Juniper EX Power Supply Sound Levels

  • Mon 08 May 2017
  • misc

In recent years, prices have come way down on used Juniper EX-series top-of-rack switches, and devices like the EX3200 and EX4200 are looking increasingly tempting as network-nerd household switches.

There's more than one flavor of modular power supply for these switches. Broadly, they come in 930 watt and 320 watt flavors. The 320 watt supplies are flush with the rear of the switch enclosure and are suitable for T and 8P variants (switches that have either 0 or 8 PoE ports). The 930 watt supplies hang out the back of the switch and are suitable for 24P and 48P variants (that is to say, switches where all the ports are capable of supplying PoE power).

In a pinch one can run the large power supply in a switch that doesn't run that much power. If memory serves, a couple of years ago I tested one of the small power supplies in a 48P switch (with no PoE devices connected) and it booted and ran fine. Can't remember if there was a warning or not.

I'll concentrate on the 930 watt power supply since it can be used in pretty much any unit that it will fit in.

They're not the same in terms of their desirability for home use. I'll go with the external markings for my sample set; what is shown when one does a "show chassis hardware" may be entirely different.

The EX-PWR-930-AC Rev A01 was made by Cherokee. At least two samples that I have investigated do not throttle their fans back after chassisd starts (about 3-4 minutes after boot). Consequently they're pretty loud in operation.

I have investigated a single sample of the EX-PWR-930-AC Rev C, which was made by Delta Electronics. Its fans throttle back after startup is complete, and it is notably quieter in operation - perhaps 5-8 dB (I have not used a meter to test, though I might decide this is a fun experiment and do this another time).

Likewise, I have investigated a single sample of the EX-PWR3-930-AC Rev A. Its behavior is indistinguishable from the EX-PWR-930-AC - that is to say, satisfactory and quiet.

It's worth the trouble if you have to live or work in the vicinity of these switches. For datacenter use? Inconsequential. Careful attention to what you're buying on eBay or arranging a swap-out with a unit in a location where you don't care may be rewarding.

Do you have an EX in use in a location where you can do a little investigation? Let me know what you find and I'll summarize.