Is there any conditions for 120 volt circuits where you can't share the neutral? I am wiring circuits for computers in a customer's new business location. I have a 3 phase service and am planning on pulling 3 phase conductors and 1 neutral. Wondering if I am missing something on these computer circuits. Also have some copiers that I am planning on doing the same with. Any comments yea or nay will be appreciated. I believe I'm right according to code, but just double checking. Thanks, Steve
A lot of attention has been given to "isolated grounds" for computers and the like. This also a real market sor surge suppression and UPS (back-up power) systems.
While not required by code, nor ever mentioned in the specs for any such system, it is my practice to NOT share the neutral between separate circuits. By running a dedicated nuetral, I avoid the whole harmonics issue. More important, to me, is that I also eliminate one source of a voltage surge- a loose neutral connection. I'll even go so far as to identify the neutrals in the panel and junction boxes.
You are correct in your understanding of the code- this is just one area where I chose to go "beyond" code minimums.
Bob, went on one last week, someone ran a 3 circuit, one nuetral to multiple outlets, simlilar to what the poster is asking. Aparently, a nuetral connection came loose in a recptacle box. All the surge protectors plugged in smoked and melted, the printer/copier burnt up, and needed boards, fire dept called, the whole mess.
For the cost of wire, and the potential for disaster, I don't do it.
Just for fairness, multiwires are good for lighting, if both circuits are matched closely.
Dnk, it's not just the cost of wire, it's also natural resources including fuel for generation.
We literally install thousands of multi-wire circuits every year and I only know of one open neutral problem we have had in the last ten years, which had been tampered with by the particular facilities maintenance staff.
John, a dedicated grounded conductor to one ungrounded conductor is not a neutral.
I have seen more open service neutrals than branch circuit or feeder neutrals by far.
[This message has been edited by Roger (edited 01-17-2006).]
Reno is right about IG. I was an installating planning rep at IBM for 5 of my years there. Isolated Ground is a waste of money. IBM stopped mentioning it in the Carter administration but the legend lives on in the mind of "experts". If you like the customer, save them some money and talk them out of it. If they really insist, money is not an issue for them so sell them "monster" super neutrals at the appropriate price. Then you can take the family to Hawaii this summer.