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.
Can I use EMT as a ground?
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P-J said:
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...
DaleHair said:
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 ***** if they have to undo one of my wire nuts...exactly! Use the Rangers!
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.
I can understand your aversion to Scotchlocks. I still run across them occasionally and hate them too.
petey_c
Senior Member
[\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...
DaleHair, I was doing some work in an office ceiling and found the previous "electrician" made a splice with plastic wall anchors...
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.
They would only be good for 15 amps.
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.
BeerguyNC61
Well-Known Member
Two demerit points off your sparky badge!!
petey_c
Senior Member
"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.
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.
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.
"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
Well-Known Member
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
Senior Member
"...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.
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.
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.
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.
