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Power consumption for PoE switch

John H. Miller
Occasional Advisor

Power consumption for PoE switch

I need some help with sizing a UPS. The specs for the 2620 24 PoE+ switch states that the maximum power rating is 39.5 W. The spec also states that this is for fully loaded PoE and 100% traffic. Now,I have 2 2510-48 switches (27W each) and 2 of the 2620 PoE+ switches (39.5W each) plugged into an APC 450VA UPS that is supposed to be capable of delivering 280W. If I add up the 4 switches I get 133W. There is nothing else plugged in to the UPS, but as I begin to bring up APs on the PoE switches the UPS eventually can't support the load. My question is this. Am I missing something about the power consumption of the 2620 or could it be that the UPS is just getting old and tired. It does have some age on it and it needs replaced, but I need to be sure about the sizing before I purchase new equipment.

Thanks - John

5 REPLIES
Vince-Whirlwind
Honored Contributor

Re: Power consumption for PoE switch

The 39.5W is the maximum amount power consumed by the switch. The switch can also provide up to 380W of power to PoE devices, which is power I think you haven't factored into your UPS needs.

John H. Miller
Occasional Advisor

Re: Power consumption for PoE switch

OK, not being a power guy, I am not sure how that all plays in to the calculation. The spec states that the 39.5W is for "...fully loaded PoE...". The 380 wats of PoE is at 54 vdc, not 120 vac. While I appreciate Vince's reply, are there any power engineers out there that can help me with this?

16again
Respected Contributor

Re: Power consumption for PoE switch

The switch turns main power (120 Volt , over here 230Volt) into PoE power.
So any Watt of PoE power delivered will also be drawn extra from mains.   (even more , since this power conversion hass lower than 100% efficiency)

My first thought:  the 39.5W is a typo , and should be 395W to begin with

Linkk
Frequent Advisor

Re: Power consumption for PoE switch

The datasheet states 22.8W idle power and 382 full PoE power. I would have calculated 405W, for full PoE+. Phones need way less W than Acess Points f.e., so you often can use less total power.

And comparing this datasheet to similar switches, I also believe this should be 395W, like 16again said.

Vince-Whirlwind
Honored Contributor

Re: Power consumption for PoE switch

I'm pretty sure it isn't a typo, just a very un-helpful way of presenting the information.

Witness - the 2620 *partial* PoE+ switch is listed with 38.5W power rating and up to 128W of PoE power.

Basically, for some reason they are telilng you the amount of power *consumed* by the switch instead of the maximum amount it could draw.