US voltages and wire colors

[TrickyDickS]

I'm an electrician in UK and have been asked to supply some power distibution equipment for use in an office that may be used in the States.

What voltages would be used to supply computers and other office equipment?

If it is wired in conduit what wire colors would be used?

In UK we use a 13amp plug generaly fitted with a 3amp fuse in the plug.

What would be used in US?

 

[alehman]

For typical single phase supplies -
120 volts, 60Hz
Hot - black, Neutral - white, Ground - green

Three phase circuits are sometimes used in pre-wired office partition systems, with receptacles wired phase to neutral -
208 volts phase-to-phase, 120 phase-to-neutral
ph. A - black, ph. B - red, ph. C - blue
neutral - white, ground - green

Receptacles are typically not individually fused, but are considered protected by the circuit breaker feeding the branch circuit (which is nearly always 15 or 20 amps). Receptacles are normally rated either 15 or 20 amps. 15 amp receptacles can be used on a circuit protected by a 20 amp breaker if there is more than one receptacle on the circuit. 20 amps is more common for commerical applications.

Sometimes separate isolated ground wires (green with yellow stripe) and isolated ground receptacles (orange) are used for electronic equipment circuits. There are different philosophies on this.

 

[jghrist]

See

http://www.homewiringandmore.com/

for some typical US home wiring. Office wiring is not much different except for the possible use of 3ø.

 

[DrewBrejda]

I agree with the previous postings. Fused receptacles are not used in the US (unless you count portable power strips, but I hesitate to use foul language).

The National Electrical Code specifies the use of white for the grounded (neutral) conductor and green for the grounding conductor. Although not a code requirement, the unofficial standard for 120/208V systems is Black for Phase A, Red for Phase B, and Blue for Phase C, if using a three-phase supply.

Receptacles may be either 15 or 20A. The 15 A receptacles may be fed with #12 wire on a 20A breaker as stated earlier (more than one on the circuit). Otherwise, use #14 but only with 15A receptacles and a 15A breaker. For a single, dedicated use receptacle, use wire and breaker to match the receptacle rating: #12 for 20A, #14 for 15A. Derating of conductors may be required based on the number of conductors in a single conduit and/or long wire runs.

You can share the neutral between phase wires, but I have found in office environments that this is not a good practice due to the harmonics generated by the switching power supplies in most office equipment. Rather than try to save money, I always run seperate neutrals but I run one ground.

 

[jbartos]

Suggestion: Visit

http://www.ae.ucdavis.edu/projweb/c...0+Basic+Construction+Materials+Methods+00.pdf

for: Wire Color Code

 

[TrickyDickS]

Someone has just told me that you can get ready made plug in wiring systems for use in raised floors. What are they like? are the used much? who makes them? are they expensive?

 

[robertb]

TrickyDickS,

You may consider AFC ACS/Unit-Fab products.

 

[jbartos]

Suggestion: Please, cut and paste my posted long link into browser.

 

[jbartos]

Suggestion: Visit

http://www.wiremold.com/shared_content/pdf/ED670.pdf

etc. for more info

 

[dpc]

I would only add a small additional comment on the NEC and wire colors:

In the US, a green wire can ONLY be used as a non-current carrying grounding conductor and for nothing else. Likewise, a white wire can only be used as a grounded circuit conductor (neutral).