NSS Maintenance and Repair Techniques 2

Question 1

When descaling a Navien condensing tankless water heater, which solution is recommended for flushing the heat exchanger?

Accepted Answer

White vinegar or food-grade citric acid solution

Answer

White vinegar or food-grade citric acid solution safely dissolves mineral scale in Navien heat exchangers without damaging internal components.

Question 2

A Navien NPE-240A displays error code E003. What does this indicate?

Accepted Answer

Ignition failure

Answer

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

Question 3

What is the minimum recommended annual maintenance task for Navien combi-boiler systems?

Accepted Answer

Inspecting and cleaning the cold water inlet filter screen

Answer

Navien recommends inspecting and cleaning the cold water inlet filter screen annually to prevent flow restriction and performance issues.

Question 4

When replacing a Navien flow sensor, which precaution is most critical before starting the procedure?

Accepted Answer

Isolating the gas supply and depressurizing the water lines

Answer

Before replacing the flow sensor, the gas supply must be isolated and water lines depressurized to prevent hazardous leaks or flooding.

Question 5

A Navien NPN-199 boiler shows recurrent short-cycling. After verifying no errors are present, what should a technician check first?

Accepted Answer

System expansion tank pre-charge pressure and condition

Answer

A waterlogged or improperly sized expansion tank is a leading cause of short-cycling in hydronic systems, causing rapid pressure fluctuation.

(NSS) Certified Navien Service Specialists Practice Test