Replies

1. 
   BrianDerr | Oct 31, 2007 08:33am | #1

   It seems that many 'heayy duty' tools come with 14 or even 16 guage lead cords. I'm guessing that this is OK so long as the run is short so as to allow for a minimum of voltage drop. As far as the smaller guage wires developing excess heat I wonder if it is fine as long as the difference is only within the range we are talking about. Any elecrticians out there? I really would like to know how much of a danger there is in mixing wire guages in 10, 12, and 14 guage circuits, such as in pigtailing off to receps and mixing lighting and recep ciircuits.

1. 
   MikeHennessy | Oct 31, 2007 02:09pm | #3

   Not an electrician, and this is probably an oversimplification, but, per code . . .

   You can use a mixture of wire guages in a circuit, so long as the breaker protecting the circuit is rated for the smallest wire in the circuit -- pigtails included. In your example, you'd need a 15A breaker even if all but 6" of wire was 10 ga., since there is some #14 in there. (This may come up in practice where, e.g., you want to run a 15A circuit, but the run is long, so you use #12 to limit the drop.)

   There is no problem in mixing lighting and recepticle circuits, so long as the circuit is properly protected with an appropriately-sized breaker. The thing that surprises a lot of folks is that you are allowed to put a 15A recepticle on a 20A circuit -- if it is not the only one on the circuit. The logic there is, as far as I can tell, that the whole current drain on the circuit won't be from any single outlet.

   Mike HennessyPittsburgh, PA

   Edited 10/31/2007 7:10 am ET by MikeHennessy

1. 
   tinkerer2 | Nov 01, 2007 07:11am | #9

   "You can use a mixture of wire gauges in a circuit so long as the breaker protecting the circuit is rated for the smallest wire in the circuit."

        A variation of this rule is or was that a #14 switch wire may be used when wiring a single light on a  circuit protected by a twenty ampere breaker. 

1. 
   MikeHennessy | Nov 01, 2007 08:32pm | #10

   Didn't know that -- one more useful piece of info in my bag-o-tricks.

   Thanks!

   Mike HennessyPittsburgh, PA

2. 
   MikeHennessy | Oct 31, 2007 02:00pm | #2

   I've always wondered about cord reels in general. If you run wires closely packed, you need to de-rate them due to the heat build-up. I would think that if you ran 20A through 50' of #12 that was wound tightly on a reel, you could really generate some BTUs! It may be that this unit is really only good for 15A in use -- thus the #14 lead. The #12 is used in the reel because it must be de-rated since it's on a roll. 

   Just a guess.

   The unit's current rating must be marked somewhere on the unit or the packaging. If you can find it, let us know what it is.

   Mike Hennessy
   Pittsburgh, PA

1. 
   Jfrostjr | Oct 31, 2007 03:49pm | #4

   Mike,I've wondered the same thing but have used my cord reel for years with no problems.I might only extend 3'-4', which leaves a lot of wire in the reel container. No problem. I use it for my 'hand' power tools - routers, belt sander, jig saw etc.Frosty"I sometimes think we consider the good fortune of the early bird and overlook the bad fortune of the early worm." FDR - 1922

2. 
   ttttaqw | Oct 31, 2007 04:53pm | #5

   The box and reel do say 15A so I guess I should have caught that. It sounds like what most replies are saying is that even if it were all 12awg, it would still have a 15A rating due to the tightly wound wire.

1. 
   HWG | Oct 31, 2007 07:57pm | #6

   I would expect a "12 gauge" reel to have nothing less than 12 ga anywhere in the circuit -- just my thought.Woody

3. 
   colebearanimals | Oct 31, 2007 09:35pm | #7

    

             Is that lead cord in question stranded? I'm sure it's not solid wire.

             I've heard that stranded copper has the same current capacity as the next larger size in solid copper. If this is true then your # 14 should be good?

             Any experts out there?

                                                               Paul

4. 
   BarryO | Nov 01, 2007 02:10am | #8

   I have two of those cord reels from Grizzly.  I think they're fantastic for their intended use; i.e., for convenience outlets for portable tools.  They're great for things like routers, sanders, etc.  'even for those times I pull the miter saw out into the middle of the shop for rough crosscutting of long boards.  'wouldn't do without 'em.

