Guest " " Posted February 18, 2009 Share Posted February 18, 2009 OK....the basic question is when using MC or BX, since the metal jacket is tied to ground, isn't that a bigger neutral? Both the neutral and the metal jacket terminate at the mains box and to take it a step furthur, the neutral gets tied into the mains physical ground...which the metal jacket of the run gets bolted into. So basically, when you have metal jacketed runs.....you have more effective gauge as a neutral...the neutral conductor itself, plus the equiv gauge of the mass of the metal jacket....be it MC or BX. Different than romax, which relies strickly on the conductor identified as the neutral. Quote Link to comment Share on other sites More sharing options...
Guest " " Posted February 18, 2009 Share Posted February 18, 2009 " I've used BX (steel jacket, no ground)" The only way for the jacket not to be a ground is for the jacket not being terminated at the mains box. Once connected...the jacket becomes a ground...no way around that. Quote Link to comment Share on other sites More sharing options...
Hifi jim Posted February 18, 2009 Share Posted February 18, 2009 OK....the basic question is when using MC or BX, since the metal jacket is tied to ground, isn't that a bigger neutral? Both the neutral and the metal jacket terminate at the mains box and to take it a step furthur, the neutral gets tied into the mains physical ground...which the metal jacket of the run gets bolted into. So basically, when you have metal jacketed runs.....you have more effective gauge as a neutral...the neutral conductor itself, plus the equiv gauge of the mass of the metal jacket....be it MC or BX. Different than romax, which relies strickly on the conductor identified as the neutral. Some confusion here, with MC or BX, you are getting another ground conductor through the jacket. The neutral is separate until it finally bonds with the ground in the main panel. Hope this helps. Quote Link to comment Share on other sites More sharing options...
Hifi jim Posted February 18, 2009 Share Posted February 18, 2009 " I've used BX (steel jacket, no ground)" The only way for the jacket not to be a ground is for the jacket not being terminated at the mains box. Once connected...the jacket becomes a ground...no way around that. Yes. I should have clarified that it had no dedicated ground wire. I was answering another electricians inquiry with the same trade talk I'm used to. Sorry for the confusion. Quote Link to comment Share on other sites More sharing options...
mark electro Posted February 18, 2009 Share Posted February 18, 2009 O.K. I stand corrected... BX is still code correct according to NEC 320. I just dont like it! MC is generaly the armored cable of choice. Quote Link to comment Share on other sites More sharing options...
Hifi jim Posted February 18, 2009 Share Posted February 18, 2009 O.K. I stand corrected... BX is still code correct according to NEC 320. I just dont like it! MC is generaly the armored cable of choice. I hear ya Mark. Using BX forces you to carry around a Roto-Split all day... I hate that! Hope work is better down your way, baaaad up here. Quote Link to comment Share on other sites More sharing options...
Guest " " Posted February 18, 2009 Share Posted February 18, 2009 " Some confusion here, with MC or BX, you are getting another groundconductor through the jacket. The neutral is separate until it finallybonds with the ground in the main panel. Hope this helps." Ok..now we are getting somewhere....if I were to shut off the power and use an ohm meter to measure the resistance from the neutral to ground...on either side of the circut..I would get zero...since once properly installed...they become one and the same...therefore...from a current carrying perspective...the current runs thru both the neutral and the metal jacket...it does not only run thru the neutral conductor...therefore.....I would always have more neutral current conductance capabilty in MC or BX than I would in romax....therefore...if I'm using BX or MC...I really do not need to double the size of my neutral wire since it's already far greater than double. Correct? Quote Link to comment Share on other sites More sharing options...
mark electro Posted February 18, 2009 Share Posted February 18, 2009 OK....the basic question is when using MC or BX, since the metal jacket is tied to ground, isn't that a bigger neutral? Both the neutral and the metal jacket terminate at the mains box and to take it a step furthur, the neutral gets tied into the mains physical ground...which the metal jacket of the run gets bolted into. So basically, when you have metal jacketed runs.....you have more effective gauge as a neutral...the neutral conductor itself, plus the equiv gauge of the mass of the metal jacket....be it MC or BX. Different than romax, which relies strickly on the conductor identified as the neutral. Speakerfritz, What I was origionaly trying to say is the larger neutral will help clean the power to your equipment by helping to clean the sine wave of the distortions created from other loads on the system. The steel jacket will not help because it is only 10% as conductive as the copper in the wire. (aluminum is about 65% as conductive. So when you factor the conductivity of the jacketing in effeciency is lost. Quote Link to comment Share on other sites More sharing options...
mark electro Posted February 18, 2009 Share Posted February 18, 2009 quote] I hear ya Mark. Using BX forces you to carry around a Roto-Split all day... I hate that! Hope work is better down your way, baaaad up here. I carry the roto split anyway. They use a lot of MC- AP here. Has to be split. Work is the same here. Very thin. Quote Link to comment Share on other sites More sharing options...
Hifi jim Posted February 18, 2009 Share Posted February 18, 2009 Ok..now we are getting somewhere....if I were to shut off the power and use an ohm meter to measure the resistance from the neutral to ground...on either side of the circut..I would get zero...since once properly installed...they become one and the same...therefore...from a current carrying perspective...the current runs thru both the neutral and the metal jacket...it does not only run thru the neutral conductor...therefore.....I would always have more neutral current conductance capabilty in MC or BX than I would in romax....therefore...if I'm using BX or MC...I really do not need to double the size of my neutral wire since it's already far greater than double. Correct? Nope. While the ground and neutral do bond and eventually become one, the ground is designed as a safety while the neutral is designed to be a current carrying conductor. Try not hooking up your neutral conductor to an outlet, will a device plugged in still work even if it's properly grounded? Quote Link to comment Share on other sites More sharing options...
Arkytype Posted February 18, 2009 Share Posted February 18, 2009 You should only measure "zero" ohms between the neutral and ground bus at the service entrance which is the box the meter loop is attached to. At this point (and this point only) the neutral and grounding conductors should be bonded together. There should be a ground rod driven close to the meter box and connected to this common buss. Inside the breaker box in your house the neutral and grounding busses are separate; so while you might measure a low resistance between them, it won't be "zero" because you are reading the resistance of the ground (literally) and the neutral wire running back to the bonding point. There should also be a ground rod connecting the ground buss in the breaker panel. The only time a grounding conductor will be carrying and current is when there is a fault. Hopefully the breaker will trip before injury or damage occurs. Our electric coop suggested (after I had cad welded three buried eight-foot copper ground rods!) that the ground wires from the meter loop to my service panel be connected together. I suspect, my house ground is better than their single ground rod hence the suggestion. Since the wiring is in an underground conduit from the house to the pole, it wasn't possible to retrofit a new ground. If you have aluminum wiring feeding your breaker panel and it is over five years old, turn off the main breaker feeding your panel, clean the bare ends of the feeder wires (two hots and a neutral).Then treat the ends (as well as the inside of the lugs with Noalox. It will act as an anti-oxidant and anti seizing agent. . Lee Quote Link to comment Share on other sites More sharing options...
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