NSS Diagnostics and Troubleshooting 2

Question 1

A Navien NPE series tankless water heater displays error code E003. What does this indicate?

Accepted Answer

Ignition failure

Answer

Error code E003 on Navien NPE units indicates an ignition failure, meaning the burner did not ignite after the set number of attempts.

Question 2

When a Navien combi-boiler shows low water pressure (error E407), what is the FIRST corrective action?

Accepted Answer

Check and repressurize the heating system to 12–15 PSI

Answer

E407 indicates low system pressure; the first step is to repressurize the heating loop to the recommended 12–15 PSI range before further diagnosis.

Question 3

A technician finds a Navien NPN boiler short-cycling with no error code displayed. Which component should be inspected first?

Accepted Answer

Differential pressure switch

Answer

A faulty or obstructed differential pressure switch can cause the unit to short-cycle by falsely signaling flue blockage or proving combustion air issues.

Question 4

What does a Navien error code E012 typically indicate on a tankless unit?

Accepted Answer

Outgoing water overheating

Answer

E012 on Navien tankless units signals an outgoing water temperature overheat condition, triggering a safety shutdown.

Question 5

During a combustion analysis on a Navien unit, CO readings are elevated. Which adjustment should a technician make first?

Accepted Answer

Adjust the air-to-fuel ratio via the gas valve offset

Answer

Elevated CO typically indicates a rich combustion condition; adjusting the gas valve offset corrects the air-to-fuel ratio before other interventions.

(NSS) Certified Navien Service Specialists Practice Test

(NSS) Certified Navien Service Specialists Practice Test

NSS Diagnostics and Troubleshooting 2