Can I use EMT as a ground?

[petey_c]

Dgonza9, Although that chart you showed and the NEC say that it's permissible to fit 16, 12 AWG wires in 3/4" EMT, another section of the NEC states that you can only have a 40% fill in that pipe. That's about 6, #12s. http://www.lanshack.com/DesigningConduitRuns.aspx
As has been said, you can use EMT as a ground, but I always run a ground wire anyway. I've seen runs of conduit rust away in the middle.
Were you pulling solid or stranded wire? Stranded is much easier to pull. You can use wire lube or Ivory liquid dish detergent to ease the pull. If you can use two 45s instead of a 90 that will also make pulling easier. You can use LBs (or LR/LL s) http://www.google.com/imgres?imgurl...efurl=http://www.amazon.com/Cantex-Industries . They allow you to get closer to your boxes.
The more couplings you use the more chances there are to have the "head" get stuck. Since you're right up there near Chicago land (where they use pipe for everything electrical...), you could probably give an electrician the measurements and have him (or her) bend the pipe for you for a couple of bucks. Too late now though.
The Divine Comedy was a good read, especially the liner notes (Penguin Publishing) that showed what Dante was referring to. I would've been lost without them. Good luck, Pete

 

[Dgonza9]

Dgonza9, Although that chart you showed and the NEC say that it's permissible to fit 16, 12 AWG wires in 3/4" EMT, another section of the NEC states that you can only have a 40% fill in that pipe. That's about 6, #12s. http://www.lanshack.com/DesigningConduitRuns.aspx
As has been said, you can use EMT as a ground, but I always run a ground wire anyway. I've seen runs of conduit rust away in the middle.
Were you pulling solid or stranded wire? Stranded is much easier to pull. You can use wire lube or Ivory liquid dish detergent to ease the pull. If you can use two 45s instead of a 90 that will also make pulling easier. You can use LBs (or LR/LL s) http://www.google.com/imgres?imgurl...efurl=http://www.amazon.com/Cantex-Industries . They allow you to get closer to your boxes.
The more couplings you use the more chances there are to have the "head" get stuck. Since you're right up there near Chicago land (where they use pipe for everything electrical...), you could probably give an electrician the measurements and have him (or her) bend the pipe for you for a couple of bucks. Too late now though.
The Divine Comedy was a good read, especially the liner notes (Penguin Publishing) that showed what Dante was referring to. I would've been lost without them. Good luck, Pete

Hmmmmm... Whoever wrote that code book needs to learn about something called a "logical fallacy. I don't get the contradiction in the code book. Does it make sense somehow that I can't see or is it really a contradiction? Why would they tell you you can "fit" that many wires in the pipe, but then later say to only fill it 40%?

I have 10 wires in mine. 8 #12 and 2 #10 for neutral and ground. They are stranded. I just plugged my numbers into an iPhone app "Conduit Fill Calculator" based on NEC 2007 code. For 10 #12 wires it says 3/4" EMT. Not sure how that fits in with the information you provide, which seemed to be a different code "569."

Once I used the lube they pulled easy. From what I read in the NEC book, it said that beyond 9 wires you have to consider it to have only 70% ampacity. But that would still be fine for my application.



Congrats on reading "The Divine Comedy." Did you read all three books? And more importantly, congrats on enjoying it. My students are starting it now and many of them dig it. They argue endlessly about the concepts of justice and sin.

 

[yjfun]

You have to look at the code book as a source of information as well as being a safety guideline. It gives you the size of the wire and the size of the conduit as information so that you can calculate how many wires will fit in accordance with the fill capacity. Some installations allow a larger fill capacity than others and sometimes you are putting different size wires in the same conduit so you need the sizing information to do your calculations.

You also don't need to count the neutral wires for the ampacity de-ration but you do need to count them for conduit fill.

16 #12 THHN conductors is 40% fill on a piece of 3/4 EMT

 

[Dgonza9]

So the chart I had was correct. I also plugged in all the conductors and their sizes into the iPhone app I mentioned. It also states that 3/4" is acceptable and is based on 2007 NEC Codebook.

I'm finding it hard right now to pigtail the #10 wires to share the ground and neutral wires on each receptacle. They seem to want to come out of the pigtail cap. I need to get caps sized for 3 #10 wires. I mine are sized to hold only 2.

 

[lschiavo]

3M Ranger 512. Only wire nuts we use.

 

[yjfun]

I like the red Ideal wire nuts myself. I know it's old school and makes for a more permanent installation but you could solder and tape the connections.

 

[hxcpunk71]

I like the 3M tan and red combination wire nuts

 

[lschiavo]

I like the 3M tan and red combination wire nuts

It's yellow and red now. 212 and 512 respectively. Best wire nuts out there IMO.

 

[lschiavo]

I like the red Ideal wire nuts myself. I know it's old school and makes for a more permanent installation but you could solder and tape the connections.

No disrespect to you but Ideal can shove their product...at least the last time I considered it. I once opened a ceiling box with at least 50 connections...more than half of the nuts were laying on the back of the box cover. Must have been vibration...never a problem with Rangers.

 

[P-J]

No disrespect to you but Ideal can shove their product...at least the last time I considered it. I once opened a ceiling box with at least 50 connections...more than half of the nuts were laying on the back of the box cover. Must have been vibration...never a problem with Rangers.

That must have been one huge electrical box. Mounted in the ceiling?

I'm standing in awe at the prospect of that wiring layout...

 

[DaleHair]

I opened a j-box once an all the wirenuts fell out, looked at the wires and did not see any marks that looked like the wirenuts were actually screwed on. It could be that someone only gave the wirenuts a half twist.

