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Navien E030 — Exhaust Overheating
Your Navien shut down because the exhaust (flue) temperature climbed too high — usually the same scale or flow problem behind E016, now showing up in the exhaust.
$99 dispatch and diagnosis fee — waived if you approve the repair
E030 fires when the exhaust temperature leaving the unit exceeds Navien's safe threshold — roughly 230°F — for more than about ten seconds. The unit shuts down to protect the venting and itself.
The root cause usually isn't the exhaust itself. When the heat exchanger is scaled or water flow is restricted, heat that should go into your water goes up the flue instead — so E030 and E016 often share the same fix: a descale and a flow check. Occasionally it's an exhaust-recirculation or venting problem.
What causes E030
1. Scale in the heat exchanger
Same root as E016. Mineral scale forces excess heat into the exhaust instead of the water, driving flue temperature over the limit. A descale resolves most cases.
2. Restricted water flow
A dirty inlet strainer, partially closed valve, or low pressure reduces the water available to absorb heat, so more of it exits as hot exhaust.
3. Exhaust recirculation or venting issue
If exhaust is being drawn back into the intake, or the vent run is undersized or partly blocked, flue temperatures read high. We inspect the vent termination and routing.
4. Exhaust thermistor fault
A faulty exhaust temperature sensor can misreport. We confirm the reading is real before replacing parts.
What you can safely check first
- Check the cold-water inlet filter and confirm every supply valve is fully open, exactly as you would for E016.
- One reset is reasonable. If E030 returns, heat is going somewhere it should not and the unit needs looking at.
- If you ever smell exhaust indoors or a carbon-monoxide alarm sounds, get everyone out and call 911 or the gas utility first, then call us.
When to stop and call us
E030 means flue temperature past its limit, which is a venting and heat-transfer question rather than a code to clear. It needs a descale, a flow check, and the venting inspected by a licensed plumber.
Need Navien repair on the South Shore?
An error-code guide can explain the symptom. If your home is in Hull, Quincy or our surrounding South Shore service area, Johnson Bros. can help with the next step: diagnosing your Navien boiler, combi boiler or tankless water heater.
The house has no heat
Tell us whether every room is cold or just one heating zone, and whether the boiler display shows a code.
Boiler and no-heat repairThe taps have no hot water
Check whether it affects one fixture or every hot tap. Tell us if you have a tank, a tankless heater, or a boiler that also heats your water.
Help with no hot waterBoth stopped working
Mention both symptoms when you call, especially with a combi boiler. Have the brand, model and displayed code ready if you can read them safely.
Navien service and repairCalls are answered 24/7. Call for urgent no-heat or no-hot-water trouble; we will confirm appointment availability. Online booking does not guarantee immediate dispatch.
Local service: Hull heating repair · Quincy · Weymouth · Hingham · Braintree · Abington.
Smell gas? Leave the house first, then call the gas utility or 911 from outside. Do not use switches, phones or anything that sparks inside the building, and do not go looking for the source. Call us afterwards, once it is safe, for the repair.
Seeing E030 on your Navien?
Book online and we will diagnose the actual cause, explain what we find, and price the repair before starting.
Navien E030 FAQs
What does Navien error code E030 mean?
E030 is an exhaust over-temperature lockout. The unit measured the flue temperature above its safe threshold — around 230°F — for more than about ten seconds and shut down to protect the venting and itself.
What causes E030?
Most often the same thing behind E016: scale in the heat exchanger or restricted water flow pushing extra heat into the exhaust. It can also be an exhaust-recirculation or venting problem, or, less commonly, a faulty exhaust temperature sensor.
Is E030 dangerous?
The lockout itself is protective — the unit stopped to prevent overheating the venting. It is not an emergency on its own. But if you ever smell exhaust indoors or a carbon-monoxide alarm sounds, treat that as an emergency: get everyone out and call 911 or the gas utility, then call us.
How much does E030 repair cost?
The $99 service fee sends a licensed technician out to diagnose the problem. Approve the repair on the spot and the fee is not charged at all; decline it and the $99 covers the visit. Because E030 usually resolves with a descale and a flow/venting check rather than major parts, the cost is typically predictable.
Other codes on this unit? See all Navien error codes.
Why South Shore homeowners choose Johnson Bros.
Navien E030 diagnosed properly
We diagnose the cause rather than clearing the code and hoping. You get an upfront price before any work starts.
Not sure what's wrong? Send a photo or videoBooking online is the quickest way to hold the next open appointment. Call instead if it is urgent and you would rather talk to someone.
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Related services
All Navien error codes
The other codes this unit can show, and what each one means.
Navien service and repair
Installation, service and repair for Navien equipment on the South Shore.
Water heater repair and replacement
Repair and replacement options for tank and tankless water heaters.
Family Plan
Members get 10% off, priority scheduling, and the $99 fee waived even if you decline the quote.
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Navien E030 diagnosed properly
We diagnose the cause rather than clearing the code and hoping. You get an upfront price before any work starts.
Call for urgent help now. Book online when you want the next available fit for your schedule.