power requirement for single rack

Posted on 2016-07-16
Medium Priority
Last Modified: 2016-08-02
Hello experts,

I want to put a single rack 42 U in a room with 5 Switches, each switch has dual power supply adapters and they are POE+ with 1100 watts.

Just wandering how to calculate the power consumption on this rack and what will be required to keep it running 24x7?

A detail explanation will be great as I will add more racks with time.

Question by:Habib Z
  • 3
  • 2
  • 2
  • +1
LVL 33

Accepted Solution

Dr. Klahn earned 2000 total points
ID: 41715023
Per the description above:

  • each rack contains 5 switches
  • each switch contains two power supplies
  • each power supply is 1100 watts

5 x 2 x 1100 = 11,000 = 11 kW

Figure a 10% extra power pull at startup if each unit is powered on individually in sequence (12.1 kW).  If the rack is US 120V, you'll need 100A service and socket.  The maximum power pull occurs only at startup, so this configuration rack will require 37,000 BTU of cooling.

Figure a 50% overhead extra power pull at startup if all units are powered on simultaneously (16.5 kW).  For US 120V, you'll need 150A service and socket.  The maximum power pull occurs only at startup, so this configuration rack also requires 37,000 BTU of cooling.

These are the maximum draw figures and imo you should design to these, not to what the racks normally draw.
LVL 93

Expert Comment

ID: 41715026
you can measure the total current drawn, with a current clamp meter like fluke offers

then you have an idea of the current and power needed
LVL 93

Expert Comment

ID: 41715702
but all these  calculations give only an estimate - while measuring gives the actual consumption
up to you to decide which way you go
WEBINAR: GDPR Implemented - Tips & Lessons Learned

Join the WatchGuard team on Thursday, March 29th as we recount some valuable lessons learned in weighing the needs of a business against the new regulatory environment, look ahead at the two months left before implementation, and help you understand the steps you can take today!


Author Comment

by:Habib Z
ID: 41715827
nothing is placed now I just want to know before putting rack.
LVL 93

Expert Comment

ID: 41715894
then you can't possibly measure anything
contact an electrician, they should know
LVL 23

Expert Comment

by:Danny Child
ID: 41716061
I think the calc above is wrong, in terms of factoring each PSU at its full rating of 1100W.

The switches are factored that they 'could' run on a single PSU if needed, and there will be a safety margin on them already.  

So, I would say that you work on 5 x 1100 W = 5500 W = 5.5 kW

The calc tools above in Shaik's post are good, but they are fairly manufacturer specific, and don't seem to list standard Cisco kit, for instance.  If you post the models of the actual switches themselves, then we can check the manufacturer's recommendations.
LVL 33

Expert Comment

by:Dr. Klahn
ID: 41716063
I concur if the power supplies configured with one as redundant backup.  Unfortunately the problem statement didn't say whether both supplies are active or whether one is backup.

Author Comment

by:Habib Z
ID: 41719798
Is there a power consumption tool from Cisco? I am looking for Cisco readings.

Featured Post

Free Tool: ZipGrep

ZipGrep is a utility that can list and search zip (.war, .ear, .jar, etc) archives for text patterns, without the need to extract the archive's contents.

One of a set of tools we're offering as a way to say thank you for being a part of the community.

Question has a verified solution.

Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.

Have a better answer? Share it in a comment.

Join & Write a Comment

On Beyond Tools A conversation I recently had with the DevOps manager of a major online retailer really made me think about DevOps monitoring tools (https://www.onpage.com/devops-incident-management-tool/). The manager and I discussed how sever…
Want to create a VM?  Here's how you do it.
After creating this article (http://www.experts-exchange.com/articles/23699/Setup-Mikrotik-routers-with-OSPF.html), I decided to make a video (no audio) to show you how to configure the routers and run some trace routes and pings between the 7 sites…
How to fix display issue, screen flickering issue when I plug in power cord to the machine. Before I start explaining the solution lets check out once the issue how it looks like after I connect the power cord. most of you also have faced this…

627 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question