Members SteinbergerHack Posted March 18, 2006 Members Share Posted March 18, 2006 Originally posted by sandfly Check out these links if you don't think he can use 14 gauge wire I didin't say he couldn't - I actually said it would be fine...go back and look at my first post in the thread. Since you think figuring out a 277 lighting load is so easy Uh, yeah. It's a heck of a lot easier than a breaker coordination study, arc-flash submittal, or a fault current analysis. Do you even know ohm's law ? Yup. And Faraday's and Maxwell's equations, which you seem to conveniently ignore. ....... How much current does a 60 watt light bulb connect to a 277 load use ? Dude, I'm a district service operations manager for an electrical equipment company. I've sent over 15 years in the electrical industry in field service, plant engineering, manufacturing, and R&D. I'm familiar with NEC, NEMA, IEC, UL, CE, and plenty of other regulatory requirements. I also know that if we designed products only to meet those limits and ignored physical reality, we would be bankrupt, because our products would fail in the real world far too often. BTW, you would never run a single 60W bulb off of a 277 line, BUT: You haven't given enough information to determine the current. Wattage is real power, but current draw is based on apparent power - VA. THe two are only equal when current and voltage have exactly the same harmonic content and are exactly in phase with each other. Assuming unity power facter, the current draw would be just over 1/5 A. However, since most 277 lighting loads are ballast driven (not incandescent), you would have to know the ballast's expected power factor to give a correct answer. Think power factor doesn't matter? Ever gone into a building where the original wiring had a half-sized neutral? Know what happens when the loads change over time to include lots of switching power supplies (and maybe some VFDs for the HVAC)? Ever seen a neutral conductor burn up, even though the load measured balanced? Know why it happens? You can't ignore phase and frequency - they DO make a difference in the current flow. They don't teach that very effectively in the 2-year electrician classes (you generally don't need to know it to wire houses & apartments), but it's real. Link to comment Share on other sites More sharing options...
Members walfordr Posted March 18, 2006 Members Share Posted March 18, 2006 Originally posted by SteinbergerHack BTW, you would never run a single 60W bulb off of a 277 line, .. You can't ignore phase and frequency - they DO make a difference in the current flow. They don't teach that very effectively in the 2-year electrician classes (you generally don't need to know it to wire houses & apartments), but it's real. And since a speaker wire is carrying AC to a reactive load that calculator is just plain wrong. http://www.ibiblio.org/obp/electricCircuits/AC/AC_11.html Link to comment Share on other sites More sharing options...
Members sandfly Posted March 18, 2006 Members Share Posted March 18, 2006 Originally posted by SteinbergerHack Yup. And Faraday's and Maxwell's equations, which you seem to conveniently ignore.Dude, I'm a district service operations manager for an electrical equipment company. I've sent over 15 years in the electrical industry in field service, plant engineering, manufacturing, and R&D. I'm familiar with NEC, NEMA, IEC, UL, CE, and plenty of other regulatory requirements. I also know that if we designed products only to meet those limits and ignored physical reality, we would be bankrupt, because our products would fail in the real world far too often.BTW, you would never run a single 60W bulb off of a 277 line, BUT:You haven't given enough information to determine the current. Wattage is real power, but current draw is based on apparent power - VA. THe two are only equal when current and voltage have exactly the same harmonic content and are exactly in phase with each other. Assuming unity power facter, the current draw would be just over 1/5 A. However, since most 277 lighting loads are ballast driven (not incandescent), you would have to know the ballast's expected power factor to give a correct answer. I'm not ignoring any theory . I just asked a hypothetical ohms law question . Just trying to find out what you know ..... And of course your not going to run a single incandescent bulb on a 277 circuit . Originally posted by SteinbergerHack Think power factor doesn't matter? Ever gone into a building where the original wiring had a half-sized neutral? Know what happens when the loads change over time to include lots of switching power supplies (and maybe some VFDs for the HVAC)? Ever seen a neutral conductor burn up, even though the load measured balanced? Know why it happens?. Sure PF matters but were talking about 10 foot of 14g wire to hook up an amp and speaker cabinet . Not wiring an auto plant . Or trying to figure how efficient a transformer is . Originally posted by SteinbergerHack You can't ignore phase and frequency - they DO make a difference in the current flow. They don't teach that very effectively in the 2-year electrician classes (you generally don't need to know it to wire houses & apartments), but it's real. I know that . But once again were just talking about 10 foot of wire to hook up an amp head to a speaker cabinet . I also went to school for longer than just two years . The only homes I have wired were side jobs . I usually work in auto plant . You know hooking up things like Variable Frequency Drive .......... RPM=Vxf/PV= voltage f= frequencyP=poles Link to comment Share on other sites More sharing options...
Members SteinbergerHack Posted March 18, 2006 Members Share Posted March 18, 2006 Originally posted by sandfly I'm not ignoring any theory . I just asked a hypothetical ohms law question . Just trying to find out what you know OK, fair enough. Sure PF matters but were talking about 10 foot of 14g wire to hook up an amp and speaker cabinet . Sure. The reason I pushed back (probably a bit too aggressively) is that I've seen WAY too many people assume that an AC circuit is just like a DC circuit, then apply Ohm's law incorrectly, ignoring capacitive and inductive loads. Speakers ARE non-linear loads and are frequency dependent, so you need to assume in your sizing that you have a good bit more current than a DC analysis indicates. NEMA wiring codes are aimed at 60Hz, which is darn near DC, and a good bit lower than we use in guitar amps; Agreed, it's OK for a 10-foot cable, but if you were looking at a 50-footer to go to the other side of the stage with a 100W head.... Personally, I use a double-the-current rule of thumb to cover the inductive portion, which leaves you at 13 ga or better; 14 ga would be marginal in this application, and you'd be burning up a bit more than 3 watts in the speaker wire itself. You may be happy with this, but I wouldn't recommend it - I'd say go for 12 ga. I also went to school for longer than just two years . OK, sorry if I came off as condescending. Again, I've heard way too many guys who had a little bit of knowledge make pronouncements that seemed valid, but were overly simplistic. I usually work in auto plant . You know hooking up things like Variable Frequency Drive .......... VFDs are neat, but they can be a real headache for us. It seems that we continually get calls saying our drives our not working properly, when in fact, it's a load issue. There are a lot of HVAC guys who don't really get the VFD programming, so they automatically assume that that's where the problem is....oh, well. Again, sorry if I came off as condescending - I think we see where we're both coming from..... Link to comment Share on other sites More sharing options...
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