Grounding a rack by creating a mechanical “bond” – making a connection from metal device to metal rack, and then ensuring that the entire unit is properly grounded – ensures a safer install. “If you have a short or something in the system, in any particular product, proper grounding of the entire unit will keep the user safe from any electrical shock,” says Middle Atlantic’s Nyron Kahrim. “If you ground to a central point, it gives you a single path of the charge to go directly to a single ground source and it doesn't escape.”
And that ground can even eliminate unwanted noise – but there are caveats. “I think where the challenge comes in is that the equipment manufacturers that are doing our audio and video gear, don't all have the same grounding philosophy inside the unit,” says Vince Luciani of SurgeX, “and that’s where some problems come from.”
Luciani continues, “All units have a metal chassis, and normally the safety ground is that third wire in the power cord that’s connected to the chassis. If there's an electrical short and the chassis becomes energized with a 120 volts, that there is a path over which the current can flow so that a breaker will trip and it'll turn off the power coming to it. So there’s a 99% chance that you're already grounding your system, right?
“So you've got your rack with your piece of equipment bolted to the rack. Now you've got metal touching metal, that's one path for a ground run. Then you've got your electrical outlet. That's also connected to the chassis ground, and that's another path. What happens is you get all these multiple paths of grounds going on, and this is where ground loops come from,” says Luciani – and those ground loops can be responsible for all manner of racket, especially the annoying 60-cycle hum.
Luciani has advice: “The best way to track down these problems is if you're going to ground something externally, ‘star’ ground everything to a single point -- don't run thing A to B, B to C, C to D in a chain – you’ll never be able to troubleshoot quickly.”
Interested in learning more? Check out the CEDIA Podcast “The Power Show 2020.”