Exercise: Look over the sketch and my interpretation of it. Then make a list of what you would recommend changing.
1. If the intent of the boiler bypass was to prevent sustained flue gas condensation the installer will discover this doesn’t work. The only assured way of preventing sustained flue gas condensation is to measure boiler inlet temperature and partially restrict hot water flow to low temperature load when necessary. If we assume all the loads including the radiant panel circuits are high temperature loads there really is no need for the bypass.