S.21 — DHW Mode Fan Start-up Error (EcoTEC Pro / EcoTEC Plus)

What does S.21 mean?

This error indicates a problem during the initial phase of the EcoTEC Pro / EcoTEC Plus boiler's fan starting up when operating for domestic hot water (DHW) production.

• Fan start-up fault in DHW mode
• Fan component issue

Click steps to track your progress.

1. 1

   Turn off the boiler at the main electrical supply for a few minutes, then restart it.

2. 2

   Check for any physical obstructions around the boiler's air intake and flue.

3. 3

   If the error reoccurs, contact a qualified heating engineer to inspect or replace the fan unit.