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Bill wrote:
On 12/6/2010 10:50 AM, Bill wrote: Someone suggested (I could not locate the post) that if I wanted quiet fluorescent lights, then I should look for those with an "A" rating. Putting that detail aside temporarily. What would be the practical differences between a "standard electronic ballast with 20 THD" and an "instant on electronic ballast with 10 THD"? Bill Trying, usually, to answer questions for myself before and after I post, I ran across the following tidbit. It isn't that helpful though. BTW, I have no reason to believe THD is accumulated if fixtures are wired in a series, but I would certainly be interested in knowing if anything of that nature is true. THD stands for Total Harmonic Distortion. The distortion is feedback caused by deviation from the sinusoidal waveform. The industry standard is less than 20%. If the THD is very high (around 150%), an electrical fire can occur. Magnetic ballast run 90%-120% THD. The information above was copied from : http://www.ace-ballast.com/articles/...last_Questions Bill Interesting stuff Bill. Though - I doubt I'll worry much about THD on the next flourescent light I purchase. -- -Mike- |
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On 12/6/2010 11:01 AM, Bill wrote:
On 12/6/2010 10:50 AM, Bill wrote: Someone suggested (I could not locate the post) that if I wanted quiet fluorescent lights, then I should look for those with an "A" rating. Putting that detail aside temporarily. What would be the practical differences between a "standard electronic ballast with 20% THD" and an "instant on electronic ballast with 10% THD"? Bill Continuing to research my question, evidently low THD is better for the components in the lighting system (capacitors, etc) and may provide lower cost in the form of the longer life for the system. Pitiful question: If 8 fluorescent fixtures are wired in a series, and the ballast in one of them fails, do all of the lights go out? Assume a "modern" fixture. If the answer to the question above is yes, this suggests "Lew's wiring design" should be wired (using 12-3 THHN) with 2 parallel (pairs of) circuits with 4 fixtures wired on each row. Then if one of the fixtures went bad only two of them would go out (either the ones on L1 or the ones on L2 in a given row). Is this correct? Alternately, I could use 8 parallel circuits, 2 for each row, then if one of the luminaire's failed, then it, and it alone, would go out. Taking a step back, this is equivalent to wiring 2 branch circuits each wiring 8 fixtures in parallel. Everything basically correct? Bill |
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On 12/6/2010 2:09 PM, Mike Marlow wrote:
Bill wrote: On 12/6/2010 10:50 AM, Bill wrote: Someone suggested (I could not locate the post) that if I wanted quiet fluorescent lights, then I should look for those with an "A" rating. Putting that detail aside temporarily. What would be the practical differences between a "standard electronic ballast with 20 THD" and an "instant on electronic ballast with 10 THD"? Bill Trying, usually, to answer questions for myself before and after I post, I ran across the following tidbit. It isn't that helpful though. BTW, I have no reason to believe THD is accumulated if fixtures are wired in a series, but I would certainly be interested in knowing if anything of that nature is true. THD stands for Total Harmonic Distortion. The distortion is feedback caused by deviation from the sinusoidal waveform. The industry standard is less than 20%. If the THD is very high (around 150%), an electrical fire can occur. Magnetic ballast run 90%-120% THD. The information above was copied from : http://www.ace-ballast.com/articles/...last_Questions Bill Interesting stuff Bill. Though - I doubt I'll worry much about THD on the next flourescent light I purchase. You'll probably save $14 too! I'm considering purchasing about 15--and I want 'em quiet! : ) When I built my last computer, I used a fanless graphics card and tossed in an extra $100 for a quiet (decent quality) power supply. No hard drives either--SSD. Maybe having quiet is a lot like having a sharp Brad point drill... : ) Bill |
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Bill wrote:
