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UPS Requirements for Cisco Switch

Posted on 2014-01-07
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Last Modified: 2014-01-28
Hello Experts,

We are going to deploy network a building with 3 floors. Each floor has a cabinet and it will hold 4-5 switches in the cabinet.

Mainily following devices will be connected to them

- PC
- Cisco Access Points PoE
- IP Telephone PoE
- CCTV cameras
- IP TV.


I need to a UPS for each floor. Therefore please can you help in selecting UPS likespecs
- How much power need for Switch on UPS
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Question by:cciedreamer
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Expert Comment

by:ryan80
ID: 39761760
Samir, what model switches? If you look at the spec sheets, it will tell you the owe draw for the switch.
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by:cciedreamer
ID: 39761769
HI,

3560X and 3750 X Series Switch
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Expert Comment

by:Jordan Medlen
ID: 39761899
We use APC 2000 series UPS systems in all of our IDFs. The largest IDF has around 8 switches, 2960S series, and these hold up just fine. We have two and then an APC transfer switch to supply power to the switches themselves.
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by:cciedreamer
ID: 39761986
We will have 4 3560X Series Switch and 1 3750X

How much watt is required for UPS
How many Units ?
How long it can handle we are looking for 1 hour ?
How much watt required for 1 switch ?
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by:ryan80
ryan80 earned 200 total points
ID: 39762128
here is the datasheet for those switches.

http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps6406/data_sheet_c78-584733.html

I can help you further but need to know what the exact model number is. As you can see the power requirements are all different based off of the model, varying based off of port count, what type of POE, and whether it will be full POE (meaning every port can supply POE at the same time).

If we were to use as an example 4 3560X and 1 3750X with able to supply 435W of POE, they would each pull up to 715W of power under full load, or 3575 W total. A 5000 KVA UPS will give you about 12 minutes of run time for that load.
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by:cciedreamer
ID: 39762606
Hi

Thanks

We will have 1  WS-C3750-12S-E
and 4 WS-C3560X-48PF-S

And we are looking for UPS to take the load.
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by:cciedreamer
ID: 39762918
Also I want all the 48 PoE ports to work at same time
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by:cciedreamer
ID: 39762994
Hi,

This is my collection from cisco data sheet.

power calculation
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Expert Comment

by:ryan80
ID: 39763037
I think that you need to estimate what kind of load you are going to realistically be using and base it off of that. Those switches are rated at 4750 Watts maximum which is a decent amount of power to draw. However, realistically you will be using less than that. I would figure out what the draw will be from the POE devices that you will be plugging in and base it off of that to get a clear picture of what is going on.

Also an hour run time is a pretty long time. If you lose power typically you will want to have a generator to switch over to, or start shutting down after a minute or two.

But if you want something to give you that kind of run time, you can look at this

SYA8K16PXR - a 8 kVA Symmetra that will give you an hour run time. So you know, you are looking at a 5 foot tall UPS so you will need room for a separate cabinet. You will also need a 240V input circuit with either a 50A or 100A breaker. It will cost about $12,000.
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by:cciedreamer
ID: 39763057
Thanks
We are going to use Cisco AP and IP Telephones
1 Switch will be seprately dedicated for IP Telephones I am there watt consumtion.
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by:cciedreamer
ID: 39763061
And 15min run time is fine with us for UPS and we have generators
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by:ryan80
ID: 39763421
Realistically this would probably be fine and will get you 10 minutes of run time, which if your generator has not kicked on before that, it isnt going to.

SUA5000RMT5U - much more reasonable 5U and about $3000.
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by:cciedreamer
ID: 39764844
How about this UPS


GE Digital Energy VH Series UPS Model 3000 3000VA 3KVA Rackmount/

Thanks
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Expert Comment

by:ryan80
ID: 39765001
You would need two of those to provide enough power and you would get about 6 minutes of run time. I don't see the exact specs for that model, I would check with the manufacturer first.
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by:cciedreamer
ID: 39765088
Please can you providee the UPS specs that can fulfill requirements. and runtime for.15min

Thanks
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Expert Comment

by:ryan80
ID: 39765424
I was basing my numbers off of a 4000 watt draw for the switches. This is a little less than the max draw rated for the switch. You will have to estimate the actual draw based off of the devices that you have connected.

So you will need a ups or multiple, that can supply 4000 watts. You need to look up the runtime on the manufacturers site.
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Author Comment

by:cciedreamer
ID: 39766442
If I calculate for each cabinet as follows

1 X WS-C3750-24S-E = 350W
4 X WS-C3560X-48PF-S = 1100 x 4 = 4400 watt

Total 350 + 4400 = 4750 watt

In this case what UPS I should get ?

 WS-C3750-24S-E  will have fiber uplinks to all floor switches
 WS-C3560X-48PF-S will have PC's, Cisco AP, IP TV's, CCTV and IP Telephones will be connected to it.


