causes of electrical fires??

If you're going to get the NEC, Might want to get the NEC handbook which also has pictures and examples. Can get that here...
http://www.nfpa.org/catalog/product.asp?pid=70HB08&order_src=A291&cookie_test=1

And use that along with a residential wiring book which says it uses the 2008 NEC.

As to Arc Fault breakers, basically the 2008 says every room but those with GFCI. HOWEVER my state (Oregon) has modified the 2008 to be bedroom only. Also my state has exceptions for new GFCI rules.

Many people are having trouble with vacuum cleaners and a few other appliances tripping arc fault breakers. I would advise only installing Arc Fault breakers where required due to these problems.

Then other states are going by 2005 NEC rules or older. I think one island on Hawaii still goes by 1993 rules!

Anyway what is required is a local thing. The rules can even be different within a state (city different from rural), so find out what is required for your specific area and where you can get a copy of you areas modifications to the rules (if any).

This shows how different various states are with the NEC rules...
(The final word on this is your local inspector, not this map!)
http://www.nema.org/stds/fieldreps/NECadoption/implement.cfm

jar546 said:

This may help to prime you for the test.

Basement, junction box. Metal 4" x 4" x 2-1/8" deep with cover and ground screw properly placed. No devices, internal clamps, plaster or extension rings on or in the box. Just wires and wire nuts except for the compression sleeve on the equipment grounds.

There were eight (8) 12/2 NMB cables entering the box.

Questions:

1) Is the box properly sized?

2) What is the box fill?

3) What size box needed?

Click to expand...

I'll start by giving my answer based off what I would do. I would say it is overfilled and I wouldn't put more than 4-5 wires max in that box. 4 is probably the most I would use and it would be a square box. I wouldn't know the fill and if I had the scenerio in front of me, I'd go by looks. I know that is not the "Correct" answer, but it should be safe.

Now if I were taking the test and having a posted 2008 NEC in front of me, here is my answer...

Is this a round box or a square box?

1) A 4x4x2-1/8 metal box (Round houses 9 conductors) (Square houses 13 conductors). So NO on both counts.

2) 18. The black and white wires account for 16, the ground wires account for 1. I am also adding 1 for the grounding clamp per 314.15(B)(2) of the NEC dealing with Clamp Fill states internal clamps should account for 1.

3) 4-11/16 x 2-1/8 square

what are the main things that cause an electrical fire?

Click to expand...

There is only one thing that causes fire. Heat.

Heat usually comes from poor connection/terminations/splices.

Copper conducts electricity well. A loose connection builds up carbon where the electricity is jumping a gap. Carbon doesn't conduct well and the connection gets progressivly worse. In the right conditions the connection can get hot enough and act like a heating element to start a fire.

No response on the "Test"?

No way you can put 8 cables in a skinny 4x4. This is just from common sense perspective and not code perspective.

A thick 4x4 would fit them, but it would be tight. And why in the world would you have 8 cables in a junction box anyway?

You would need a larger box than 4x4. I don't know what "fill" is.

GabeS said:

No way you can put 8 cables in a skinny 4x4. This is just from common sense perspective and not code perspective.

A thick 4x4 would fit them, but it would be tight. And why in the world would you have 8 cables in a junction box anyway?

You would need a larger box than 4x4. I don't know what "fill" is.

Click to expand...

I don't think of the 4x4 box mentioned in code as being "skinny", but I agree, I'd never put that many in either. May be deemed "safe" via code, but too hard to mess with in my opinion.

Fill, is referred to as the number of conductors. a 12/2 wire has 2 conductors + the ground. My understanding is all the grounds only count as 1 conductor, but I could be wrong. I didn't know what it was either until I looked through the NEC....

Well with a 4x4 you could have 2 circuits or more
2 in, 2 out to the next box
Some people put a single gang triple switch - that's 3 wires to the devices. Say even 2 single gang double switches - that's 4 wires
I'd never do it, but I'm sure someone somewhere has

Scuba_Dave said:

Well with a 4x4 you could have 2 circuits or more
2 in, 2 out to the next box
Some people put a single gang triple switch - that's 3 wires to the devices. Say even 2 single gang double switches - that's 4 wires
I'd never do it, but I'm sure someone somewhere has

Click to expand...

The wires don't really add up that quickly for combination switches, because you can run 3 wire cable. A deep 22.5 inch single gang box can handle a quad switch. One 14/2 coming in (2), two 14/3 going out (6), ground for all (1), and (2) for the switch. Total fill is 11, which works for 14 gauge (2 cu in per) with 0.5 inches to spare.

