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Navien · Tankless water heater troubleshooting

Hot water slow to reach fixtures - Navien NPE-2

What is going on

Long wait for hot water at the taps.

Likely causes

  • No recirculation return line
  • Recirculation mode not set

Check in this order

  1. A2 models use Internal Recirculation (2-way valve set to INT) for faster delivery, or External Recirculation (valve set to EXT) with a return line from the farthest fixture.
  2. S2 models need an external pump and return line (or NaviCirc valve).
  3. Set Menu > 1. Recirculation Settings to Always On, Intelligent, Weekly or HotButton.
  4. Built-in pump limits on external recirculation: 100 ft equivalent of 1/2 in. copper or 500 ft of 3/4 in. copper; longer runs need an external pump.

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

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Source: Navien NPE-A2/S2 User's Information Manual (20049624A), 5.1, p.16; Navien NPE-A2/S2 Installation Manual, 3.4.2, p.27-29. Written in our own words; check the manual for your exact model.

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.