Wire size

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  #1  
Old 08-28-07, 10:11 AM
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Wire size

I ran a new 20-amp circuit with 12/2+G Romex. At the end of this circuit I would like to tie in a swag light that is wired with 14/2+G. The only load on this branch would be the swag light with a bulb not to exceed 100 watt. Is the 14/2 safe, or do I need to replace it with 12/2? PS the total load on the circuit should be well within the 20-amp circut limits. Thanks
 
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  #2  
Old 08-28-07, 11:02 AM
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You need to change the wire to #12 or the breaker to 15a. Changing to #12 wire is best practice otherwise in the future someone seeing #12 at the box might change the breaker back to 20a.
 
  #3  
Old 08-28-07, 01:20 PM
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I wasn't quite sure what the 14/2 was referring to. If you want to use 14/2 NM (eg: Romex) on a 20A circuit, as Ray said, it can't be done.

If the 14/2 is really the lamp cord (zip cord) that's part of the fixture you are wiring - AND the 14/2 is part of the UL listed fixture (not added on afterwards), then you're okay. Most light fixtures can get away with using smaller wire because the rules for UL listing are slightly different.
 
  #4  
Old 08-28-07, 03:46 PM
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I submit for consideration and discussion Art 240.5- Protection of -- Fixture wires.

(B) (2) reads----- "Fixture wire shall be permitted to be tapped to ( a Branch-Circuit conductor ) in accordance with the following----- (1) 20 amp Branch-Circuits---- #18 AWG, up to 50 ft of run lenth"

We may presume a tap of #18 wire that extends to 50 ft would require an approved Wiring Method between the point of the tap and the fixture connection. If STV extends , say, 20 ft of 14/2 NM cable from the box where the 14/2 "taps-off" the #12 conductors to the fixture-connection, it would appear to be Code-compliant with the understanding that the load is a "fixed-load" that limits the current in the tap-conductors to the ampacity of the fixture-wire..
 
  #5  
Old 08-30-07, 09:25 AM
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Wire Size

What will happen if you use different gauge? Example, connecting #12 to existing #14.
 
  #6  
Old 08-30-07, 11:03 AM
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There is no problem because the ampacity of the #12 conductor exceeds the rating of the 15 amp breaker which limits the current to 15 amps.

The "hydraulic anology" ? ---- You need to run a 1" water line for a water-flow of X GPM's for a distance of X feet , allowing for a pressure- loss in the line of 3% . If you run X/2 ft of 1" from the "source" ( the half-way point) and then finish the run with 1 -1/4 " (because you had these lineal feet of 1" & 1-1/4 "on hand" ) , the pressure loss is lowered.

If ( for some reason )you had to extend wiring from a circuit wired with #14 , and extending the wiring with #14 for the given distance would result in excessive voltage-drop, you would connect a larger gauge wire to the #14. It's still a 15 amp circuit, because the rating of the breaker, not the wire gauge, determines the Branch- Circuit rating. That's why a 15-amp Branch-Circuit can't always be converted into a 20 amp B-C simply because a #12 wire connects to a 15 amp breaker.
 
  #7  
Old 08-30-07, 12:48 PM
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The problem is that "fixture wire" is a code-defined type of wire. Type NM-B is NOT fixture wire.

Check Article 402.
 
  #8  
Old 08-30-07, 03:21 PM
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I think everyone is missing Pattbaa's point about a tap using nm-b 14 from nm-b 12. The run of 14 is not or does not have to be fixture wire rated and you do not have to use a 15 amp breaker. We do this all the time in commercial.
Consider running 300 feet to a bank of eleven 115 volt fans rated 1.5 amps. Total load is 16.5 amps. I would run #8 thhn in conduit to hold the voltage drop to a point where I then might step down to #12 awg for the remainder of the run. At each fan I would use 14/2 as a switch loop because the load on the 14 is fixed by the fan. I would still use a 20 amp breaker so that the branch circuit rating can handle the load of all the fans running at the same time. Conductors sized to art. 430. Same principle with the light only there may be a temperature rating consideration for the branch circuit conductors. But thhn and nm-b can connect to any luminaire fixture wire I can think of.

Roger
 
  #9  
Old 08-30-07, 06:04 PM
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Taps have their own special rules. I am well aware of the use of taps in commercial and industrial environments yet I question the wisdom of discussing them in a forum that is geared to the DIYer working on his residence.
 
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Old 08-30-07, 06:07 PM
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fans, motors or lights?

doesn't table 430 deal with motors, typically demanding local thermal or wired OC protection? The poster is talking a lamp, which is not going to have any seperate OCP. I don't think table 430 applies, and you need to either not use 14awg or use 15a OCP device.
 
  #11  
Old 08-30-07, 06:20 PM
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You can only tap a conductor that way if it's I believe 18 inches or less. This is pretty much so you can add a little pull chain fixture anywhere there is a line running. The answer is no, it needs to be 12 gauge or a 15 amp breaker. Just use 12 gauge. I try to wire entire houses in 12 gauge except for the dedicated 15 amp circuits, such as a garbage disposal. If its 18 inches or under, I believe you can even tap a 14 ga off of a 6 gauge no matter what the ampacity is. These are the very limited guidlines of the tap rules in the nec.
 
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Old 08-30-07, 06:21 PM
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Yes, Article 430 applies to motors and in the example cited by Roger 430 may indeed be the applicable article.

In Article 430 the circuit breaker at the source is for short-circuit protection and the motor will have overload protection provided by the motor starter.

