Navien NFB-C E353 — Water Pressure Sensor
E353
Water pressure sensor. The control detected the water pressure sensor output outside the normal 0.5–3.5 V range for three seconds and initiates boiler shutdown, so check the sensor wiring and replace the sensor.
Applies to
This low-water or pressure protection code is displayed by the front-panel display on NFB-C models (NFB-301C, NFB-399C), as documented in NFB-C Installation and Operation Manual, Ver 1.0 (Feb 2024) — error codes cross-checked against the NFB-C Service Manual (250116) (Ver 1.0). Codes can differ between controller generations, so always check the manual that matches your unit.
Controller: front-panel display. Source manual: Ver 1.0 (2024-02).
Why a code is not a diagnosis
A water-pressure or low-water code can mean a genuine leak or empty system, a failed expansion tank, a faulty fill valve, or a sensor problem. The appliance does not distinguish these.
Safe things to observe
- Read the pressure gauge and compare it with the normal cold-system pressure your installer set.
- Look for drips or wet spots near the appliance, pipes and the relief-valve discharge.
Do not
- Do not keep re-pressurizing a system that keeps losing water.
- Do not cap a relief-valve discharge pipe.
How professional service helps
- A technician finds and repairs the leak, checks the expansion tank and fill assembly, and verifies the sensor circuit.
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.
Water pressure sensor
The water pressure sensor is the electronic gauge that tells a modern boiler's control how much pressure the heating loop is under.
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…
Every boiler part explained — what it does, how it fails and what a technician checks.
Documented for Navien NFB-C Commercial Boiler.
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
- NFB-C Installation and Operation Manual, Ver 1.0 (Feb 2024) — error codes cross-checked against the NFB-C Service Manual (250116) · Ver 1.0 · accessed September 7, 2026
Facts checked September 7, 2026. Last updated September 7, 2026. Technical reviewer: not yet assigned.