Are you sure about no geothermal? You may be correct.
I had a geothermal heat pump that was open looped in that it took water from the well and removed the heat from it and dumped it in a dry well that I made. However, the backup (emergency) heat was, as you describe, from a high volume/high recovery water heater.
Geothermal units do well keeping the temperature within a few degrees very inexpensively but they don’t seem to bring the temp up very fast from say 55 to 70. That’s where my system water heater came into work.
Aside from that, I don’t know what to tell you to call it.
The pics I have are not very clear about the configuration. One is in the attic, and two are in the crawl space. This is a townhouse built in 1997, and there’s not enough property to run 100 feet of line underground, and I don’t think there’s a well, or a vertical loop. There are definitely water lines running to and from the water heater to the furnace, but not to the outside compressors.
The client is having an HVAC company coming on Thursday. I may try to attend their evaluation to learn something, but I have an inspection that afternoon.
Without more info I would call it a HP with hot water backup Mike you always need to look at the outside unit if there is one and look for a reversing valve. If you don’t know what one looks like Google it and get a pic.
A geo thermal is just like any other system with one major change which is the cooling medium for its condenser where it comes from and what it is. The cooling medium can be a ground loop, a well, a water pond. Remove the outdoor condenser fan and add a another type of cooling medium and you have a geo thermal HP.
Ya got it correct there will be two coils at theAHU one for the heat pump and one for the hot water. Hot water is the aux as mentioned by others. Yes it is a heat pump with just a different aux no big deal;-)