Don't Let Your Power Distro Fool You

I love power distros with built-in panel meters. You can tell at a glance what the incoming voltage and frequency is so you won't blow up any of your gear before you turn on the circuit breakers, and you can monitor the current with the push of a button. But don't make the mistake of thinking that you're power distribution gear is safe as long as the current on the meter doesn't exceed the ampacity of the feeder cable if you have more than one distro linked in a daisy chain because the on-board meter only reads the current being used by loads connected to the output of that distro, not the current passing through it. If you have feeder cable coming into the rack and feeder cable connected to the pass-throughs, the current coming into the rack is the combination of the current being used by the loads connected to the rack and the current being used by all of the downstream distros. You could, for example, have 300 amps being used by the first distro, and 200 amps being used by the second distro, and your feeder cable will be passing 500 amps but the amp meter will read 300 amps. Don't be fooled!