Panasonic water heater shows H13 and shuts down; often related to flue or ventilation problems.

Carbon monoxide hazard: Do not operate the heater if you suspect flue blockage. Ensure adequate ventilation and consider installing a CO detector.

• 1. Inspect exhaust terminal:
  • Check outside the building that the flue terminal is not blocked by snow, leaves, or nests.
  • Clear any obstructions.
• 2. Check flue routing:
  • Look for crushed, disconnected, or sagging sections of the flue pipe.
  • Ensure joints are properly sealed and supported.
• 3. Verify installation length: Compare the actual flue length and number of elbows with Panasonic's maximum specifications in the installation manual.
• 4. Inspect exhaust pressure switch (qualified persons):
  • Remove the front cover.
  • Locate the pressure switch and its tubing to the flue.
  • Ensure tubing is not kinked, blocked, or cracked.
• 5. If H13 persists after clearing flue: The pressure switch or sensor may be faulty and should be tested and replaced by an authorized technician.