Telephones and AP's will be PoE.

Thanks I appreciate your help.
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Expert Comment

by:ryan80
ID: 39766828
The 4750 would be the max out could ever be for those switches do you could use that number to be safe.
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by:cciedreamer
ID: 39767500
How many ampere required for Cisco Switch 3560x and 3750x series. ?
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by:cciedreamer
ID: 39773317
Please can you help me how many amps required for 3560x and 3750x series

thanks
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by:cciedreamer
ID: 39773329
Actually I am going to request power supply to cabinets PDU.

How many amps socket should i request ?

Thanks
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Accepted Solution

by:
Craig Beck earned 200 total points
ID: 39791488
Switches require different amounts of current, depending on the PSU and input voltage.  For example, a 3750X with a 1100W PSU would require 12A at 110VAC but only 6A at 240VAC.

This link (Table 14) shows the requirements...

http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps6406/data_sheet_c78-584733.html
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Expert Comment

by:noci
ID: 39791502
Also you have to keep in mind that the batteries in the UPS will wear out in a few years, so you will have to allow for that too.
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by:ryan80
ryan80 earned 200 total points
ID: 39791507
Sorry Samir,

I know that I wrote up a response a while ago to your question, but I guess it had a problem posting.

You are using 4750 watts maximum. Watts is volts x amps. You are running 220 volt power, so 4750/220=21.6 Amps, say 22 rounding up. You will not want the cirucuit to be running higher than 80% for any extended period so 22/.8=27.5. So you would want a 30 amp plug at 220 VAC to run to the switches.

For the wall outlet to supply the UPS, check the documentation. They will specify what the input supply needs to be.
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by:Craig Beck
ID: 39791522
I think generally anything up-to a 3KvA APC UPS will be fine with a 13A input, but above that you'll require a 16A or 32A supply.  Don't take my word for it though - but every 3KvA APC UPS I've installed came with a 16A C20 receptacle and appropriate 13A C19 plug.

If you go bigger, like the 8KvA SURT8000RMXLI you may need a 63A supply as it has a 32A hard-wired output AND several 16A and 13A outlets which can be used simultaneously.
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by:dlethe
dlethe earned 100 total points
ID: 39791529
Ryan80 gives the best advice, but surprisingly the real-world numbers can vary a significant amount.  There are other factors such as ambient temperature and varying loads over the course of the day.

Oversize your UPS and you throw money away, undersize and go down, or worse, have a fire.

So here is another suggestion.  Use Ryan's estimate for budgetary purposes, but install one floor first w/o the UPS temporarily. Have the electrician use an ammeter to monitor load over a week, and size it appropriately.  Then you know exactly what to buy.

Certainly select your UPS vendor, negotiate pricing, but also negotiate speedy delivery, and just tell them you need 3 and aren't 100% sure how many KVA you need until you measure it appropriately.

I've seen too many people do large operations on paper and then get burned.   Also you might also consider lightning protection & generator at the same time.  It is a heck of a lot cheaper to do this now, than later.   Also look at power sequencers.  You can save a lot of money if you get power sequencers that bring up racks of equipment up after automatic 60 second delays or whatever instead of all at once.

This also saves money because you have to look at peak power when things get started up ... not so much for telco equipment, but it is absolutely vital for disk drives.'

Also don't underestimate power requirements for multicore processors and storage.
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by:Craig Beck
Craig Beck earned 200 total points
ID: 39791537
You will need to take into account peak power where PoE is being used if your switches are fully populated.

APC have a power calculator which will help.  It lets you tell the calculator which devices you're using, how many you have, how long you want them to run for, etc...

http://www.apc.com/tools/ups_selector/
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Expert Comment

by:ryan80
ID: 39791542
Exactly, that it's what I was pointing out earlier, especially given the fact that these are Poe switches. Realistically you are not going to use the max wattage, unless you know that you are loading every port with something that draws the max output.

If you can, loading it up as recommended above us a great idea.
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by:ryan80
ID: 39791547
Posted to soon,

Everything being said, I still like to size it for close to the max draw, as long as budget isn't a huge issue. If your equipment craps out because it can't meet the load one day, no one is going to care that you saved a couple thousand.
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Expert Comment

by:pgm554
ID: 39791568
Just use APC's sizing tool:

http://www.apc.com/tools/ups_selector/US/en/server/device

A no brainer.
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by:Craig Beck
ID: 39791582
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by:dlethe
ID: 39791647
be warned .. their sizing tool is well known for overestimating on the high side .... go figure, a manufacturer's tool designed to tell you how much product you need to buy ;)
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by:Craig Beck
ID: 39792049
I agree with that.

From experience I know that a SURTD3000RMXLI will give 15 mins runtime for two four-switch 2960S stacks with an average load.  If you tell the calculator that you want to be able to provide 15 mins runtime and have an extra 5% load capacity for expansion it will tell you that you need the same UPS for one stack only.
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Author Comment

by:cciedreamer
ID: 39792060
Thank You Guys for help.

