UPS advice

[teech 0]

Hi,

 

First time for me to use a UPS device on an install so please forgive my ignorance.

 

The customer doesn't want to spend much on one. I've seen devices with AVR +/-25% another with +/-10%, what does this mean and is the lower the better?

 

Is simulated sine wave ok to use?

 

For a 4ch DVR system, is 500VA ok to use?

 

Is there anything else I should look for in a spec?

 

Thanks!

[SDM Group 0]

Don't forget to take into account the cameras and computer/peripherals as well as the DVR when doing your calculations, assuming they are all powered from the head end.

[mike_va 0]

AVR lower is better. I've actually had mine kick on towards the high side! Never would have noticed the overvoltage, but I heard the beeper go off and looked over at the rack (which also has built in voltage and current display meters) and that's what it was.

 

500VA may only be good for 300W look at the specs. I have a sticker put on mine reminding me what my UPS can actually do.

 

Sim sine wave is fine but can mean a wide variety of things in practice...

 

Get a unit with an inexpensive replacement battery if possible. I brought home a rack mount APC UPS with dead batteries once with the hope of replacing the batteries, but they were a fortune (this was a very large unit).

[Birdman Adam 0]

Watts are different from VA. Size accordingly! VA takes into account the reactive load. Computers are not purely resistive loads. A computer may draw 200W, but when you add in the reactive part, its actually pulling 250VA. Same for some camera PSUs (they are SMPS's just like computer PSUs).

 

Keep the AVR percentage as low as possible, but 10% is fine. 25% could be scary for computers! Think about it: 25% of 120V is 30V, so a 25% AVR could go as high as 150V, or as low as 90V.

 

500VA will probably be fine with a 4CH DVR, and camera PSUs.

[teech 0]

Thanks Birdman, apologies for my ignorance..learnt a lot!

 

Thanks Mike. Is the main difference between pure sine wave and sim sine wave just the time to turn on? When I was checking a spec, the time difference is so small, does it really make a difference as the cost difference is a lot?

 

Is it necessary to get one with an LCD screen or just get a cheaper version with LEDs?

 

Thanks.

[rory 0]

I would also suggest a separate AVR if they can afford it (normally half the price of the UPS), I have been witnessing alot of various brands of UPS fail with AVR recently during a couple months of massive power outages, surges, and brownouts here. In fact the AVR is the most important as that is what protects the hardware - I have seen them along with UPS catch fire from huge surges also, so nothing is 100%.

 

Additionally UPS can be prone to failure in where when there are constant power outages and brownouts, they occasionally dont send power back to the devices - not something one wants happen to a security system (then again a generator or solar might be best also).

 

If one is privileged enough to have clean consistent power in their area though, then a simple UPS should suffice.

[teech 0]

Thanks Rory.

 

So the AVR that's built-in to the UPS is different to a standalone AVR?

[Birdman Adam 0]

The difference between a real, pure sine wave and a 'fake' simulated sine wave is this:

 

 

In the red you can see the real sine wave. All electronics designed for the voltage this is put out at will like it. In the blue, you can see a crudely simulated sine wave. Some UPS will do a better job than that (ie have more 'steps')... Bottom line is some electronics don't like this! It may make transformers as well as SMPS's buzz loudly, motors may run a bit hotter, etc, etc. Inductive loads (motors, fluorescent ballasts), can get mad.

 

As an example, on my laptop, when I'm using my car inverter (same output of a UPS running off the battery), a horrible 60Hz tone is inducted into any audio lines I have. It sounds just like a square wave (harsh, not smooth). This shows that anything but a pure sine wave can be funny with electronics! Its no big problem, but can be annoying.

 

Overall, the difference between a real and simulated sine wave is not usually a big deal. BUT, if you are running super-sensitive electronics, you should consider a real sine wave unit! UPS's with a large output (like 2000W), usually come with real sine wave.

 

On the AVR: The difference depends... It could be the same, or not! It all depends on how serious the designer was who created the thing... AVR is usually not too big a deal when utility power is typically well controlled. But when you live in the Bahamas, power can be VERY unreliable (as Rory has stated).

[teech 0]

Thanks Adam. Much appreciated for taking the time to explain.

 

Thanks again.