i have a tx950w corsair but my load is only below 650w (used thermaltake power supply calculator).
is it okay to plug it to a 500va ups? will i be safe?
as of the moment im out of budget to buy a new ups with 1000 to 1500va.
we usually have power flux & brownouts here. i only need not less than 3 to 5mins to give power from the ups to shut down my pc if ever a brownout will occure and can that ups handle it?
chances are you will get less than 1 minute to turn off your system so i would say its cutting it to close... sometimes my pc will take 1.30 to close depending on what was running and what needs to be stopped.
any ups will clean up your current frequency and allow smooth operation of the pc but you really do need to at least match your max wattage and preferably double it to give the best possible chance of saving your data... so i would say no to using it as a power reserve. but if you have dirty current then yes it will help clean the input of power spikes and variance.
For your UPS, the trick is wattage, must have enough wattage to handle the draw on it. You amperages simply give you the amount of time the battery will provide power. Think of the wattage as octane, amperage as fuel quantity.
Can't hurt though - My i5 machine (see sig) is connected to a 340W UPS (tower only, nothing else) I've only overdrawn it once but I had a 170W TV plugged into it also. The most draw I have seen from my tower only, is about 325W (GPU & CPU OC'd and 100% Stressed).
My UPS is 340W 600va... at full load I have 30 seconds to shut down, at idle I have up to 20 minutes - It would depend upon your usage at time of power loss.