# Uninterruptible Power Supply

Let's say you have a UPS 550 Watts (1100 VA). How much current or watts does the unit itself used? This is important when your source itself is limited by the wiring.. let's say all your computers total 500 Watts and the wiring is sized for roughly that.. Would the UPS draw more current or power than 500 Watts?

Another thing. If the UPS only has approximated sine wave.. could mostly PSU (power supply unit) let's say from the Honeywell Addressible Control Panel take it?

## Answers and Replies

russ_watters
Mentor
Let's say you have a UPS 550 Watts (1100 VA). How much current or watts does the unit itself used? This is important when your source itself is limited by the wiring.. let's say all your computers total 500 Watts and the wiring is sized for roughly that.. Would the UPS draw more current or power than 500 Watts?
Look at the actual ratings on the nameplate of the UPS. Given that 1100VA would be 550W at only a 0.5 power factor, I'm thinking maybe you are looking at both the input and output ratings...

...also, unless you mean there is other stuff on the circuit, I don't think there a circuit is allowed to have such a low capacity anywhere.

Last edited:
Look at the actual ratings on the nameplate of the UPS. Given that 1100VA would be 550W at only a 0.5 power factor, I'm thinking maybe you are looking at both the input and output ratings...

...also, unless you mean there is other stuff on the circuit, I don't think there a circuit is allowed to have such a low capacity anywhere.

The 500W (1100VA at 0.5 power factor) is the output. I was describing the following.

Let's say the AC wire (input) is very small and has capacity for 500 W only. And all my equipments (output) are 500W. When I used the UPS. Would the power drawn still 500W (input).. or would there be additional say 50 Watts from the UPS circuits itself? Let's not complicate it by ignoring the power factor.

russ_watters
Mentor
The
When I used the UPS. Would the power drawn still 500W (input).. or would there be additional say 50 Watts from the UPS circuits itself? Let's not complicate it by ignoring the power factor.
Yes, the input power is higher than the output power - by how much depends on how heavily loaded the UPS is. At full load it could be as little as 2%.

Tom.G
Gold Member
A few more things to consider for question #1:
• the power factor of the load(s)
• the battery charging current of the UPS when the power is restored after an outage will be in addition to any loads.
Answer to #1: Yes.

Question #2: Contact the manufacturer, that is not a device commonly used by the folks here.

I just talked to APC technical support now. They said when the battery was drained and power came back.. the unit won't automatically turn on and you have to charge it first for 6 hours before it is turned on. Is this the normal for all UPS brand?

Well. I need a UPS where the unit will turn on after electricity came back even if the battery is drained. This is because I'll use it on a server that is unattended and I don't want it to be off when power comes back. What brand should I look for? Anyone has tried any UPS here.

"...need a UPS where the unit will turn on after electricity came back even if the battery is drained..."

Not a good idea, IMHO, as you have no guarantee that, should the mains go off again, there will be enough UPS power stored for an orderly shut-down.
Murphy's Law...
Hence the usual configuration to stay shut down until re-started manually.

FactChecker
"...need a UPS where the unit will turn on after electricity came back even if the battery is drained..."

Not a good idea, IMHO, as you have no guarantee that, should the mains go off again, there will be enough UPS power stored for an orderly shut-down.
Murphy's Law...
Hence the usual configuration to stay shut down until re-started manually.

I don't need any orderly shut-down.. it's just a CCTV at a remote location where it can reboot at any time... so there is no UPS that can do this?

Tom.G
Gold Member
when the battery was drained and power came back.. the unit won't automatically turn on and you have to charge it first for 6 hours before it is turned on.
The key phrase here is "...when the battery was drained...
If the battery is NOT drained, as during a brief outage, the 6 or so APC units I've used all automatically switch back to line power. I've been lucky enough to always catch an outage soon enough to manually shut everything down before killing the batteries. (Those things are Expensive!) BTW, battery life under light usage is three to four years, after that the runtime decreases rapidly. The estimated runtime reported by the software that comes with the UPS is a fair indicator of battery condition. When it reports 20%-25% less runtime than when new, it's time to order new batteries.

As I was typing this @Nik_2213 brought up a good point; install enough batteries to carry thru until you can get there.

As I was typing I see the added post that clean shutdown isn't needed. Perhaps your best bet is to have a computer system that runs on 12 or 24VDC and use your own batteries and a charger. That way you can restart almost immediately upon power restore. That's how burglar and fire alarms work.

Cheers,
Tom

Looking at the problem sideways, if you were planning to run the IPCAM from a wall-wart plugged into a {$} UPS, could you instead use a much larger capacity car-type 'Recreational' battery, a battery charger and a 12-volt in-car converter instead ? Something like a$20....
121AV Universal In Car Multi - Voltage DC to DC Power Adapter with 6 Connectors (1.5v DC/3v DC/4.5v DC/6v DC/7.5v DC/9v DC/12v DC) 2000 mAh
But remember to get a fused version or wire your own, to be sure to be sure...
Plus a \$10 car trickle-charger...