Labels are produced, as noted in Photovolatics in buildings, Guide to the installation of PV Systems (2nd Edition) (DTI/Pub URN 06/1972).
The labels have been used by several companies that have passed MCS accreditation.
Digital - HERE.
Screenprinted - HERE.
8 Types of Label sold are;
1. Solar PV Module Danger - contains live parts during daylight.
2. Inverter - Isolate AC and DC before carrying out work.
3. PV Array DC Junction Box Danger - contains live parts during daylight.
4. PV System - main AC isolator.
5. Do not disconnect DC Plugs and sockets under load - turn off AC supply first.
6. DC Cable Danger - High Voltage
7. PV Array DC Isolator Danger - contains live parts during daylight
8. Warning Dual supply Do not work on this equipment until it is isolated from both mains and on-site generation supplies.