Best Practice - Power Loss Recommendations

Good morning everyone, quick question. We just installed a couple of Juniper EX4400x switches which have redundant power supplies. Currently, all 4 power cables run into a power management bar and from there the bar is plugged into a APC SMT1500 UPS. Problem is if these switches were to loose conventional power this UPS cannot keep the supply of power for even a minute. Is it normal practice to connect one supply on each switch to a wall outlet, is this ok?

That doesn’t seem correct, my old Entertasys switches would run for 20-30 minutes on the same size (maybe same model) UPS, and they were power hungry. Are you running a bunch of POE devices which increase the load? If so I suggest something in the APC SMX line of Smart-UPS, I generally buy the 2200 size and get an extra 2200 size battery to attach to it for longer run time. The product listing says you can add up to 10 additional batteries. example:

Feel free to chose a different model or options (like network card), I have several of these for different computer based equipment and servers.

You should probably look at the amount of power draw (assuming you have an LCD on the UPS) and figure out how much battery you need.

Or is the UPS old and need new batteries? Replace every 3 years to be safe. Yes the batteries will go bad and split the cases without triggering a self test error. When they do this your only sign is short run time when the power goes out. The faceplate comes off, one or two screws, and the battery unplugs and slide out. Slide replacement back in and plug it in. On the SM line of supplies, battery replacement is generally allowed to be done hot.

Battery was just replaced in the UPS about 2 months ago to be used for this upgrade, not alot of PoE devices. I removed the power cable to test and under 40 secs, 20% of the battery was drained, remember there are 4 X 550W PSU running off this 1500W battery. So that was a real world test with this UPS.

I would say you need something a lot bigger, but I’d still check the real draw. Those supplies should not be drawing all 550w, two of them should be at idle (25 watts for the fans?). No way that those switches draw 1100 watts each without a lot of heavy POE+ or POE++ devices attached, and if that was 120volts then you’d likely be at or over the rating of the power strip (2200 watts is roughly 19 amps at 120 volts).

I have a C1500 UPS on my switches (Extreme 5400 series x3), and they are drawing 126 watts total. These are 2x190 watts and 1x 550watts power supplies and running only 5 POE devices at about 7 watts each device. Over 80 ports (copper) active, 2 SFP+ ports (fiber) and both stacking ports to form a complete ring (DAC cables). Granted these are brand new and way more efficient than the previous Enterasys C5 switches, but I don’t think I ran over 250 watts with 5 of the C5 switches running (same POE draw). My C1500 says approximately 77 minutes of time. Either you are drawing a lot more power, or something is wrong with the UPS.

I found a data sheet that says the EX4400-24x should be drawing around 126 watts with no POE, the 48 port F version draws even less without POE devices, and the 48 port MP 183 watts with no POE devices. Looks like base power should be 350-400 watts (for the pair) at normal operation without POE devices. That should be around 15+ minutes of power.

In the switch user interface does it show you how much power the supplies are providing? Or does the UPS have the LCD so you can see how much power the devices are drawing from the UPS? If no LCD (UPS), how many bars/dots does the load meter show?

I’m wondering if this could be an oddity with the UPS… Can you move 1 each supply to the second bank on the back of the UPS? It shouldn’t make any difference but worth a try.

The UPS does indicate that the 4 PSU’s are running at 24% load capacity. I’ll see if I can toggle and get an actual draw.

24% should be more than 40 seconds. At 100% I think they rate these UPS at 2 minutes.