Hi Ryan. Sorry for replying on an old post. I’m busy with the same installation and I’m still not convinced about either of the water flow directions. I also bought the Sun Pays unit but decided to get a Geyserwise controller. Geyserwise suggests feeding from cold water side and Sun Pays suggests from hot water side with no controller. I notice in your diagram you show the pump on the return side from panel which is contrary to what Sun Pays suggest. Is this not part of your problem?
geyserwise switches the pump on cold side only if there is a temp differential of 7deg. What does my head in is if this cold water will be extracted from the geyser or the main supply which is under higher pressure. Any thoughts on this?