Still, in my opinion, these are not appropriate points for discussion regarding the original question posed by a DIYer working within his residence. They are appropriate for a professional electrician working in an industrial or commercial building.
 
  #13  
Old 08-30-07, 11:18 PM
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Furd:

Sit down I'm going to say something that you won't believe....."I agree with you".

Pattbaa asked for discussion. So I discussed. Then gave a different example other than lights... but if you wish change the fans to lights you just don't apply 430 and 430.52 or 430.53 and stay in the world of luminaire fixture you must also be aware of the definition a branch circuit conductor as defined by the NEC.

A switch leg tap using # 14 awg from a branch circuit of #12 is allowed but it is still part of the branch circuit and 240.4 applies.. more accurately 240.4(d). Since the 14 awg by defintion is a branch circuit conductor the only way this switch leg tap complies is if we protect the branch circuit with a 15 amp breaker not a 20 amp breaker. Tap conductors of 14 awg (pigtails) to a receptacle on a 20 amp branch circuit are not allowed period.

Now looking back on my first post I made an error in stating the breaker does not need to be 15 amp this was incorrect. It does need to be 15 amp. So gotta eat a little crow on that one.

I gave the fan motor example to show where this situation can occur and be compliant.

Roger
 
  #14  
Old 08-31-07, 11:45 AM
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A #14 conductor connects to a #12 conductor. The #14 must be considered a "tap" conductor , not a Branch-Circuit Conductor, because it has an ampacity of less than the conductor it connects to.

The #12 conductor at the connection-point is joined to the wiring that extends from the 20 amp circuit-breaker, so the #12 at the connection-point is "The Branch-Circuit Conductor.

The Code permits tapping #18 "Fixture Wire" to a #12 conductor and then extending from the tap-point to a fixture not more than 50 ft away.

The obvious intent of the Code is that the connected-load, the fixture, is a "fixed-load" that limits the current in the tap conductor to the ampacity of the #18 wire.

STV wants to know if he can connect a 1-amp fixture-load to a #12 conductor via a #18 fixture wire to a #14 conductor , which is the "tap" conductor of the #12. Since the Code permits a tap of #18 off a #12 for a distance of 50 ft, I consider this to be Code-compliant.
 
  #15  
Old 08-31-07, 01:00 PM
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Patt:

IMO anything connected to the 12 that is not the fixture wire or fixture wire rated (nec stops here) of the luminiare is a branch circuit conductor by definition of branch circuit by the NEC...Conductors between the final over current device and the outlet(s). I think you have to apply the over current rules for small conductors to your example.

I'll concede that I'm not real sure on this one but I don't believe it would be allowed. It would not be allowed for recessed cans.

Roger
 
  #16  
Old 08-31-07, 01:51 PM
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Originally Posted by PATTBAA View Post
Since the Code permits a tap of #18 off a #12 for a distance of 50 ft, I consider this to be Code-compliant.
I interpret this as the number 18 being "fixture wire" which is like lampcord and part of the light assembly. Not something that someone would slice off of in the future (well, then again, people do strange things). The number 14 is non metallic sheathed cable, which is not fixture wire nor part of the assembly. It is something that someone might throw a junction box in and splice off of.
 
  #17  
Old 08-31-07, 05:51 PM
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PATTBAA wrote:

"STV wants to know if he can connect a 1-amp fixture-load to a #12 conductor via a #18 fixture wire to a #14 conductor , which is the "tap" conductor of the #12. Since the Code permits a tap of #18 off a #12 for a distance of 50 ft, I consider this to be Code-compliant."

No, stvdlf stated that he wanted to "tie in a swag light that is wired with 14/2+G." to a circuit wired with 12/2+G Romex (one must assume that he meant 12-2/g type NM-B cable) with a 20 ampere OCPD.

He (she?) NEVER mentioned using "fixture wire" for this connection.

I have never seen any single-bulb swag light fixture that was factory wired with 14-2/g cable. Most likely that swag lamp is wired with a "listed fixture wire" of something much less than number 14 conductors. Therefore the logical assumption is that the stvdlf desires to run a number 14 type NM-B cable assembly between the new 20 ampere circuit and the point where the swag lamp's fixture wire is terminated.

Since as far as we know this unknown type of "14/2+G" cable is not "fixture wire" as defined by the NEC your statement that "The Code permits tapping #18 "Fixture wire" to a #12 conductor..." is not applicable. As I stated previously, "fixture wire" is a specific code-defined type of wire.

The wire that is factory connected to a standard base light fixture that connects to the circuit conductors is fixture wire. The wire that is factory connected to the ballast of a fluorescent light assembly is fixture wire. The wire from the lamp base in a swag lamp that follows the suspension to the connection box is fixture wire. Type NM cable is NOT fixture wire.

I have seen many 1,000 foot spools of "fixture wire" and have run a fair amount of it myself. It is commonly used in EMCS (Energy Management and Control Systems) where it is run according to Class One rules and often occupies wireways with power circuits of various voltages. This wire must always be run through raceway and is not code-approved for "open" wiring. I have NEVER seen code-designated fixture wire sold at any retail outlet.

Again I refer you to Article 402.
 
  #18  
Old 08-31-07, 06:29 PM
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let's make this a little easier

to the original poster. make sure all the interior wall wiring is 12awg on this entire circuit. This will address the issue of Code compliant.

the lamp already uses 18awg inside the chain, etc, very likely SPT1 or whatever. We are going to assume this is UL listed and this wire is intact, per manufacturer of the lamp.

You actually asked about "safer", which is subject to opinion and lets not go there.
 
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