I feel like I go through this every time. How many receptacles per circuit? An open office plan with two receptacles per person (computer, monitor, maybe printer). Ideally I think the two receptacles would be on different circuits. What are you usually doing?
A little more info? 'Open Office'; is that cubicles (partitions) If so, are they pre-wired? Most usually are 3 circuits of various configirations. ie: two GP circ/one Iso Grd circuit, oversize neutral, two (2) EGC's.
Four person cubicals with internal wiring are often done with three circuits. That's 3 circuits per 4 people. My current project are connected desks but the wiring is in a raised floor with a separate floor recessed servicenter per desk (person).
No more than 3 cubes per 20A circuit. If you put 4 cubes on a 20A circuit you *will* have problems. Not in all areas, but in enough that you'd be kicking yourself. Most people will be fine with 2 duplex receptacles, but a few will need more. If you have modular cubes, either buy extra receptacle modules to plug in for these people as needed, or buy some surge supressors. (Not power strips, they're not legal! Surge supressors, however... gold!)
Each laser printer or copier will need a dedicated circuit if you go by strict NEC, though 2 can share without much issue. Be kind and put in a dedicated circuit for the coffee maker/microwave area, too.
If we are talking about cubicles, one circuit per three cubes is probably the maximum we would ever want to go, and that's with monitors and hard drives only. Printers and copiers need their own dedicated circuits, although I've heard with the latest ones you might get a couple on one circuit. I'd want to know the nameplates. If you are talking about several more cubes than three, I'd definitely add another circuit at least for every three more, but I've rarely had to make that decision because the installations should have been engineered and inspected. In talking to the guys that build the cubes, the main call back they get electrically is when there are multiple circuits and they lose the neutral because of heat. The neutral should be oversized to be on the safe side. The guys told me that when they have trouble, the neutral has usually crumbled because it was crystalized. Do you know, or have you ever undergone the experience of losing a neutral in a circuit configuration where two or three phases share the neutral? If it drops out, the phases are rerouted thru what's left of the neutral that connects the recepticles and meets in the equipment. "Smoke on the waaaaater...."
Thanks for the input. They are not real cubicals. Basically rows of desks that face each other. Each will have a floor servicecenter with two duplex receptacles (and data/tel outlets). I was thinking three circuits per four desks (one circuit per two for one receptacle and one circuit per four for the other receptacle) so each desk actually has two circuits. I don't know if the modular wiring system (America Cable Systems or whomever) can be run that way though.
#181500 - 10/13/0803:54 AMRe: Open office plan receptacles per circuit.
I just worked with some modular desks while rearranging a computer lab.
They were wired with a 4 circuit buss, consisting of a 3 phase circuit [3-#12 phase legs (black/red/blue), #10 Neutral(white w/black stripe), #12 ground(green)], and a isolated ground circuit [#12 phase leg(pink), #12 neutral (white w/red stripe), and #12 ground (green/yellow)]
The outlets were numbered for a specific circuit, and could be placed anywhere on the buss. I think the tables actually had two busses, but only one was in use. Two outlets could be installed on each buss per table.