Navien NFC-175, Service Manual

Page: 75 / 138

NFC Service Manual 75 Version 1.0
Scenario2
Is gas valve operating
normally?
Does the main gas valve
have proper voltage?
Is gas valve open?
Check the flame rod Power OFF the unit
Check that gas valve is open and
check gas supply pressure
Check connector
Check the voltage between the RED-YELLOW
(#1 and #2) of CNG1: 22-24 VDC
Check the voltage between the RED-WHITE
(#1 and #3) of CNG1: 22-24 VDC
Insufficient gas supply pressure can cause “Ignition
Failure”.
* Normal gas pressure:
LP=8” – 13.5” W.C; NG=3.5” - 10.5” W.C
Yes
No No
No
Yes
Yes
Scenario3
Is the flame detection
device normally operating?
Is the flame current
detected?
Restart unit
Check connector
(#1 of CNI1)
Clean or replace the flame rod
Check whether ground circuit is
properly installed.
Check the current #2 of CNI1: DC 1 - 20μA
(see page 50-51 for Wiring Diagram)
Yes
No No
Yes
Access the Status Information menu to check
Item #14 for Flame State (see page 36).