You'll probably save $14 too! I'm considering purchasing about 15--and I want 'em quiet! : ) When I built my last computer, I used a fanless graphics card and tossed in an extra $100 for a quiet (decent quality) power supply. No hard drives either--SSD. Maybe having quiet is a lot like having a sharp Brad point drill... : ) I put the cheapest 4 foot fixtures Home Depot sold in my garage - 15 of them. At the time, those $8 fixtures used a -10 degree C ballast. I figured 14 degrees F was good enough for me since my garage never gets that cold. They are dead quiet. Can't tell you what the THD is on them - don't really care. They were cheap, work well and are quiet. Unfortunately, Home Depot's cheapest now is $9 and change, and it does not use a low temp ballast like that. Can't remember what they are now, but it seems to me they might be something like 50 degrees F. -- -Mike- |
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On Mon, 06 Dec 2010 14:26:03 -0500, Bill
wrote: On 12/6/2010 11:01 AM, Bill wrote: On 12/6/2010 10:50 AM, Bill wrote: No comment. gd&r Someone suggested (I could not locate the post) that if I wanted quiet fluorescent lights, then I should look for those with an "A" rating. Putting that detail aside temporarily. What would be the practical differences between a "standard electronic ballast with 20% THD" and an "instant on electronic ballast with 10% THD"? My first guess would be price. Continuing to research my question, evidently low THD is better for the components in the lighting system (capacitors, etc) and may provide lower cost in the form of the longer life for the system. But is it cost-effective? Some people are downright proud of their simple fluor lamp fixtures, asking several hundred dollars for the same quality you get in a $50 fixture. Downright Festerful, and sellin' that name! Pitiful question: If 8 fluorescent fixtures are wired in a series, and the ballast in one of them fails, do all of the lights go out? Assume a "modern" fixture. Bzzzzzzzzzzzzzzzzzt! E R R O R ! If the answer to the question above is yes, this suggests "Lew's wiring design" should be wired (using 12-3 THHN) with 2 parallel (pairs of) circuits with 4 fixtures wired on each row. Then if one of the fixtures went bad only two of them would go out (either the ones on L1 or the ones on L2 in a given row). Is this correct? Residential fixtures are wired in parallel, not series, Bill. _Always_. -- You can't wait for inspiration. You have to go after it with a club. --Jack London |
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Bill writes:
On 12/6/2010 11:01 AM, Bill wrote: On 12/6/2010 10:50 AM, Bill wrote: Someone suggested (I could not locate the post) that if I wanted quiet fluorescent lights, then I should look for those with an "A" rating. Putting that detail aside temporarily. What would be the practical differences between a "standard electronic ballast with 20% THD" and an "instant on electronic ballast with 10% THD"? Bill Continuing to research my question, evidently low THD is better for the components in the lighting system (capacitors, etc) and may provide lower cost in the form of the longer life for the system. Pitiful question: If 8 fluorescent fixtures are wired in a series, and the ballast in one of them fails, do all of the lights go out? Assume a "modern" fixture. Why would you ever wire them in series? Each ballast needs to be connected to the next in parallel when they're on the same circuit. Some two-lamp ballasts (usually older magnetic) will wire the lamps in series, and losing a single lamp (bulb) may cause the other bulb to not light. This is generally not a problem with electronic ballasts. If the answer to the question above is yes, this suggests "Lew's wiring design" should be wired (using 12-3 THHN) with 2 parallel (pairs of) There is no such thing a "12-3 THHN". The ballast in each fixture must be wired in parallel with respect to all other ballasts on the same circuit the same way one wires multiple incandescent fixtures on the same circuit. ----black------------+----------------+----------------+ | | | ballast1 ballast2 ballast3 | | | ----white------------+----------------+----------------+ scott |
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Mike Marlow wrote:
Hey - you got it! Though 8 circuits would be crazy. You're looking at maybe 2 circuits in your garage. Multiple switched runs, but all of them on 1 or 2 circuits. Thank you for working your way through my previous post. I know I still haven't mastered the jargon. "Switched" seems like an unlikely term for what I think of as a "split". Hopefully we're talking about the same thing. I've been saving "switching" for those things they put on the walls! :) To avoid "cycling the breakers", Lew advised running 12-3 from two 20 Amp breakers (it would not have occurred to me to do that). I'm thinking of this lighting as a 4 by 4 grid (or so), with rows 4' apart: L1 L2 L1 L2 L2 L1 L2 L1 L1 L2 L1 L2 L2 L1 L2 L1. The 2 hots each split at the beginning of row 1, going down row 1 and also to the beginning to row 2, similarly for common and ground, etc. Intuitively, I'd use 12-3 romex to the first box in the attic, exiting the box with 12-3 THHN for row 1 and row2 into the interior of the garage. The longer I think about it, the more connections I want to stuff into a junction box (but I have to consider the box capacity of course). It seems like a natural "4 (juntion) box" problem. I'm not yet sure where to locate the other junction boxes after the first. I've definitely made some progress in understanding this! 16 fixtures wired in parallel Without a wad of wires! Cool! Beautiful even! : ) Bill |
