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jacquesl03
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Netpower 16P max PoE out contradictory

Wed Aug 12, 2020 10:43 am

The datasheet is either contradictory or unclear, and Mikrotik support via my distributor seems to be just interpreting the datasheet.

The data sheet states:
Max PoE-out on low (< 30 V) voltage: 5.6 A (2.8 A per 8port group, max 1.1 A per port)
Max PoE-out on high (> 30 V) voltage: 2.8 A (1.4 A per 8port group, max 0.6 A per port)
Max power consumption: 316 W

Now by doing the math, the max power consumption shows that one can use a total of 2.8A low voltage AND 1.4A high voltage per group of 8 ports, but Mikrotik support wants to say that the total wattage budget is shared (ie ~80w per group of 8). This would say that the max power consumption on the datasheet is incorrect.

Can someone verify this explicitly without just interpreting the datasheet?
 
Elans
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Re: Netpower 16P max PoE out contradictory

Wed Aug 12, 2020 12:30 pm

Both inputs can be used simultaneously, therefore, per 8 ports you can have ~150W (24V & 57V PSU are used).
As example, 4 ports with low voltage, 4 ports for high voltage (per 8 port group):
24 (V) x 2.8 (A) = 67.2W
57 (V) x 1.4 (A) = 79.8W

If you will use 24(V) and 57 (V) PSU at the same time, in total you can have ~150W per 8 ports.

As mentioned in brochure:
When using both the high and low voltage adapters, the netPower will automatically choose the correct PoE standard and voltage, based on the devices you connect to each port. You can also specify it manually.
https://i.mt.lv/cdn/product_files/netPo ... 200700.pdf
 
dduck313
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Re: Netpower 16P max PoE out contradictory

Wed Jan 06, 2021 8:26 pm

I have plan to use this thing with:
Ether01-08: 8x RBD22UGS-5HPacD2HnD-15S (set to high - 48v) [written 15w so its about 0.3125A x8 = 2.5A]
Ether09-16: 8x RBSXTG-5HPacD (set to low - 24v) [written 12w so its about 0.5000A x8 = 4A]
can this thing handle what i need if i use both 24v n 48v psu?
Or I need to put:
Ether (even) to RBD22UGS
Ether (odd) to RBSXTG
Please explain, because there is not enough manual for this thing. Not funny if I bought this thing n cant use it.
This thing IS NOT A CHEAP TOY so I wanna make it clear first. Thanks.
 
ZPrime
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Re: Netpower 16P max PoE out contradictory

Wed Sep 08, 2021 1:39 am

I have plan to use this thing with:
Ether01-08: 8x RBD22UGS-5HPacD2HnD-15S (set to high - 48v) [written 15w so its about 0.3125A x8 = 2.5A]
Ether09-16: 8x RBSXTG-5HPacD (set to low - 24v) [written 12w so its about 0.5000A x8 = 4A]
can this thing handle what i need if i use both 24v n 48v psu?
Or I need to put:
Ether (even) to RBD22UGS
Ether (odd) to RBSXTG
Please explain, because there is not enough manual for this thing. Not funny if I bought this thing n cant use it.
This thing IS NOT A CHEAP TOY so I wanna make it clear first. Thanks.
Based on everything I can find about this device, you would need to split your "high/48v" and "low/24v" devices between the two port groups.
So you'd connect 4x RBD22UGS to the left group (ports 1-8) and then 4x RBSXTG on the same, and then repeat with the other port group (9-16).
So if you did odd/even that would accomplish the same thing, but you don't have to do it that way (you could go 48v 1-4, 24v 5-8, then 48v 9-12 and 24v 13-16).

Again, if my understanding of this device is correct. ;)

What I want to know - if the device has both low voltage and high voltage PSUs attached, which one does the netPower itself draw from, the low or the high voltage? I.e. where do we have to subtract the 16W of power that the switch itself can draw?
 
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Re: Netpower 16P max PoE out contradictory

Wed Sep 08, 2021 2:02 am

I do not understand correctly what you mean about port group.
You can mix 48V and 24V on any port
for example ether1 can be 48V and ether2 24V, without separate port groups.

About the power to itself, is drained on less used source.
 
biomesh
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Re: Netpower 16P max PoE out contradictory

Wed Sep 08, 2021 6:24 am

From what I see on mine, it draws power from the highest voltage source, not the one with the least load.
 
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mkx
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Re: Netpower 16P max PoE out contradictory

Wed Sep 08, 2021 8:37 am

From what I see on mine, it draws power from the highest voltage source, not the one with the least load.

It seems that general principle for all MT devices which can take more than one power input (e.g. POE-in + barrel connector) is that there's simply a diode on each power input connected to common internal power bus. Diodes block power from input power bus from escaping through other power inputs (which might even damage alternative power sources). And keeping in mind the way diodes operate it's clear that highest voltage power supply provides power to the unit - voltage on internal power bus is voltage of highest voltage power supply minus voltage drop over a diode (typically around 0.6V) ... current generally doesn't flow from lower towards higher voltage, hence lower voltage power supply can't supply power.
Connected to internal power bus then there's power regulator dropping voltage to whatever needed by board electronics.

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