Re: Apprentice needs help with multiwire branch circuits.
kevin,
modular furniture is pre wired to accomidate different wiring methods. since most or many of the loads used within this type furniture call for "dedicated" circuits the manufacturer provides separate neutrals for each circuit plus a common ground conductor (green). the system you are relocating is being fed by a multiwire branch circuit ---three hots and a common neutral and a common ground conductor. you will have no other choice than to splice the single neutral incoming conductor to the three individual neutral conductors of the furniture, then the ground and each hot conductor to the appropriate furniture circuit. this will work--but it is not the recommended method by most computer manufacturers. the first instruction is to connect this equipment to a dedicated circuit --you do not have one in that module. so the typical set up is a computer -- printer -- fax. and maybe two or three desks powered by this same multiwire branch circuit. what sometimes occurs is due to the instantainious current flow on the common neutral conductor and the resistance to clear that current back to the source, it effects the voltage between the other circuits being fed by this same common neutral and data can be lost and/or connections disconnected within the computer equipment.
another, issue here is harmonic currents, which can cause the same effect due to the neutral currents not cancelling each other out due to the difference in their frequency at the common point which would be the module's neutral splice. years ago much of the modules were constructed with what was called "super-neutrals" or number ten neutral conductors within the furniture module. harmonic problems are on the decline since computerized equipment is manufacturered differently today.
on a standard multiwired branch circuit with normal loads the common neutral carries the maximum unbalanced load between all phase currents. if "a" carried 10 amps and "b" carried 15 amps, and "c" carried 15 amps --- the neutral conductor would carry the maximum unbalanced betwen all phases or 5 amps....
the correct method for computerized equipment for office furniture modules is dedicated circuits---separate neutrals for each circuit and a common ground!! my .02!
