Hey,
I have a request for a bid on a gig. The client is in a very modern office building, three phase of course.
He has a cube farm of 30 cubicles in three rows. He called me a while back for a power outage, I restored the breaker and sent a modest bill. The rows have ten cubicles each. The electrical spine of the cubicles permits as many as four circuits, but each row is served by three circuits, with one 12 ga neutral (worrisome if he gets a high current due to a third harmonic). The circuit that tripped had four cubicles on it. I am now rating each cubicle at 6 amps, so that is a limit of three per 20 amp circuit. (Each cube has a fast cpu and two flat screen monitors).
But he wants more cubes in this area. He wants four rows of twelve. Two of the circuits come up thru the floor, and will be in the walk way in the new arrangement, so just disconnecting them and pushing them back down their conduit, and likewise disconnecting them at the panel and winding them up and taping them off does not bother me too much :whistling2:.
I think I am going to bring him four runs of conduit in the ceiling, with four circuits each. Black, red, blue, pink, (the color code in the whip from the cubicles) with two 10ga neutrals, and an isolated ground, allowing the conduit to be the chassis ground.
Six current carrying conductors requires a 20% derating, 12 ga thhn with 90 degree insulation derates to 24 amps, so the hots should hold up ok, but what can I expect on the 10 ga neutrals that are going to return the current from two three phase circuits each? Will they hold up?
I have a request for a bid on a gig. The client is in a very modern office building, three phase of course.
He has a cube farm of 30 cubicles in three rows. He called me a while back for a power outage, I restored the breaker and sent a modest bill. The rows have ten cubicles each. The electrical spine of the cubicles permits as many as four circuits, but each row is served by three circuits, with one 12 ga neutral (worrisome if he gets a high current due to a third harmonic). The circuit that tripped had four cubicles on it. I am now rating each cubicle at 6 amps, so that is a limit of three per 20 amp circuit. (Each cube has a fast cpu and two flat screen monitors).
But he wants more cubes in this area. He wants four rows of twelve. Two of the circuits come up thru the floor, and will be in the walk way in the new arrangement, so just disconnecting them and pushing them back down their conduit, and likewise disconnecting them at the panel and winding them up and taping them off does not bother me too much :whistling2:.
I think I am going to bring him four runs of conduit in the ceiling, with four circuits each. Black, red, blue, pink, (the color code in the whip from the cubicles) with two 10ga neutrals, and an isolated ground, allowing the conduit to be the chassis ground.
Six current carrying conductors requires a 20% derating, 12 ga thhn with 90 degree insulation derates to 24 amps, so the hots should hold up ok, but what can I expect on the 10 ga neutrals that are going to return the current from two three phase circuits each? Will they hold up?