Need help choosing a UPS (plus general UPS tips)

[Pentium100]

Plugging your UPS into a surge protector: In order for your UPS to get the best power available, you should plug your UPS directly into the wall receptacle. Plugging your UPS into a surge protector may cause the UPS to go to battery often when it normally should remain online. This is because other, more powerful equipment may draw necessary voltage away from the UPS which it requires to remain online.

This is if your surge protector is too weak or the other equipment connected to it is very powerful. Actually, it is advisable to connect a UPS to a decently sized surge protector - in the event of a big surge, the cheaper surge protector will blow up instead of the expensive UPS. I have installed a surge protector near the circuit breakers (the protector looks like a circuit breaker).

[Freedom Kira]

It's probably best to only have the UPS connected to the surge protector, too. I think the APC quote there assumes you would plug other things into the surge protector.

[chubbysumo]

The emulated sine-waves should not cause any problems.  The psu in the computer turns it into a flat line anyway.

nope, AC to DC conversion usually results in a slightly bumpy wave, since no converter is 100% perfect.  An AC power source converted to a DC output usually looks like this on an oscilloscope(there are 2 waves, there, 1 for unfiltered, and 1 filtered, most decent PSUs have a filter).



I would love a UPS for my system, but the UPS that I would need to power my system is way to expensive(my rig draws close to 900w from the wall under full stress use).  I may get a UPS for my router and modem tho, because that would be pretty cheap.

[nstgc]

Isn't there a way to rig up two PSUs? If you did that you could run two UPSs, one for each...which would still be pricey.

[Pentium100]

nope, AC to DC conversion usually results in a slightly bumpy wave, since no converter is 100% perfect.  An AC power source converted to a DC output usually looks like this on an oscilloscope(there are 2 waves, there, 1 for unfiltered, and 1 filtered, most decent PSUs have a filter).

That is true for a unregulated power supply. A regulated supply has very small ripple.

Computers use switching power supplies that are more complicated than that.

First the 220V mains power is rectified to give 310VDC. Older power supplies just use a diode bridge, newer ones use a more complicated circuit to have a higher power factor. Then the DC gets chopped at high frequency and goes trough a transformer, then it is rectified again. A chip regulates the output voltage by controlling the duty cycle of the switching.

Computer PSUs have high frequency ripple but no 50/60Hz ripple. A computer power supply without PFC could be connected to 310VDC or a square wave for all it cares. PFC may act differently.

Isn't there a way to rig up two PSUs? If you did that you could run two UPSs, one for each...which would still be pricey.

Two smaller UPSs would not be a lot cheaper than one big UPS. Also, while you can use multiple PSUs for a PC (powering different devices - one for all hard drives, another for everything else etc), the load would not be distributed between them - one would use more power. There are redundant PSUs that balance the load if they both work, but they are really expensive.

[nstgc]

I was just making a suggestion. Besides if you have enough money to build a computer that regularly eats up 900W, chances are you can pay for two UPS and a dual PSU...thingy.

[bork]

When you start push 1000W systems, you should look into running a dedicated 20A for it (if your running 120V.)  A normal 15A circuit should be limited to about 1300~1500 watts of continuous use.  If you are running two systems of this size, you are exceeding the limits of the power circuit.  A dedicated 20A circuit also uses a larger wire gauge that will have less of a power drop when pulling a heavy load across it which in turns puts less of a strain on the power supply.

If you are building a system with these large power draws, you are going out of whats is normal for a home PC.  You are entering into an area that requires a bit of planning to make sure you have the right power and cooling designed to support these things.  The support will cost just as much as the system itself; what ever the system cost you will need to double that price tag for the total cost.  One system you might get away with whats available but just ask anyone with two of these beast has went through to make it work.

[Pentium100]

Not really, I have more than one PC and the total power consumption is 1.2 - 1.5kW. Room cooling is required (especially in summer) but it was not that expensive - I just used to use a big fan and an aluminium airduct (25cm diameter). Now I'm in a different room and want to make it better, so I bought a filter (the fan pulls a lot of dust from outside), some valves and will make a semi-permanent system, currently it is incomplete.

Still, I paid for the rack more than I paid for the cooling. Or the UPS. It is connected to one outlet (my country uses 230V). An electric kettle uses more power (2kW) than my whole system.

[kitamesume]

^ replace that kettle with an induction type, imho at least theres units which uses less than 1KW, heh.

edit: wait, wouldnt more efficient PSUs be more preferred when you start pushing 1000W rigs? since even a difference of 5% is 50watts =o

[Pentium100]

^ replace that kettle with an induction type, imho at least theres units which uses less than 1KW, heh.

edit: wait, wouldnt more efficient PSUs be more preferred when you start pushing 1000W rigs? since even a difference of 5% is 50watts =o

At 1kW it would take 8 minutes to boil 1.5L of water (assuming perfect heat transfer).

As for the efficiency - while 5% difference is 50W, it is still just 5%. However, more powerful PSUs are more efficient - if they weren't, they would melt since the ATX PSU form factor is too small or would require really powerful (and loud) fans. After all, a 60% efficient 1kW PSU would dissipate 670W as heat.