NSS Maintenance and Repair Techniques 4

Question 1

A Navien NPE unit installed on LP gas is producing soot on the heat exchanger after only six months. What is the most likely root cause?

Accepted Answer

The unit was not converted to LP operation and orifices remain sized for natural gas

Answer

If the unit was not properly converted to LP (propane) with correct orifices and pressure settings, rich combustion results in soot formation on the heat exchanger.

Question 2

Which Navien error code specifically indicates a problem with the exhaust thermistor or an over-temperature exhaust condition?

Accepted Answer

E030

Answer

Error code E030 on Navien units indicates an exhaust high-temperature condition or exhaust thermistor fault, signaling a potential venting or combustion issue.

Question 3

When replacing a Navien primary heat exchanger, what must be done with the condensate drain tubing connections after reassembly?

Accepted Answer

They must be reconnected and tested for leaks before firing the unit

Answer

After reassembly, condensate drain tubing must be properly reconnected and leak-tested to prevent acidic condensate from draining onto electrical or gas components.

Question 4

A Navien recirculation pump runs continuously but no hot water is delivered at the fixture. What should the technician verify first?

Accepted Answer

Whether the pump direction/impeller rotation matches the system flow direction

Answer

A recirculation pump installed with incorrect flow direction will not move water through the loop, causing no hot water delivery despite the pump running.

Question 5

What is the correct procedure for priming the condensate trap on a Navien condensing unit during initial startup?

Accepted Answer

Fill the trap with water before startup to establish the liquid seal

Answer

The condensate trap must be filled with water before startup to create a proper liquid seal that prevents flue gases from escaping through the drain line.

(NSS) Certified Navien Service Specialists Practice Test

(NSS) Certified Navien Service Specialists Practice Test

NSS Maintenance and Repair Techniques 4