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Powering two devices from one ER-X-SFP port?

I can't seem to confirm this 100% from previous posts, so just want to be sure:

 

I would like to use one port from an ER-X-SFP (main basement switch) to power an ER-X (uplinked upstairs) and power a UAP-AC-Lite connected to that same ER-X's POE passthrough.  Both ER's would be used as switches only:

 

daisylink-ERs - Page 1.png

 

I just want to confirm there is enough capacity on a single ER-X-SFP POE port to power both devices like this.  

 

Thanks very much.

 

 


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Re: Powering two devices from one ER-X-SFP port?

Yes you will be fine.  From the datasheets

 

https://dl.ubnt.com/datasheets/edgemax/EdgeRouter_X_DS.pdf

https://dl.ubnt.com/datasheets/unifi/UniFi_AC_APs_DS.pdf

 

ER-X SFP max output 12W per port, 50W total

ER-X max draw 5W, average draw in my experience 2W

UAP-AC-Lite max draw 6.5W, average draw in my experience 3.5W

(total) max draw 11.5W, average draw in my experience 5.5W

 

I have a setup exactly like this:

 

ER-X SFP ->(50m cable)-> ER-X ->(2m cable)-> UAP-AC-Lite and it has been flawless since I installed it (about 2 years)

 

The ER-X SFP is on the 2nd floor (it powers a UAP up there as well), the ER-X and UAP are on the main floor.  It's nice because the ER-X SFP is on a UPS so everything is backed up during an outage with one UPS.

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Deleted Account
Posts: 0

Re: Powering two devices from one ER-X-SFP port?

Yes you will be fine.  From the datasheets

 

https://dl.ubnt.com/datasheets/edgemax/EdgeRouter_X_DS.pdf

https://dl.ubnt.com/datasheets/unifi/UniFi_AC_APs_DS.pdf

 

ER-X SFP max output 12W per port, 50W total

ER-X max draw 5W, average draw in my experience 2W

UAP-AC-Lite max draw 6.5W, average draw in my experience 3.5W

(total) max draw 11.5W, average draw in my experience 5.5W

 

I have a setup exactly like this:

 

ER-X SFP ->(50m cable)-> ER-X ->(2m cable)-> UAP-AC-Lite and it has been flawless since I installed it (about 2 years)

 

The ER-X SFP is on the 2nd floor (it powers a UAP up there as well), the ER-X and UAP are on the main floor.  It's nice because the ER-X SFP is on a UPS so everything is backed up during an outage with one UPS.

Emerging Member
Posts: 47
Registered: ‎02-09-2018
Kudos: 1

Re: Powering two devices from one ER-X-SFP port?

The single UPS idea is exactly what I was hoping to do.  Thank you for confirming!!

 

Regular Member
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Re: Powering two devices from one ER-X-SFP port?

Yep, that should work.  

 

I will say that you could run into issues depending on the length of your cables.  I tried a similar setup with an ER-X with a 24V power supply powering both another ER-X and a UAP-AC-LR a while back, that didn’t quite work (the UAP would reboot under load).  I rewired it so that the second ER-X and UAP were powered by a PoE injector and it works fine now.  Just keep an eye out for random UAP reboots.

Emerging Member
Posts: 47
Registered: ‎02-09-2018
Kudos: 1

Re: Powering two devices from one ER-X-SFP port?

The cable run to the ER-X (for me) will be in the ballpark of 38-45 feet (11.5-14m) over CAT5e.  From what I've heard, it shouldn't be a problem for POE.  

 

Thanks for the heads up.

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Registered: ‎08-19-2016
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Re: Powering two devices from one ER-X-SFP port?

To chime in, I also have an ERX-SFP and an ERX configured this way. (I needed a switch in a spot that doesn't have A/C power.) The ERX is configured as a switch and has one additional wired device on a non-PoE port.  The ERX-SFP is also powering a second UAP-AC-Lite and two Ubiquiti G3 surveillance cameras. This is within the PoE capability of the ERX-SFP by my calculations, and is working well.

 

-- Pete