The following installation manuals are available for the HCHE range:
Ambirad VCHE-HCHE Mk2 Gas - Installation Manual - August 2004 - https://www.reznor.co.uk/wp-content/uploads/2023/12/AmbiRad-VCHE-HCHE-Installation-Manual-Mk2-Gas-EN-2004-08-0408-CHEAMEN.pdf
Ambirad VCHE-HCHE Mk2 Oil - Installation Manual - February 2008 - https://www.reznor.co.uk/wp-content/uploads/2023/12/AmbiRad-VCHE-HCHE-Installation-Manual-Mk2-Oil-EN-2008-02-0802-CHEOAMEN.pdf