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15 x AP55c and POE

Ray Raginskis

Hi all,

I would like to know more about AP55c access points. I have 15 (fifteen) AP55c access points and i want to use POE switch to power them.

I have zyxel GS1900-24lhp which provides 170 watts of total budget power for devices with higher power requirements such as IP phones, IP cameras and wireless access points. It's managed switch.

AP55c max power consumption is 13w so am I right by doing this math:

170w / 13w = 13 AP55c units I can power?

I did lab this and I only could power 5 AP's. Sixth AP just wouldn't turn on.

Never had to power 15 devices with POE, maybe someone could point me in right direction here. I'm sure Im missing something here. Maybe I should ask this on zyxel forum..?

Regards

Ray



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  • 0

    Hi,

     

    the 13W should be a max value. Their standard power consumption is less. Anyhow I would recommend to calculate with the maximum value as you did. Access points might hang if they do not get enough power. 

    For this switch, I found the following remark in ftp://ftp.zyxel.com/GS1900-48/user_guide/GS1900-48_V1_Ed2.pdf :

    Remaining Power(W):  This field displays the amount of power the Switch can still provide for PoE. Note: The Switch must have at least 16 W of remaining power in order to supply power to a PoE device, even if the PoE device needs less than 16 W.

    So based on your calculation, this switch can only power 12 APs. Beside that, I see no obvious reason why your configuration shouldn't work.
     
    Can you verify that every single AP can be powered individually to rule out an AP specific issue. After that, please also check the actual power consumption when plugging the devices and the port state/configurations. Beyond that, it seems to be switch related.
     
     
    Kind regards,
     
    Dirk Bolte
  • 0 in reply to DirkBolte

    Thanks for replay Dirk.

    I tested each device seperatly and they are working.

    I did some more research after posting this and I shouldoff mentioned that AP,s are actually on a VERY long patch cable. I read on zyxel forums that POE switch have to provide more power for  device if its on long patch cable which it is in my case.

    For zyxel 1900-24hp max output per port is 30w. I have 4 devices on  long wire. And 5th one is plugged directly in switch with short cable.

    So I really do believe that switch have to provide 30w of power for 4 devices + 13w for fifth and like you said switch h itself needs 16w of remaining power.

    So here's what the math looks like.

    30w*4=120w (4ap's on long patch using 30w)

    120w+13w=133w ( fifth ap using 13w)

    133w+16w=159w (remaining power + POe switch required power. )

    170w-159w=21w (total power of switch - total consumption remaining power).

    So I will have to get more nifty POE.

    Is there any switch you would recommend?

    Regards

    Ray

  • 0 in reply to Ray Raginskis

    Hi,

     

    17W due to cable length sound very high. I haven't found a per-port display of power usage, but the overall power should give you an indication whether your assumption is correct.

     

    I cannot give you any switch recommendation. Sorry.

     

    Kind regards,

     

    Dirk Bolte

  • 0 in reply to DirkBolte

    Thanks Dirk,

     

    Either way the bottom line is that Switch can't deliver required power output.

     

    Regards

    Ray

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