FAQ
TL;DR: OP burned 8 tons of eco‑pea coal; “the driver working on the machine (PID) strives for continuous operation.” Fix by testing the fan, trying factory reset, then servicing a failed fan control path/triac if needed. [Elektroda, hajtaler, post #17106450]
Why it matters: This FAQ helps Tech/Defro owners diagnose a blower that won’t stop after reaching set temperature.
Quick Facts
- Controller reported: Tech Defro K1Pv4 on a Defro Comfort 30 kW boiler. [Elektroda, aneta07, post #17104683]
- Symptom: fan keeps running even when the display shows current equals set (e.g., 60 °C). [Elektroda, aneta07, post #17105936]
- Blower test passed; factory reset applied; behavior unchanged. [Elektroda, aneta07, post #17105936]
- Likely fault if not PID behavior: damaged fan control path/triac; service the controller. [Elektroda, tkaczu1, post #17106403]
- In machine/PID mode, the controller may run the fan continuously at low power near setpoint. [Elektroda, hajtaler, post #17106450]
Why does my blower keep running after the boiler reaches temperature?
In machine/PID mode, the controller aims for stable heat and may keep the fan spinning slowly near the setpoint. As one expert notes, “the driver working on the machine (PID) strives for continuous operation.” This is expected behavior when the temperature oscillates around the set value. [Elektroda, hajtaler, post #17106450]
How do I test the blow‑in fan and try a safe reset on Tech/Defro?
Use the controller’s built‑in fan test, as described in the manual. If the test passes, save your settings and restore factory defaults to rule out bad parameters. Re‑enter your settings afterwards and observe if behavior changes. [Elektroda, Adam-T, post #17104723]
The fan test passed and a factory reset didn’t help—what next?
Service the controller. “Most likely, the fan control path in the controller is damaged.” A shorted triac or failed output stage can keep the blower energized even at the setpoint. Only repair or replacement resolves a hardware fault. [Elektroda, tkaczu1, post #17106403]
Could a bad temperature sensor cause a constantly running fan?
Unlikely if other circuits (like the pump) react correctly to temperature. That behavior indicates the sensor reads fine. A stuck fan with good readings points back to the controller’s fan control path. [Elektroda, tkaczu1, post #17106403]
What does “triac short” mean for this boiler controller?
It refers to a failed switching component in the driver that can hold the fan output on continuously. Users reported that when the triac shorts in the driver, the fan “works constantly,” requiring service. [Elektroda, aneta07, post #17104039]
My controller hangs near 60 °C and the fan never stops. Is this known?
Yes. A user with a Comfort controller (blue desktop) saw hangs around 60 °C. During those hangs, the fan ran continuously despite exceeding the setpoint. That points to controller behavior rather than the sensor. [Elektroda, 65469, post #17104079]
Is 8 tons of eco‑pea coal in one heating season abnormal?
Context matters. For a 30 kW unit and weaker insulation, a member noted that 8 tons over winter can be quite normal. Boiler oversizing also raises consumption when modulation is limited. [Elektroda, hajtaler, post #17106450]
How much fuel did the original poster actually report using?
They reported about 8 tons of eco‑pea coal from November to mid‑March while troubleshooting the blower behavior. That concrete figure provides a baseline for comparison. [Elektroda, aneta07, post #17103722]
Which controller model is in this thread’s case study?
The system uses a Tech Defro K1Pv4 driver on a Defro Comfort 30 kW boiler. Matching your model is vital before applying settings or diagnostics. [Elektroda, aneta07, post #17104683]
Will a factory reset always stop a stuck fan?
No. In this case, the fan kept running even after restoring defaults. If PID behavior is ruled out, hardware service is the next step. [Elektroda, aneta07, post #17105936]
What heating area was mentioned for the 30 kW boiler in this thread?
About 250 m² was reported. Oversized boilers serving moderate areas tend to cycle or modulate continuously, which can keep fans active in PID mode. [Elektroda, aneta07, post #17106509]
What’s the best way to ask for help so others can diagnose fast?
Always provide the exact controller/boiler model, not just the brand. As one member quipped, saying only “I have an Opel” isn’t enough to diagnose. List setpoints, modes, and what you already tried. [Elektroda, Adam-T, post #17104075]