I used the APC calculator I got the suggestion as attached.

4200 Watts
220 Volts
Wall Socket Ampere :     4200/220 = 20amps socket

8units

Please advise
APC-UPS.jpg
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by:cciedreamer
ID: 39792081
This is my final calculation



Switch Power Calculation

1 x WS-C3750X-24S-E =    350W
3  x WS-C3560X-48PF-S = 1100W

Total 4 switches =  3650 Watts

Input Voltage = 220V

Ampere = 25 Ampere Wall Socket


UPS Calculations for all floors


Watts = 4200Watts
6000 VA
230 Voltage
25 ampere  wall Socket.
Run Time = 15 -18 minutes
Rack Mounted

Please advise

Thanks
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Expert Comment

by:Craig Beck
ID: 39792088
Hmmm I can run a fully-populated 6509-E chassis with 2x 4KW PSUs with a 6KvA UPS for nearly an hour.

The SURT6000RMXLI would easily do better than the one you posted and is £2k less.

http://www.apc.com/resource/include/techspec_index.cfm?base_sku=SURT6000RMXLI
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by:cciedreamer
ID: 39792094
Sir,

What is the spec difference between both ( my post and your post)

What will be the run time ?

Thanks
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by:Craig Beck
ID: 39792174
Run time for the one I posted is around 20 mins.  The one you posted is around 13 mins.

The major differences (I believe) is that the one you posted is a modular UPS which allows you to add a redundant unit as well as several power management PDUs, etc.
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by:cciedreamer
ID: 39792216
Hi

Just curious to know.

How do we you calculate the run time.
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Expert Comment

by:Craig Beck
ID: 39792224
The calculator will tell you the run time based on what you tell it you're going to connect, and the associated load.
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by:cciedreamer
ID: 39792229
Do you have any specific calc or formula to calculate ?

Thanks
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by:Craig Beck
ID: 39792278
No - it's UPS specific.  It depends on the batteries installed in the UPS, among other things.  The manufacturer will build their values into the calculator.
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by:cciedreamer
ID: 39793412
What if I want to have redudant power supply on switches ?

Any changes in UPS specs and calc ?
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Expert Comment

by:dlethe
ID: 39793416
they run in parallel, so while there will be a slight increase in load it won't be statistically significant.
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by:cciedreamer
ID: 39793420
Now this specs would be fine


Watts = 4200Watts
6000 VA
230 Voltage
25-30 ampere  wall Socket.
Run Time = 15 -18 minutes
Rack Mounted 2-3U
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Author Comment

by:cciedreamer
ID: 39806669
Just a last query, adding a second redudant PSU on switches will effect any load or UPS recaculation I have finalized to get UPS with following specs.

Watts = 4200Watts
6000 VA
230 Voltage
40 ampere circuit breaker.

Thanks
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Expert Comment

by:ryan80
ID: 39808088
That looks good. For redundancy you will need double the amount of ups's. It will not change the load.
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Author Comment

by:cciedreamer
ID: 39808692
Hi Thanks,
What if I connect 2 PSU of each switch to 1 single UPS. ?
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Expert Comment

by:dlethe
ID: 39808712
Don't. The idea is that you use 2 different power sources because UPSs can fail.
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by:Craig Beck
ID: 39808814
The load from the switch will be the same whether you have one PSU or 5 PSUs.

dlethe is right - If your switch has only two PSUs don't connect both supplies to the same UPS if you want redundancy.  You'd be better connecting one PSU direct to the mains for redundancy purposes.  At least this way you'd be protected by the UPS if the mains fails.  If you want to protect against fluctuations in power though you'd really want a second UPS.

If you have four PSUs you could connect two to one UPS though, as long as the other two PSUs connect to a different power source.
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Expert Comment

by:dlethe
ID: 39808822
... and i HAVE seen them fail. I have also seen circuit breakers go in one of the power distribution strips. That is why rack designers use a strip on the left, and one on the right each with different input power cables.

So even if you HAVE to use the same UPS, it is still a good idea to run two cables to it, one for each power strip.

(When you power up a rack then their is a much higher load at the beginning, especially if you have a lot of disk drives, hence the probability of circuit breakers going).
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by:cciedreamer
ID: 39812795
Thank you guys for suggestions and big help. I would close the ticket soon assigning the appropriate points.

Thanks
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by:cciedreamer
ID: 39812799
Hello craigbeck

Sire, as you have help in networking questions Please can you help with this new question

http://www.experts-exchange.com/Security/Software_Firewalls/Enterprise_Firewalls/Cisco_PIX_Firewall/Q_28348943.html

Thanks
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by:cciedreamer
ID: 39814387
Thank you guys for your help.
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