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S.15

S.15 — DHW Mode Pump and Fan Overrun (EcoTEC Pro / EcoTEC Plus)

Vaillant · Turbomax Plus Boilers

What does S.15 mean?

This indicates that both the pump and fan in your EcoTEC Pro / EcoTEC Plus boiler are running for an extended or unexpected period after a domestic hot water (DHW) demand has ceased.

Common Causes

  • Pump malfunction
  • Fan malfunction
  • Control system error

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Reset the boiler by cycling the main power off and then on.

  2. 2

    Ensure the system pressure is adequate and there are no airlocks.

  3. 3

    If both components continue to overrun, contact a qualified heating engineer to inspect them.

Browse all codes in this manual (55)
Verified technical data. Last updated: April 2026

Related Faults

F.00F.00 — Flow NTC Cable Defective or Broken (Turbomax Plus)F.00, F.04, F.05, F.10, F.14, F.15F.00, F.04, F.05, F.10, F.14, F.15 — NTC Sensor Fault (Ecomax Pro 828E)F.01F.01 — Feed Temperature Sensor (NTC) Fault or Open Circuit (Turbomax Plus)
Source: Vaillant Turbomax Plus Boilers
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