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"Bill" wrote You'll probably save $14 too! I'm considering purchasing about 15--and I want 'em quiet! : ) When I built my last computer, I used a fanless graphics card and tossed in an extra $100 for a quiet (decent quality) power supply. No hard drives either--SSD. Maybe having quiet is a lot like having a sharp Brad point drill... : ) You should have it so rough. I could never hear the quiet you mention. I have ringing in my ears so loud that a cell phone ringing is hard to hear over my ear's ringing. Take care of your hearing, out there. This crap is no fun. -- Jim in NC |
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Scott Lurndal wrote:
There is no such thing a "12-3 THHN". Someone else wrote "pull 12-3 w/ground THHN". Is that more acceptable (I understood what he was trying to tell me--2 hots, a common and a ground)? The ballast in each fixture must be wired in parallel with respect to all other ballasts on the same circuit the same way one wires multiple incandescent fixtures on the same circuit. ----black------------+----------------+----------------+ | | | ballast1 ballast2 ballast3 | | | ----white------------+----------------+----------------+ scott I think I could wire that using 2 wire connectors each connecting 4 wires, grounds extra. The picture is helpful. Thank you. Bill |
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J. Clarke wrote:
Taking a step back, this is equivalent to wiring 2 branch circuits each wiring 8 fixtures in parallel. Everything basically correct? That would be the way to do it if you want to be able to kill the power to one set and still have the other available. Yep, two light levels. The bigger the blade the more light I need. :) Bill |
Amount of lighting
On Mon, 06 Dec 2010 19:54:28 -0500, Nova wrote:
Larry Jaques wrote: snip Residential fixtures are wired in parallel, not series, Bill. _Always_. Not when my old neighbor wires them. Lights where in series, swith was parallel. He wondered why the circuit breaker tripped each time he turned the switch on. Pardon me. Let me correct the deficiency in my post, Yack. "WORKING/USABLE residential fixtures are wired in parallel, not series, Bill. _Always_." Better, oui? -- You can't wait for inspiration. You have to go after it with a club. --Jack London |
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On Mon, 06 Dec 2010 20:06:44 -0500, Bill wrote:
Scott Lurndal wrote: There is no such thing a "12-3 THHN". Right, it's 12ga THNN. One white (neutral) one black (hot), one bare (ground). 3 separate wires, if you're inside a wiremold run, for each lighting circuit. One piece of romex (for each circuit) if you're between top floor and ceiling. Someone else wrote "pull 12-3 w/ground THHN". Is that more acceptable (I understood what he was trying to tell me--2 hots, a common and a ground)? 4 separate wires if you're breaking out from the wiremold into the two circuits. The ballast in each fixture must be wired in parallel with respect to all other ballasts on the same circuit the same way one wires multiple incandescent fixtures on the same circuit. ----black------------+----------------+----------------+ | | | ballast1 ballast2 ballast3 | | | ----white------------+----------------+----------------+ scott I think I could wire that using 2 wire connectors each connecting 4 wires, grounds extra. The picture is helpful. Thank you. Haven't you bought a home wiring book yet, Bill? If not, do so. If so, try reading it, eh? ;) -- You can't wait for inspiration. You have to go after it with a club. --Jack London |
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Bill writes:
To avoid "cycling the breakers", Lew advised running 12-3 from two 20 Amp breakers (it would not have occurred to me to do that). I'm not sure what this means, but if you're running two 120v circuits using 12-3 from a pair of 20A breakers, make sure the breaker handles are tied together such that both trip if either one trips. scott |
