?
Solved

UPC Calculation Help

Posted on 2005-03-07
8
Medium Priority
?
1,095 Views
Last Modified: 2011-04-14
Hi All,

I need someone to confirm my UPS calculations for threee PCs on two diffrent batteries:

I have 3 UPSs (1400VA) each with either 20Ah or 26Ah batteries (each will take 2 batteries)

I have done the following calculations (I HAVE ROUNDED OFF):

1) PC 1
1230 Watts - 6Amps (Consumption)

Therefore:
1230*.7 = 860VA min needed

860VA:  
860VA/220V = 3.9Amps usage
20Ah Battery: 20Ah / 3.9 Amps ~ 5Hours
26Ah Battery: 26Ah / 3.9 Amps ~ 6.5Hours

Now if run on a 1400VA UPS: 1400/860 = 1.62
so:
20Ah Battery: 5Hours * 1.62 ~ 8.3 Hours
26Ah Battery: 6.5Hours * 1.62 ~ 10.5 Hours

2) PC2 & 3

500Watt Power Supply - 2.3Amps
350Watt 21" Monitor    - 1.6Amps
Totals:
850Watts - 3.9Amps

Therefore:
850*.7 ~ 600VA min needed

600VA:  
600VA/220V ~ 2.8Amps usage
20Ah Battery: 20Ah / 2.8 Amps ~ 7Hours
26Ah Battery: 26Ah / 2.8 Amps ~ 9Hours

Now if run on a 1400VA UPS: 1400/600 = 2.3
so:
20Ah Battery: 7Hours * 2.3 ~ 16.1 Hours
26Ah Battery: 9Hours * 2.3 ~ 20.7 Hours


I'm about to spend the money on the batteries so I just need to know that I didn't make any mistakes.

Thanks
Peter


0
Comment
Question by:Pete2003
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 4
  • 4
8 Comments
 
LVL 69

Accepted Solution

by:
Callandor earned 1600 total points
ID: 13476055
You did the inverse on the watts/VA calculation: divide watts by 0.625 to get VA.  See the table here to get an idea of runtime under various loads: http://www.apcc.com/products/runtime_for_extendedruntime.cfm?upsfamily=21
0
 

Author Comment

by:Pete2003
ID: 13476177
Ok ... but then are my calculations wrong .. if so where ...
0
 
LVL 69

Expert Comment

by:Callandor
ID: 13476674
> 1230*.7 = 860VA min needed

should be

1230/0.7 = 1757 VA needed

Your actual runtimes will vary, because the amount of current available will vary, depending on the load.  For example, running very close to the rated capacity will give you less runtime than you think, because of the higher current draw.  See the diagrams here for an explanation: http://www.batteryuniversity.com/partone-16a.htm  The best indicator of runtime will be the posted times at the manufacturer's website for different loads, which is in the first link I posted.
0
10 Questions to Ask when Buying Backup Software

Choosing the right backup solution for your organization can be a daunting task. To make the selection process easier, ask solution providers these 10 key questions.

 

Author Comment

by:Pete2003
ID: 13476817
ok will look ... but my UPSs are no name brands ...
0
 

Author Comment

by:Pete2003
ID: 13476838
Also I have a problem here ...

The 1st PC is actually 2 PCs, ADSL modem , hub and a monitor ...

300Watt - PC1    (1.4Amps)
300Watt - PC2    (1.4Amps)

220Watt - ADSL   (1Amp)
110Watt - Router (0.5Amps)

300Watt - Monitor (1.4Amps)

So by those calculations a 1400 VA UPS wan't be able to handle that ... I thought they shoudl be a ble to run a fe w PCs ...
0
 
LVL 69

Expert Comment

by:Callandor
ID: 13477330
Get another UPS to offload some of the devices, or get a 2200 VA UPS.  ebay has them for sale all the time.
0
 

Author Comment

by:Pete2003
ID: 13479560
ok .. but do you agree that the 1400VA will not handle the devices listed above ?
0
 
LVL 69

Expert Comment

by:Callandor
ID: 13479604
Yes, that's why I made my last recommendation.
0

Featured Post

Microsoft Certification Exam 74-409

Veeam® is happy to provide the Microsoft community with a study guide prepared by MVP and MCT, Orin Thomas. This guide will take you through each of the exam objectives, helping you to prepare for and pass the examination.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Every server (virtual or physical) needs a console: and the console can be provided through hardware directly connected, software for remote connections, local connections, through a KVM, etc. This document explains the different types of consol…
Moving your enterprise fax infrastructure from in-house fax machines and servers to the cloud makes sense — from both an efficiency and productivity standpoint. But does migrating to a cloud fax solution mean you will no longer be able to send or re…
In this video you will find out how to export Office 365 mailboxes using the built in eDiscovery tool. Bear in mind that although this method might be useful in some cases, using PST files as Office 365 backup is troublesome in a long run (more on t…
In this video, Percona Solutions Engineer Barrett Chambers discusses some of the basic syntax differences between MySQL and MongoDB. To learn more check out our webinar on MongoDB administration for MySQL DBA: https://www.percona.com/resources/we…
Suggested Courses

765 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