While you wait for answers, we may have found some information which could help you.
Click here for Thermostat Heating CommunicationThermostat issues- Siemens RDH10RF?
Rdh10 & RCR10/443-GB by seimens?
red flashing button siemens RCRIO/433?
Have I got got a faulty programmer?
Siemens RDJ10RF thermostat problem?
I cannot locate my Siemens receiver?