I just got a Samsung ML-2851 laser printer and after connecting it, whenever printing (or even idling sometimes) the lights in my room flicker. This power fluctuation seems like it would be very harmful for a computer or a monitor. Should I be concerned? I have everything hooked up to a APS UPS (printer is connected to surge only, the CPU and monitor are on battery backup section).
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Is this harmful for my ACD / Mac Pro?
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no offense, but I would be more worried as to why the lights flicker.
I'm not an electrician, but that doesn't sound right at all. Is most of your equipment loaded into one outlet? ie. are you using the UPS plus a few power bars or something?
Try spreading the equipment out if that's the case.
Cheers,
Keebler
I moved the printer into another room and the lights do not appear to be flickering. I wonder if it is because there is too much power drawing off of one electrical outlet? I have no idea either but until I can get it sorted out I am leaving the printer in a separate room.
This is not at all uncommon for many laser printers to do, though less than a few years ago. I've got an older Dell laser that did this all the time - it's upstairs for wife to use now so I don't notice as much but yes when you fire it up for print more the lights flicker. We've got 400 amp service to our house, and wired well, it just happens.
So long as you're on a UPS it's not a problem. don't worry. It's probably not even a problem if you're not on a ups, as I've never heard my UPS switch to battery mode related to the printer.
I agree that the UPS probably gives the mac pro adequate protection so long as it stabilizes over/undercurrent. The larger problem appears to be too much draw on one circuit (lighting and outlets combined) which could be risky.
Dimming lights mean a voltage sag on the circuit in question, not the whole house. So if you have 400 amp service, you can still have problems if you are overloading a single 15-20 amp circuit in one room. I've run separate 20 amp service to specific receptacles for power hungry systems (home audio, power tools, etc.). It's really not difficult to do if you have room for extra breakers in your box and relatively inexpensive for the DIYer (be mindful of electrical codes).
Well I can tell you that even if the only lights on an entire 20 amp circuit is about 100 watts worth, they will still dim when the laser fires up. Circuit never breaks, just the flicker. I think a 20 amp circuit should be enough for one household laser printer 
I've seen this on older wiring, and it's basically an issue of the laser drawing the max allowable power for a period of time (probably 15A) on a circuit that is having trouble keeping the voltage up at that current level for whatever reason. I've also seen the same noticeably happen with similar high-power items--copiers, toasters, space heaters, and of course refrigerator startup (any motor has a brief but huge power spike at startup).
Were it my house it'd probably annoy me enough to get the wiring re-done, but then I'm an engineer who works on power systems--as long as you're not overdrawing for the circuit (that is, the wiring isn't undersized to the point something is going to heat up), it should be perfectly safe.
I don't think it's likely to damage the computer, but a decent UPS (one with AVR) would guarantee you're ok--the AVR will bump the voltage up without switching over to battery (which on all but the best UPSes is probably worse than a slight voltage sag).
Of course, if you were using compact fluorescent bulbs you'd never see this (and heck, depending on how many lights you have on that circuit you might not even HAVE the voltage sag--5 100W bulbs plus a 1500W laser printer is already pushing the max current for the average household circuit even before the computer).
Were it my house it'd probably annoy me enough to get the wiring re-done, but then I'm an engineer who works on power systems--as long as you're not overdrawing for the circuit (that is, the wiring isn't undersized to the point something is going to heat up), it should be perfectly safe.
I don't think it's likely to damage the computer, but a decent UPS (one with AVR) would guarantee you're ok--the AVR will bump the voltage up without switching over to battery (which on all but the best UPSes is probably worse than a slight voltage sag).
Of course, if you were using compact fluorescent bulbs you'd never see this (and heck, depending on how many lights you have on that circuit you might not even HAVE the voltage sag--5 100W bulbs plus a 1500W laser printer is already pushing the max current for the average household circuit even before the computer).