The following installation manuals are available for the WH range:
Benson WH Olympic Gas-11 - Installation Manual - November 1995 - https://www.reznor.co.uk/wp-content/uploads/2023/12/Benson-WH-Installation-Manual-Olympic-Gas-EN-1995-11-20-45-056-Iss-1-CE.pdf
Benson WH Olympic Oil - Installation Manual - March 1996 - https://www.reznor.co.uk/wp-content/uploads/2023/12/Benson-WH-Installation-Manual-Olympic-Oil-EN-1996-03-20-45-078-Iss-1-CE.pdf