National Oilheat Research Alliance 35 Pressure reducing valve (PRV)—an isolation valve (globe, ball or gate), backflow prevention device and PRV should be installed into a tee under the air elimination device. The PRV should be connected at the same point as the expansion tank so that it senses and reacts to the pressure of the tank. Expansion tank—if a diaphragm type tank is used, it should be connected into the bottom of the tee as shown in Figure 4. It is a recommended that an isolation valve be installed to simplify service of the tank. Note that diaphragm tanks should never be installed upright or sideways as the diaphragm tends to dry out in those positions. If a steel compression tank is used, there should not be an automatic air vent installed; the tank should be connected to a ¾" tapping in the top of the separator. Circulator—the circulator should be connected so that it “pumps away” from the “point of no pressure change”—the expansion tank. This means that the suction side of the circulator should be as close as possible to the expansion tank. Isolating flanges or isolation valves are recommended to simplify service. Figure 4
NORA Advanced Hydronics
To see the actual publication please follow the link above