electrician put 12 gauge wire on 20A breaker???
jaansu
13 years ago
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btharmy
13 years agokudzu9
13 years agoRelated Discussions
14 or 12 gauge wire in remodel ?
Comments (22)I ran across this thread while searching for some info about14 and 12 gauge wire, and I was surprised by the different opinions. I'm not an electrician, though I've wired AC and DC circuits since I was a kid. A small bit of basic electromagnetism will help solve some of the things discussed here, I'll make a few points with regard to these wires... First, the power dissipated in a length or wire is directly proportional to the current squared and its total resistance. Resistance in a wire is directly proportional to the resistivity of the material its made of, the length of wire and inversely proportional to the cross sectional area of the wire. The resistivity of copper is roughly 1.68*10^-8 ohm-meters. From the description above and due to the conservation of charge and current, I would state that regardless of the load of distance of wire, each foot length of X gauge wire with N amps of current dissipates the same power irregardless of the total length of the wire. So the power used due to the resistance in the wire per unit length is the same no matter how much load is hooked to the wire. Using the resistance of a wire, you only need Ohms Law to calculate all the other properties described in this thread. Using a base of 46 meters (roughly 151 ft, SI units are need for easy calculations), I'll show some calculations of voltage drop, etc. resistivity of copper (rho), p - 1.68*10^-8 ohm-meters length, L - 46 m cross sectional area of 14 ga, A - 2.08*10^-6 m^2 Note that when you multiply the first two and divide by area, the meter units cancel and you are left with only ohms, resistance. voltage drop for 14 ga over 46 meters at 15 amps: Resistance, R = (pL)/A = .372 ohms Voltage drop (Ohm's Law) = R * I, at I = 15 amps, V drop = 5.57 V voltage drop for 12 ga over 46 meters at 15 amps: Resistance = .233 ohms Voltage drop = 3.50 V voltage drop for 12 ga over 46 meters at 20 amps: Resistance = .233 ohms Voltage drop = 4.67 V So there it is. Relative to its accepted current limit, 12 gauge has less voltage drop. But 14 ga still is within the NEC standards of You can use some algebra on the formulas above and solve for a maximum length based on a 6 volt drop. 6 = (pLI)/A => Max length L = 6A/pI Max length for 14 gauge @ 15 amps: 49.52 m => 162.4 ft Max length for 12 gauge @ 15 amps: 78.81 m => 258.5 ft Max length for 12 gauge @ 20 amps: 59.11 m => 193.9 ft Note: these are based off pure copper resistivity, any impurity in the copper used in wiring would likely cause more resistance....See MoreRunning a 20A circuit on two parallel wires gauged 15A
Comments (21)I know who the professionals in here are. I've also been using this forum for over five years. You, petey_racer, also know who's who. I don't know how long you've been here. I think you're new since my release from MSP. davidro1 probably did not. So "a bunch of people" very vaguely told him, without explanation, that he could not do it. Nobody said whether it wouldn't work, or whether it was a code violation, or whether they had any basis to their statement. When someone I don't know claims, very vaguely, that something I have asked will not work, I believe I am entitled to some semblance of a hint as to what their statement is based on. Yes, if someone with valid qualifications tells me no, they are probably right, but I still might want to understand why - and in any case, I should not be required to assume that anybody who replies to me in a forum I'm not a regular of must be a professional. It could very well be another person with even less knowledge/qualification than myself. If I asked a question, and you gave me a vague answer ("no"), I too would expect more. It is not fair to jump down someone's throat for wanting to understand an answer, and there is nothing wrong with QUESTIONING an answer from an unknown (TO THE ASKER) source. OP: Can I do this? REG1: No REG2: No REG3: Maybe RANDOM: No OP: Maybe? REG1: No, now get the hell out. Way to build a community. "Here's your answer, short and sweet, now go away."...See More12 gauge vs 14 gauge house wiring
Comments (15)"My main point is that you don't know what is going to be plugged into any outlet. I just don't see running #14 anywhere that will include an outlet. " I get your point, but I disagree. "I like for my lights not to dim when someone runs a hairdryer in their bedroom or runs the vacuum. " My own home is wired with all #12. I STILL sometimes get dimming when an A/C or the refer kick on. After doing this work for over 25 years I know this can be a normal occurrence. "And the carpet cleaner isn't continuous, but it does put you just a few amps away from your rated load. " So??? " In my own home, I may plug the saw or air compressor into any outlet - depending on where I'm working. " OK, but this is an extremely rare thing, and even then, I have been on MANY a job where this is happening with NO ill effects other than maybe the odd tripped breaker due to running two heavy loads simultaneously. "Yes, I've seen lots of overheated connections on lighter gauge wiring - particularly when someone is using a space heater. I see it mostly when the push in connections are used on outlets. " This is the the fault of the connection, NOT the wire size. Fact....See MoreWhat is the extra cost of 924' of 20A wire?
Comments (1)You can figure the price of 12/2 w ground yourself. It's commonly sold in 250' rolls. Just check on 1000'. Re: Long wire - voltage drop does figure into the design of the circuit. The person familiar with your application can determine if it's appropriate to upsize the wire to limit voltage drop over that length....See Morejaansu
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