ATAG DHW Flow Detection Fault

Furnace shows F8, no hot water even though heating may work

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

Possible Causes

Faulty DHW flow sensor or turbine, Blocked inlet filter on cold water, Sticking DHW microswitch

Safety first: Isolate power and close the cold water inlet before removing any DHW components.

Clean the cold water inlet filter/strainer at the boiler.
Locate the DHW flow sensor or turbine assembly and check for debris or limescale; clean or replace as needed.
Check the wiring to the DHW flow sensor and reseat connectors.
Restore water and power, then test hot water demand. If F8 persists, the sensor or associated electronics may need replacement by a technician.

Medium 3/5

ATAG DHW flow sensor

Check Price on Amazon

We may earn a commission from links on this page.