An installer is asked to build a system to supply both radiant floor heating and a “hydro-air” zone. All heat will be supplied from a gas-fired cast-iron boiler. The installer decides to use variable-speed injection mixing to reduce the supply water temperature to the radiant floor portion of the system and operate the radiant floor distribution pump continually to help even out floor temperatures.
The schematic to the right shows how the system was installed. Can you spot a few problems in the making?