- Boilers
- Tankless gas water heater
E004
Navien E004 on a tankless water heater: false flame detection
Risk level
High
Professional inspection is recommended.
Urgency
High
Quick answer
The heater detected a flame signal when there should be none. Navien's action is to make sure the power cord is properly grounded. Reset once with the Back button; if E004 returns, call an authorized technician.
Safety first
Stop and check this first
- Do not remove the front cover to look inside: Navien warns that operating the heater with the front cover open can cause fire or carbon monoxide poisoning, and that the cover may only come off with the power disconnected.
- If you smell gas: do not try to light any appliance, do not touch any electrical switch and do not use any phone in the building. Call your gas supplier from a neighbor's phone and follow its instructions; if you cannot reach it, call the fire department.
Safe checks you can perform
- Plug and outlet
- One reset with the Back button
- Outlet grounding test by an electrician
Leave these tasks to a qualified professional
- Do not attempt this professional task: Verify grounding
- Do not attempt this professional task: Check the flame detection circuit
What a technician must be able to justify
Technician visit
These are the steps they must carry out and show you. Tick them as they work: if steps are skipped, do not accept a part swap.
These are not instructions for opening or handling the equipment yourself. They are the checks that should support a technical conclusion.
Verify grounding
What they doThe professional measures outlet ground and checks the cord, as Navien's remedy for E004 requires.
They must show youthe ground test result.
In writingwhat was corrected.
Check the flame detection circuit
What they doIf grounding is correct, the technician inspects the flame sensing parts and wiring inside the unit with power disconnected.
They must show youthe faulty part or reading.
In writingpart replaced and why.
Before accepting a part or repair
Nothing has been shown yet. Do not accept a part swap based on the code alone.
Follow these steps
Note: Follow the documented order. An error code identifies the affected system, but it does not prove by itself which part has failed.
Plug and outlet
- Who:
- you.
- How:
- without unplugging anything wet or damaged, look at how the heater is plugged in. Navien supplies a 3-pronged grounded plug for a grounded outlet and says not to use a broken or modified cord.
- Result that matters:
- whether the plug goes straight into a 3-hole outlet.
- If there is an adapter, extension or damaged cord:
- tell the technician or an electrician; grounding must be verified with a tester.
- If it plugs straight in:
- grounding is still not proven; the outlet must be tested.
- Evidence to keep:
- photo of the plug and outlet.
Evidence: Navien NPE-A2 and NPE-S2 installation and operation manual
One reset with the Back button
- Who:
- you.
- How:
- press the Back button on the front panel. Navien's manual says resetting may solve the problem when an error appears.
- Result that matters:
- whether E004 comes back.
- If the heater runs normally:
- note the date; if E004 returns later, mention that it was reset before.
- If E004 returns:
- do not keep resetting; Navien says to contact an authorized technician, a licensed professional or its technical support.
- Evidence to keep:
- photo of the code before and after the reset.
Evidence: Navien NPE-A2 and NPE-S2 user's information manual
Outlet grounding test by an electrician
- Who:
- an electrician or licensed technician.
- How:
- tests the outlet's ground and polarity with a suitable tester.
- Result that matters:
- whether the outlet is properly grounded.
- If it is not:
- the electrical installation is corrected before replacing heater parts.
- If it is:
- the heater's flame detection circuit must be checked.
- Evidence to keep:
- the tester result in writing.
Testing an outlet means working with mains voltage.
Evidence: Navien NPE-A2 and NPE-S2 user's information manual
Still not solved
If the error persists, stop here. See what the technician must do and show you.
Where this code applies
A code is meaningful only inside the right product and version context.
Primary scope
- System
- Boilers
- Brand
- Navien
- Product type
- Tankless gas water heater
Known code variants
- calentador Navien E004
- Navien 004
- Navien E004
- Navien E004 falsa llama
- Navien E004 false flame
- Navien error E004
What it means
Navien defines E004 as false flame detection: the control saw a flame signal at a moment when the burner should be off. Navien's only owner action is to ensure the electrical cord is properly grounded; the heater has a 3-pronged grounded plug that must go into a grounded outlet. Other causes are inside the unit and need a technician. The code does not identify a failed part.
Warnings and stop conditions
- Highsource verified
Do not remove the front cover to look inside: Navien warns that operating the heater with the front cover open can cause fire or carbon monoxide poisoning, and that the cover may only come off with the power disconnected.
Evidence: Navien NPE-A2 and NPE-S2 installation and operation manual
- Criticalsource verified
If you smell gas: do not try to light any appliance, do not touch any electrical switch and do not use any phone in the building. Call your gas supplier from a neighbor's phone and follow its instructions; if you cannot reach it, call the fire department.
Evidence: Navien NPE-A2 and NPE-S2 user's information manual
Symptoms and causes
Probable causes · in order
- Grounding problemPossible
Navien's owner action for E004. Fits if the plug goes into an outlet that may not be grounded or through an adapter.
Evidence: Navien NPE-A2 and NPE-S2 user's information manual · Navien NPE-A2 and NPE-S2 installation and operation manual
- Fault in the flame detection circuitPossible
If grounding is correct, the cause is in the flame sensing parts or control, which only a technician can test.
Evidence: Navien NPE-A2 and NPE-S2 user's information manual
Virtual technician
Does E004 still appear after these checks?
Answer a few questions to narrow down the likely cause and the safest next action. Guidance only - it never replaces a professional.
Sources and technical references
- 1
Navien NPE-A2 and NPE-S2 user's information manual
Navien · 2020 · manual
- 2
Navien NPE-A2 and NPE-S2 installation and operation manual
Navien · 2026 · manual
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