ups VA needs...

[johnyb98]

Please, I need your recommendations in the buy of a UPS I wanna make.

My PSU is this one with efficiency 90% : https://www.e-shop.gr/psu-be-quiet-system-power-7-300w-p-PER.640577

 

And my monitor is this one with 34 Watt consumption : https://www.cnet.com/products/samsung-syncmaster-710n-lcd-monitor-17-1280-10-1024-tn-300-cd-m2-600-1-12-ms-vga-black-series/specs/

I have no other peripheral devices connected to the pc.

 

For AC 230V, how many min VA UPS is the one I need? The UPS I wanna buy is just for, in case of power outage, to be able to close apps, and shut down pc normally. Just that. I do not want to be able to work e.g. for 10 or 15 min or something like that. Just normally shutdown.

 

p.s. If out of recommendations to VA, you could help me in the way how to calculate by myself these VA, would be a great help and knowledge!!

 

Thank you in advance !

 

[suchamoneypit]

Your PSU model doesn't not tell us your power draw. It simply tells us what your max power draw is. I have a 1000W PSU but my system might only pull 300-450 watts. A UPS that supports 450 watts versus 1000w is very different. System specs helps. I had a 850VA backup battery which could power my at the time ~500W system for 15-25 minutes.

[Guest]

2 hours ago, johnyb98 said:

Please, I need your recommendations in the buy of a UPS I wanna make.

My PSU is this one with efficiency 90% : https://www.e-shop.gr/psu-be-quiet-system-power-7-300w-p-PER.640577

 

And my monitor is this one with 34 Watt consumption : https://www.cnet.com/products/samsung-syncmaster-710n-lcd-monitor-17-1280-10-1024-tn-300-cd-m2-600-1-12-ms-vga-black-series/specs/

I have no other peripheral devices connected to the pc.

 

For AC 230V, how many min VA UPS is the one I need? The UPS I wanna buy is just for, in case of power outage, to be able to close apps, and shut down pc normally. Just that. I do not want to be able to work e.g. for 10 or 15 min or something like that. Just normally shutdown.

 

p.s. If out of recommendations to VA, you could help me in the way how to calculate by myself these VA, would be a great help and knowledge!!

 

Thank you in advance !

 

Don't look at the VA rating of the UPS.  Look at the wattage ratings.  If they don't list a wattage rating, look elsewhere.

 

[Lady Fitzgerald]

2 hours ago, jonnyGURU said:

Don't look at the VA rating of the UPS.  Look at the wattage ratings.  If they don't list a wattage rating, look elsewhere.

 

Actually, you need to look at both. The wattage rating tells how much of a load the UPS can support. The VA rating (which, to over simplify it), is Volts x Amps and can, for this purpose be treated as Watts. It needs to be considered since it determines the maximum power draw from the wall circuit. You wouldn't want to put 2200VA on a 15A 120v (1800w) circuit. You also have to account for the power draw of other devices on the circuit. Ideally, you should limit continuous power draw on a circuit to 80% the rating of the circuit (unless you enjoy replacing dead circuit breakers).

[aezakmi]

Just now, Lady Fitzgerald said:

Actually, you need to look at both. The wattage rating tells how much of a load the UPS can support. The VA rating (which, to over simplify it), is Volts x Amps and can, for this purpose be treated as Watts. It needs to be considered since it determines the maximum power draw from the wall circuit. You wouldn't want to put 2200VA on a 15A 120v (1800w) circuit. You also have to account for the power draw of other devices on the circuit. Ideally, you should limit continuous power draw on a circuit to 80% the rating of the circuit (unless you enjoy replacing dead circuit breakers).

yeah but sometimes they just put "1000 VA" on the site and don't mention anything about efficiency, usually cheap 1000VA UPS can only give 450 or 500W for a brief moment before depleting

 

2200VA @80% is less than 1800W

[Lady Fitzgerald]

Just now, aezakmi said:

yeah but sometimes they just put "1000 VA" on the site and don't mention anything about efficiency, usually cheap 1000VA UPS can only give 450 or 500W for a brief moment before depleting

 

2200VA @80% is less than 1800W

If a UPS manufacturer can't be bothered to list the wattage rating (it's usually in fine print when it is listed), then follow jonnyGURU's advice and look elsewhere.

[Guest]

The PF rating on a UPS is "worst case".  They can assume that PF is .50, .60, .70.. whatever.  It's not a trustworthy number.

 

And I'm quite sure by this day and age, 99% of the people on this forum have PSUs with APFC, which would have a PF of .99 which would mean that VA is equal to W (more or less), so it makes sense to just look at the Watts.

 

[Lady Fitzgerald]

1 minute ago, jonnyGURU said:

The PF rating on a UPS is "worst case".  They can assume that PF is .50, .60, .70.. whatever.  It's not a trustworthy number.

 

And I'm quite sure by this day and age, 99% of the people on this forum have PSUs with APFC, which would have a PF of .99 which would mean that VA is equal to W (more or less), so it makes sense to just look at the Watts.

 

Did you not read what I posted and where the heck did power factor come from? The loss from a PF less than unity is only a tiny percentage of the difference between the VA and the wattage rating (battery charging current and parasitic power draw being the rest). One still needs to consider the VA rating as well as the watt rating to ensure the UPS won't overload the circuit it will draw from.

[Guest]

4 hours ago, Lady Fitzgerald said:

Did you not read what I posted and where the heck did power factor come from? The loss from a PF less than unity is only a tiny percentage of the difference between the VA and the wattage rating (battery charging current and parasitic power draw being the rest). One still needs to consider the VA rating as well as the watt rating to ensure the UPS won't overload the circuit it will draw from.

