Navien E517 Fault Code: Causes, Fixes & Repair Costs
What does the Navien E517 fault code mean?
The E517 code appears on Navien boilers when the unit's self-diagnostic system detects that the DIP switch configuration is invalid or unrecognised. DIP switches are small physical toggle switches found both on the boiler's front panel and on the main PCB (printed circuit board). They tell the boiler how it is set up — things like system type and installation parameters. When these switches are in a combination the boiler doesn't recognise as legitimate for your model or installation, it raises E517 and locks out to prevent incorrect operation. This fault almost always requires an engineer to inspect and correct the switch positions or assess the PCB.
General guidance only — not a substitute for professional advice, and not certified by a Gas Safe engineer. Always have your specific appliance assessed by a qualified professional. Any gas work must be carried out by a Gas Safe registered engineer. If you smell gas or suspect carbon monoxide, leave the property and call the National Gas Emergency line on 0800 111 999.
Common causes
- Incorrectly configured DIP switches Common
The most common trigger for E517. During installation or following a service, one or more DIP switches may have been set to a position that creates an invalid combination for the specific Navien model or installation type. Even a single switch in the wrong position can cause the board to reject the configuration entirely.
- DIP switch inadvertently moved Sometimes
Vibration over time, or accidental contact during a previous service visit, can cause a DIP switch to shift slightly out of its intended position. The change may be subtle but enough for the control board to flag an error.
- Faulty or damaged PCB Rare
If the DIP switches are verified to be in the correct positions and the fault persists, the PCB itself may be misreading the switch states due to a hardware fault, corrosion on the switch contacts, or internal PCB failure. In this scenario, the board will need replacing.
How to fix it
- Reset the boiler once using the Back button on the front panel DIY safe
Press the Back button on the Navien front panel to attempt a reset. A one-off glitch can occasionally trigger E517, and a single reset may clear it. If the code returns immediately or after a short time, do not keep resetting — move on to the next step.
- Do not attempt to access or adjust the DIP switches yourself Gas Safe engineer
Although the front panel DIP switches are visible, adjusting them without the correct reference documentation for your exact Navien model and installation type risks making the configuration worse. Accessing the internal PCB switches requires opening the boiler casing, which must only be done by a Gas Safe registered engineer.
- Contact a Gas Safe registered engineer to inspect and verify the DIP switch settings Gas Safe engineer
An engineer familiar with Navien appliances will refer to the model-specific configuration chart to confirm the correct switch positions for your installation. They will compare the current switch states against the required settings and make any necessary adjustments safely.
- If the switch positions are correct, ask the engineer to assess the PCB Gas Safe engineer
When the DIP switches are confirmed to be in the right positions but E517 persists, the PCB is likely misreading those states. The engineer may test the board's continuity and switch contact resistance. If the board is faulty, a replacement PCB will be needed.
- Call a Gas Safe registered engineer if you haven't already done so Gas Safe engineer
E517 is not a fault a homeowner can safely resolve beyond a single reset attempt. Always verify any engineer you contact is listed on the Gas Safe Register (gassaferegister.co.uk) before booking.
Parts you may need
- Navien main PCB (control board) · from £280
- DIP switch assembly / front panel switch board · from £45
The exact spare depends on your boiler's GC number (on the data badge). Check this against the part before buying.
Typical repair cost
Expect to pay roughly £80–£350, depending on the underlying cause.
Frequently asked questions
Can I fix the Navien E517 myself by flipping the DIP switches?
It is strongly advised that you do not attempt this. While the front panel DIP switches may be accessible without fully opening the casing, setting them incorrectly can cause further faults or unsafe operation. The correct configuration depends on your exact Navien model, system type, and installation setup — information that requires the manufacturer's documentation to interpret correctly. In the UK, any work inside the boiler casing must be carried out by a Gas Safe registered engineer. Limit your involvement to a single reset attempt using the Back button.
How much does it cost to fix a Navien E517 fault in the UK?
If the fix is simply correcting the DIP switch positions, you are typically looking at a call-out and labour charge of around £80–£150 for the engineer's time. If the PCB is found to be faulty and needs replacing, the part alone can cost £180–£400 depending on the specific Navien model, with total repair costs including labour typically falling in the £280–£500 range. Always get at least two quotes and confirm the engineer is Gas Safe registered before any work is carried out.
Why has E517 appeared after a recent boiler service?
This is a plausible scenario. During a service, an engineer may have adjusted or accidentally disturbed a DIP switch. If E517 appears shortly after a service visit, contact the engineer who carried out the work and ask them to return to verify the switch configuration — a reputable engineer should do this at no extra charge.
Will my boiler work at all while showing E517?
No. E517 is a lockout fault, meaning the boiler will not fire while the code is active. You will have no heating or hot water until the fault is resolved. If you are without heat in cold weather, contact a Gas Safe engineer promptly and mention the specific error code when you call so they can come prepared.