Hey Ross. I was just admiring your work--very nice. I don't know if you used PVC water pipes on the hot side, but I'll warn you that the Ecotemp produces water temps high enough to cause PVC to swell and blow out--especially right at the outlet from the heater.
Mine did. PVC cannot be heated over 140 degrees F or it softens and bursts. I did replace my damaged pipes with more PVC but I attached a thermocouple to the hot outlet from the heater that cuts the battery power and thereby shuts the unit down. I set the tc at 120 degrees F. Once the pipe cools the tc reconnects the battery and the heater reignites