Vaillant · Heat pumps · Vaillant aroTHERM plus with uniTOWER plus
S.284De-icing flow temperature too low
Name in the manufacturer's documentation (service manual): De-icing flow temperature too low
[1]
In plain words (editorial)
The flow temperature during defrosting is too low (below 5 °C). The heat pump restarts; after three unsuccessful restarts it switches off and shows fault F.741. The manual says to check whether enough heat is available from the heating circuit.
When to call a service technician: If F.741 appears, contact a heating engineer.
✎ editorial – written from the cited sources, not a manufacturer statement. Status: draft.
For technicians
Steps given by the manufacturer (source text)
- Check whether sufficient heat energy is available from the building circuit[2]
Notes from the documentation
- If the flow temperature is below 5 °C, the heat pump is restarted. If the flow temperature is still not sufficient after three unsuccessful restarts, the heat pump is switched off and the fault message F.741 is displayed. Check whether sufficient heat energy is available from the building circuit.[3][4]
⚠ Work on refrigerant circuits, mains electricity and PV DC wiring is for qualified technicians only.
The Polish page has more detail (plain-language explanation, safe checks, guides): Read in Polish →
Sources
Every statement has a footnote to the document and PDF page. “Quote verified” means the quote was found automatically in the text of that page.
- [1] Vaillant uniTOWER plus VIH QW 190/6 E – Operating, installation and maintenance instructions (0020291525_05) (0020291525_05) , p. 58 official manufacturer document quote verified
S.284 De-icing flow temperat
- [2] Vaillant uniTOWER plus VIH QW 190/6 E – Operating, installation and maintenance instructions (0020291525_05) (0020291525_05) , p. 58 official manufacturer document quote verified
Check whether sufficient heat energy is available from the building circuit
- [3] Vaillant uniTOWER plus VIH QW 190/6 E – Operating, installation and maintenance instructions (0020291525_05) (0020291525_05) , p. 58 official manufacturer document quote verified
If the flow temperature is below 5 °C, the heat pump is
- [4] Vaillant uniTOWER plus VIH QW 190/6 E – Operating, installation and maintenance instructions (0020291525_05) (0020291525_05) , p. 58 official manufacturer document quote verified
If the flow temperature is below 5 °C, the heat pump is restarted