I am installing a video/data link for our helicopter and a relay to our main office. They will be on top of a 22 story building downtown. There is a lightning protection system to bond the 10' aluminum masts. Inside the penthouse is a 120v ups circuit that fed old eq and the ups panel is located several floors down. There is a MCC 277/480v in the penthouse. The eq rack and it's components have to be bonded but this place has no 'building ground'. I know the grounding should be done at the service entrance and proceed from there. That's 22 floors down. Should I bond to building steel? Or the ground bus in the MCC? I'm worried about making a loop between the MCC and the UPS panel, especially with the difference in potential. I know alot of this rack stuff the green with lands on the eq case. The Ups is hardwired neutral and ground so it is not a sepratley derived system. Thanks in advance for any help you guys can give.