User Guide
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Panel Radiator
Design Manual
Panel Radiator Design Manual | 12.2009
Technical specications are subject to change without prior notice
Two-Pipe System Options
Figure 12 illustrates two common two-pipe congurations.
Fig. 12 Two-pipe System Options
Drawing not to scale
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Option 4: Two-Pipe Direct Return System
Option 5: Two-Pipe Reverse Return System
Pressure Bypass Valve
Benets of Two-Pipe Systems:
1. Each radiator is supplied with the same
temperature water maximizing radiator output.
2. No limit to the number of radiators on a two pipe
system loop; the supply and return mains must be sized
for maximum ow. Follow the guidelines in Table 10 for
sizing the supply and return runs. Use 1/2” copper or
PEX tubing to connect radiators to main runs.
3. Individual radiator control is easily done using
thermostatic sensor heads. Use constant circulation with
outdoor reset control for optimum system performance. A
central thermostat can be used for on/off control;
however, thermostat location governs overall system
control and may override individual room control.
Requirements for Two-Pipe System:
• Two main distribution pipes are needed; one for
the supply to the radiators and a second pipe for the
return to the boiler.
• A pressure actuated bypass valve (Part No.
3L602502 for a 3/4” Danfoss valve) connected between
supply and return mains is necessary on constant
circulation systems with thermostatically controlled
radiators to prevent dead-heading the pump. This bypass
valve is not needed on thermostat controlled systems if
the radiators are not equipped with thermostatic sensor
heads.