POE supply for 3 x 951Ui-2HnD

RouterOS Wireless Networking
1

Has anyone managed to achieve the following.
I want to install 3 pieces of 951Ui-2HnD on the same network, the 2 will be configured as CAP and the other will be guest router and the CAPS Manager with its wifi interface as CAP. The wan will be an adsl router with its own dhcp server in another area close to the area where the 951Ui-2HnD are going to be installed (I need 2 different and seperated networks, so PPOE is not an option for the wan router).

My question is related mostly with the power supply of the the three 951Ui-2HnD via passive POE. I want to power supply the ether1 POE in of the caps manager RB and from its ether5 POE out port supply the other 951Ui-2HnD ether1 POE in port. From the previous 951Ui-2HnD ether5 POE out port supply the last 951Ui-2HnD.

How many A and V power supply will be sufficient for the three 951Ui-2HnD ?
(I calculated a power supply of 24V at 1A, by assuming that the total wattage is 7W per 951Ui-2HnD multiplied by 3 = 21W, divided by 24V is almost 1A).

Are the 951Ui-2HnD able to be connected and operate fine in this way with ethernet cables?
(The max A of the ether5 POE out is 500mA, so 7W divided by 24V is almost 300mA so it is supposed to work)

2

Your calculations are correct. Anyway, most of the time routers need 3-4w.

3

if i understand 3 rb951Ui:

chain1.jpg
rb951Ui is rated at 7watt

you have to use a 24volt power supply with at least real 1amp without voltage drop

included power supply of rb951Ui is 0.45amp

is important be sure of power supply dont lower the voltage under load because if voltage lowers too much number 1 rb951Ui PoE output can overcome the 500ma limit.


if i was you i will test that setup before to implement it putting all radios ar maximum tx power and maximum load to measure the voltage drop at the rb951ui number 3 to be sure, and off course measure power consumption.

be sure of test startup cycle and take in mind the length of cable can lead to voltage drop and current increasing

4

Yes chechito you understood right.
I am planning to use an UBIQUITI POE-24-24 (24V, 1A, 24W).
The only limitation is the 500mA of the ether5 output, which is on the limit of each RB (8W divided by 24V = 0.333A), so the first one is going to supply the other two with 0.666A > 0.5A of the ether5.

I will try it or I will go for a hex poe lite.

Thank you very much.