HVACopediaNavien · Tankless water heater
E782 Main / panel communication abnormal
What the control is telling you
The front panel and main controller are not communicating.
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
Likely causes
- Loose or damaged panel cable
- Panel or main board fault
Test and repair steps
- Turn off power and check the cable between the front panel and the main PCB.
- Turn power back on.
- Fix given phone Navien Technical Support, 1-800-519-8794.
Settings for these units
- Installation clearances (indoor / outdoor) · Navien NPE-2
- Water quality limits and flushing schedule · Navien NPE-2
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Source: Navien NPE-A2/S2 User's Information Manual (20049624A), 5.2 Understanding Error Codes, p.18. Summarized in our own words; check the original manual for your model.
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For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.