Navien tankless water heater code E047
Your series decides which reading applies. Across the 2 Navien series documented here, code E047 is listed as exhaust thermostat: open or short circuit (1 series) and exhaust thermostat fault (1 series). Find your series in the table below, where those readings route to a professional.
What code E047 means on each Navien series
| Series | What it means | Verdict | Typical cost |
|---|---|---|---|
| NPE-2 | Exhaust thermostat: open or short circuit | Call a pro | $150–$600 |
| NPE-A / NPE-S | Exhaust thermostat fault | Call a pro | $150–$600 |
Each row opens the full page for that generation. We hold manuals for NPE-2 and NPE-A / NPE-S, and each one gets its own reading of code E047 — what Navien documents, what you can safely check yourself, and what the repair should cost.
What each manual actually says
The table above compares 2 series in four columns, which is enough to route you and not enough to explain anything. This is the Navien wording behind each row, one entry per manual, so you can see where the 2 readings of code E047 agree and where they part company.
NPE-2 — Exhaust thermostat: open or short circuit
The exhaust thermostat's circuit is reading open or shorted, so the heater no longer knows how hot the flue is. Navien's instruction is to contact technical support. Note the wording changed between generations: the original NPE manual calls this "abnormal operation: exhaust thermostat", while the NPE-2 manual names the fault as an open or short circuit.
NPE-A / NPE-S — Exhaust thermostat fault
The exhaust thermostat is not behaving. This generation words it as an abnormal operation of the exhaust thermostat; the NPE-2 manual narrows the same code to the thermistor being open or short circuit. Either way it is the device that watches flue temperature, and Navien's instruction to the owner is to contact technical support.
Does it matter which Navien you have?
NPE-2 and NPE-A / NPE-S all route code E047 the same way: a professional, at $150–$600. That makes it one of the Navien numbers you can act on before working out which unit you own.
Which Navien do you have?
On the 2 series that report code E047, the model number on the rating label starts NPE — match yours against the 13 listed below. You can also use the full model-number decoder.
Where this comes from
Source: Navien NPE-2 User's Information Manual (p. 17), read Aug 2026 — the manufacturer's own documentation for this Navien range.
Source: Navien NPE Operation Manual (NPE-A / NPE-S) (p. 16), read Aug 2026 — the manufacturer's own documentation for this Navien range.
Parts, guides and symptoms behind code E047
Code E047 on these 2 Navien series points at 1 part and 1 symptom, each named by the manufacturer's own procedure for this code.