After a lot of searching I have found that there is a Heat recovery unit for hot water from refrigeration systems which transfers heat from refrigerant into water.
What astonishes me, I have found only this one manufacturer making it, available for home use. Is it really not that effective, or just people are not aware of this opportunity to save some energy/money?
Maybe the commercial out-of-box solution is not (yet) available.
I have written to the company and got no response about availability in my country (Slovakia). On the regular Condenser unit, there is no option to access coolant in hot state (between compressor and condenser, as far as I know).
Would it be safe to ask a professional to open the device and extend the coolant tube from compressor towards condenser, to have it go through Heat Recovery Unit? I would do it with an old appliance, so voiding the warranty is not an issue.
Simplification
Assuming this scenario is possible, Would it be much less effective to drive hot cooland through pre-heat water tank directly (without heat recovery unit)? Of course, using water tank with tubes designed for coolant. This could greatly simplify the system, as there would be no need for water circulation pump.
Of course, in all scenarios with water tank I assume the water inside is cold (used frequently), and that coolant tubes would be split and connected by a technician who would in the end refill the coolant medium to a proper amount. Maybe the question could be: Can regular AC devices installing technician do this?
More extreme DIY
Going even more crazy in brainstorming, would it be safe to build the condenser of an external unit into the pre-heat water tank? It is weather resistant, and is getting wet anyways every time it goes in reverse mode, while heating. I would have concern only about the pressure made by water onto the condenser.
Simplification, and maybe something more practical
Comparing to above scenario, would it be effective using regular, factory made boiler, with coolant heat exchanger tube (from previous example), with coolant compressor?
Does it exist? Coolant compressor out of the box, without condenser, ready for installation (with internal consumer-grade AC unit)?
