# 15 or 20 Amp

The designer has no control over what a user will plug into a circuit with receptacles on it. That is the reason for 240.4(D) in the first place. I am not the one who brought up the bad breaker idea. I just pointed out when the O/C device doesn't operate you are looking at the possibility of drawing available fault current.
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Careful here. You can't use a 20A breaker unless _everything_ leading to the plug and the plug itself is rated at 20A. That means using 12-guage wire and a 20A rated plug (it has one prong socket that looks like a T).
If you have have more than one outlet on that breaker, they must _all_ be rated at 20A and _all_ wire connecting them must be 12-guage.
You're probably better off with two 15A breakers. You can use 14-3 wire to run two circuits through one cable as long as each of the hot wires is on a different phase. With this set-up, usually all top plugs are on one circuit and all bottom plugs are on the other making it easier for a person plugging things in to balance the load. Of course, tripping one will necessarily trip the other since it is required to have both trip together.
I got a "Simplified Electrical Code" book from Home Depot before I did my work. It's really quite easy, but there are a lot of requirements. I have 240A (at 120V) coming in to my kitchen -- I have only 200A (at 120V) service to my house! But that's code for a kitchen...
And whatever you do... Get a permit and get it inspected!!! It cost me \$140 for a permit for my kitchen, including both inspections (one "rough-in" before the drywall went up and one when it was all complete). If you ever had a fire and there was even the posibility it had to do with uninspected work, your insurance company could refuse to pay.

Very true, but that's not the problem of the breaker. The breaker is designed to protect the parts of the circuit that are hidden within the structure of the house (i.e. wiring and outlets). If you plug a 1/4 watt 10 ohm resitor in to an outlet, you're perfectly within the limits of the circuit, but I guarantee that you'll see some nice fireworks from the resistor.
Anybody know what guage Christmas light wire is? Probably 16-gauge stranded, good for 10A, as I recall.
Brian ( snipped-for-privacy@precidia.com )
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wrote:

Which is why I specifically said: "If you can, check the temperature along the length of the light strings, as well as the house wiring."
The wiring in the wall could get quite hot without tripping the breaker. It's not common, but it does happen, and once is enough to kill somebody.
BB
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wrote:

Unless you are specifically know that specific receptacle is going to need to be rated 20 amps, you use a 15 amp receptacle.
Just incase you want to look it up: http://www.urlbee.com?358 last question, references the table on page 70-56
hth,

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This "15 amp receptacle" thing comes up about once a week around here. For the record. all receptacles listed in the US are 20a rated for feed through. It is only the individual socket that is 15a rated on a NEMA 5-15 and that corresponds to the 15a plug that will fit in it. As long as you have more than one outlet you can put a 15a on a 20a circuit. A standard duplex receptacle is TWO outlets.
The split wired kitchen receptacle thing is in Canada, not the US. I believe they also have the rule about 15a receptacles NOT being on 20a circuits. Maybe we should always preface our comments with NEC or CEC.
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If they're rated for 20A feed-through, then that's the rating that matters since a single appliance cannot draw more than 15A without having a different plug configuration.

It's the code in Ontario; I can't say for sure what it is in the rest of Canada, but it's probably the same since I believe Ontario pretty much copies that federal recommendations. It's always a good idea to check your local building codes, though, because there are differences.
Brian ( snipped-for-privacy@precidia.com )
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BinaryBillTheSailor@Sea++.com wrote:

Whoee! Guess I don't really have to say anything after looking at the comments that follow in this thread. Bill, you are a study!
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On Wed, 24 Nov 2004 07:04:17 GMT, "George E. Cawthon"

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I will throw in my \$.02 worth here.
I currently have a "data center" in one of my bedrooms. In there I run a number of machines, and all on a 15A circuit. I have had all the following up and running at the same time:
1 dual processor Compaq server(8A) with 4 internal disk drives and two attached storage arrays (6A each). 1 quad processor Compaq server(8A) with 4 internal disk drives and one attached storage array(6A). 1 homebuilt computer system with two 800Mhz processors, three internal disk drives, two external disk drives, and a 20" monitor. I'm not sure what the power requirements are, but the monitor says 3A. Can probably figure 6A for the whole thing. 1 HP Laserjet 4M+ printer (7.6A) with duplex attachement. That would certainly be mostly for warm-up, but I would imagine it would still draw a couple of amps while printing. 1 Epson Color dot matrix printer 1 fax machine. Plus my DSL modem, router, network switch, and maybe a couple of lights. (All Amp ratings are directly off of the labels on the back of the equipment.)
This 15 amp circuit runs all of this just fine. It looks like the circuit is way over subscribed, but the ampere ratings are maximums which will **most likely** only come into play when the equipment is initially turned on. I left all of this equipment up and running for a few days a while back and there was no problem. No circuit breaker tripping, No smell of burning plastic. :-) But this is just about the limit. I fired up another computer which is pretty much a "normal" 2.4Ghz machine with a 21" monitor, tape drive, and scanner, and the circuit breaker tripped after a couple of hours.
I'm sure that if I came in and just threw a switch and had everything all come on at the same time, the CB would just laugh at me and say "uh, NO!", but everything gets paced. I have it set up so that when I turn on a machine, the monitor comes on first, then the external storage array (if there is one), then the computer. While the computers with attached storage arrays are coming up, then the disk drives in the arrays will be spun up one at a time. Once the computer is fully booted then I can go to the next system.
The bottom line of all this is that if you just have one computer system, even if it is on steroids, 15A will most likely be fine.
wrote:

