Conductors in a conduit

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Old 04-08-09, 08:39 AM
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Conductors in a conduit

Hi, this is my first post. I have looked at my wiring books based on the NEC code but they seem to be missing the number of a given wire size that can be put in a conduit although they list it for boxes etc. I will need to buy a EMT bender to run these wires so I need to know before I buy. Oh, the question. What size conduit to run 4- #4 wires? I find a 1" will work on some charts online but also know everything online isn't always correct. And just to make it easier, I will possibly derate the neutral and ground to a #6.
Thanks,
Grumple
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Old 04-08-09, 08:52 AM
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The annex sections of the NEC (available at your library) tell you how many wires of a given size and type can go into a conduit of a given size and type. This only covers "fill" concerns. You also need to take "derating" concerns into account.

You told us four wires. You told us #4. You told us EMT. The one piece of information you didn't tell us was what kind of wire. If I assume regular THHN, then NEC table C.1 tells me that you need 1" EMT.

If you reduce the size of the neutral and/or ground, the answer potentially changes (although the conduit requirement would not get any bigger).

Note: You used the word "derate" improperly. "Derate" has a specific meaning in electrical wiring and it relates to ampacity. When you reduce a wire size, you are not "derating."
 
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Old 04-08-09, 09:19 AM
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Hi John,
Thanks for the info and clarification on the word "derate". I guess I meant make smaller but was also reading about derating for heat related loss. I am using THHN for this job. Usually everything I have wired in the past was cut and dries simple. This job is different in the sense the neutral is going to be used for control circuit items like lights and small blower motor. The #4 wires are going to be used for heater elements. I like to use the proper colored wires and not marking tape as its my own personal workshop and the local wire places would have to special order the white in a #4. So seeing the neutral has minor amp requirements I figure I can use a #6 in white and go with a smaller ground most likely a #6 in green. Sound right?
Thanks,
Grumple
 
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Old 04-08-09, 09:31 AM
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Originally Posted by Grumple View Post
Hi John,
Thanks for the info and clarification on the word "derate". I guess I meant make smaller but was also reading about derating for heat related loss. I am using THHN for this job. Usually everything I have wired in the past was cut and dries simple. This job is different in the sense the neutral is going to be used for control circuit items like lights and small blower motor. The #4 wires are going to be used for heater elements. I like to use the proper colored wires and not marking tape as its my own personal workshop and the local wire places would have to special order the white in a #4. So seeing the neutral has minor amp requirements I figure I can use a #6 in white and go with a smaller ground most likely a #6 in green. Sound right?
Thanks,
Grumple
What size of breaker will you have on this circuit? That will help sizing the grounding wire.

Jim
 
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Old 04-08-09, 09:38 AM
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Originally Posted by Grumple View Post
I like to use the proper colored wires and not marking tape as its my own personal workshop and the local wire places would have to special order the white in a #4. So seeing the neutral has minor amp requirements I figure I can use a #6 in white and go with a smaller ground most likely a #6 in green.
I would concern myself less with the insulation color in the larger gauges. You save money by buying all the same color wire on a reel and using tape. That is, you have fewer "reel ends" leftover. Of course, if code requires only a smaller neutral and ground, that may save you some money. But I've found that most of the stuff that is special order is not special order because I am the only one smart enough to use it.

If you look at any number of commercial installations, as the wire sizes get larger, you see less and less different-colored insulation. It's fairly unusual to see individual wires this large in anything but black in the AC world. In DC distribution you will see gray fabric over rubber as well as some black, red and white, and quite often green for ground.

If you're bending pipe, increase the number of pull boxes or conduit bodies beyond the minimum to reduce the need to use a wire puller-- or as some would improvise, a pickup truck bumper.
 
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Old 04-08-09, 09:39 AM
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Originally Posted by rukkus11 View Post
What size of breaker will you have on this circuit? That will help sizing the grounding wire.

Jim
Hi Jim,
I was going with a 70 amp breaker, but I may need to increase that if I increase the heaters in the future. That is why I am going with #4 instead of #6 for the main load for the elements. So if I bump the current draw up to 75 amps for instance I would be covered. Putting in a #6 ground is no big expense at the present as copper has come down recently. Please advise though.
Thanks,
Grumple
 
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Old 04-08-09, 09:46 AM
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Originally Posted by ArgMeMatey View Post
I would concern myself less with the insulation color in the larger gauges. You save money by buying all the same color wire on a reel and using tape. That is, you have fewer "reel ends" leftover. Of course, if code requires only a smaller neutral and ground, that may save you some money. But I've found that most of the stuff that is special order is not special order because I am the only one smart enough to use it.

If you look at any number of commercial installations, as the wire sizes get larger, you see less and less different-colored insulation. It's fairly unusual to see individual wires this large in anything but black in the AC world. In DC distribution you will see gray fabric over rubber as well as some black, red and white, and quite often green for ground.

If you're bending pipe, increase the number of pull boxes or conduit bodies beyond the minimum to reduce the need to use a wire puller-- or as some would improvise, a pickup truck bumper.
ArgMeMatey,
I hear ya. I used to live around the Milwaukee area too, in Mukwonago. Anyhow, I understand the use of the tape and the black only wire and special order comment. I just don't see the need for a neutral to be a #4 to run a 120v lightbulb and a small blower motor. Now the #4's for the heater elements I understand just fine. I always use a pull box or more depending on the length of the run. I wired my whole workshop and everything in it so far. Thanks for your comments.
Grumple
 
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Old 04-08-09, 11:27 AM
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Originally Posted by Grumple View Post
Hi Jim,
I was going with a 70 amp breaker, but I may need to increase that if I increase the heaters in the future. That is why I am going with #4 instead of #6 for the main load for the elements. So if I bump the current draw up to 75 amps for instance I would be covered. Putting in a #6 ground is no big expense at the present as copper has come down recently. Please advise though.
Thanks,
Grumple
You can use a #8 for your grounding wire. That's good up to 100 amps.

Jim
 
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Old 04-08-09, 12:08 PM
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Originally Posted by rukkus11 View Post
You can use a #8 for your grounding wire. That's good up to 100 amps.

Jim
Jim,
I thought I could go down to a #8 but wasn't sure on the max amps.
Thanks,
Grumple
 
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Old 04-08-09, 12:30 PM
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Originally Posted by Grumple View Post
Jim,
I thought I could go down to a #8 but wasn't sure on the max amps.
Thanks,
Grumple
No Problem.
Jim
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