So, I want to connect 23 Ap's using PoE. The Switch is a 500w 24 port switch. May I use every single port with PoE without causing trouble on the Switch?



It's a UniFi switch of 24 ports. I'm going for the 500 watt model, but it would be a great save if the 250 Watt could also work.

I'm trying to switch 23 UniFi AP AC Long Range which can work with PoE at 24v with 0.5amp.

  • 1
    Each model for a manufacturer may have different specs. Please provide the make and model of the switch as well as the devices you want to hang off of it. AP's, phones...etc....AND they're peak and normal power consumption specs. If you provide the data, your question can get answered. Welcome to the site. Cheers! – Citizen Jul 9 '16 at 5:54
  • I really think you should ask the manufacturer about this. From the spec on the WAP, is says that it will use a maximum of 6.5W, and that should work with the switch. I have a problem with that figure for an 802.11ac WAP; it seems quite low. – Ron Maupin Jul 9 '16 at 15:50
  • Esp. when their own specs say it's a 12W draw (not counting line loss) Bank on it asking for 30W -- then these things aren't "PoE" compliant devices (802 standards are for 48vdc, unifi uses 24v in most of it's products) – Ricky Beam Jul 9 '16 at 20:20
  • I'm also having trouble to understand how a WAP with those specs can actually work at full power with only a 24v and 6.5w it looks kinda low for me. In fact, when choosing the Switch, I was wondering if using another's company switch could handle these WAP's as they aren't 48v. Also, using PoE injector pump up to 48v so I'm unsure about relying on it until some WAPs begin to smell like fried chicken. – HumbertoWoody Jul 10 '16 at 19:53
  • The correct POE injector (as supplied with one-packs, or as purchased separately for 5-packs) is a 24V injector, so I don't know what you are talking about "pumped up to 48V..." - As already commented, I run 24V UBNT stuff off Microtik 24V passive switches (RB260GSP, specifically, since it fills a need for my network, inexpensively) – Ecnerwal Jul 10 '16 at 23:24

It rather depends on what is real. 24V 6.5W is not 24V 0.5 A - but I think the latter number is just what the default (passive) POE power brick is, and they are oversized somewhat by default.

24V 0.5A would be 12W. 24 of those would be 288W and require the 500W switch.

6.5W X 24 ports would be 156W and the 250W would be fine.

Actual data update - not having the time free to muck up my network for this pro bono question, I checked the POE-Brick input against my Kill-A-Watt, and got a peak actual draw of (drumroll, please) 4 Watts (even with the radios blasting away on high power, which is not how I normally run them.)

VA is a bit worse at 8, but that's just the poor 120VAC power factor into a lightly-loaded 12 Watt AC/DC power supply. So, whatever inefficency is involved in the power brick and the draw of the radio is 4 watts or less (observed.) Call it 4.499 if you like, or call it 5 - regardless, this would appear to confirm the 6.5W worst case maximum draw as a very reasonable specification. To the original question, this means that 23 or 24 APs would be easily powered from a 250 watt (24V passive) POE switch.

If 802.3 af/at is something the OP is more comfortable with, the (slightly more expensive) UAP-AC-Pro model is of that 48V POE flavor, but it has a maximum draw spec of 9W, which likely means that a 250W POE switch will not be able to run 23-24 of them, since the Watt rating of POE switches seems to typically include the power needed to run the switch itself.

  • I have a real problem believing a multi-radio, 802.11ac WAP uses a maximum of 6.5W. Most multi-radio, 802.11ac WAPs require PoE+. – Ron Maupin Jul 10 '16 at 0:58
  • Their first generation AC ran much hotter (reputedly, I never bought any.) These ones (UAP-AC-LR) waste less power. It will take some screwing around (meaning I won't do it tonight) before I can plug one into a switch that will give a power consumption (actual) reading, but I have the single-radio 2.4(n) version (UAP) sitting on a switch that gives me a reading drawing 2.76 - 3.54W (actual.) – Ecnerwal Jul 10 '16 at 3:49
  • So, should I go for 500 watt powered switch? I'm really concerned about this because I could connect 1-5 WAP's to AC but the rest really need to be PoE. – HumbertoWoody Jul 10 '16 at 19:44
  • They are ALL POE - connecting them to AC just means connecting a POE injector (supplied in one-packs, extra for 5-packs.) There's no need to do that "near the AP." If you particularly want 48V POE, get the UAP-AC-Pro, it's 48V af/at (and 9W each, so you'll want the 500 for sure). Without rearranging enough stuff to get the fussy numbers from the µTik, my Kill-a-Watt says 4 watts peak (actual) and 8VA (not the greatest power factor) for the AC input to the POE injector running the UAP-AC-LR - so I think you can believe 6.5W peak on the DC side of things without fear, if testing beats conjecture – Ecnerwal Jul 11 '16 at 0:30

I don't know the exact model you are using, but the specs I read say 48V @.5A. That's 24 watts (and is more inline with similar APs)

23 ports @ 24W = 552 Watts. So, no, you can't power all the devices. Also don't forget to account for 50-75 watts for the switch itself.

  • That exact WAP model (datasheet) says is it passive 24V @ .5A, and a maximum power consumption of 6.5W. I just don't see an 802.11ac WAP using that little power. – Ron Maupin Jul 9 '16 at 19:51
  • PoE switches are all 48v – Ron Trunk Jul 9 '16 at 19:53
  • 1
    This one does 24V passive PoE: dl.ubnt.com/datasheets/unifi/UniFi_PoE_Switch.pdf – Ron Maupin Jul 9 '16 at 19:54
  • @RonTrunk UniFi does their own stupid. They do have a few 802 compliant devices, but 99% of their crap is a proprietary 24v system. – Ricky Beam Jul 9 '16 at 20:23

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.