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What happens when the power company "throws the switch"?
The real question is if you are running a NEW circuit, would you run 15 or 20. Since the cost difference is negligible why wouldn't you run the 20? The 15a breaker in your outlet/surge strip will give you that 15a protection people wanted but you can still have some excess capacity at the wall for other equipment.
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Greg wrote:

I have no idea what the difference in cost would be if an electrician did the work, but the cost difference between 14 and 12 gauge wire is really minimal. I would never wire anything with less than 12 gauge wire even if using a 15 A breaker. In fact, I would use 10 gauge for any long runs or if I anticipated a large amperage motor being used; the only problem is that 10 gauge tends to be a bitch to work with. Newer vacuums draw at least 12 amps and can lower the voltage sufficiently to dim lights. Compounding the voltage drop problem is they have really long cords of fairly low gauge and that can't be good for the motor. As a factual point, our Hoover is rated at 12 A but the appliance cord is stamped 17/2. Hoover must know something different, because the appliance cord should be a minimum of 14 gauge for a 3 percent voltage drop at the motor.
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On Wed, 24 Nov 2004 07:36:09 GMT, "George E. Cawthon"

IMHO:
Some very good points about preventing voltage drop, but having the attitude of always going with a higher gauge wire is very costly and not necessary. 14 awg wire is 'rated' for 20 amps(even higher depending on what temp you calc for, I know I must use the 60C per NEC), but being a small guage wire it falles under NEC 240.4(d) saying I can only use 14 awg for a 15A circuit( 25% cut).
So, the breaker is the most limiting device in the circuit and now it makes no sense to just spend money on the cable by going to a higher size. Infact it's already built into the code, instead of using 14awg for a 20a branch, you are forced to use 12awg, so why further restrict your self to using 12 awg for a 15a if nothing else tells you to do so?
What I woudl do if I had to money to burn, run an isolated ground, and install tvss's to protect the computer equipment.
later,
tom @ URLBee.com
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Vacuum cleaner cord has it's own listing category (type SVxx) and the motor/cord assembly is an engineered system. The voltage drop is taken into account when they design a vacuum. In fact you would violate the listing if you did put a 14 ga cord on one. It really has nothing to do with what we are talking about here
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Hmmm... 17GA wire has a resistance of about 5ohms/1000ft(*). Assuming a 10ft vaccum cord, you have have about 0.1ohm of total resistance.
Thus, you would dissipate about 12A*12A*0.1ohm = 14.4Watts of heat during operation (over the length of the cord) and have a voltage drop at the motor of 12A*0.1ohm = 1.2V. 14GA wire has about 1/2 the resistance and thus would dissipate 1/2 the amount of heat and 1/2 the voltage drop.
Would a 0.6V change in voltage at the motor really violate the listing?
(*) I'm assuming that the rating of 5ohm/1000ft is for single conductor and not the "round trip" (i.e. double) distance. If I'm wrong, cut the calculated numbers in half.
Brian ( snipped-for-privacy@precidia.com )
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Any modification whatsoever invalidates the listing. It's no longer "as tested". Also consider that all wire is not made of the same material, and two wires of same gauge may have quite different specs as far as resistance. The type of configuration, flexibility, flex fatigue, and the cover also make a difference.
BB

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how does the cover make a differance?
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On 24 Nov 2004 20:44:34 GMT, snipped-for-privacy@aol.com (Playintennis5274) wrote:

Differences in heat dissapation.
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True legally but not practically. Any design for home use has to assume variances in voltage well beyond the 0.6V range, so such a modification would certainly not exceed the design specifications.
Brian ( snipped-for-privacy@precidia.com )
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Regardless of personally lax attitudes about it, ANY modifications violate the listing, and for practical purposes, makes all previous testing and measurement completely worthless. Legal? If there is a fire or accident involving the altered device, expect the lawyers and insurance companies to focus all their attentions and energy on the fact it was modiffied, regardles if the modification actually played any part whatsoever.
BB
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BinaryBillTheSailor@Sea++.com wrote:

That's what I said. It's true legally, but not practically. Perhaps you should read what I wrote instead of just flaming.
Brian ( snipped-for-privacy@precidia.com )
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