I'm looking for a water to water or refrigerant to water GSHP or VRF heat pump to be used solely for residential domestic hot water. The coil will need to be an internal double wall vented hot water generator coil suitable for potable water. I see several desuperheater coils with these specs but curiously I can't find the "main" heat pump coil with these specs. I'm trying to avoid a second "geo storage" tank and go directly from the heat pump to domestic hot water tank like a desuperheater, but with larger capacity (> 40 kBTUH). I've contacted several manufacturer's with no luck. Curious to know if anyone knows of any and why these don't seem to exist anymore.
Mitsubishi has a refrigerant-to-water heat exchanger in their City-multi VRF lineup, but you have to add an additional heat exchanger (probably in the tank) to move the heat from Mitsubishi's non-potable rated heat exchanger into the potable water tank.
It might be easier just to "stack" multiple "plug-n-play" air-to-water heat pumps together to get the capacity you need...such as units from Sanden, Chilltrix or Space Pak/Solstice. I'm guessing you might have already investigated these options, though...
Thanks John & Bill. Bill your experience is one reason why I wanted a larger heat pump with more capacity for a colder climate. John we are thinking along the same lines, but I hadn't thought about Space Pak/Solstice - thanks that was helpful.