Steve, Jerry,

I agree with both of you on the valve being regulatory. As to it's purpose here, I think it is a poor choice in this application. Looking at the system design, in the event the H/W is well above scalding temp, the regulating valve would likely close. This presents a problem with the recirc pump that it is likely to fail prematurely do to loss of flow over repeated occasions. Steve called it out well with the commercial applications for numerous fixtures requiring hot water immediately. That being the case, it is tempered at the mixing valve having both hot and cold inlet / outlet and serving numerous fixtures, ie, a bank of showers or scrub sinks.

Pat