Cisco power supply and APC UPS question

[sullyjman]

Good afternoon, I am running a 4507 with the Power Supples PWR-C45-2800ACV

http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps4324/product_data_sheet09186a00801f3dd9.html

Can I plug this power supply into this UPS unit?

http://www.apc.com/products/resource/include/techspec_index.cfm?base_sku=SMX3000RMLV2UNC&tab=models

[jlukemorgan · Accepted solution]

Jason:

Depending on the actual load being less than the 100% capability of the power supply, yes. 

However, your power cable may not be allowed per the NEC.   That would need to be referenced.

The TWLK cable for the 2800 is an L6-30.  

The output of the UPS is on NEMA 5-15R, 5-20R and L5-30. 

I'd recommend an UPS with higher wattage and an L6-30 output(s) and/or a PDU with dual outputs that match the input connector to your switch power supply.

-Luke

[sullyjman]

Thanks for the update Luke, the UPSs were already purchased before I started to work here .  That is pretty much what I feared and kind of guessed *sigh*   Do you have a link for a PDU I could purchase that would fullfill my needs, since someone has already made one bad purchase.  I dont want to make another.

Thanks again for your help

[jlukemorgan]

Jason:

Let me get back to you on this..  Your single-phase output on the UPS is going to limit your options quite a bit.  

How much Power over ethernet are you running?

# ports and type/class of devices (IP phones, Wireless Access points, etc)

What power cables do you have for the power supplies on the switch?

There's several options and I'm sure the most popular one will be the least cost and that's what I'll make a recommendation on.

-Luke

[jlukemorgan]

Jason:

My guess is that 2800w power supply is looking for two legs of AC in to make the DC stable on the switch.   I've installed a lot of 45XXx over the years but I never have more than 100 ports of active POE on them as most buildings have lots of computers and printers and a few VOIP phones and access points.  

Now, those power supplies are pretty fault tolerent and well built.  They can take (probably) swing voltage from 40-240V and 50-60Hz.    You can wire up the L6-30 into the TWLK cable and only have 20A of 120V on one leg from the output of your UPS.     You just have a single 30A hot, neutral and ground and a dead leg for hot into the power supply.   You use half the power supply.  

The capacitors on the power supply will just have to absorb that and deal with it.   That's their job.  Short term batteries. 

One thing you need to realize is that you don't have to have two full-capacity 2800w circuits for the switch.   The 2800 is a reference number and that's based on a lot of inneffiencies in the entire system.  

You've got at max a 2800w load and either 1 or two power supplies will feed it.    Two power supplies will be slightly less efficient than one but you're not pulling 5600w.   

If you could, answer the questions above on the number of POE devices you've got and we can work a solution to solve the power to the switch and to your nodes.  

You've got a lot of expensive, quality gear and the best solution isn't always to double up and re-buy what you've got.  

I am going to recommend a metered PDU so that you can watch the amperage as when you approach the limit of what your wires can haul, you need to pay attention to the national electric code.

If you can PM me, do.

-Luke