HVACopediaNavien · Tankless water heater
E762 Vent pipe not properly inserted
What the control is telling you
The vent installation detector (VID) does not see the vent pipe fully inserted in the exhaust collar. The unit will not run.
Applies to: Navien NPE-A2 (built-in recirculation) and NPE-S2 condensing tankless water heaters: NPE-150S2, NPE-180A2/S2, NPE-210A2/S2, NPE-240A2/S2; also Navien NPN non-condensing tankless water heaters: NPN-160U/180U/199U (universal, indoor or outdoor with vent kit) and NPN-120E/160E/180E/199E (outdoor only)
Likely causes
- Vent pipe not pushed fully into the collar
- Wrong pipe size or deformed pipe
- Pipe pulled out or misaligned
Test and repair steps
- Warning: carbon monoxide hazard - do not bypass the VID.
- NPE-2 pipe must be 2 in., cut square and deburred, lubricated with water and inserted 2-3/4 in. (70 mm) to the bottom of the collar; tighten the clamp (8 mm socket).
- NPN (indoor models) 5 in. concentric pipe inserted 1.3 in. (34 mm) and secured with the self-tapping screw.
- Put a straight piece on the collar first. Do not fit a street elbow right at the collar.
- Replace damaged or deformed pipe and support the vent every 4 ft horizontally.
- After fixing, test the exhaust joints for leaks with a bubble test.
Settings for these units
Installation clearances (indoor / outdoor) · Navien NPE-2
| Side | Indoor | Outdoor |
|---|---|---|
| Top | 9 in. (229 mm) | 36 in. (900 mm) |
| Back | 0.5 in. (13 mm) | 0.5 in. (13 mm) |
| Front | 4 in. (100 mm) | 24 in. (600 mm) |
| Sides | 3 in. (76 mm) | 3 in. (76 mm) |
| Bottom | 12 in. (300 mm) | 12 in. (300 mm) |
Vent clearance to combustibles is 0 in.
Outdoor: use the Navien Outdoor Vent Kit; keep 3 ft from an eave to the top of the vent terminals; mild climates only.
Water quality limits and flushing schedule · Navien NPE-2
| Hardness | grains/gal (mg/L) | Treatment | Flush frequency |
|---|---|---|---|
| Soft | 0-4 (0-60) | None | None |
| Moderately hard | 4-7 (61-120) | None required | Once a year |
| Hard | 7-9 (121-160) | Softener or Navien PeakFlow recommended | Once a year |
| Very hard | 9-12 (161-200) | Softener or PeakFlow highly recommended | Residential once a year; commercial twice a year |
| Extremely hard | >12 (200) | Softener or PeakFlow required | - |
Other max levels: hardness 200 mg/L, chloride 250, copper 1.0, iron 0.3, manganese 0.05, sulfate 250, TDS 500, zinc 5, chlorine 4 mg/L; aluminum 0.05-0.2 mg/L; pH 6.5-8.5.
Flushing is advised when no treatment device is installed; use white vinegar or a tankless descaler.
- Installation clearances (indoor / outdoor) · Navien NPN
Models that show this code
14 models in Navien NPE-2, Navien NPN
Other codes on the same units
- E615 Input and memory abnormal
- E736 Cascade communication abnormal
- E740 Outdoor temperature sensor abnormal (with air handler)
- E760 Flushing / service alarm
- E773 Wrong gas type detected
- E782 Main / panel communication abnormal
- E785 Flow switch / sensor abnormal (with air handler)
- E788 Gas type mismatch: DIP switch vs panel setting
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Source: Navien NPE-A2/S2 User's Information Manual (20049624A), 5.2 Understanding Error Codes, p.18; Navien NPE-A2/S2 Installation Manual, 3.6.2, p.44-45; Navien NPN-U/NPN-E Installation Manual, 3.5.1, p.37-38. Summarized in our own words; check the original manual for your model.
Homeowner looking at this code? See what it means for you and when to call a technician.
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