Amount of lighting
Bill writes:
Scott Lurndal wrote: There is no such thing a "12-3 THHN". Someone else wrote "pull 12-3 w/ground THHN". Is that more acceptable (I understood what he was trying to tell me--2 hots, a common and a ground)? When wire is referred to with a hyphen (e.g. 12-3), that means that there are three AWG12 conductors encased in an outer jacket. Typically, such cables are type "NM" (non-metallic sheathed) or "UF" (underground feeder). w/G adds a non-jacketed conductor in the outer jacket that is designated the grounding conductor. Most XX-3 w/g cables include red, black, white and unjacketed conductors. THHN is a wire "type" code used for single conductors that are routed typically through some form of chase (electrometallic tubing (EMT) or nonmetallic tubing, wiremold raceway, etc.). THHN may not be used without an enclosing raceway of some form (note that if your light fixtures are mounted end-to-end and there is a nipple or length of EMT connecting them, then the fixtures themselves become a raceway and THHN is allowed from the head fixture through the rest in the row). scott |
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Scott Lurndal wrote:
writes: To avoid "cycling the breakers", Lew advised running 12-3 from two 20 Amp breakers (it would not have occurred to me to do that). I'm not sure what this means, but if you're running two 120v circuits using 12-3 from a pair of 20A breakers, make sure the breaker handles are tied together such that both trip if either one trips. scott Because??? |
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Larry Jaques wrote:
Haven't you bought a home wiring book yet, Bill? If not, do so. If so, try reading it, eh? ;) Will do. |
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Bill wrote:
Scott Lurndal wrote: There is no such thing a "12-3 THHN". Someone else wrote "pull 12-3 w/ground THHN". Is that more acceptable (I understood what he was trying to tell me--2 hots, a common and a ground)? That person simply mispoke - or does not understand. THHN is pulled as individual wires. -- -Mike- |
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wrote:
On 07 Dec 2010 03:36:02 GMT, (Scott Lurndal) wrote: writes: Scott Lurndal wrote: There is no such thing a "12-3 THHN". Someone else wrote "pull 12-3 w/ground THHN". Is that more acceptable (I understood what he was trying to tell me--2 hots, a common and a ground)? When wire is referred to with a hyphen (e.g. 12-3), that means that there are three AWG12 conductors encased in an outer jacket. Typically, such cables are type "NM" (non-metallic sheathed) or "UF" (underground feeder). w/G adds a non-jacketed conductor in the outer jacket that is designated the grounding conductor. Most XX-3 w/g cables include red, black, white and unjacketed conductors. THHN is a wire "type" code used for single conductors that are routed typically through some form of chase (electrometallic tubing (EMT) or nonmetallic tubing, wiremold raceway, etc.). THHN may not be used without an enclosing raceway of some form (note that if your light fixtures are mounted end-to-end and there is a nipple or length of EMT connecting them, then the fixtures themselves become a raceway and THHN is allowed from the head fixture through the rest in the row). scott And thhn in a raceway on a "split" circuit (2 breakers tied together - both sides of the service - 230 line to line) requires SEPARATE NEUTRALS for each circuit, while NMD for the same application shares the neutral. At least that was the requirement when we rewired the new office. Evidently for safety. You're less likely to find NMD on an office wall? JustGuessing, Bill |
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Mike Marlow wrote:
Bill wrote: Scott Lurndal wrote: There is no such thing a "12-3 THHN". Someone else wrote "pull 12-3 w/ground THHN". Is that more acceptable (I understood what he was trying to tell me--2 hots, a common and a ground)? That person simply mispoke - or does not understand. THHN is pulled as individual wires. No, he understands just fine (and we're going to pitz him oft again if we're not careful)! He has caused me to consider installing a shop pole and swapping out one of the lights on the outside of my garage shop for one of red or cherry! :) Bill |
