Stumbled upon a guide that the installers and maintenance teams adhere to, contains codes for reporting etc, might be interesting.
Scroll down to Page 8 onward.
https://mocopa.org.uk/wp-content/uploads/2018/03/MOCOPA-guide-version-3.5.pdf
Scroll down to Page 8 onward.
https://mocopa.org.uk/wp-content/uploads/2018/03/MOCOPA-guide-version-3.5.pdf