Navien NCB-H E001 — Heat Exchanger Overheat
E001
Heat exchanger overheat. The control displays E001 when the space heating water temperature at the heat exchanger outlet thermistor rises above 212 °F (100 °C), and the unit auto resets below that temperature but must be manually reset after three consecutive overheats. The table classifies it as 3,2, Manual RESET / Auto RESET.
Applies to
This overheating code is displayed by the front-panel display on NCB-H combi boiler models (NCB-190/060H, NCB-190/080H, NCB-240/110H, NCB-240/130H, NCB-250/150H), as documented in NCB-H Installation and Operation Manual, section 11.7 Understanding Error Codes. Codes can differ between controller generations, so always check the manual that matches your unit.
- Navien NCB-H Combi
- Navien NCB-190/060H
- Navien NCB-190/080H
- Navien NCB-240/110H
- Navien NCB-240/130H
- Navien NCB-250/150H
Controller: front-panel display. Source manual: see sources (2021-02).
Why a code is not a diagnosis
An over-temperature code protects the heat exchanger or venting; it does not reveal whether the cause is low water flow, a failed pump, trapped air, fouling or a sensor fault.
Safe things to observe
- Note the code and whether rooms or hot water are still working.
- If you see steam, melted wiring or smell burning, switch the appliance off at its service switch and call a technician.
Do not
- Do not reset the appliance repeatedly while the cause is unknown.
- Do not remove covers or bypass any high-limit device.
How professional service helps
- A technician checks pump operation, flow, system pressure and the cleanliness of the heat exchanger.
- Combustion and safety devices are verified with an analyser and the manufacturer's procedure after any repair.
Where ROMA provides on-site service
On-site service is currently offered in Greater Vancouver, BC, including Vancouver, Burnaby, Richmond, Surrey, Coquitlam, North Vancouver, West Vancouver, New Westminster, Port Coquitlam, Port Moody, Delta, Langley, Maple Ridge, Abbotsford, Chilliwack, White Rock, Pitt Meadows, Tsawwassen, Anmore, Lions Bay, Belcarra, Bowen Island, Mission. Everything else on this site is reference information you can use anywhere in Canada.
Parts and service
Parts commonly involved
These parts appear in the documented text for this alert. A code reports a condition, not a failed part — a technician confirms the cause by testing before anything is replaced.
Heat exchanger
The heat exchanger is where a boiler transfers heat from the burner flame to the water that heats your home.
What a technician checks →Thermistor / NTC sensor
A thermistor is the small temperature probe — technically a negative temperature coefficient, or NTC, resistor — that tells a boiler's control how…
What a technician checks →
Service for this alert
- Gas Boiler Repair
Licensed gas technicians from ROMA Heating & Cooling diagnose and repair residential and light-commercial gas boilers across…
- Gas Boiler Replacement
ROMA replaces old, failed or inefficient gas boilers in Greater Vancouver, handling removal, venting and gas-supply changes,…
Every boiler part explained — what it does, how it fails and what a technician checks.
Documented for Navien NCB-H Combi.
Frequently asked questions
Can I clear this code myself?
Clearing a code without fixing its cause usually just brings it back. Note the code, check the safe items on this page, then call a licensed technician. If your appliance manual describes a user reset for this exact code and it stays away, no call may be needed.
Boiler locked out? Call with the alert text ready.
The brand, model and this alert are passed along when you request service online, so the technician arrives prepared.
On-site service in Greater Vancouver, BC. ROMA lists “Open 7 days” on its site; call to confirm same-day availability.
Sources and verification
- NCB-H Installation and Operation Manual, section 11.7 Understanding Error Codes · accessed September 7, 2026
Facts checked September 7, 2026. Last updated September 7, 2026. Technical reviewer: not yet assigned.