NSS Combustion and Venting Systems

Question 1

What vent pipe material is approved for use with Navien condensing tankless water heaters?

Accepted Answer

PVC/CPVC Schedule 40

Answer

Navien condensing units are Category IV appliances requiring PVC or CPVC vent pipe rated to handle acidic condensate and the temperatures of condensing exhaust.

Question 2

What venting category classification applies to Navien condensing units?

Accepted Answer

Category IV

Answer

Category IV appliances operate with positive vent pressure and produce flue gases below the dew point, requiring corrosion-resistant, pressure-tight vent systems like PVC.

Question 3

What is the minimum required clearance between a Navien vent termination and an operable window or door?

Accepted Answer

12 inches

Answer

A minimum of 12 inches clearance from operable windows, doors, and gravity air intakes is required per Navien installation guidelines to prevent combustion products from re-entering the structure.

Question 4

In a concentric (coaxial) vent system on a Navien unit, which pipe carries the exhaust gases?

Accepted Answer

The inner pipe

Answer

In a concentric vent system, the inner pipe carries hot exhaust gases to the outside while the outer pipe draws fresh combustion air into the unit.

Question 5

What is the required slope for horizontal vent pipe runs on a Navien condensing unit?

Accepted Answer

1/4 inch per foot back toward the unit

Answer

Horizontal vent runs must slope back toward the unit at 1/4 inch per foot so acidic condensate drains to the unit's condensate trap rather than pooling in the pipe.

(NSS) Certified Navien Service Specialists Practice Test

(NSS) Certified Navien Service Specialists Practice Test

NSS Combustion and Venting Systems