CRS112-8P-4S-IN PoE power output question

Hardware MikroTik hardware general
1

Hello, I have a practical question about PoE device power consumption.

The general CRS112-8P-4S-IN comes with 95W adapter. That leaves about 80-85W for devices. I will have 8 PoE devices with total consumption of some 149 W nominally, which is at the max output for the Switch.

There are two Power Adapters to add to the standard 28V one, 48POW and 48V2A96W.

I am confused in how they work. How does this switch deliver power to PoE devices in regards to adapter? Are the two adapters (on different voltages) work in tandem, or separately? And how to calculate total power input for the total power output?

I presume that the 48POW would be adequate to add, to be able to deliver required 150 W.

Any info appreciated.

2

With both power adapters connected, it is possible to select PoE out voltage per port. And it seems that device itself will run off power supply providing higher voltage.

Note that CRS doesn’t do any voltage conversion … what gets in, gets out. Also observe PoE out current ratings … it’s 0.45A per port at 48V and 1A per port at 28V. If you plan to power “standard PoE devices” (conforming to 802.3 af/at), you need 48V power adapter and that will limit PoE out to around 21W per port. But even using 48V2A96W power adapter that means only 4 or 5 ports near full load.

3 
[rextended@SWITCH] /interface ethernet poe> monitor [find]
               name: ether1     ether2     ether3     ether4     ether5     ether6     ether7     ether8
            poe-out: forced-on  auto-on    auto-on    auto-on    auto-on    forced-on  forced-on  forced-on
        poe-voltage: low        low        low        low        low        high       low        low
     poe-out-status: powered-on powered-on powered-on powered-on powered-on powered-on powered-on powered-on
    poe-out-voltage: 26.1V      26.1V      26.2V      26.1V      26.2V      49.6V      26.1V      26.1V
    poe-out-current: 224mA      213mA      125mA      127mA      116mA      178mA      277mA      252mA
      poe-out-power: 5.8W       5.5W       3.2W       3.3W       3W         8.8W       7.2W       6.5W

ether1 AF60-LR (airFiber 60 LR)
ether2 RB921UAGS-5SHPacD (NetMetal 5SHP)
ether3 RB921GS-5HPacD r2 (mANTBox 19s)
ether4 RB921GS-5HPacD r2 (mANTBox 19s)
ether5 RB921GS-5HPacD r2 (mANTBox 19s)
ether6 Cambium PMP 450i [48V]
ether7 AF5XHD (airFiber 5XHD)
ether8 AF5XHD (airFiber 5XHD)

4

Thanks guys. I will have situation similar to @rextended: with three higher power devices (cameras, 18w) and five smaller ones (CAP ac at 13W). As the PoE output is input passthrough, I presume the proposed standard 48POW will be adequate to split it between the PoE and PoE+ devices, otherwise I wouldn’t be able to power them all.

I see that @rextended forced output for high voltage for cambium, so I guess it is selectable.

5

I prefer set for default all to low, and set high only when needed, not to auto, for prevet catastrophic errors, and I force non-mikrotik device to on for prevent problems
short-circuit protection is everitime active, also on forced-on

6

In this case you can split load between the two power inputs, cAP ac can take passive PoE in from as low as 17V. The standard 28V power adapter will power them marveously.

7

Thank you, appreciated.

I will order the switch + 48POW.