Quote:
Originally Posted by mrd
Sounds like a very fun project 
In regard to hacking an inverter-based system, I suppose the targets would be the compressor and the digital expansion valves. So first you need a "brain" to run the system, maybe an arduino or a pic or whatever is desired. Then you need to interface it with the compressor and valves. The thermistors and what not can be ignored and use your own if that's easier, rather than reverse engineering them as well.
The compressor may have its own dedicated hardware controller, as I'd imagine the compressor manufacturer wants to sell its unit to other vendors, and the simplest way would be to dedicate a cheap controller and provide a simple interface for controlling the compressor. In that case, you need to decode the communication protocol to that controller. This is probably the most difficult hurdle. Maybe something here..?
Inverter Control Module : Hitachi Appliances, Inc.
The valves should be really simple to decode, I think a youtube video described them as acting like stepper motors. They probably just have a reset command and positioning commands.
Once you have that down, I'd start the software with safeguards to protect the compressor. Then write up a test suite to go through various possible control schemes, and use sensors to measure efficiencies of each. Developing good theories and automating testing here will get the setup optimized quickly. Sensors can be integrated as desired to meet theoretical operation.. |
Maybe it wouldn't be required to completely re-engineer the control system of the inverter type heat pumps. They do seem to do a pretty good job as they are.
I'm thinking that instead, it might be possible to build a refrigerant-to-water heat exchanger and pump that can convince the outdoor unit that it is actually a factory-built air handler.
The existing air-handler (AKA: indoor unit) has:
- An air flow redirecting vane & motor system (useless)
- A variable-speed air circulating fan (useful... there are available variable-speed water circulation pumps that respond to external control)
- An IR receiver module (useful with the IR remote control)
- Air filtration system (useless)
I don't know if there is any intelligence in the air-handler or not. I do know that there are four wires that connect it to the outdoor unit. I assume that two are power...
This approach seems much more direct, and likely to succeed. In addition, it probably would apply to most inverter heat pumps and require little modification.
So, if you're really itching to do an Arduino project, maybe it could do some arbitration between the hydronic unit and whatever part of the system is sending signals, and perhaps looking for status signals.
-AC_Hacker