#2 Sanyo 24KHS72 AC/HP Install Project (Oct 2011)

[AC_Hacker]

Originally Posted by Mikesolar

I must have missed this post somehow. AC, my thoughts are that the refrigerant volume of the BPHX needs to be similar to that of the the indoor coil unless there is an accumulator which isn't that likely on your unit.

I think you might be right about the refrigerant volume/accumulator issue... I'll look into that.

Originally Posted by Mikesolar

On the control side, I have seen that there are PWM signals with a start and end pulse that communicate a remote control with the outdoor unit on the inverter models. Yours is probably a lot simpler but finding out what the thermister values on the inside unit are would be a start. Have you got those handy?

I don't have the indoor unit, but if I did I think I might have some chance at being able to communicate with the outdoor unit.

I have looked into this issue and have studied the work that others are doing on this, and have come to the conclusion that 'breaking the code' is going to be too difficult. I have talked to some local electronics guys with way more experience and equipment than I have, in signal analysis and the problem is not trivial.

The best advice I have gotten, is to look at how the present circuit board is laid out and 'hi-jack' the control lines from the existing microprocessor. I have looked closely into this approach and I think that it is the best possibility.

The compressor isn't variable speed, it's just on & off. So I have decided to proceed along these lines.

I'll still need to account for:

• compressor power
• crank case heater power
• reversing valve power
• fan motor power
• monitoring frost buildup on the evaporator

I think I can make an Arduino control these things through the existing, decapitated circuit board.

This approach will be less elegant, but more possible for me to do.

Best,

-AC