Our Voltimum Experts answer your questions on a daily basis in our Technical Expertise area. This one, about cable tray and ladder and the minimum cable CSA required for earth bonding, is answered by SELECT:
Also, what is the minimum cross-sectional area of earthing cable for the earth bonding of IT cable trays?
Answer: Unless the metal cable support system introduces a potential that does not already exist in the location in which the system is installed, it would not need to be bonded.
However, in practice you would normally bond the cable tray to prevent any potential coming into the building from any another location.
You should use Table 54.8 from BS7671: 2008 (the 17th Edition) to determine the correct size of conductor.
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