[Richard]

Hmmmm, I think Ron outed me. I’ll post of pic, but it is a prototype, not quite ready for mass consumption. Ron was in serious need of a board, so he was willing to be the long term tester.

   

A couple of things worth mentioning. The bank of 8 relays is available from Amazon for about 12 bucks. They are triggered by the 12V signal from the tstat. They are also optoisolated so the tstat should be protected from any 120V shennigans. This board will only work with SCS units that already have the external contactors for the compressors. https://www.amazon.com/HiLetgo-Channel-M...B00LW2GA5Y

The one logic puzzle is how to get the board to give all six functions of the tstat, lo fan, hi fan, lo AC, and hi AC with just four inputs. I’ll post the schematic when I have a chance but one of the relays is wired in series with the Compressor 1 circuit, so that when Compressor 2 comes on the outside fan switches to hi speed. 

While at Bella Terra, @"Roger 1" had built a similar setup except he had used relays that will handle 30 amps, so it is possible to build a board that will work without the external relays. I also saw that Roger used a sheet of polycarbonate to mount his relays and attachment terminals. 

I already ordered the supplies to build some prettier versions. I’ll post those pics, the parts links, and the schematic when I finish so that others can build some if they want them. 

I do not know what the longevity of the relays will be. Ron is the beta tester.