conductors in pipe

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Joseph mulherin

Joseph mulherin

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How many current carrying conductors can go in a 3/4 emt with three current carrying conductors with the new rule pulling neutrals for each conductor. I think its seven thhn or thwn
 
Depends on the size of the conductors among other things. For example #12 THHN can have 9 CCC's with derating and still be good for 20 amps. (30*70%=21 amps). Not sure what you mean by the new rule for individual neutral conductors. MWBC's are still permitted by the NEC just with some newer restrictions.

Welcome to the Forum. :)
 
current carrying conductors

current carrying conductors

Thanks for responding the new code says every circuit has to have separate neutral now so if I'm pulling three number twelves in a 3/4 emt you also need three neutrls. and when pulling over three current carrying conductors you get in to de rating. I figured it was seven number twelves. when they are current carrying circuits
 
Joseph mulherin said:
How many current carrying conductors can go in a 3/4 emt with three current carrying conductors with the new rule pulling neutrals for each conductor. I think its seven thhn or thwn
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As with any other raceway and conductor fill - size matters, do you want to give more details of what you are asking about?

As mentioned there is no rule against using multiwire branch circuits, just more extra details that go with them then there once was.

If you are talking about how many 12 AWG conductors could be pulled without the need to change conductor size because of ampacity adjustments - the magic number is usually not to get more then 9 current carrying conductors in the same raceway, as this still leaves you at 70% ampacity adjustment and is usually still enough to not need to increase conductor size, at least for conductors in the 14 - 6 AWG sizes. So if you run three phase MWBC's you can have 3 sets of all three phases and the three associated neutral conductors - gives you 12 total conductors in the raceway but only nine count as current carrying for ampacity adjustment reasons. If you only have single phase supply (not from a wye system though) then you can have 4 sets of line A line B and 4 associated neutrals - still 12 total conductors before you get into needing to adjust conductor size.
 
current carrying conductors

current carrying conductors

infinity said:
Depends on the size of the conductors among other things. For example #12 THHN can have 9 CCC's with derating and still be good for 20 amps. (30*70%=21 amps). Not sure what you mean by the new rule for individual neutral conductors. MWBC's are still permitted by the NEC just with some newer restrictions.

Welcome to the Forum. :)
Click to expand...

.like I was saying each circuit has to hat a separate neutral when pulling three twelves current carrying they need a separate neutral and when pulling over three current. carrying carrying conductors there's are factors to figure in so seven twelves that would be a neutral for each circuit which would be six plus a ground making seven being the max now in 3/4 emt right
 
Joseph mulherin said:
How many current carrying conductors can go in a 3/4 emt
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Check out Informative Annex C in the back of the code book for a quick reference to how many like conductors can fit into a raceway.

The "3 current carrying factor" relates to conductor ampacity and on its own is not a factor in determining how many conductors are allowed in a raceway. Those rules can be found in Art 310 along with other important things to consider when selecting conductors for a circuit.
 
The NEC does not prohibit the use of multi-wire branch circuits. You are permitted to us a single neutral with more than one ungrounded conductor. (job specs, often forbid the use of multi-wire circuits)
 
current. carrying conductors

current. carrying conductors

I figured seven in 3/4 emt thanks for your help I will look up those sections in the code book as a new member do I need to do anything other than register some places I go it tells me I'm not allowed there boy advice on what I need to. do or what I'm missing thanks guys
 
Joseph mulherin said:
.like I was saying each circuit has to hat a separate neutral when pulling three twelves current carrying they need a separate neutral and when pulling over three current. carrying carrying conductors there's are factors to figure in so seven twelves that would be a neutral for each circuit which would be six plus a ground making seven being the max now in 3/4 emt right
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3/4 EMT can handle sixteen 12AWG THHN/THWN conductors. How many of them are considered current carrying for ampacity adjustments will make a difference in whether or not they can all be on 20 amp overcurrent devices.

