First let me say the rack mount ears for the RB4011iGS+RM are simply terrible. Ugh.
Second - I replaced an older 2011 with a 4011. The 4011 PS cable is shorter than the 2011 and too short to reach. Does anyone know the max amp draw of the 4011. I see the amp draw per port - but not the draw for the device.
The OEM 4011 psu is 24V 1500ma
I have an older 2011 psu rated 24V 1200ma with a cord that reaches.
Is the 2011 psu ma output powerful enough? I suppose I could extend the OEM 4011 cord a couple feet as well, but don’t want to hack the cable.
Since it comes with a PS of 24V 1.5A that is the suggested.
Otherwise you should measure the current draw of the device under full load and see how much current it draws.
Specs say that max power draw without attachments (whatever those might be) is 18W. At 24V that translates to 0.75A. If your old 2011 came with 24V 1.2A power adapter, then you should be fine. Only Krishna knows if the old PA is still capable of delivering its rated current though …
Thanks mxk. Ohm’s law is good. It dawned on me I should just do the calculation but your beat me to it . You are a scholar and gentlemen!
I think you are right - should be plenty of headroom. I have another 4011 on the way and plan on measuring my killowatt meter and measure one and report back.
Can someone tell me why the manufacturer gives this product with a 24V 1.5A since as you say it works with no problem at 24V 0.8A?
For me the answer is that there is a reason for this.
Am just really curious to have your opinion since you easily ignore the PS ratings the manufacturer gives for his equipment.
I suspect the cost to produce a 1.5 amp power supply versus a 1:00 amp power supply is very small, for example. I believe these standards change over time and probably 1.5 and a 24 volt supply has become somewhat of a standard. so mikrotik just needs to make sure the power supply meets the minimum amp requirement to drive the board more doesn’t make any difference.
You do want to have that room up above the minimumrequirements for a CPU Max and things like that but it’s probably not twice the amount of power that it requires drive the entire board.
Mikrotik decided to source that power supply because it met the minimum requirements had enough headroom probably works with a number of their other devices and could just slim down there skus.
For one thing: specs say that max power draw is 33W (without mentioning “without attachments”), which at 24V is 1.375A. I’ve never seen MT explanation what attachments are. But RB should definitely come with PA capable of powering the device when configured with all allowed peripherials. OTOH if device owner knows that device is not going to power any attachments it is fine to go with lower-specced (but still adequate) PA. It surely is owners responsibility to ensure flawless operation …
In addition to that it’s what @RackKing writes: for manufacturer like MT it’s cheaper (and easier) to use fewer part types even though they might be over-specced in some uses and they cost slightly more than right-specced ones … but economy of volume drives prices down.
So… I did some testing with a 4011, 3011, and hAP ac^2. I measured these using a Kilowatt EZ P3 using the appropriate OEM PSU. I had 5 Ethernet devices connected when taking the measurements.
RB4011 Specifications
PSU: 24V - 1500mA
Max Power: 33 W
Max without attachments: 18 W Measurements
Amps: 1.2
Volts: 15.4
Watts: 18.48
RB3011 Specifications
PSU: 24V - 1200mA
Max Power: 30 W
Max without attachments: 10W Measurements there is
Amps: 0.9
Volts: 10.6
Watts: 9.54
hAP ac^2 Specifications
PSU: 24V - 1200mA
Max Power: 21 W
Max without attachments: 15 W Measurements
Amps: 0.7
Volts: 9.1
Watts: 6.37
The power draw on the hAP ac^2 is a little strange… unless it assumes a number of wireless clients connected - which I did not do. Seems low.
Anyway - the 3011 24V - 1200mA PSU did power the 4011 with no perceived issues. HOWEVER - there is very no/little headroom. So depending on what the “attachments” are and add it to it could be a problem. So @Zacharias, I am with you. In a production environment I would not chance the smaller power supply. It may work forever without issue Still not a chance I want to take.
I am left, however, wondering how Mikrotik comes op with their calculations and what "attachments: include. I also found some discrepancies between the web specs and the PDF brochure.
Hope this helps others. It was fun to go through the exercise.
Cheers!
The measurements seem odd to me. Power adapters should be supplying power at rated voltage until current exceeds rated max current. None of the measurements showed nominal voltage.
So I wonder if used instrument is capable of measuring when voltage is not really DC … switching power supplies can produce lots if AC components. I guess for relevant measurement one would need a high quality stable DC supply and observe current peaks as well (RB devices use DC-DC converter which itself is a switching device).
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My thoughts would be the RB2011 PSU has had many years in service and closer to failure due to heat and the usual failure of electrolytic capacitors.
. You are a scholar and gentlemen!