NSS Product Knowledge and Specifications 3 — Questions and Answers
Question 1: Which venting materials are approved for use with Navien NPE series condensing tankless water heaters?
- Type B gas vent and galvanized steel only
- PVC, CPVC, and ABS (Correct answer)
- AL29-4C stainless steel only
- Polypropylene and Type B only
Correct answer: PVC, CPVC, and ABS
NPE series units accept PVC, CPVC, and ABS vent piping because their low flue gas temperatures are safe for plastic materials.
Question 2: What is the minimum natural gas supply pressure required for proper NPE series unit operation?
- 2.0" W.C.
- 3.5" W.C. (Correct answer)
- 5.0" W.C.
- 7.0" W.C.
Correct answer: 3.5" W.C.
Navien NPE series units require a minimum natural gas supply pressure of 3.5" W.C. to achieve rated performance.
Question 3: What is the maximum allowable static gas supply pressure for Navien NPE series natural gas units?
- 7.0" W.C.
- 10.5" W.C. (Correct answer)
- 14.0" W.C.
- 17.5" W.C.
Correct answer: 10.5" W.C.
The maximum static natural gas pressure for NPE series units is 10.5" W.C.; higher pressures can damage the gas valve.
Question 4: What vent pipe diameter options are available for Navien NPE-180A installations?
- 1.5" or 2" only
- 2" or 3" only (Correct answer)
- 3" or 4" only
- 2", 3", or 4"
Correct answer: 2" or 3" only
The NPE-180A supports 2" or 3" vent pipe, with 3" recommended when total equivalent vent length exceeds the 2" limit.
Question 5: What size condensate drain connection is provided on Navien NPE series units?
- 1/2"
- 3/4" (Correct answer)
- 1"
- 1-1/4"
Correct answer: 3/4"
NPE series units have a 3/4" condensate drain connection that must be piped to an approved drain location.
Question 6: What is the minimum clearance required from the flue exhaust terminal to an operable window or door on an NPE installation?
- 6 inches
- 12 inches (Correct answer)
- 18 inches
- 36 inches
Correct answer: 12 inches
ANSI/NFPA 54 and Navien installation requirements mandate at least 12 inches of clearance from the vent terminal to any operable window or door.
Question 7: What is the minimum ambient installation temperature for a Navien NPE series unit installed in an unheated space?
- 32°F (0°C)
- 34°F (1°C) (Correct answer)
- 40°F (4°C)
- 50°F (10°C)
Correct answer: 34°F (1°C)
NPE series units require a minimum ambient temperature of 34°F to prevent internal water from freezing during standby.
NSS Product Knowledge and Specifications 3
Which venting materials are approved for use with Navien NPE series condensing tankless water heaters?