Navien NPE-2 Code E047
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.
Call a proThe verdict
Call a licensed plumber
A sensor fault, and an inexpensive part — but it lives in the exhaust path of a gas appliance and it is the sensor that protects against a hot flue. That combination makes it a service call, not a DIY swap.
Typical cost: $150–$600
US estimate for parts and labor. Prices vary by region and by who does the work — see how we estimate costs.
What the manual says
The meaning above is transcribed from the manufacturer's diagnostic documentation for the NPE-2 — not averaged across the brand.
Source: Navien NPE-2 User's Information Manual (p. 17), read Aug 2026 — the manufacturer's own documentation for this exact series.
What you can safely check
Before anything else: if you smell gas, stop here, leave, and call your gas utility.
- Turn the heater off and leave it off.
- Contact your installer or Navien technical support.
Frequently asked questions
How is E047 different from E030?
E047 says the exhaust sensor circuit is broken. E030 says the sensor is working and the exhaust is genuinely too hot. Same part of the unit, opposite conclusions.
Code E047 on other Navien series
The same code number can mean something different on another series — make sure you're reading the page for your exact unit: