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mcnick50
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poe question

Thu May 05, 2022 5:13 pm

hello i have 1 CRS328-24P-4S+RM and i bought a PowerBox Pro which it will be power with poe. my question is will the poe be enough to power 4 ip cams?
 
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Re: poe question

Thu May 05, 2022 6:16 pm

will the poe be enough to power 4 ip cams?

Are you asking if one PoE output port from the CRS328 can drive 4 cams via the PowerBox? If so, that seems dicey. By my math, you only have about 4 W of power per port under this configuration. That's 48 V nominal from the CRS328 @ 450 mA = 21.6 W. Subtract the 6 W the PowerBox itself needs, leaving 15.6 ÷ 4 = 3.9 W per port.

The hungriest cam I have here is a modern 4K camera configured for high video compression, and it's drawing ~120 mA, so at 48 V nominal, that's nearly 6 W of draw. A less hungry 1080p cam is drawing about 5 W.

I expect that there are IP cams that will run from the 3.9 W available, but you'll have to sacrifice something to get it: lower resolution, lower frame rate, poorer compression, or some combination of the three.

It'd be much better to home-run those cams back to the CRS328, which has plenty of grunt for this task. The 21.6 W number from above is then per-port rather than fanned-out through the PowerBox, and you don't have the PowerBox's overhead, either.

There are limits above this, but you're highly unlikely to run into them, and if you do, you can take advantage of the fact that these switches group PoE according to the underlying switch chip groupings, so even if you do manage to overload one group, you can rebalance things by spreading the PoE load to the other groups.
 
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Re: poe question

Thu May 05, 2022 8:46 pm

is it better to use MT48-480095-11DG to power the powerbox pro?
 
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Re: poe question

Thu May 05, 2022 9:12 pm

is it better to use MT48-480095-11DG to power the powerbox pro?
surely

is better to feed the power via barrel jack connector than PoE in if you want to power other devices across the powerbox
 
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Ca6ko
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Re: poe question

Thu May 05, 2022 9:18 pm

It is more correct to use PowerBox Pro with its own 48 V power supply. Some cameras may not start, then switch on POE out = forsed on
 
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Re: poe question

Thu May 05, 2022 9:22 pm

is it better to use MT48-480095-11DG to power the powerbox pro?

Run an outdoor power + Ethernet distribution unit from an indoor rated power supply? Why ever for?

If you're using it outdoors, I'd imagine something like this would be more appropriate. Overkill, but maybe you have more than one PowerBox, so they could share.

If you're using it all indoors, I'm back to recommending home-runs for each PoE powered camera.

Another option: run only 2 or 3 cameras per PowerBox. Nothing says you have to run 4 cameras from it. With fewer loads, each device can draw more power.
 
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Re: poe question

Thu May 05, 2022 11:43 pm

can i use both poe in and MT48-480095-11DG on the powerbox pro?
Last edited by mcnick50 on Thu May 05, 2022 11:47 pm, edited 1 time in total.
 
mcnick50
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Re: poe question

Thu May 05, 2022 11:47 pm

is it better to use MT48-480095-11DG to power the powerbox pro?

Run an outdoor power + Ethernet distribution unit from an indoor rated power supply? Why ever for?

If you're using it outdoors, I'd imagine something like this would be more appropriate. Overkill, but maybe you have more than one PowerBox, so they could share.

If you're using it all indoors, I'm back to recommending home-runs for each PoE powered camera.

Another option: run only 2 or 3 cameras per PowerBox. Nothing says you have to run 4 cameras from it. With fewer loads, each device can draw more power.
it's going to be installed under a roofed patio so no rain no water
 
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Re: poe question

Fri May 06, 2022 9:14 am

can i use both poe in and MT48-480095-11DG on the powerbox pro?
What's the point of that?
Power will be drawn from the power supply as long as it is running. When the power supply is switched off, the POE will automatically switch on. But as the load is too high for the port, the protection will switch it off. This will result in a cyclic reboot
 
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Re: poe question

Fri May 06, 2022 9:34 am

When the power supply is switched off, the POE will automatically switch on. But as the load is too high for the port, the protection will switch it off. This will result in a cyclic reboot

That brings us back to the earlier suggestions:

  1. Home-run the cameras to the CRS328; or
  2. Run fewer cameras per PowerBox, so the PoE-powered fall-back does work as you wish; or
  3. Run 4 cameras per PowerBox, but turn off PoE on the CRS328 port running to the PowerBox, since it can't help.

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