down this road already and found a great, economical and simple solution.

I have a 3.5 ton WaterFurnace 2 stage GSHP I retrofitted into a bungalo with a Hi-Velocity ducting system. I have it running on an open loop with a Grundfos 1/2HP submersible pump and a small typical pressure tank. The well is roughly 60 feet. The same pump died a few months before the 5 year warranty expired and I was lucky to get another at no cost. This time around I knew I had to figure out a way to stop the short cycling of the pump or it would die the same way in no time. I had been debating on installing a variable speed pump, but the cost was so high it was ridiculous to do so and be feasable. Finally after about a week of reading about pumps and how to install them for various specs, I found an easy solution. All I had to do was bring up the water pressure switch/pressure tank to a range of 40-60 PSI instead of the default 20-40 PSI the switch is set in most homes. You see, when the GSHP starts, the open loop valve opens and the submersible starts pumping. Now here is the cool part... the submersible can't reach the 60 PSI until the GSHP closes the valve. So in other words, the subersible starts with the GSHP and both keep running non stop until the GSHP stops and closes the valve. The result is that you eliminate the short cycling exactly like a variable speed pump. As far as water pressure goes, I have no complaints in the shower. Can I notice a difference in water pressure when the GSHP turns on? Yes, but nothing unbarable because the pressure is usually still high. With stage 1 running, the pump keeps around 50-55 PSI on the gage without anything else running. With stage 2 running, the pressure is around 45-50 PSI. I'm sure this would need to be adjusted depending on your setup, but the idea remains the same. If you size a submersible just right to your system with correct water pressure, you should be ok. I'm not sure I could have done this if I had a 3/4 HP submersible. Maybe, but my water pressure would have been pretty high, lol.

That was my solution and its been 3 years now without any issues.

A DIY with well supported opinions

Yhat is a great work around and solution for you.  The problems start when you have multiple water usages that do not allways get used.  Domestic+geo+irrigation+pool maintanance= a seriously imbalanced load for water usage.  In the early 80's we drilled a seperate supply well for the geo and put the right sized pump on a pump start relay.  that is a old idea that is "new again".
Eric

How often do you see all of these installed in a home, lol (Domestic+geo+irrigation+pool maintanance)?

My scenerio was for most homeowners out there. We are a family of 5 (3 kids under 4 yrs of age). I've seen the system running with the dishwasher, washing machine, bathub getting filled and possibly a toilet or sink all running at once. I know I get a significant pressure/flow drop, but still, if this happens for a few minutes, once a month, I can't justify switching to a variable speed pump just for that. My 1/2 HP (+/- 10 gpm) seems plentyful for what I need and can live with. This would probably be the same for most out there.

However, if you had all those you mentioned in a home, I'ld imagine they would need to have a second well. Heck, if they had all of those, chances are they have the money to get a second well anyways.

That's cool though what you mentioned about the '80s and sizing the pump with a start relay! Alot of people seem to over think things these days instead of just keeping it simple. The simpler the system, the less chances of failure points.

Andre
"We never have time to do things right the 1st time, but we always have time to fix it later!"