Navien E016 (heat exchanger overheating): what to check

Navien display

E016

“Overheating of heat exchanger”

NPE-A2, NPE-S2, NPN · NPE-2 User's Information Manual, p. 17; NPN User's Information Manual, p. 22
Owner checks, then technician

What it means

E016 is Navien’s code for overheating of the heat exchanger. Navien’s remedies deal with the water side: clean the cold water inlet filter and flush the heat exchanger NPE-2 User’s Information Manual, p. 17; NPN User’s Information Manual, p. 22. Navien says the inlet filter must be cleaned periodically to keep proper water flow, and it ties flushing to water hardness NPE-2 Installation & Operation Manual, pp. 15, 26.

Check these first

1. Turn the heater off for at least 30 minutes, then turn it back on. The NPN table and the NR-21DU remote manual list this as the first step; the NPE-2 table does not NPN User’s Information Manual, p. 22; NR-21DU Remote Controller Manual, p. 30.
2. Clean the cold water inlet filter. To get it out you drain the heater: put a bucket underneath, turn the heater off with the Power button, close the gas valve, close the cold water supply valve (or the water main if there is none), and open all hot water taps. On NPN models, also open the water drain plug. Then remove the cold water inlet filter and let the heater drain NPE-2 User’s Information Manual, pp. 11–12; NPN User’s Information Manual, pp. 16–17.
3. Rinse the filter under cold running water and scrub it with a brush if needed. Refit and tighten it (on NPN models, close the water drain plug), then refill the heater by reversing the draining steps NPE-2 User’s Information Manual, p. 13; NPN User’s Information Manual, pp. 17, 19.
4. Flush the heat exchanger, or have it flushed. You need a bucket of 5 gal or larger, a cleaning solution diluted with water, 3 hoses and a water circulation pump. The manual starts with the heater turned off at the Power button and its power supply disconnected, then the hot and cold water valves closed; the pump circulates the solution through the heater for at least 45 minutes; fresh water then rinses it for 5 minutes, and the inlet filter gets cleaned again before the power is reconnected NPE-2 User’s Information Manual, pp. 12–13; NPN User’s Information Manual, pp. 17–18. The hoses connect to valves on the hot and cold water lines, which the manual labels A through D.
5. Reset the heater. On NPE-A2 and NPE-S2 models, press Back NPE-2 User’s Information Manual, p. 10. On NPN models, press Reset on the front panel, or OK on the remote for outdoor models NPN User’s Information Manual, pp. 12, 21.

Navien calls flushing “a somewhat complicated procedure” and says to contact an authorized technician or licensed professional if you are unsure of any step. Improper maintenance can void the warranty NPE-2 User’s Information Manual, p. 12; NPN User’s Information Manual, p. 17. For the solution, it names white vinegar or a solution made for tankless water heaters NPE-2 Installation & Operation Manual, p. 15; NPN Installation and Operation Manual, p. 14.

When to call a licensed technician

• E016 returns after the rest period, a clean inlet filter and a flush NPE-2 User’s Information Manual, p. 16; NPN User’s Information Manual, p. 21.
• You would rather not flush the heat exchanger yourself. The manual names an authorized technician or licensed professional for this.
• The heater shows signs of damage from overheating. Close the manual gas shut-off valve and do not run the heater again until a qualified technician has inspected it. If the heater overheats, or the gas supply fails to shut off, close the gas at the manual gas valve NPE-2 User’s Information Manual, pp. 5, 9.

Notes for different models

The 30-minute rest appears in the NPN table and the remote manual, not in the NPE-2 table. Page references inside the tables differ: the NPE-2 table sends you to p. 13 for the filter and p. 12 for flushing, the NPN table to p. 19 and p. 17.

NPE-A2 models have a second filter, the recirculation inlet filter, and a pump drain plug. Both come out or open during draining, and the recirculation filter is cleaned along with the cold water inlet filter NPE-2 User’s Information Manual, pp. 11–13.

Navien recommends flushing once a year for homes with water harder than 4 grains per gallon (above 60 mg/L) when no treatment device is installed NPE-2 Installation & Operation Manual, p. 15; NPN Installation and Operation Manual, p. 14.

Related Navien codes

• E030 “Exhaust overheating (the water heater shuts down when the flue temperature exceeds 149 °F (65 °C)”
• E760 “Flushing/service alarm”

All Navien codes

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