Pete

PeteD said:

The wires don't really add up that quickly for combination switches, because you can run 3 wire cable. A deep 22.5 inch single gang box can handle a quad switch. One 14/2 coming in (2), two 14/3 going out (6), ground for all (1), and (2) for the switch. Total fill is 11, which works for 14 gauge (2 cu in per) with 0.5 inches to spare.

Pete

Click to expand...

Not if the lights are not in the same area
No reason to run 14-3 to an outside light, then to an overhead light, then to another light in another room, then to a light in a bathroom, then to another outside light on the other side of the house
And not if the runs are 12-2, which is what the "test" referred to
And yes I have seen that many switches in 1 place, but they used a 4 gang box for more room

overload

HOW does a circuit get overloaded if it has the proper sized wire for the circuit breaker?

Scuba_Dave said:

Not if the lights are not in the same area
No reason to run 14-3 to an outside light, then to an overhead light, then to another light in another room, then to a light in a bathroom, then to another outside light on the other side of the house
And not if the runs are 12-2, which is what the "test" referred to
And yes I have seen that many switches in 1 place, but they used a 4 gang box for more room

Click to expand...

I agree that it probably doesn't make sense from a practical standpoint. This situation would more likely in occur one room. Two lights in a single fixture and a light and a fan in another fixture for example, each controlled independently.

My comment was not meant to be directly related to the example (which was just a junction box - no switches or internal clamps), but rather to point out the box fill calcs can work for these combo switches and the box is not overly-packed.

Pete

Master Brian said:

Is this a round box or a square box?

1) A 4x4x2-1/8 metal box (Round houses 9 conductors) (Square houses 13 conductors). So NO on both counts.

2) 18. The black and white wires account for 16, the ground wires account for 1. I am also adding 1 for the grounding clamp per 314.15(B)(2) of the NEC dealing with Clamp Fill states internal clamps should account for 1.

3) 4-11/16 x 2-1/8 square

Click to expand...

First if it is a 4x4 it can't be round now can it?

Second on the test you will be taking the only correct answer will come from the book not from what we think

jwelectric said:

First if it is a 4x4 it can't be round now can it?

Second on the test you will be taking the only correct answer will come from the book not from what we think

Click to expand...

Well, the 2008 NEC stated a 4x4 round/octagone box! So, don't ask me, ask whomever wrote the code!

2nd, I know it isn't what I think. I just said what I would have done previous to reading code, which would have been correct, even though I didn't know the code. I stated that to show that not everyone whom does DIY stuff is an idiot and not all connections done by a DIY'er are incorrect and out of code. Common sense goes a long way!

So were my answers correct or not?

jwelectric said:

First if it is a 4x4 it can't be round now can it?

Second on the test you will be taking the only correct answer will come from the book not from what we think

Click to expand...

My question here is, if the code doesn't list a 4x4 size, they list is as 4 square or 4 round, am I supposed to guess? A 4" dia octagon/round box would still be 4x4 would it not? I would assume 4x4 means square, but I've also taken enough tests to know you don't assume on a test like this! It turns out to be "in material" in this case as there is obiously more conductors than either box will handle....

You state you are an instructor, I would think you would know better.....

Here is a screen shot of the 2008 NEC, please show me where they state 4x4 as being square.

Try to think of this as preparation for dealing with inspectors and the counterman at the supply house city desk.

The original question stated that there was a "junction box. Metal 4" x 4" x 2-1/8" deep", so the box in question can't be round.

Square metal boxes provide maximum box volume and would make the best choice for a junction box with multiple conductors. That's not to say you can't use an octagon box as a junction box as long as your fill requirements are minimal.

I stand prepared to head to the dunces corner if I got any of this wrong, but at least I'll have learned something new.

Master Brian said:

My question here is, if the code doesn't list a 4x4 size, they list is as 4 square or 4 round, am I supposed to guess?

Click to expand...

No I suppose that you should take your own advice you mentioned here;

Master Brian said:

Common sense goes a long way!

Click to expand...

If something is as long as it is wide or let’s say something was 4x4 then it must be square or at least this is what I was taught in the fifth grade.

Master Brian said:

So were my answers correct or not?

Click to expand...

Not

Master Brian said:

My question here is, if the code doesn't list a 4x4 size, they list is as 4 square or 4 round, am I supposed to guess? A 4" dia octagon/round box would still be 4x4 would it not?

Click to expand...

