If you are bored.....

[steve66]

Here is a question to ponder if you are bored.

Under Texas law, Mr. Sly (an ex-enron executive) can not be forced to give up his house if he is sued.

What is the ampacity of his 3/0 GOLD (instead of copper or alumnium)panel feeders?

Steve

 

[electricman2]

Re: If you are bored.....

18 or 24 carat?

 

[bphgravity]

Re: If you are bored.....

Resistivity of materials

metal resistivity,
nano-ohm-meter
silver 14.71
copper 15.80
gold 20.11
aluminum 25.00
zinc 54.55
iron 87.10
lead 193.00
mercury 983.96

(These are at room temperature)

 

[a.wayne3@verizon.net]

Re: If you are bored.....

John it would make a difference 18 or 24

 

[steve66]

Re: If you are bored.....

bphgravity is onto the same thing I am thinking.
But the first thing I was thinking about is:

Does the code allow conductors made of gold? (I guess I should have asked that first.)

Second, how would you determine the allowable ampacity?

Third, plug the resistivity for alumnium into your formula for the amps. Does it give the same values as table 310.16. If not, why???

24 carat of course, electricman2. Nothing but the best for our ex-execs

Steve

 

[iwire]

Re: If you are bored.....

Originally posted by steve66:
Does the code allow conductors made of gold?

No, 110.5

Originally posted by steve66:
Third, plug the resistivity for alumnium into your formula for the amps. Does it give the same values as table 310.16. If not, why???

310.16 is concerned with the operating temp of the conductors to prevent insulation damage, this would be different than what the conductor itself is capable of carrying.

[ April 15, 2004, 06:23 PM: Message edited by: iwire ]

 

[steve66]

Re: If you are bored.....

Iwire:

Darned your good. I have been wondering for a while what the code would say about conductor of other materials, and I decided to post the question when I ran across 110.5 today.

But what about the last sentance "Where other materials are used, the size shall be changed accordingly." I guess that only applies to conductors that are not copper as "otherwise provided in this Code". (I'll tell Mr. Sly to have the panelboard made out of gold instead of the feeders )

Since bph provided the numbers, I post what I was thinking. Al and Cu should have the same temp. for the same power loss per unit length (assume for a minute the thermal properties of both materials are the same). Power is proportional to (I^2) * R *C where R is the resistivity, and C is a constant. Do a little math (I'm a math geek as well as a code geek) and:
I(gold) = I(copper)*sqrt(15.8/20.11) = 176 amps for 3/0 at 75 deg.

For alumnium, I(alumnium) = I (copper)*sqrt(15.8/25) = 159 amps.

So the 159 amps is very close to table 310.16 value of 155 amps. I wonder if the small difference is due to different thermal properties of the materials that I assumed?

Steve

 

[websparky]

Re: If you are bored.....

I wonder if he has any flexable cords where he should have permanent wiring??

Most likely has a freezer plugged into a GFCI in his garage and the receptacle is mounted at 12" AFF.

 

[charlie b]

Re: If you are bored.....

He probably has his grounded outlets upside down as well.

 

[wanderer20001us]

Re: If you are bored.....

Copper has higher thermal conductivity (269 units) than Gold (169.0 units). This would imply that gold would produce less heating of the insulation given the slightly higher resistivity.

Also, Gold has a smaller coefficient of Thermal Expansion (7.9) than cooper(9.2) or aluminum(12.9). Therefore, Gold would be less likely to cause loose connection during load/heat cycles.

Silver is the ideal way to good, though.

 

[steve66]

Re: If you are bored.....

I was suprised that gold has more resistance than copper. But that is bulk resistance. I think gold actually has less contact resistance and that's why it is used on some electronic connections. Maybe the contact resistance is better because of differences in the way copper corrodes.

Now that I have that out of my system....I will refrain from posting any more "hypothetical" questions before I get labeled "that crazy guy" (if its not already too late)

 

[ryan_618]

Re: If you are bored.....

Originally posted by bphgravity:
Resistivity of materials

metal resistivity,
nano-ohm-meter
silver 14.71
copper 15.80
gold 20.11
aluminum 25.00
zinc 54.55
iron 87.10
lead 193.00
mercury 983.96

(These are at room temperature)

Bryan, thanks for posting this. I think I'll rub a thin layer of mercury all of over me before I look at anything energized.

 

[websparky]

Re: If you are bored.....

Too Late !