BoilerFaultCodesWhat the manual says
Manufacturer manualPump and fan running (warm start)
From this model's manual
Verified against the Vaillant Ecomax 613 installation & service manual, page 45.
What causes this fault?
This code appears when the boiler activates its pre-heat function to ensure hot water is delivered to your taps as quickly as possible. It is a standard operational sequence where the pump and fan run briefly to warm up the internal heat exchanger. Your boiler hasn't stopped working; it is simply preparing itself for use.
DIY fix possible
Check if the comfort mode or pre-heat setting is turned onWait a few minutes to see if the status changes to a normal heating codeMonitor for any actual fault codes starting with F if the boiler fails to fire
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