Set Appliance State:

Ensure NO demands
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Navigate to d.0 in the diagnostic codes menu and check its value - click HERE for guidance on how to access the diagnostic codes.
Is the value set to a kW output suitable for the CH system that the appliance is attached to?
Note:
The kW output can only set between certain values depending on the appliance. See the table below for the range of outputs for each appliance.
ApplianceHeating Output (kW)
ecoMAX 824/2 E11 to 19
ecoMAX 828/2 E13 to 23
ecoMAX 835 E10 to 27