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"Bill" wrote in message ... Scott Lurndal wrote: writes: To avoid "cycling the breakers", Lew advised running 12-3 from two 20 Amp breakers (it would not have occurred to me to do that). I'm not sure what this means, but if you're running two 120v circuits using 12-3 from a pair of 20A breakers, make sure the breaker handles are tied together such that both trip if either one trips. scott Because??? You do not want to have the possibility that one circuit has faulted and the other still is hot in the same enclosure. You could still have a hot circuit in there, when you think that it does not have juice to it. By connecting both together, if one trips, you are assured that they both have been shut off, and limit the possibility of getting a hold of a hot wire or hot energized light switch or light. -- Jim in NC |
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On Mon, 06 Dec 2010 23:17:59 -0500, Bill wrote:
Larry Jaques wrote: Haven't you bought a home wiring book yet, Bill? If not, do so. If so, try reading it, eh? ;) Will do. Which? HAR! -- You can't wait for inspiration. You have to go after it with a club. --Jack London |
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Larry Jaques wrote:
On Mon, 06 Dec 2010 23:17:59 -0500, wrote: Larry Jaques wrote: Haven't you bought a home wiring book yet, Bill? If not, do so. If so, try reading it, eh? ;) Will do. Which? HAR! Besides Stanley's book, which hasn't served me well in the past, I have a Better Home & Gardens, "Step-By-Step BASIC WIRING published in 1980, and a book I picked up this summer at Menard Inc: Step by Step Guide Book, Home Wiring (which has 50 pages of wiring diagrams). Unfortunately, I think most of the questions I have or will have concern the physical aspects rather than the logical aspects. Spent much of last evening reading about conduit (EMT). Spent too much time reading fluorescent light fixture specs... I can recite long cryptic model numbers from memory! : ) About the same as shopping for components for a computer. Bill |
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Lew Hodgett wrote:
BTW, in the future, if you want to work on your lighting system, either learn how to trouble shoot it hot or hire an electrician. Lew With 15 or 16 fixtures wired in parallel circuits it seems the most likely thing to malfunction is a fixture. Armed with a design schematic and a voltometer, I know how to test for the presence or absence of current. It's a pretty open system--compared to an automobile transmission, for example. Where does your concern lie? Regards, Bill |
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Lew Hodgett wrote:
Run #12 AWG, THHN wire from switches to fixtures as previously described. Grab a beer and enjoy looking at you new lighting system and the $1,000 it took to get it done. If you come in a few bucks under $1K, buy some brad point drills. You think maybe we should scale it back some? I was starting to get concerned what it could cost for the heating and air-conditioning to keep the paint-strippers satisfied! (Don't tell SWHMBO I said that). I'll have to sleep on it. My BS is still in the box, my DP is on order, and I don't have a TS. Not only that, some of my most creative interests lie in luthery rather than cabinet making, so I'm not positive I need so much ambient lighting (still there's a point to be made in not doing things "half way"..). My point is that what I affectionately refer to as my "shop" is not very advanced at this point in time--though it's electrical wiring puts it and I a mile ahead of where it and I were at the same time last year. You provided me with the most focused approach though, and I appreciate your advice, so I printed out your suggestions. As you know, I have a workbench or two to build too, and a birdhouse and some handplanes to make. And a math problem to solve too (a real stumper! ;) ). It's freezing outside tonight...good weather for design! $200 or $1000--it's "just a "car repair". As you know, one of the most valuable things is time... The "dreaming" though, that we all do I think, is one of the closest things to being a kid at Christmas time. The dreaming gets us through the trials and tribulations, no? Ho, Ho, Ho (was heard outside the stipple-ceiling'ed hore-house)! And to all a good nite! : ) Bill |
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In article , Bill
wrote: I'll have to sleep on it. My BS is still in the box, my DP is on order, and I don't have a TS. Not only that, some of my most creative interests lie in luthery rather than cabinet making, so I'm not positive I need so much ambient lighting Well, you may not need as much light over the whole shop, but you'll want a lot of bench lighting (easy to come by) for all the fiddly work that instruments require. I was amused with your comment in another post regarding "the bigger the blade, the more light I need" - I find it works the other way, actually; though the light may not need to be all over the shop for what you are doing with little blades. -- Cats, coffee, chocolate...vices to live by |
