This article discusses the various ways to provide multiple water temperatures from a single heat source.
Many hydronic heating systems use two or more types of heat emitters that require different water temperatures to be supplied simultaneously. For example, one part of the building may be heated by tubing embedded in a concrete floor slab, while another portion is heated by fin-tube baseboard or panel radiators. These two subsystems can have significantly different supply temperature requirements that must be simultaneously provided by the system.
There are several ways to provide multiple water temperatures from a single heat source. These include use of multiple "intelligent" mixing assemblies, as well as a technique known as submixing, which uses one intelligent mixing assembly along with one or more "dumb" mixing valves. This article will discuss the strengths and weaknesses of both approaches.