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Vaillant VU 446/5-5 / VU 606/5-5 fault F.22

Safety shutdown: water deficiency

Gas boiler

What it means

Safety shutdown due to insufficient or no water in the product.

Likely causes

  1. Filling pressure fallen below 0.05 MPa (0.5 bar)
  2. Water leak in heating system
  3. Frequent pressure drops due to unresolved leak or venting issue
  4. Insufficient/no water in the product.
  5. Interruption in the wiring harness

Where to start

  1. Check displayed pressure value on screen (flashes if below 0.1 MPa / 1.0 bar)
  2. Top up the heating water to restore pressure
  3. Monitor pressure value on display - it flashes until pressure of 0.11 MPa (1.1 bar) or higher is reached

The full answer, free

  • 2 more checks in order
  • The readings and component tests from the manual
  • How to put it right, step by step
  • The manual page for this fault (page 60), right under the answer
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Safety: Isolate gas and power before you open the case. If you have been into the gas side, do a tightness test, and a combustion and flue check before you hand back. Gas Safe (UK) or RGI (Ireland) work only.

From the Vaillant manual for the VU 446/5-5 / VU 606/5-5. Check the model on the data plate before you order parts.

Other Vaillant VU 446/5-5 / VU 606/5-5 fault codes