 

[lschiavo]

That must have been one huge electrical box. Mounted in the ceiling?

I'm standing in awe at the prospect of that wiring layout...

It was a big box. Maybe 14x. Industrial setting...mounted on a beam. Can you imagine? I'm not sticking my hand in there...just shut off every breaker and sort it out. All for $hitty wire nuts...

 

[lschiavo]

I opened a j-box once an all the wirenuts fell out, looked at the wires and did not see any marks that looked like the wirenuts were actually screwed on. It could be that someone only gave the wirenuts a half twist.

I've been twisting them since I was 9. I was instructed well. My father was very anal about it. It takes some force. Limp wrists need not apply.

Now, all my guys bitch if they have to undo one of my wire nuts...exactly! Use the Rangers!

 

[DaleHair]

I prefer Buchannan B caps but a wing does make it easier to tighten.

 

[mux]

That must have been one huge electrical box. Mounted in the ceiling?

I'm standing in awe at the prospect of that wiring layout...

Was it this box?

 

[duckdogs]

Only if u want to die....

 

[lschiavo]

I prefer Buchannan B caps but a wing does make it easier to tighten.

I have not used those (Ideal)...How easy to they come off? A Ranger is almost as hard CCW as it it CW. That impresses me.

 

[lschiavo]

Was it this box?

View attachment 55611

Not that big...but a lot more wires

 

[yjfun]

After getting to experience the original scotchlocks I never could go back to 3M wirenuts. But hey that's why we have a variety available right? To each their own.

 

[lschiavo]

After getting to experience the original scotchlocks I never could go back to 3M wirenuts.

I can understand your aversion to Scotchlocks. I still run across them occasionally and hate them too.

 

[petey_c]

[\QUOTE]16 #12 THHN conductors is 40% fill on a piece of 3/4 EMT[/QUOTE] I read the table wrong, compounding that, 16 #12s seemed like it was too many. It took me three days to go get the code book out of my truck. I looked at the tables and the math worked out. In my mind's eye it still looks like alot. Thanks for helping me see.
DaleHair, I was doing some work in an office ceiling and found the previous "electrician" made a splice with plastic wall anchors...

 

[yjfun]

I think it seems like to many because the only time we would put that many wires in a 3/4 conduit is control work. If you were to put 16 #12 wires in a 3/4 during normal construction the de-ration would kill any load carrying capacity.

They would only be good for 15 amps.

 

[lschiavo]

[\QUOTE]16 #12 THHN conductors is 40% fill on a piece of 3/4 EMT

I read the table wrong, compounding that, 16 #12s seemed like it was too many. It took me three days to go get the code book out of my truck. I looked at the tables and the math worked out. In my mind's eye it still looks like alot. Thanks for helping me see.
DaleHair, I was doing some work in an office ceiling and found the previous "electrician" made a splice with plastic wall anchors...[/QUOTE]

Per 310.16 90-degree #12 copper THHN is rated at 30A. Say we have (3) 240 Circuits and (3) 120V circuits. Thats a total of 9 current carrying wires (don't count the neutrals or ground). That could be 13 total wires with neutrals and ground.

We derate the wire per table 310.15B2a. For 9 conductors that is 70% (30Ax0.7)=21A. Still good for #12.

If we go up to 10 current carrying conductors, we have to derate to %50. #12 is only good for 15A then.

 

[yjfun]

Yes I should have specified current carrying vs non current carrying wires for the deration.

Thank you Ischiavo.

 

[BeerguyNC61]

Two demerit points off your sparky badge!!

 

[petey_c]

"Say we have (3) 240 Circuits and (3) 120V circuits. Thats a total of 9 current carrying wires (don't count the neutrals or ground). That could be 13 total wires with neutrals and ground."
See, that's where I have a problem. With properly balanced, single phase 240V circuits the neutrals aren't considered current carrying conductors (ccc). With 120V circuits, the only time the neutrals aren't carrying current is when the device(s) are not in the circuit (off or unplugged). I'd think, if you're calculating the 120V hots as ccc's, then the neutrals also have to be considered as well. The number should be 12, not 9 and derate accordingly. I looked in the NEC and wasn't able to find anything clear.

 

[yjfun]

Article 310.15(B)(4)(a)

"A neutral conductor that carries only the unbalanced current from other conductors of the same circuit shall not be required to be counted when applying the provisions of 310.15(B)(2)(a)"

So I would understand it to mean that the neutral doesn't count as current carrying if you are using it with only one phase conductor but it would count if you were using 2 or more phase conductors.

The next section of the code specifies that on a 3 phase Y system that if you use 2 or all 3 of the phase legs then you do have to count the neutral as current carrying but it doesn't say anything about using both legs of a 120/240 single phase system.

 

[thargrav]

It's legal to use EMT for safety ground only, that would be the bare wire in a romex cable. It's not legal or safe to use EMT as a electrical ground or "common wire".

 

[petey_c]

"...but it doesn't say anything about using both legs of a 120/240 single phase system." I think the first section you quoted covers that.
So I think we're at 10 conductors; six 240V "hots", three 120V "hots" and a single 120V neutral (since it's not carrying unbalanced current) for the third 120V hot.

 

[yjfun]

I think that the first section covers it also I was just pointing out that there was nothing that specifically referenced that type of system.

This is why the code is so confusing to people.

I would differ from your opinion in that I would interpret the code to mean I don't have to count the neutral on any of the 120 volt circuits (in this application) because unless you have exactly the same load on each of the two phases for the shared neutral it would not be balanced therefore making that neutral part of an unbalanced circuit and not applicable to deration.