In your search engine type: worcester digistat. go to the link that says D 10 RF DIGISTAT & DIGISTAT OPTIMISER. The web address is www.worcester-bosch.co.uk/installer/products/lpg-boilers
This link will take you to a web page where you can find the answer to your problem. You will have to download a PDF file. In this from page 7 to page 13 is al the info you will need. You can print these out for further use.
Hope this helps.
Howell Evans, March 2010