Navien E030: abnormal exhaust temperature, causes and fixes

A condensing tankless heater is designed to pull so much heat out of the exhaust that the exhaust leaves the unit relatively cool. When the exhaust runs hot, the Navien shows E030 and stops.

That makes E030 a close relative of E016. Both usually point to heat that is not getting into the water.

What to check first

1. Check when the unit was last descaled.
2. Clean the cold water inlet filter.
3. Look at the vent pipes where you can see them, and make sure nothing is disconnected or crushed.
4. Turn the unit off for several minutes to let it cool, then restart it.

Common causes

Scale in the heat exchanger

Scale keeps heat from reaching the water, so more of it goes up the vent. Descaling is the usual fix.

Restricted water flow

A clogged inlet filter or a problem with the flow adjustment valve means less water moves through the heat exchanger to absorb heat.

Venting problems

Incorrect vent materials, a damaged vent or an exhaust sensor fault can also trigger E030. Navien vents most condensing models in plastic pipe, which is why exhaust temperature is monitored closely.

When to call a technician

If E030 comes back after descaling and cleaning the filter, have a licensed installer inspect the vent, the exhaust sensor and the heat exchanger.