Dave, Kabbot… Good catch. Since the Garn is a heat supply, the colors on that side are backwards, as your input side will be the hottest water. As drawn in # 71, the Garn side is getting heat from the HX instead of supplying heat to it.
Counter-flow is sort of counter intuitive, but the rule in any heat exchanger is that your best results will come when the flows run OPPOSITE each other… The flow arrows are right, and the house side is drawn correctly, but the Garn side colors are definitely backwards.
