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Vaillant · Heat pumps · Vaillant aroTHERM plus with uniTOWER plus

F.735Evaporation temperature too high

Name in the manufacturer's documentation (service manual): Evaporation temperature too high[1]

In plain words (editorial)

The evaporation temperature is too high for compressor operation – the temperature on the source side (heating mode) or in the building circuit (cooling mode) is too high, or too much external heat enters the environment circuit.

When to call a service technician: Contact a competent heating engineer (installer or Vaillant customer service).

✎ editorial – written from the cited sources, not a manufacturer statement. Status: draft.

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. [1] Vaillant uniTOWER plus VIH QW 190/6 E – Operating, installation and maintenance instructions (0020291525_05) (0020291525_05) , p. 61 official manufacturer document quote verified F.735 Evaporation temperature too high
  2. [2] Vaillant uniTOWER plus VIH QW 190/6 E – Operating, installation and maintenance instructions (0020291525_05) (0020291525_05) , p. 61 official manufacturer document quote verified Temperature in the environment circuit (heating mode) or building circuit (cooling mode) too high for compressor operation
  3. [3] Vaillant uniTOWER plus VIH QW 190/6 E – Operating, installation and maintenance instructions (0020291525_05) (0020291525_05) , p. 61 official manufacturer document quote verified Feed-in of external heat into the environment circuit too high due to increased fan speed
  4. [4] Vaillant uniTOWER plus VIH QW 190/6 E – Operating, installation and maintenance instructions (0020291525_05) (0020291525_05) , p. 61 official manufacturer document quote verified Check the system temperatures
  5. [5] Vaillant uniTOWER plus VIH QW 190/6 E – Operating, installation and maintenance instructions (0020291525_05) (0020291525_05) , p. 61 official manufacturer document quote verified Check the refrigerant filling volume for overfilling
  6. [6] Vaillant uniTOWER plus VIH QW 190/6 E – Operating, installation and maintenance instructions (0020291525_05) (0020291525_05) , p. 61 official manufacturer document quote verified Check the EEV (does the EEV move to the limit stop? Use sensor/actuator test)
  7. [7] Vaillant uniTOWER plus VIH QW 190/6 E – Operating, installation and maintenance instructions (0020291525_05) (0020291525_05) , p. 61 official manufacturer document quote verified Check the sensor for the evaporation temperature (depending on the position of the 4-port diverter valve)
  8. [8] Vaillant uniTOWER plus VIH QW 190/6 E – Operating, installation and maintenance instructions (0020291525_05) (0020291525_05) , p. 61 official manufacturer document quote verified Check the volume flow in cooling mode
  9. [9] Vaillant uniTOWER plus VIH QW 190/6 E – Operating, installation and maintenance instructions (0020291525_05) (0020291525_05) , p. 61 official manufacturer document quote verified Check the air volume flow in heating mode