Navien Boiler Error Codes: Causes & How To Fix Them

Last Updated on February 10, 2025

Navien boilers are known for their efficiency, reliability, and cutting-edge technology. However, like any heating system, they can sometimes run into issues. If your Navien boiler is displaying an error code, it’s crucial to understand what it means and how to fix it. 

In this guide, we’ll walk you through the most common Navien boiler error codes, their causes, and the steps you can take to resolve them.

Understanding Navien Boiler Error Codes

Navien boilers are equipped with an advanced diagnostic system that displays error codes when something goes wrong. These codes help homeowners and engineers identify issues quickly, making troubleshooting easier.

Below is a breakdown of the most common Navien boiler error codes and their solutions.

Common Navien Boiler Error Codes & Fixes

1. E001 – Overheating Error

Cause:

• Blocked heat exchanger: Over time, debris and sludge can accumulate in the heat exchanger, restricting water flow and causing overheating.
• Limescale build-up: In hard water areas, limescale deposits can form inside the boiler, reducing heat transfer efficiency.
• Poor water circulation: A failing circulation pump, airlocks, or a closed valve can hinder proper water circulation, leading to overheating.

Fix:

• Check for blockages in the heat exchanger by inspecting for restricted water flow. A professional flush may be required.
• If limescale build-up is suspected, a descaling treatment or a water softener can help prevent future accumulation.
• Ensure the circulation pump is functioning correctly. If it’s noisy or slow, it may need replacement or servicing.
• Bleed radiators and check for trapped air that could be obstructing circulation.
• Verify that all valves are open to allow smooth water movement.

2. E002 – Low Water Pressure

Cause:

• Water leak in the system: A leak in the boiler or central heating system can cause pressure loss.
• Faulty pressure sensor: A malfunctioning sensor may incorrectly detect low pressure.
• Insufficient water in the system: If the system hasn’t been topped up recently, pressure may drop below the required level.

Fix:

• Check the pressure gauge on the boiler; if it reads below 1 bar, the system needs repressurising.
• Inspect radiators, pipes, and boiler connections for visible leaks. If a leak is found, a professional repair may be required.
• Refill the boiler using the filling loop until pressure reaches between 1-1.5 bar, then reset the unit.
• If the issue persists, the pressure sensor might need to be replaced. A Gas Safe engineer can diagnose and resolve this.

3. E003 – Ignition Failure

Cause:

• Faulty gas supply: If gas flow is interrupted, the boiler cannot ignite.
• Blocked burner: Soot or debris can clog the burner, preventing proper combustion.
• Defective igniter: A worn-out or damaged igniter won’t generate a spark to ignite the gas.

Fix:

• Ensure the gas supply is turned on. If other gas appliances aren’t working, check if there’s a supply issue.
• Clean the burner to remove carbon build-up. If excessive, professional cleaning may be required.
• If the igniter is clicking but failing to ignite, it may need replacement. A Gas Safe engineer should handle this repair.

4. E004 – Flame Loss

Cause:

• Low gas pressure: Insufficient gas flow can cause the flame to extinguish.
• Dirty or damaged flame sensor: The sensor detects the flame; if dirty or faulty, it may fail to register ignition.
• Blocked flue: A flue obstruction can prevent proper ventilation, causing the flame to go out.

Fix:

• Check if other gas appliances are working. If not, there may be an issue with the gas supply that needs attention from the gas provider.
• Clean the flame sensor using fine sandpaper to remove oxidation or dirt build-up.
• Inspect the flue for blockages like bird nests, debris, or snow. If blocked, carefully clear the obstruction.
• Ensure the gas valve is fully open and functioning correctly.

5. E012 – Exhaust Overheating

Cause:

• Blocked flue or ventilation system: A blocked exhaust can cause gases to overheat within the boiler.
• Poor heat exchange efficiency: A dirty or damaged heat exchanger can struggle to dissipate heat properly.

Fix:

• Inspect the flue for blockages or obstructions and clear them as needed.
• Clean the heat exchanger to remove soot, dirt, or limescale build-up.
• Ensure the boiler is properly ventilated and installed according to manufacturer guidelines.

6. E016 – Heat Exchanger Overheating

Cause:

• Limescale build-up: Hard water can cause scale to accumulate in the heat exchanger, reducing efficiency and causing overheating.
• Blocked pump or flow sensor: If water flow is restricted, heat cannot dissipate properly, leading to overheating.

Fix:

• Descale the heat exchanger using a descaling solution or hire a professional to perform a power flush.
• Check that the circulation pump is running smoothly. If it’s faulty, repair or replace it.
• Inspect and clean the flow sensor to ensure accurate readings and proper water movement.

7. E030 – PCB Error

Cause:

• Faulty PCB (Printed Circuit Board): If the PCB is damaged, the boiler’s electronic controls may fail.
• Loose or damaged wiring: Loose connections or broken wires can disrupt the boiler’s communication system.

Fix:

• Turn off the boiler and restart it after a few minutes to see if the error clears.
• Inspect all wiring connections and ensure they are secure. If damaged, professional repair is needed.
• If the PCB is faulty, a replacement may be required. This should only be done by a qualified Gas Safe engineer.

Preventing Navien Boiler Errors

While some issues are unavoidable, regular boiler maintenance can help prevent error codes from appearing in the first place. Here are a few tips:

✅ Check boiler pressure regularly – Maintain a pressure of around 1-1.5 bar.
✅ Bleed radiators – This removes trapped air that can affect circulation.
✅ Schedule an annual service – A Gas Safe engineer can check for potential boiler problems.
✅ Keep the flue clear – Ensure there are no obstructions in the venting system.
✅ Use a magnetic filter – This prevents sludge build-up in the system.

When to Call a Professional

While some boiler issues can be resolved with basic troubleshooting, others require professional assistance. If you’re experiencing recurring error codes, leaks, or strange noises, it’s best to contact a Gas Safe registered engineer.

Ignoring persistent boiler issues could lead to higher energy bills, reduced efficiency, or even safety hazards.

Stop Wasting Money on Boiler Repairs – Get a Free Quote Today!

If your Navien boiler keeps breaking down, those constant repairs can quickly add up—not to mention the frustration of being left without reliable heating. Older or faulty boilers also tend to be less efficient, meaning higher energy bills and more wasted money in the long run.

Instead of pouring cash into ongoing fixes, it might be time to invest in a new, energy-efficient boiler that saves you money and keeps your home warm hassle-free.

At Eco Happy, we make the process easy with free, no-obligation boiler quotes so you can explore your options with confidence.

✅ Lower your energy bills with a high-efficiency system.
✅ Avoid costly breakdowns and unexpected repair costs.
✅ Enjoy reliable heating with expert installation.

Don’t wait until your boiler fails completely—request your free quote today!

Final Thoughts

Understanding Navien boiler error codes can save you time and money by helping you diagnose and fix minor issues yourself. However, for more serious problems, professional servicing is always the best approach. 

Regular maintenance is key to keeping your boiler running efficiently and preventing unexpected breakdowns.

If your Navien boiler is displaying an error code and you’re unsure how to proceed, don’t hesitate to contact a qualified heating engineer.