The following installation manuals are available for the RHC21 4000 / 8000 range:
RHC21 4000 - Installation Manual - February 2022 - https://www.reznor.co.uk/wp-content/uploads/2023/12/Reznor-RHC21-4000-Installation-EN-2022-02-D301346-Issue-3.pdf
RHC21 4000 and 8000 Condensate Kit - Installation Manual - September 2021 - https://www.reznor.co.uk/wp-content/uploads/2023/12/Reznor-RHC21-4000-and-8000-Condensate-Kit-EN-2021-09-D301415-issue-0.pdf
RHC21 8000 - Installation Manual - February 2022 - https://www.reznor.co.uk/wp-content/uploads/2023/12/Reznor-RHC21-8000-Installation-EN-2022-02-D301319-Issue-3.pdf
RHC21 Propane - Product Guide - https://www.reznor.co.uk/wp-content/uploads/2023/12/RHC21-Propane-Installation-Instruction-Addendum-D301383.pdf