Hi,
I want to buy a UPS wfor a PE2800 but I'm mnot sure wich one to choose. is 1000 VA enough or do I need the 1500 VA version?
1) APC Smart-UPS 1000 VA Black SMART UPS 1000 VA BLACK 1000 VA LINE-INTERACTIV [SUA1000I] 2) Power Supply Apc-ups 1500va Floorstand Incl Control Cable Usb And Com Port Output Power 980w
Other suggestions are also welcome As long as they can talk to the apcd service of that centos 4.4 box.
euroka
On Tue, May 29, 2007 at 07:33:39PM +0200, Euroka wrote:
I want to buy a UPS wfor a PE2800 but I'm mnot sure wich one to choose. is 1000 VA enough or do I need the 1500 VA version?
The size you want depends on two things: 1) Must be powerful enough to drive all the equipment you want 2) How long you want to survive on battery
I have a 1500VA UPS powering the following equipment
Pentium D dual core 3Ghz, 5 hard disks, 2Gb RAM Pentium 4 2.4Ghz, 2 hard disks, 1 Gb RAM Pentium III 800Mhz, 4 hard disks, 1Gb RAM AMD 2500, 1 hard disk, 1Gb RAM Celeron 1200, 1 hard disk, 512Mb RAM Sun Ultra 5, 1 hard disk, 256 RAM 19" LCD display router, cable-modem, switch etc etc KVM
The monitor is currently in standby mode. "apcaccess" says LOADPCT : 70.0 Percent Load Capacity BCHARGE : 100.0 Percent TIMELEFT : 7.2 Minutes
Basically I'm using it to protect me from momentary outages, not from long term failures. 7 minutes is long enough for APCupsd to shutdown the machines.
Hmm... I might need to get a second one, soon! Or else get my act together and _use_ the Pentium D machine and virtualise some of the others :-)
Euroka wrote:
Hi,
I want to buy a UPS wfor a PE2800 but I'm mnot sure wich one to choose. is 1000 VA enough or do I need the 1500 VA version?
- APC Smart-UPS 1000 VA Black SMART UPS 1000 VA BLACK 1000 VA
LINE-INTERACTIV [SUA1000I] 2) Power Supply Apc-ups 1500va Floorstand Incl Control Cable Usb And Com Port Output Power 980w
Other suggestions are also welcome As long as they can talk to the apcd service of that centos 4.4 box.
euroka
CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
Euroka,
Generally, bigger is better. 1500 VA is certainly within the capability of a 15 AMP typical US wall outlet.
Bob...
On 5/29/07, Bob Chiodini bob.chiodini@nasa.gov wrote:
Euroka,
Generally, bigger is better. 1500 VA is certainly within the capability of a 15 AMP typical US wall outlet.
Getting a little OT here, but how does one match up the VA ratings of the UPSs (and battery backups) with the power supply wattage ratings?
Mark Hull-Richter wrote:
On 5/29/07, Bob Chiodini bob.chiodini@nasa.gov wrote:
Euroka,
Generally, bigger is better. 1500 VA is certainly within the capability of a 15 AMP typical US wall outlet.
Getting a little OT here, but how does one match up the VA ratings of the UPSs (and battery backups) with the power supply wattage ratings?
One COULD spring for about 25 bucks and pick up one of these neat little gadgets: http://www.p3international.com/products/special/P4400/P4400-CE.html You can google for a source. Mine came from some place called 3Gorillas.com.
On 5/29/07, Mark Hull-Richter mhullrich@gmail.com wrote:
Getting a little OT here, but how does one match up the VA ratings of the UPSs (and battery backups) with the power supply wattage ratings?
Watts = Volts x Amps. I usually use a sliding scale based on # of machines.
On 5/29/07, Jim Perrin jperrin@gmail.com wrote:
Watts = Volts x Amps. I usually use a sliding scale based on # of machines.
I knew that (duh!).
That has to be the stupidest marketing strategy ever devised. Most people (yeah, me too) know that, but why can't they SAY so instead of using "VA"?...
Not your/our problem - just grousing.
Thanks.
Mark Hull-Richter wrote:
On 5/29/07, Jim Perrin jperrin@gmail.com wrote:
Watts = Volts x Amps. I usually use a sliding scale based on # of machines.
