Error Code E016: Navien Water Heater – Heat Exchanger Overheating Troubleshooting Guide
Navien Error Code E016 indicates that the heat exchanger temperature has risen beyond safe operating limits. When overheating occurs, the system shuts down to prevent damage to internal components and ensure safe operation. This guide explains what E016 means, why it happens, and the steps you can safely take before calling a technician.
What Error Code E016 Means
E016 is an overheating error.
The heat exchanger is getting too hot during operation, and the unit automatically stops heating to protect itself. Overheating is often caused by restricted water flow, scale buildup, or conditions that prevent proper heat transfer.
Common Causes of Navien Error Code E016
E016 typically appears when the heat exchanger cannot dissipate heat properly due to:
- A clogged cold‑water inlet filter
- Scale buildup inside the heat exchanger
- Restricted water flow through the system
- Blocked or partially closed water valves
- Debris or sediment in the plumbing system
- Prolonged operation under high‑demand conditions
- Internal overheating conditions that trigger a safety shutdown
Because overheating can damage the unit, the system shuts down immediately when this code appears.
How to Fix Navien Error Code E016
These steps follow Navien’s safety‑first logic and focus on what a homeowner can safely check.
Step 1 — Turn Off the System and Allow It to Cool
Shut the unit off and wait at least 30 minutes.
This allows the heat exchanger to cool and resets the overheating condition.
Step 2 — Clean the Cold‑Water Inlet Filter
A clogged inlet filter restricts water flow and is one of the most common causes of overheating.
- Remove the filter
- Rinse out debris and sediment
- Reinstall it securely
Restoring proper flow often resolves the issue.
Step 3 — Flush the Heat Exchanger
Scale buildup inside the heat exchanger reduces heat transfer and causes temperatures to rise.
A full system flush helps remove:
- Mineral deposits
- Sediment
- Scale buildup
If you are not familiar with flushing procedures, a technician should perform this step.
Step 4 — Check Water Valves and Flow
Ensure that:
- All water valves to and from the unit are fully open
- There are no obstructions in the plumbing
- Water flow is steady and unrestricted
Low flow can cause rapid overheating.
Step 5 — Restart the System
After cleaning the inlet filter and ensuring proper flow, restart the unit.
If E016 returns, the issue may involve deeper scale buildup or internal components that require service.
When to Call a Professional
You should contact a qualified technician if:
- Cleaning the inlet filter does not resolve the issue
- The unit overheats again after cooling down
- The heat exchanger requires a full descaling
- Water flow appears restricted but the cause is unclear
- You are unsure whether it is safe to operate the heater
Overheating can cause long‑term damage if not addressed promptly.
Related Navien Error Codes
These codes are often associated with ignition or combustion issues: