Navien NaviCirc Installation And Operation Manual page 21

6. Locate the TB1 connection on the PCB and attach the external
pump wire and solenoid valve assembly to this connector.
7. Locate the 10-switch set of dipswitches on the front panel and
verify that DIP SW2 is ON for EXTERNAL recirculation.
ON
1 2 3 4 5 6
21
TB1
ON
7 8 9 10 1 2
1-OFF
2-ON
3-OFF