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Larry Jaques wrote:
On Mon, 06 Dec 2010 19:54:28 -0500, Nova wrote: Larry Jaques wrote: snip Residential fixtures are wired in parallel, not series, Bill. _Always_. Not when my old neighbor wires them. Lights where in series, swith was parallel. He wondered why the circuit breaker tripped each time he turned the switch on. Pardon me. Let me correct the deficiency in my post, Yack. "WORKING/USABLE residential fixtures are wired in parallel, not series, Bill. _Always_." Better, oui? -- You can't wait for inspiration. You have to go after it with a club. --Jack London Much better. ;-) -- Jack Novak Buffalo, NY - USA |
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Morgans wrote:
"Bill" wrote in message ... Scott Lurndal wrote: writes: To avoid "cycling the breakers", Lew advised running 12-3 from two 20 Amp breakers (it would not have occurred to me to do that). I'm not sure what this means, but if you're running two 120v circuits using 12-3 from a pair of 20A breakers, make sure the breaker handles are tied together such that both trip if either one trips. scott Because??? You do not want to have the possibility that one circuit has faulted and the other still is hot in the same enclosure. You could still have a hot circuit in there, when you think that it does not have juice to it. By connecting both together, if one trips, you are assured that they both have been shut off, and limit the possibility of getting a hold of a hot wire or hot energized light switch or light. The wiring arrangment using 12/3 for two feeds is called an "Edison Circuit". Because the two circuits share a common neutral there is a good chance that when one breaker trips the outlet/device affected can still have a live neutral, being back fed through a device plugged into the non-tripped circuit. This is the reason the two breakers should trip together. I know my local code requires it and I think it's specified by the NEC. See: http://www.phy.ornl.gov/divops/ESH/98-2.html -- Jack Novak Buffalo, NY - USA |
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On 12/7/2010 10:05 AM, Nova wrote:
Morgans wrote: "Bill" wrote in message ... Scott Lurndal wrote: writes: To avoid "cycling the breakers", Lew advised running 12-3 from two 20 Amp breakers (it would not have occurred to me to do that). I'm not sure what this means, but if you're running two 120v circuits using 12-3 from a pair of 20A breakers, make sure the breaker handles are tied together such that both trip if either one trips. scott Because??? You do not want to have the possibility that one circuit has faulted and the other still is hot in the same enclosure. You could still have a hot circuit in there, when you think that it does not have juice to it. By connecting both together, if one trips, you are assured that they both have been shut off, and limit the possibility of getting a hold of a hot wire or hot energized light switch or light. The wiring arrangment using 12/3 for two feeds is called an "Edison Circuit". Because the two circuits share a common neutral there is a good chance that when one breaker trips the outlet/device affected can still have a live neutral, being back fed through a device plugged into the non-tripped circuit. This is the reason the two breakers should trip together. I know my local code requires it and I think it's specified by the NEC. See: http://www.phy.ornl.gov/divops/ESH/98-2.html Thanks for the link. It leads one to think (and that's usually good!). Bill |
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Bill wrote in :
Yep, two light levels. The bigger the blade the more light I need. :) Bill You'll find this is a "V" shaped curve... The smaller the blade, the more light you'll need as well. Puckdropper -- Never teach your apprentice everything you know. |
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On 12/7/2010 10:05 AM, Nova wrote:
The wiring arrangment using 12/3 for two feeds is called an "Edison Circuit". Because the two circuits share a common neutral there is a good chance that when one breaker trips the outlet/device affected can still have a live neutral, being back fed through a device plugged into the non-tripped circuit. This is the reason the two breakers should trip together. I know my local code requires it and I think it's specified by the NEC. See: http://www.phy.ornl.gov/divops/ESH/98-2.html Then what's keeping all of the "live neutrals" from any of the other circuits in the panel from raising their evil heads at any time? -- The Ground (!), right? So, IF the former circuits are well-grounded, then it seems the "Edison's Circuit" issue will not be a problem. Of course, that's a crucial, "IF". Correct??? Regards, Bill |