I did what you posted and I'm telling you that you're not correct.  That's why I replied.

 

Look at some of the UPS's out there.  The VA and Wattage rating are no where close to each other.

 

VA is not just simply "Volts * Amps" like Wattage, though that's literally what VA stands for.  VA is apparent power.  Watts is real power.  To know wtts, you take the VA and divide by the PF.  That's where the PF in my reply comes from.

 

https://powerquality.eaton.com/thoughtleadership/power-protection/va-vs-watts.asp?cx=9

 

So when they say a UPS supports 1000VA, that could (and usually does) mean that the UPS supports 1000VA, but at .60 PF (the "high end" of the typical "worst case scenario").  Which is only 600W.  If your PSU has APFC and a PF of .99, that would be 990W to 1000VA.  A much closer ratio.

 

None of the UPS's I've seen advertise their VA rating without taking a low PFC into consideration. They tell you the VA based on a worst case scenario PF.  A 600VA UPS never supports 600W.  A 450VA UPS never support 450W, etc.

 

That's just the way they are labeled.

 

350VA, but only 180W:  https://www.amazon.com/Tripp-Lite-INTERNET350U-Desktop-Battery/dp/B00007FHDP (.52 PF)

400VA, but only 225W:  https://www.amazon.com/AmazonBasics-Standby-UPS-400VA-Outlets/dp/B073Q48Z95 (.56 PF)

600VA, but only 300W: https://www.amazon.com/APC-BX600L-LM-Back-UPS-600VA-120V/dp/B01FIG3J6M (.50 PF?!?!)

 

They do this because, let's say they claimed to have a 600W UPS.  But your 600W PSU has a PF of .60 because it doesn't have PFC.  Let's say the UPS supports 900VA, but you don't know that.  You only know that it supports 600W.  If the UPS doesn't support 1000VA, the PSU will overload the UPS with apparent power, even though the real power is within spec.

 

So really... if your PSU has APFC, ignore the VA rating and look at only the wattage rating.

 

But, going back to what I ORIGINALLY said, what PSU is this?  We still don't know what PSU the OP has.  And what kind of power outages are being experienced?

 

If the user is only experiencing brown outs or power sags, a good PSU with full range input and decent hold up time might not even care.

 

[Lady Fitzgerald]

3 hours ago, jonnyGURU said:

I did what you posted and I'm telling you that you're not correct.  That's why I replied.

 

Look at some of the UPS's out there.  The VA and Wattage rating are no where close to each other.

 

VA is not just simply "Volts * Amps" like Wattage, though that's literally what VA stands for.  VA is apparent power.  Watts is real power.  To know wtts, you take the VA and divide by the PF.  That's where the PF in my reply comes from.

 

https://powerquality.eaton.com/thoughtleadership/power-protection/va-vs-watts.asp?cx=9

 

So when they say a UPS supports 1000VA, that could (and usually does) mean that the UPS supports 1000VA, but at .60 PF (the "high end" of the typical "worst case scenario").  Which is only 600W.  If your PSU has APFC and a PF of .99, that would be 990W to 1000VA.  A much closer ratio.

 

None of the UPS's I've seen advertise their VA rating without taking a low PFC into consideration. They tell you the VA based on a worst case scenario PF.  A 600VA UPS never supports 600W.  A 450VA UPS never support 450W, etc.

 

That's just the way they are labeled.

 

350VA, but only 180W:  https://www.amazon.com/Tripp-Lite-INTERNET350U-Desktop-Battery/dp/B00007FHDP (.52 PF)

400VA, but only 225W:  https://www.amazon.com/AmazonBasics-Standby-UPS-400VA-Outlets/dp/B073Q48Z95 (.56 PF)

600VA, but only 300W: https://www.amazon.com/APC-BX600L-LM-Back-UPS-600VA-120V/dp/B01FIG3J6M (.50 PF?!?!)

 

They do this because, let's say they claimed to have a 600W UPS.  But your 600W PSU has a PF of .60 because it doesn't have PFC.  Let's say the UPS supports 900VA, but you don't know that.  You only know that it supports 600W.  If the UPS doesn't support 1000VA, the PSU will overload the UPS with apparent power, even though the real power is within spec.

 

So really... if your PSU has APFC, ignore the VA rating and look at only the wattage rating.

 

But, going back to what I ORIGINALLY said, what PSU is this?  We still don't know what PSU the OP has.  And what kind of power outages are being experienced?

 

If the user is only experiencing brown outs or power sags, a good PSU with full range input and decent hold up time might not even care.

 

I give up. You are completely missing the point.

[Guest]

On 10/4/2018 at 9:36 PM, Lady Fitzgerald said:

I give up. You are completely missing the point.

If you were better at making a point, maybe I wouldn't miss it.  Maybe try explaining what your actual point is?

 

On 10/4/2018 at 12:56 PM, Lady Fitzgerald said:

You wouldn't want to put 2200VA on a 15A 120v (1800w) circuit. You also have to account for the power draw of other devices on the circuit. Ideally, you should limit continuous power draw on a circuit to 80% the rating of the circuit (unless you enjoy replacing dead circuit breakers).

In what scenario, in this day and age, would someone pull anywhere close to 2200VA from a wall outlet with a modern PC?  Especially one that is drawing upwards of 1800W?

 

On 10/4/2018 at 1:35 PM, Lady Fitzgerald said:

One still needs to consider the VA rating as well as the watt rating to ensure the UPS won't overload the circuit it will draw from.

 

Only if the PC has horrible power factor.  THAT is why keep asking what PSU the OP has.  

 

I think you're arguing just for argument sake.