   That said, I wouldn't use one for powering 'large power tools'.  Code says extension cords aren't supposed to be used as long-term replacements for building wiring, so I wouldn't recommend one for use with a stationary tool; even if you do use one, it's good practice with heavy-current-draw equipment to keep the cord's length as short as practical.  Other points:

   -- As with any other piece of electrical equipment, the reel should always be used in accordance with its UL listing.  The UL label on these particular reels specifies a maximum current of 15A; don't use it for more than this.  Folks get into trouble with cord reels when they use lightweight-gauge reels (lighter than the Grizzly reels in question) at currents above their Labelling, and make it worse by leavling most of the cord on the reel.  The combination of current draw they were never designed nor tested for, plus the concentrated heating in the wound-up reel, can lead to troube.

   --At 15A, that 4-ft. length of 14AWG is contributing neglible additional voltage drop.  You're already getting almost 2 volts of voltage drop from the 40 feet of 12AWG on the reel.  The 4-ft. 14AWG stub is only contributing an additional 0.3 volts, versus 0.2 volts if it was 12AWG instead.  How much voltage drop you may get at 20A is immaterial, since UL says you're not supposed to use this at 20A.

   --Some of the responses here a re-stating the oft-heard (on the internet) statement that "14 gauge is only good for 15 amps, and 12 gauge is only good for 20 amps", with the assertation that this is true for all wire types, in all circumstances.  It's not.  These may be the ampacity limits in the section of the Code most commonly applied to branch circuit wiring, but branch circuit ratings are not applicable to other wiring applications, and these limits don't even apply to branch circuits on all cases.  In the case of the cord reels, the applicable rating is whatever UL tested to, and what UL has determined is safe for the reel in question.  Also, since the UL label doesn't say any different, and this this reel comes with a 15A plug, it is safe to use on any branch circuit on which  receptacles that mate with this plug are permitted; i.e., it can be plugged into receptacles on either 15A or 20A branch circuits.

   
   

   ---

   Edited 10/31/2007 7:14 pm by BarryO

1. 
   BrianDerr | Nov 02, 2007 08:31am | #11

   extension cords are typically the same guage as house wiring. I think the code is not concerned with voltage drop so much as other hazards like tripping on the cords, damage, being partially plugged in, etc.
   You know in the owners manuals, where it says how much cord you ought to run a tool on? They never say to include the distance the receptical is from the panel . . . or the panel from the transformer.

1. 
   BarryO | Nov 06, 2007 10:10pm | #12

   extension cords are typically the same guage as house wiring.

   Most aren't.    Just look in the extension cord aisle in Home Depot.  Most are 18 gauge; the "heavy duty" ones that people are tempted to use with power tools are usually 16, maybe 14, gauge.    Yes you can buy heavier, but the tool manufacturers are worried about the people that don't.

   You know in the owners manuals, where it says how much cord you ought to run a tool on? They never say to include the distance the receptical is from the panel . . . or the panel from the transformer.

   They don't have to.  While there is no normative reference in the NEC to voltage drop, there are informative guidelines that feeders should be limited to no more than 2% voltage drop, and branch circuits are limited to no more than 3%, for a worst-case drop of 5% at maximum load.  Add this to the line voltage tolerance limits in the ANSI C.84-1 standard, and the tool vendor knows what voltage range they should expect their tools to experience in normal conditions, and over which they should be designed to operate.   The clauses in the owners manuals concerning extension cord lengths are intended not to mess this up.

1. 
   BrianDerr | Nov 07, 2007 05:52am | #13

   I am a pro carpenter and only use 12 and 10 guage cords. I guess many homeowners might be tempted to buy cheap cords. As to your second point (where did I learn this? I thought it was common knowledge), it seem to me that anything over 2% is recommended against in general for what we think of as power tool use. If your already down to 3% on a branch circuit and you go to plug your tablesaw in on a cord, well, I wouldn't want to plug in my saw to begin with! I do not disagree with your comments about feeders, but, for the cords I use, branch circuits equal exension cords. I also do not disagree that some manufacturers take this into account as a percentage perhaps in their guidelines but every situation is unique. Think we killed this ol' horse yet? Take care.

5. 
   PaulMassachusetts | Nov 07, 2007 06:20am | #14

   You ccan calculate voltage drop since  Volts=Resistance(ohms)   x Current(amps) 

   I got the resistance in ohms per foot from the web:

   #12  .00187
   #14  .00297
   #16  .00473

   A ten foot #14 cord with 15 amps throuh it would have:

    .00297 ohms per ft  x  10 ft  x   15 amps=   Volts dropped along the cord=0.45 volts

   That means a 20 foot cord would (double the ten foot length) drop about 0.9 volts.  You can do a quick calculation with other size wires. This gets more complicated because depending on the type machine a few volts might make a difference and on another machine it would not matter much. Don't forget also that there may be a few volts drop from the breaker box to the plug outlet. .