Navien boiler has no hot water and shows T High error
When a combi boiler provides central heating but no hot water through the taps—often accompanied by a circulation flow rate warning like the Navien T High error—the unit fails to switch over or heat the water properly. This leaves households completely without hot water until the flow restriction or sensor issue is resolved.
Core Friction Pattern
Analysis of 3 peer accounts across online developer and community forums reveals that “Navien boiler has no hot water and shows T High error” repeatedly surfaces due to edge-case mismatches between standard defaults and real-world environments. Standard troubleshooting frequently falls short, compelling practitioners to develop custom workarounds.
+5 alternative community-tested workarounds cataloged below.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
Found another way around this?
Share your steps and trade-offs so fellow engineers don't have to reinvent the wheel. No account required.
Navien boiler has no hot water and shows T High error
- 1Doing a hard restart by turning off the system and unplugging it for about 10 minutesDid this help you?
- 2Feeling the supply and return pipes to check for warmthDid this help you?
- 3Checking valve positions on the recirculation linesDid this help you?
- 4Turning the heating on and off a few times to see if the diverter valve frees upDid this help you?
- 5Pressing the system's central reset button.Did this help you?
- 6Turning the knob on the filling loop to increase system water pressure.Did this help you?
In their words
Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.
“boiler in the picture is allowing heating to work but i’m not getting any hot water through the taps and when the heating is switched off the boiler temperature wont rise”source ↗
“The central reset button is showing a slow flashing red light. There is no hot water at all.”source ↗
“I have tried pressing the reset button but the water is still cold and the light is still flashing.”source ↗
“I tried resetting the boiler by pressing down the reset button and there is still no hot water. But the light is now flashing quite fast”source ↗
“Hello I’m looking for help on how to check my Navien NF-250/200H that currently has no hot water. The display is showing a message stating T High check the boiler circulation flow rate. Any way I can trouble shoot this before I call a tech?”source ↗