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Bill wrote:
On 12/7/2010 10:05 AM, Nova wrote: The wiring arrangment using 12/3 for two feeds is called an "Edison Circuit". Because the two circuits share a common neutral there is a good chance that when one breaker trips the outlet/device affected can still have a live neutral, being back fed through a device plugged into the non-tripped circuit. This is the reason the two breakers should trip together. I know my local code requires it and I think it's specified by the NEC. See: http://www.phy.ornl.gov/divops/ESH/98-2.html Then what's keeping all of the "live neutrals" from any of the other circuits in the panel from raising their evil heads at any time? -- The Ground (!), right? So, IF the former circuits are well-grounded, then it seems the "Edison's Circuit" issue will not be a problem. Of course, that's a crucial, "IF". Correct??? Regards, Bill The problem arises is you break the neutral path abck to the box when servicing an outlet or device. The neutral may be hot even though the breaker for that branch has been switched off. -- Jack Novak Buffalo, NY - USA |
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In article ,
Scott Lurndal wrote: When wire is referred to with a hyphen (e.g. 12-3), that means that there are three AWG12 conductors encased in an outer jacket. Typically, such cables are type "NM" (non-metallic sheathed) or "UF" (underground feeder). w/G adds a non-jacketed conductor in the outer jacket that is designated the grounding conductor. Most XX-3 w/g cables include red, black, white and unjacketed conductors. THHN is a wire "type" code used for single conductors that are routed typically through some form of chase (electrometallic tubing (EMT) or nonmetallic tubing, wiremold raceway, etc.). THHN may not be used without an enclosing raceway of some form (note that if your light fixtures are mounted end-to-end and there is a nipple or length of EMT connecting them, then the fixtures themselves become a raceway and THHN is allowed from the head fixture through the rest in the row). Thanks for the clarification. Sitting here in the UK I'd been wondering what all your american abbreviations meant :-) -- Stuart Winsor Midland RISC OS show - Sat July 9th 2011 |
Amount of lighting
On 12/7/2010 12:33 PM, Nova wrote:
Bill wrote: On 12/7/2010 10:05 AM, Nova wrote: The wiring arrangment using 12/3 for two feeds is called an "Edison Circuit". Because the two circuits share a common neutral there is a good chance that when one breaker trips the outlet/device affected can still have a live neutral, being back fed through a device plugged into the non-tripped circuit. This is the reason the two breakers should trip together. I know my local code requires it and I think it's specified by the NEC. See: http://www.phy.ornl.gov/divops/ESH/98-2.html Then what's keeping all of the "live neutrals" from any of the other circuits in the panel from raising their evil heads at any time? -- The Ground (!), right? So, IF the former circuits are well-grounded, then it seems the "Edison's Circuit" issue will not be a problem. Of course, that's a crucial, "IF". Correct??? Regards, Bill The problem arises is you break the neutral path abck to the box when servicing an outlet or device. The neutral may be hot even though the breaker for that branch has been switched off. Thank you, I get it. It seems like an extra wire is a small price to pay to avoid this dilemma! And, if I ever get electrocuted, at least I might be able to figure out Why! If I got electrocuted and couldn't figure out why it would Pi$s me off! ; ) Bill |
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On Mon, 06 Dec 2010 23:02:40 -0500, Bill wrote:
Scott Lurndal wrote: writes: To avoid "cycling the breakers", Lew advised running 12-3 from two 20 Amp breakers (it would not have occurred to me to do that). I'm not sure what this means, but if you're running two 120v circuits using 12-3 from a pair of 20A breakers, make sure the breaker handles are tied together such that both trip if either one trips. scott Because??? Because 1) - it is code. 2) if one circuit trips and you assume the wire is "dead" you could be - the black could be dead, and the red live, and a lifted neutral (which is common to both) would be LIVE. |
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