New Proposal - NEC Table 300.19(A)

[erickench]

Hi Guys, okay I'm gonna submit a few proposals for the 2014 NEC since I've detected a few problems. I haven't obtained a copy of the new 2011 NEC but I will eventually. One problem that sticks out like a sore thumb is the above NEC table. I had mentioned this on a previous thread that I started but nobody commented on it so I'm assuming that everybody is dumbstruck at what I pointed out. This table seem's to have incorrect spacing numbers for the following:

size of wire Al or Cu-clad Cu
18 AWG through 8 AWG 100 feet 100 feet
6 AWG through 1/0 AWG 200 feet 100 feet
2/0 AWG through 4/0 AWG 180 feet 80 feet

Now the problem is that the 18 thru 8 AWG is smaller than the 6 thru 1/0 AWG but the spacing is less. If you look at the table the spacing is progressively larger as the wire gauge becomes smaller. The spacing given as 100 feet is incorrect. It should be larger than 200 feet. Also, the spacing for the 6 thri 1/0 AWG for copper is the same as the 18 thru 8 AWG. The spacing given as 100 feet is incorrect because it is the same as the spacing given for the 18 thru 8 AWG which is smaller wire. It should read somewhere between 100 and 80 feet as given for the 2/0 thru 4/0 AWG wire. The numbers that I will propose will be 220 and 100 feet respectively.

 

[Dennis Alwon]

I bet it is because aluminum in the small size will tend to give way easier then copper. The copper distance is the same from 1/0-18, however 18 aluminum spaced too far would probably pull apart from the weight. Just a guess.

 

[infinity]

Although I agree with your logic, you seem to be making assumptions and have not provided any substantiation for the new footage distances you propose.

 

[erickench]

Well I could substantiate by making a few calculations.

(100 + 80)/2 = 90 feet

(100/90) x 200 = 222 or 220 feet

 

[Dennis Alwon]

You better explain those numbers in the calculation. IMO, the numbers in the table are correct but we'll see. I think it has to do with the tensile strength of the aluminum.

 

[erickench]

You better explain those numbers in the calculation. IMO, the numbers in the table are correct but we'll see. I think it has to do with the tensile strength of the aluminum.

Dennis it really doesn't have anything to do with tensile strength. I'm not commenting on the different spacings between the two conductor materials. All I'm saying is that for a given material the spacings have to increase proportionally as the wire sizes become smaller. There are two mistakes in this table.

 

[infinity]

Dennis it really doesn't have anything to do with tensile strength. I'm not commenting on the different spacings between the two conductor materials. All I'm saying is that for a given material the spacings have to increase proportionally as the wire sizes become smaller. There are two mistakes in this table.

Again IMO you're making an assumption. I would suggest that you find the ROP that put those tables in there in the first place and see the method that they used to calculate the distances.

 

[erickench]

Well I wouldn't know where to look for this ROP. I can explain my calculations and reasoning in my proposal and see if they accept it. But IMO this problem sticks out like a sore thumb and I can't believe that they would just ignore it.

 

[Dennis Alwon]

Maybe Tensile strength isn't the correct term but it seems the extra small gauge of #18 alumin. being unsupported for long lengths may put too much stress on the conductor. That is what I was getting at. Perhaps as a copper conductor it is not as much a problem. I am betting these numbers were engineered but who knows.

 

[480sparky]

Well I wouldn't know where to look for this ROP.

Click here.

I can explain my calculations and reasoning in my proposal and see if they accept it. But IMO this problem sticks out like a sore thumb and I can't believe that they would just ignore it.

Take an hour or two and start reading the ROP. It's an eye-opener. Proposals aren't accepted just because 'it sounds like a good idea.'

 

[erickench]

Dennis look at the table closely. As the wire sizes get smaller for the same material the spacings become larger. These two spacing numbers are not increasing in proportion as all the others are.

 

[infinity]

I am betting these numbers were engineered but who knows.

My thought too. The table originated from some specific data and has been in there for a long time. In order to get the proposal accepted Eric will have to provide some substantiation that the original table is incorrect. Not to take the wind out of Eric's sails, but IMO the table is likely correct for the reasons that Dennis mentioned.

 

[Dennis Alwon]

Click here.

I don't see anything in that ROP that will help. You need to find the year that section was added.

 

[Dennis Alwon]

Dennis look at the table closely. As the wire sizes get smaller for the same material the spacings become larger. These two spacing numbers are not increasing in proportion as all the others are.

I realize that Erick, but I think it has to do with the incredible small size of #18 wire and being alum. You see the copper size is the same for the first two rows-- 18-1/0. They would have made that one row except that the aluminum properties are different and come into play with long distances.

I have nothing at all to substantiate my claim and I say go for it. If anything it will be a learning experience for all.

 

[erickench]

Is there any reason why the spacing for No. 18 Al shouldn't be larger than 200 feet? Start at the bottom of the table and work upwards for aluminum. You'll see the spacings become increasing larger. Why does it say 100 ft spacing for the smallest wire gauge listed in the table when No. 6 AWG is 200 ft? Why should the smaller wire size i.e. No. 8 have shorter spacing than no. 6? It's pretty obvious that the lighter wires need less support than the heavier ones.

 

[infinity]

Is there any reason why the spacing for No. 18 Al shouldn't be larger than 200 feet? Start at the bottom of the table and work upwards for aluminum. You'll see the spacings become increasing larger. Why does it say 100 ft spacing for the smallest wire gauge listed in the table when No. 6 AWG is 200 ft? Why should the smaller wire size i.e. No. 8 have shorter spacing than no. 6? It's pretty obvious that the lighter wires need less support than the heavier ones.

We're agreeing with your logic but for you to get this proposal through you'll need some substantiation. Can you prove that the table is indeed flawed?

 

[iwire]

Looking at the 2011 draft they did make a change to that table.

The change was from 'wire size' to conductor size.

No change in the actual requirements.

I sure can't tell if it is a mistake or not, I tend to believe it is not.

As Dennis said go for it and see what they say.

 

[iwire]

Here is the Table from the 2011 draft.

 

[Dennis Alwon]

Eric, I want you to understand that I am not trying to take the wind out of your sails. You may be totally correct on this. Someone the other day asked why bare copper in free air had less ampacity rating than one with a jacket. That took me for a loop but I suspect there is some reason.

The red flag, for me, on this section is the 2 rows used at the top that have the same distances for copper but it changes for aluminum.

If you really exaggerate what you are saying then we can say that a wire that is 40 gauge alumin. , if they made one, could have a vertical spacing of 1000 feet..... I don't think so..

 

[erickench]

Well as it stands now they don't have a spacing rule for No. 40 AWG and probably never will. I wrote out the proposal on the form in a word file. I just need to know if could just type in my signature and email it or do I have to print it, sign it, and then send it to them through the post office.