On the covered Navien tankless water heater, E016 means overheating of the heat exchanger. First, turn the heater off for at least 30 minutes, as Navien directs, then restart once. Then: Navien's checks: clean the inlet water filter, check the high limit switch, the dipswitch settings, the water adjustment valve, and the heat exchanger, where a flush may be necessary; and for A models check pump operation. Repeated E016 means the heat exchanger needs flushing.
Differential
Likely causes of “Navien tankless water heater code E016”, and how to tell them apart
- 1
Scale in the heat exchanger
What separates it Repeated E016
How to confirm Flush the heat exchanger
- 2
A faulty high limit switch
What separates it False overheating
How to confirm Technician checks the switch
- 3
A wrong dipswitch setting
What separates it The unit runs wrong
How to confirm Technician checks
- 4
A pump fault on A models
What separates it Poor circulation
How to confirm Technician checks the pump
Before you touch a setting
Record this first — changing settings destroys the evidence
- Whether it is an A model
- Whether the code repeats
Try in this order
0 of 7 completedWhat to do first
ReversibleTurn the heater off for at least 30 minutes, as Navien directs, then restart once.
Correct only the documented fault domain
ReversibleNavien's checks: clean the inlet water filter, check the high limit switch, the dipswitch settings, the water adjustment valve, and the heat exchanger, where a flush may be necessary; and for A models check pump operation. Repeated E016 means the heat exchanger needs flushing.
Turn the heater off
ReversibleFor at least thirty minutes.
Restart once
ReversibleThen test.
Clean the inlet water filter
ReversibleCarefully.
Arrange a flush
ReversibleIf E016 repeats.
Check your water hardness
ReversibleTreat if hard.
Model-specific
What is true of this model and not of its siblings
- Overheating
- Scale, low flow or a faulty limit switch make the heat exchanger overheat, and the unit shuts down to protect itself.
- Navien's checks
- Clean the inlet water filter, check the high limit switch, the dipswitch settings, the water adjustment valve and the heat exchanger, where a flush may be necessary; on A models check the pump.
- Prevention
- Yearly flushing and water treatment prevent most repeats.
- What overheating tells you
- Heat that cannot leave the heat exchanger, because scale coats its walls or flow is too low, makes it overheat. The limit switch trips and the heater shuts down. A heater that has not been flushed for years is the usual suspect.
- The thirty-minute rest
- Navien asks you to turn the heater off for at least thirty minutes before restarting, so the exchanger cools. Restarting a hot heater only trips the limit again.
- A flush is routine
- Flushing with vinegar or a descaler through the service ports clears scale. Many owners have it done yearly. Where water is hard, a scale inhibitor or a softener upstream protects the exchanger.
- Keeping a service record
- Write down the date of each flush and the water hardness. Navien's heat exchangers are sensitive to scale, and a record shows a technician or the company how the unit has been looked after, which can matter for a warranty claim.
Stop boundary
When this stops being a self-service repair
- !Turn the heater off for at least thirty minutes, as Navien directs
- !Repeated E016 means the heat exchanger needs flushing
Evidence ledger
Sources behind this answer
Exact questions
Common questions
What does E016 mean on a Navien tankless water heater?+
Overheating of the heat exchanger.
How long should I wait?+
At least thirty minutes.
What does repeated E016 mean?+
It needs flushing.
Who does the flush?+
A technician or a trained owner.