Is the only way to make water up to this loop to do it manually? Or do you have a backflow and pressure regulator on the makeup water line?
Keep in mind since you have added a lot of water to the system recently, you should have the chemical treatment levels rechecked to ensure there is enough protection in the loop.
Building Physics Rule #1: Hot flows to cold.
Building Physics Rule #2: Higher air pressure moves toward lower air pressure
Building Physics Rule #3: Higher moisture concentration moves toward lower moisture concentration.