I knew that (duh!).
Watts = Volt-Amps IF the power factor is =1. Power factor is based on the reactance of the load. A purely resistive load has a PF=1. Google << watts vs volt-amps >> for more info, e.g. http://www.vabiomed.org/documents/tech0003.htm.
The power supplies I have measured in servers have a power factor close to 1. But I have measured consumer machines with a power factor considerably different than 1. That cute little power meter mentioned earlier in this thread (the "Kill-a-Watt") will measure it.
Dan
On Tuesday 29 May 2007, Dan Halbert wrote: ...
Watts = Volt-Amps IF the power factor is =1. Power factor is based on the reactance of the load. A purely resistive load has a PF=1. Google << watts vs volt-amps >> for more info, e.g. http://www.vabiomed.org/documents/tech0003.htm.
The power supplies I have measured in servers have a power factor close to 1. But I have measured consumer machines with a power factor considerably different than 1.
Worth knowing here is that even if you have something with pf=1 you wont get those 1500 watts out of a 1500VA UPS. UPSes are often, what they call, power factor 0.9 or 0.8. This means that you'll never get more than 1200W or 1350W out of a 1500VA UPS regardless of the pf of your load.
That said, modern powersupplies I've tested lately have all been better than 0.9 and most even >0.97.
/Peter
On Tue, 29 May 2007, Mark Hull-Richter wrote:
On 5/29/07, Jim Perrin jperrin@gmail.com wrote:
Watts = Volts x Amps. I usually use a sliding scale based on # of machines.
That has to be the stupidest marketing strategy ever devised. Most people (yeah, me too) know that, but why can't they SAY so instead of using "VA"?...
This formula is correct for a resistive load; however, it completely ignores the reactive load. The correct formula is:
watts = power_factor X volts X amps
You consume volt-amps, but can only use for amps. There are various regulations in place regarding the minimum power factor -- decent power supplies have a power factor of better than 90%.
Steve Friedman
Mark Hull-Richter wrote:
On 5/29/07, Jim Perrin jperrin@gmail.com wrote:
Watts = Volts x Amps. I usually use a sliding scale based on # of machines.
That has to be the stupidest marketing strategy ever devised. Most people (yeah, me too) know that, but why can't they SAY so instead of using "VA"?...
Actually, I think there's a technical reason why they don't say 1500W instead of 1500VA. And if you look at the specs for the 1500VA unit, it doesn't work out to 1500W.
http://www.apcc.com/resource/include/techspec_index.cfm?base_sku=SUA1500
Output Power Capacity 980 Watts / 1440 VA Max Configurable Power 980 Watts / 1440 VA Nominal Output Voltage 120V
I don't remember enough of my electrical stuff to say why (it has to do with DC to AC conversion... I think... and maybe some RMS stuff?).
Thomas Harold wrote:
Actually, I think there's a technical reason why they don't say 1500W instead of 1500VA. A
Computers are not a passive load in the way that a heating element would be, they tend to have a very capacitive load characteristic. As a result, the voltage cycle and current cycle will be out of phase. This means that, while the voltage x amperage is equal to approx 1500W, there will not be 1500 watts of power delivered.
P=VxA only holds true if they are in phase and so using VA is correct.
On Tue, May 29, 2007 at 02:55:02PM -0400, Jim Perrin wrote:
On 5/29/07, Mark Hull-Richter mhullrich@gmail.com wrote:
Getting a little OT here, but how does one match up the VA ratings of the UPSs (and battery backups) with the power supply wattage ratings?
Watts = Volts x Amps. I usually use a sliding scale based on # of machines.
Which is correct for DC circuits, but not for AC. A 1500VA UPS does not provide 1500Watts of power. And given the output of UPS's aren't necessarily perfect sine waves, it gets more complicated.
A typical APC 1500VA UPS has around 860->900Watts of power.
The answer to Mark's question is "check the manufacturers web site" :-)
Stephen Harris wrote:
On Tue, May 29, 2007 at 02:55:02PM -0400, Jim Perrin wrote:
On 5/29/07, Mark Hull-Richter mhullrich@gmail.com wrote:
Getting a little OT here, but how does one match up the VA ratings of the UPSs (and battery backups) with the power supply wattage ratings?
