I have a refrigerant to air heat pump. Maybe there is an intuitively obvious answer to the question, can't you just replace the refrigerant to air coil with a refrigerant to water coil and use the existing air handler, compressor, etc from the existing HP? I understand that there would be change required in the control system. Is this something that is totally rediculous?

By the time you finished ALL the needed changes you would have more money, and no warranty, in the "new" unit. If you want a GSHP...buy a GSHP.

Bergy

I just find it hard to believe that if the refrigerant is compatible, the basic replacement of the condensing coil and control changes is as expensive as a complete new unit. All that is changing is the air to refrtgerant coil for a water to refrigerant coil and the controls. I understand that the wells and pump associated are extra, but they are the same on a new system as on a refitted system. Hard to get my mind around where the extra money is going.

You could use existing air handler and air coil but you would replace the outdoor ASHP with a GSHP. Then add loops or plumbing. So no you don't have to throw out everything.
However.....split systems often have shorter warranties, and depending on the system you have, your efficiency might be inferior (due to size of existing fan coil). You may also have an R-22 system that may or may not be convertable to refrigerants that won't soon be out of production.
At a time when it appears you'll only have to pay 70 cents on the dollar for a heat pump purchase, I have to agree with Bergy you should start from scratch.
Joe

I've done it, but it isn't for the faint of heart.

Nor was the result anything remotely warrantable or serviceable by anyone using published procedures.

And they build well. The worst time to save on equipment is when you can get it for 30% off.
j

"I had about 20 yrs. experience with refrigeration when I built it but I didn't have the help of forums like this and others that are now available."

I didn't have the 20 years but grasped the basic concepts from engineering classes.

I was single at the time and so just about married the system during its evolution...anything is doable with a commitment of time and $.

I'm with Joe now - my WF is quiet, efficient, and well laid out. I'm sure the other leading brands are comparable - looking nothing like the Frankenstein I had in a side yard for 10+ years.

If you are a DIY with a good grasp on refrigeration, another thought would be the E-Bay angle. Even if there is trouble with it, it would be much easier to rebuild something than to create it from something it's not.
Joe

When installing a new Heating, Ventilating and Air Conditioning (HVAC) system, one of the most important factors to consider is the cost of the unit over its lifespan. It is likely that over the 20-year life of an HVAC system, the energy costs for running it will be the overriding factor for how much money is actually spent on the system. Costs for having it serviced are something else to add into this equation, and there is now a special consideration to take into account: HVAC refrigerant. For your heating and air conditioning needs, you should consider installing a newer heat pump that is both energy efficient and uses a newer, more sustainable refrigerant.

Another topic. Does anyone have any experience on high velocity air conditioning? I saw one with regular condensers but have a 1200 cfm blower. Ducts are 2 inches in diameter (average 5 outlets per ton.. Its usually used in SIPS/ICF homes, though some use it for areas that are impossible to duct.

B11,

Threads are free - I suggest you start your own, including a relevent description in the title since you are asking about something new

What you say is doable. It is just a wee bit more complicated than exchanging the coil - but certainly do-able. If you look on line you can find a new GSHP for about the cost of a ASHP and then you don't have to convert the unit. Not sure of the value of your time but that would be my approach. The real challenge is to get the well field and pumping right.

IMO, if you enjoy the process, go for it. But newer systems made for the task will be less hassle, more efficient (better compressors) and more maintainable.