Exactly what do you mean by "The washers on my worster [sic] boiler key seems to big"?
The manual should tell you exactly how to pressurise it.
Exactly which Worcester Bosch Greenstar do you have? There's several manuals available here:
https://www.worcester-bosch.co.uk/professional/support/literature/greenstar-si-combi-installation-instructions
Ghhh, September 2023