I think that even a fifth grader would know that anything that was the same on two sides would know that it is a square. I hope that you would know the difference between an octagon and a square. If my third grade math has not left me an octagon has eight sides and would need more numbers than just two. It would look something like this




As for a round box I think it is pretty easy to recognize as it is a circle.

Master Brian said:

You state you are an instructor, I would think you would know better.....
Here is a screen shot of the 2008 NEC, please show me where they state 4x4 as being square.

Click to expand...

One of the hardest things that any instructor has to overcome is the ignorance of the student. When a student thinks they already have the answers to questions it is really hard for the instructor to point anything out.
As to the NEC stating a box as being a 4x4, the members of the code panels feel that anyone that is messing around with electricity should already know a little something about shapes such as something being a 4x4 would be square.

Now I am not trying to sound mean or ugly but as you said yourself. “a little common sense goes a long wayâ€

4x4 is two dimensional. Doesn't say the height of the box. 4x4x4 would be a cube. 4x4 doesn't apply to circles. Radius and diameter apply to circles.

A circle can't have a measurement of 4x4. It's impossible because it doesn't have any sides. It could have a 4" diameter. But that doesn't mean 4x4.

4x4 means length x width.

Volume is lenght x width x height.

Pie times radius squared is the area of a circle.
Two pie radius is the circumference.

A square is the same on all sides.

I think you need to go back and look at a 4" octagon metal box, they aren't shaped as your picture shows. Well, they are an octagon, but the sides aren't equal as your picture shows. So, I can easily see someone just saying 4x4 box, maybe you in your advance state as an instructor would never do that, but others might....

I am however glad you finished 5th grade....when you further your education with a college degree and beyond, you'll surely learn not to assume anything!

Maybe I am wrong, please explain! Afterall you are the teacher, please teach! Was I wrong on what I would have done prior to reading the code? I am certain, I was correct! If not please enlighten me there as well. 4 wires max wouldn't have been overfill on any 4" box that is 2-1/8" deep. Crazy part is my common sense tells me, putting much more than that isn't safe, I didn't need to pass any test to tell me that. In my opinion taking the home owners test is just passing through the hoops....but if that's what it takes then fine.

Maybe I didn't read the code correct and that really comes from not wanting to waste a bunch of time flipping through online pages to check on the a couple of things.

One of the hardest things that any instructor has to overcome is the ignorance of the student. When a student thinks they already have the answers to questions it is really hard for the instructor to point anything out.

Click to expand...

I haven't seen you point anything out, you skirt around acting arrogant, that is it! What I have learned in life, is the people whom are the most successful are the ones not whom think they know it all, but the ones that surround themselves with those smarter than they. I've never claimed to know it all, which is why I am here asking questions! I question why you are here, because all you want to do is mock and act like you know it all, when you clearly don't or you woudn't be here. Some are here to learn, others are here because they truly want to be useful, you seem to be here merely to self promote. Have at it!!

As to the NEC stating a box as being a 4x4, the members of the code panels feel that anyone that is messing around with electricity should already know a little something about shapes such as something being a 4x4 would be square.

Click to expand...

Is that a fact! You probably asked each and every one of them! I actually don't see the NEC stating a box being 4x4. NEC states it as being 4" square or 4" round/octagonal. You and one other person stated 4x4! NEC, was much more clear....they obviously didn't want confusion....

As for the common sense, I am paying attention to mine and disregarding you from here on out....

GabeS said:

4x4 is two dimensional. Doesn't say the height of the box. 4x4x4 would be a cube. 4x4 doesn't apply to circles. Radius and diameter apply to circles.

A circle can't have a measurement of 4x4. It's impossible because it doesn't have any sides. It could have a 4" diameter. But that doesn't mean 4x4.

4x4 means length x width.

Volume is lenght x width x height.

Pie times radius squared is the area of a circle.
Two pie radius is the circumference.

A square is the same on all sides.

Click to expand...

If this is pointed at me, I understand what a square, circle and octagon are. I also realize that people state things that aren't 100% correct, so if there is any question, one should clearify. A simple, it was a square box, would have sufficed! Instead, there is no response and the response from the instructor isn't even a real response, it's heckling! I assume he is an instructor so he can self-promote....

What amazes me is how threatened some people are by people whom do things themselves. I don't know if they are threatened because they feel food is being taken off their plates or if they are threatened because someone else might be capable of doing on the side, what their life focus is....

It wasn't directed at you. Just at the general discussion of the entire post. I can't believe we are telling each other basic geometry. I doubt that's why people are on this forum.