Tankless Water Heater Error Codes Explained
Tankless units flash a short code on their display when something goes wrong, and that code actually tells you a lot before a technician ever shows up. Here is what the most common ones mean.
| Common Issue | What It Usually Means |
|---|---|
| Ignition failure code | Gas supply, ignitor, or venting problem |
| Flow sensor error | Restricted flow, often scale buildup |
| Overheat protection triggered | Exchanger overheating, frequently scale related |
| Flame failure during operation | Gas pressure or venting issue mid cycle |
| Remote controller communication error | Wiring or controller fault, not usually urgent |
Why the Exact Code Matters
Manufacturers use different numbering systems, so a code on a Rinnai unit does not mean the same thing on a Rheem or Navien unit. When you call, have the exact code and the brand ready. It cuts diagnosis time significantly and often lets us bring the right part on the first visit instead of a second trip.
When It Is Not Actually an Error
A brief cold water sandwich, a short burst of cold water between hot cycles, is normal tankless behavior, not a malfunction. Do not confuse this with an actual displayed error code, which is a specific number or letter combination the unit is actively showing.
Got a code flashing right now? Call (877) 560-1148 and read it to us.
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