Navien NCB-180 Service Manual page 84

Scenario2
Is gas valve operating
normally?
Yes
Check the flame rod
Scenario3
Is the flame detection
device normally
operating?
Yes
Restart unit
Does the main
NO
gas valve have proper
voltage?
Yes
Is gas valve open?
Yes
Power OFF the unit
NO
Is the flame current
detected?
Yes
Check connector
(#1 of CN2)
NO
Check connector
Check the voltage between #1 and #2 of CN 16:
22-24 VDC
Check the voltage between #1 and #3 of CON 4:
22-24 VDC
(see page 56 for Wiring Diagram)
NO
Check that gas valve is
open or check LP supply
In case of LP gas model, low gas pressure can
cause "Ignition Failure".
* Normal gas pressure: 8.0 - 13.5" w. c.
Clean or replace the flame rod
NO
Check whether ground circuit is
properly installed.
Check the current #1 of CN 2: DC 1 - 20μA
(see page 56 for Wiring Diagram)