The following installation manuals are available for the GRH range:
Benson GRHL - Installation Manual - September 2001 - https://www.reznor.co.uk/wp-content/uploads/2023/12/Benson-GRHL-Installation-Manual-EN-2001-09.pdf
Benson GRHU - Installation Manual - September 2001 - https://www.reznor.co.uk/wp-content/uploads/2023/12/Benson-GRHU-Installation-Manual-EN-2001-09.pdf