Watts = Volts x Amps. I usually use a sliding scale based on # of machines.
Which is correct for DC circuits, but not for AC. A 1500VA UPS does not provide 1500Watts of power. And given the output of UPS's aren't necessarily perfect sine waves, it gets more complicated.
A typical APC 1500VA UPS has around 860->900Watts of power.
The answer to Mark's question is "check the manufacturers web site" :-)
Wow! What a smart bunch you all are. I was about to reply to the initial post and explain VA vs Watts, but im wayyyyyyyyy to slow. (Well to be fair, it takes longer for the bits and bytes to get here (down under) )
Seriously though ... i worked for a company which moved buildings, didnt spec the power right and ended up in a situation where the servers would run fine from UPS, with the UPSes consuming about 70% of the available power (i think 42A from the 60A outlet or something like that), *BUT* when a power cut happened and the UPSes took over they needed to recharge when the power came back. 5 UPSes x ~15A charging current = immediately tripping the fuse and starting a cycle that can only be broken by turning off half the UPSes until the other half have charged. My numbers may not be correct but this is the gist of it.
The solution they should have used; Spec your UPSes based on the load from servers (dont even *tell* the power/building engineers how much power the servers consume - they *dont* need to know as the servers will *never* draw power from the grid). Then tell the engineers (or do it yourself) what the power requirements of your *UPSes* are when they are CHARGING FLAT OUT. This will always be far higher than any normal running situation.
Regards,
MrKiwi
Mark Hull-Richter spake the following on 5/29/2007 11:32 AM:
On 5/29/07, Bob Chiodini bob.chiodini@nasa.gov wrote:
Euroka,
Generally, bigger is better. 1500 VA is certainly within the capability of a 15 AMP typical US wall outlet.
Getting a little OT here, but how does one match up the VA ratings of the UPSs (and battery backups) with the power supply wattage ratings?
The industry standard is roughly 60% of VA is the Watt rating of the UPS. So a 1000 VA UPS would be "near" 600 Watts.
On Tue, 2007-05-29 at 11:32 -0700, Mark Hull-Richter wrote:
Getting a little OT here, but how does one match up the VA ratings of the UPSs (and battery backups) with the power supply wattage ratings?
You can convert VA to watts with the following formula:
W = VA / sqrt(2)
Don't forget to give yourself a little wiggle room from there for short burst overages.
Euroka wrote:
I want to buy a UPS wfor a PE2800 but I'm mnot sure wich one to choose. is 1000 VA enough or do I need the 1500 VA version?
That probably depends on how many drives you have installed (along with how much run-time you want, and how much you want to pay for replacement batteries every few years).
There's also the option of getting a 1500VA model (APC Smart-UPS 1500VA Silent Alarm SUA1500X413) with a silent alarm, and I'm not sure whether they make it in a 1000VA model. If you have alternate notification methods and dislike the noisy alarms, that might be an option.
Our PE2800 is hooked up to a 1500VA unit, has 6 drives installed, and I think it lights up 2 out of 5 load indicators. I don't have current numbers on the amount of runtime that gives us. And there might be one or two other lightweight (KVMs) pieces of equipment attached.
On Tue, 29 May 2007, Thomas Harold wrote:
Our PE2800 is hooked up to a 1500VA unit, has 6 drives installed, and I think it lights up 2 out of 5 load indicators. I don't have current numbers on the amount of runtime that gives us. And there might be one or two other lightweight (KVMs) pieces of equipment attached.
FWIW, I have four PE2900's (one 16GB and 4 x 3.0 GHz cores, the others 4GB and 2 x 3.0 GHz cores, each with 2 x 300 GB SAS 10K), and an MD-1000 shelf with 15 x 300 GB SAS 10K disks, with each of the two power supplies in all five units going to a separate 3000VA UPS (thus, two UPS's, equally loaded). Total runtime on full mains outage is 25 minutes.
Steve
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Chris Mason (Lists) -
Dan Halbert -
Euroka -
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MrKiwi -
Peter Kjellstrom -
Robert -
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Thomas Harold