Oliver,

Thanks for responding. I think you have the best solution we have heard of - we will all be very grateful if we can solve this annoying problem. A few questions for you:

1) Will you be willing to sell me this "more simple adapter"? You're obviously far more versed in electrical engineering than I am. I currently have the setup with 1 fridge and 2 fridge/freezers which each have a Frigoboat W50F compressor. The 1 fridge has a built in thermostat and the 2 fridge/freezers have this thermostat: https://penguinfrigo.co.uk/product/frigomatic-twin-thermostat-for-fridge-or-freezer/.    Those are fed to the E51385 Box. 

2) My system uses fresh water to cool the fridges. I assume I can put a temp sensor in the freshwater return? The additional complication not necessary for me, but if you think it drastically improves efficiency, I'm willing to do it.

3) Also, given my basic setup, is there a way to coordinate the compressor run times without adding the MCU? I believe I could reduce pump duty cycle if the fridges/freezers would try to run at the same time. Again, if it's too complicated, I don't need it.

4) Is there a 12v pump available? I would rather use the 12v output of the E51385 than put in another relay.

I would assume if I use a 24v motor, the way to get 24v would be to use the E51385 output to control a Hella relay, which would then pass through 24v that I get from the posts near the chain wash pump. Since I'm at 80%+ duty cycle, I would rather not have a relay that is energized all the time for heat, longevity and energy consumption reasons.

Your solution is the best we've seen and I'm sure many of us will want to copy it. I'm hoping it is something that can be installed and managed by someone without your technical skills.

Thanks in advance

--
Scott 
2007 A54 #69
SV Tengah
http://www.svtengah.com