water balancing

Is this a return line because a reverse return line doesn't make a lot of sense?

Return lines are simply to reduce the cost and energy input to the processes.

Rigth rigth.... It's does do sound like a three way temp control valve were most of the time I see these puppys close by the Air Handlings or Heat Transfers Units to serve like a by-pass and returning back to HVAC mechanical room very probably. Most of these puppy's are computer controlled now by an energy management station somewhere in the building if I'm rigth. I don't sure in which kind of unit you are working but that sound mainly like for the purposes of temperature and energy management control some how like the pal' pointed before. And review the blueprint or part diagram for accurate diagnostic. Also is good to know for what is was designed for and the regular detective work involve in order to determine cause of trouble if that the case. Easy does it and don't forget to 'Lock Out and Tag' energy for safety before work on any piece of equipment. Where a Helmet as double insurance all around just in case. Hang in There and Enjoy the Task.

All Good for The Moment,

MC

The Two Pipe Reverse Return Hydronic Loop uses more pipe than the two pipe direct return hydronic loop but the flow is more balanced and even than the two pipe direct return hydronic loop therefor less hydronic water balancing is required

Yeah... It does sound smart thougth. You got the picture. It is like some kind of set-up to make the loop flowing tour probably by-passing the valve itself a little to achieve temperature an energy management some how. Nice feedback pal' and thanks again. Hey ya' all have a great one now. Hast le Vis''..! Hee haaa hii hee.... Lock and Tag Out for Safety.. Have Fun. Don't rush into nothing.

Keep it Running...!

MC