Current Rating Using #8/3 NM-B Conductor

[James L]

Wouldn't the wires over heat though on longer runs...

I suppose if you ran it out a couple thousand feet you could turn it into a heating cable

or if someone brought a generator on the property?

I don't follow this one

 

[electrofelon]

I suppose if you ran it out a couple thousand feet you could turn it into a heating cable

When I lived off grid, I had a 12V diversion controller for my wind turbine (most small wind turbines need to run constantly whether you need the power or not so you have to burn it off with big resistor). I ultimately had 12V heating elements in a water heater, but for a period of time I needed a dump load so I took a bunch of 14 thhn (dont remember the length (it was 60A at about 14V) and threw it in a bucket of water. Worked good!

 

[mbrooke]

I suppose if you ran it out a couple thousand feet you could turn it into a heating cable

Chapter 9 table 9 gives 2 ohms per 1000 feet of #12. A 650 foot run would never trip the OCPD as I'm crunching the numbers?

I don't follow this one

I'm humbly thinking reduced short circuit current at the source, which could increase the breaker's opening time.

 

[James L]

Chapter 9 table 9 gives 2 ohms per 1000 feet of #12. A 650 foot run would never trip the OCPD as I'm crunching the numbers?

I believe it. I was joking a bit with a couple thousand feet, but started to think it's realistically several hundred.

I'm humbly thinking reduced short circuit current at the source, which could increase the breaker's opening time.

I'm thinking

 

[mbrooke]

I believe it. I was joking a bit with a couple thousand feet, but started to think it's realistically several hundred.

Crunching the numbers I keep running into the same thing. Maybe I'm doing something run, however at the same time the whole 250% OCPD rule doesn't feel right. At least not without some type of run lenghth restriction in the code.

I'm thinking

So I did find this:

American wire gauge - Wikipedia

en.wikipedia.org

According to the graph #12 can only handle 235 amps for in 10 seconds.

However at 235 amps a 40 amp THQL breaker takes upwards of about 10 seconds to open.

Reading up on Kohler specs it seems that a typical generator delivers about 300% its rated current for 10 seconds.

So, 235 / 3 = 78 amps, times 208 x 1.73= 28 kw. So in theory any generator under 30kw would automatically not provide enough short circuit current for rapid opening...? Hhmmm

 

[James L]

When I lived off grid, I had a 12V diversion controller for my wind turbine (most small wind turbines need to run constantly whether you need the power or not so you have to burn it off with big resistor). I ultimately had 12V heating elements in a water heater, but for a period of time I needed a dump load so I took a bunch of 14 thhn (dont remember the length (it was 60A at about 14V) and threw it in a bucket of water. Worked good!

Pretty cool

My first experience with a cable-accidentally-turned-heating-element was when I was hanging a large entry chandelier from a scaffold. I got it all mounted and wired, and was waiting for someone on the floor to find the switch to turn it on, but he couldn'tfind it. While I was waiting, I was standing there holding on to the chain, and suddenly my hand felt like it was on fire

It took a bit to realize that the lamp cord was getting super hot. I immediately knew I needed to look in the wiring compartment of the fixture. And for whatever reason, the lamp cord h+n were tied together with a wire nut.

 

[LarryFine]

And for whatever reason, the lamp cord h+n were tied together with a wire nut.

My guess: It was a used chandelier from a house where the electrician was having trouble getting paid.

Like the mason who breaks the glass secretly embedded in the chimney flue only after receiving final payment.

 

[ttjangu]

This one always has me second guessing it. So, 8/3 MC is allowed for 50 amps but have to use 6/3 NM for 50 when all terminals are 75 degree c or better? I think what gets me is the pre assembled cable part on the mc.