So what is going on with this system? Well it is a combo of home run piped radiators with actuators that are controlled by a room thermostat and then the manifold ports with out actuators are running together. The zones valves open as needed for each larger zone. There is a boiler and several pumps (not in picture) that are located on another floor. This type of plumbing would also work for Fan Convectors.
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Home Run Method (Works well with PEX Manifolds)
Quantity X - Hydronic Radiators and Fan Convectors
Quantity X - Radiant Heat Pex Manifollds and Actuators
Quantity X - Copper and Brass Fittings
X = Various Amounts of Product needed - dependant on actual system
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Example of how to pipe a Hydronic Radiator or Fan Convectors with PEX, Manifold and Actuators. Also one loop does not have an actuator on it and this goes to a radiator that always gets heat when any loop is activated. This could also be just going to a Radiant PEX floor in this configuration.
Example of how to pipe Hydronic Radiators or Fan Convectors with 3 Zone Valves. Pumps and Boiler not in picture and are on a different floor.
Example of how to pipe a Hydronic Radiator or Fan Convectors with PEX, Manifold and just 1 Actuator. So any loop that does not have an actuator - will supply heat to that loop when the zone valve calls for heat for the manifold or the loop with the actuator.