Norman
Guest
Hi John.
“2.1.4.2 Cable Type and Installation Method
To minimise the risk of faults, PV D.C. cable runs should be kept as short as practicable.”
Source: MCS Guide to the Installation of Photovoltaic Systems 2013.
You can download a .pdf copy for free here:
https://www.microgenerationcertification.org/mcs-standards/mcs-standards