Navien E760 (flushing/service alarm): what it means

Navien display

E760

“Flushing/service alarm”

NPE-A2, NPE-S2, NPN · NPE-2 User's Information Manual, p. 18; NPN User's Information Manual, p. 23
Technician

What it means

E760 is a maintenance alarm. All three Navien tables give it one remedy: have the installer perform routine service NPE-2 User’s Information Manual, p. 18; NPN User’s Information Manual, p. 23; NR-21DU Remote Controller Manual, p. 32. The remote manual also describes a scale alarm that comes on when the heater needs cleaning, and its illustration shows that alarm as “A.760” NR-21DU Remote Controller Manual, p. 27; the text does not state that A.760 and E760 are the same alarm. The manuals do not say whether the heater keeps heating while E760 is displayed.

Check these first

1. Call your installer and ask for routine service. That is the only remedy the tables list NPE-2 User’s Information Manual, p. 18; NPN User’s Information Manual, p. 23.
2. Compare your water hardness with Navien’s flushing guidance. With no water treatment device installed, Navien recommends flushing once a year for homes with water harder than 4 grains per gallon (above 60 mg/L), and no flushing for soft water. Above 12 grains per gallon (200 mg/L), it calls a water softener or Navien’s PeakFlow treatment required NPE-2 Installation & Operation Manual, p. 15; NPN Installation and Operation Manual, p. 14.
3. If you plan to flush the heat exchanger yourself, use the procedure in your user’s manual NPE-2 User’s Information Manual, pp. 12–13; NPN User’s Information Manual, pp. 17–18. It needs a bucket of 5 gal or more, a diluted cleaning solution, 3 hoses and a water circulation pump. Navien calls it “a somewhat complicated procedure” and warns that improper maintenance can void the warranty NPE-2 User’s Information Manual, p. 12. For the solution, it names white vinegar or a product made for tankless water heaters NPE-2 Installation & Operation Manual, p. 15.
4. On the NR-21DU remote, holding OK for 2 seconds deactivates the scale alarm, and “RST” shows for 3 seconds NR-21DU Remote Controller Manual, p. 27. Deactivating the alarm is not the routine service the tables ask for.

When to call a licensed technician

• For the routine service itself, per the table. If you are unsure of any flushing step, the user’s manual sends you to an authorized technician or licensed professional NPE-2 User’s Information Manual, p. 12.
• To change the alarm settings on an NPE-A2 or NPE-S2. The installer menu has a “Descaling Reminder” (No Alarm, 6, 12 or 24 months; default No Alarm) and a “Service Notif Time” (0 to 3,650 days in 10-day steps; default 1,820 days). Navien says the installer menu must be set by a qualified professional NPE-2 Installation & Operation Manual, pp. 98, 100.
• To change the alarm setting on an NPN. Front-panel DIP switch 8 turns the “Limescale Detection Alarm” on, with a 12-month interval, or off NPN Installation and Operation Manual, p. 49.

The manuals describe these settings separately from the E760 table entry. None of them says which setting, if any, produces E760.

Notes for different models

Navien uses different names in different documents: “Flushing/service alarm” in the code tables, “Descaling Reminder” in the NPE-2 installation manual p. 100, “Limescale Detection Alarm” in the NPN installation manual p. 49 and “scale alarm” in the remote manual p. 27. The remote manual also says you can change the scale warning intervals p. 27.

The flushing table in the NPE-2 installation manual adds a commercial frequency of twice a year for hard water; the NPN table lists residential use only NPE-2 Installation & Operation Manual, p. 15; NPN Installation and Operation Manual, p. 14.

Related Navien codes

• E016 “Overheating of heat exchanger”
• E030 “Exhaust overheating (the water heater shuts down when the flue temperature exceeds 149 °F (65 °C)”

All Navien codes

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