I think I know what you are trying to ask, but there is no straight answer. You need to figure out load(s) needed to supply, minimum conductor ampacity, ampacity adjustments, raceway fill for most every run you make. You do kind of see trends after you have been doing this long enough and can tell what is acceptable and what isn't often without doing any precise calculations, but still is no straight answer that always applies to what I think you are trying to ask.

I could run fifteen 12 AWG THHN/THWN in a 3/4 EMT plus 12 AWG equipment grounding conductor if supplying 5 three phase motors that only need a minimum branch circuit ampacity of 15 amps - because the adjustment factor @90C for 15 current carrying conductors puts 12 AWG at 15 amps. And the thing with motor circuits is the branch circuit overcurrent protective device may even be allowed to be up to 25 or 30 amps pretty easily on these circuits. You can't do that with general purpose 120 volt receptacle circuits though, you need to figure them as being able to handle full 15 or 20 amp depending on the overcurrent device. You could have sixteen 12 AWG conductors supplying nothing but 15 amp receptacle circuits though, and all 16 being current carrying conductors.
 
conductors in conduit

conductors in conduit

I'm new at this forum I'm trying to learn how to navigate my way around so bare with me. ok 120 volts 277 volts you use to could share your neutral now you have to pull a separate neutral for each circuit,there is a exception in the code book,but I've have only saw one person do this exception,do you follow maybe I'm not giving enough details
 
Joseph mulherin said:
I'm new at this forum I'm trying to learn how to navigate my way around so bare with me. ok 120 volts 277 volts you use to could share your neutral now you have to pull a separate neutral for each circuit,there is a exception in the code book,but I've have only saw one person do this exception,do you follow maybe I'm not giving enough details
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The code does not say you need a separate neutral for each ungrounded conductor. Because of the following rule, many designers are requiring a neutral for each ungrounded conductor, but the code does not require that.
210.4(B) Disconnecting Means. Each multiwire branch circuit shall be provided with a means that will simultaneously disconnect all ungrounded conductors at the point where the branch circuit originates.
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That sounds good why they would do the deprecate neutrals.

The inconvenience of turning off three circuits when you only need to turn off one or if one trips all three would.

Now.

What if or do they make a way to go thru a single pole breaker with a circ. ?

As to feed three single pole breakers from the three pole breaker so only one circ will trip or be able to be turned off ?
And seems that article would still be satisfied.

Not to high jack. Thinking out loud
 
Rethinking though. Where the branch circuit originates would now be the single pole breaker and not the three pole breaker. So. Guess that wouldn't work
 
Joe. What they are saying is as the panel that feeds your circuits. It has 3 hots and 1 neutral. The 3 hots share that 1 neutral. You can wire 3 circuits the same way. 3 hots from 3 separate phases (ABC) sharing 1 neutral. Depending on what the circuits are feeding you would not have to count the neutral as a "current carrying " or you would have to count it as one.

So 3 hots and a neutral could be 4 wires and 3 current carrying conductors. OR 4 wires and 4 current carrying conductors. Depends what your feeding.
 
ritelec said:
That sounds good why they would do the deprecate neutrals.

The inconvenience of turning off three circuits when you only need to turn off one or if one trips all three would.

Now.

What if or do they make a way to go thru a single pole breaker with a circ. ?

As to feed three single pole breakers from the three pole breaker so only one circ will trip or be able to be turned off ?
And seems that article would still be satisfied.

Not to high jack. Thinking out loud
Click to expand...
Hate 210(4)(B). Hate 210(4)(B). Hate it so much it keeps me from sleeping at night.
 
Joseph mulherin said:
I'm new at this forum I'm trying to learn how to navigate my way around so bare with me. ok 120 volts 277 volts you use to could share your neutral now you have to pull a separate neutral for each circuit,there is a exception in the code book,but I've have only saw one person do this exception,do you follow maybe I'm not giving enough details
Click to expand...
You need to stop listening to hearsay of others and read what is written in 210.4. There is very little prohibitive language in there, there is additional requirements in there that you must comply with if you choose to use a multiwire branch circuit.

Not counting the neutral as a current carrying conductor for ampacity adjustments is found in 310.15(B) and conditions where it may be considered non current carrying (for ampacity adjustment reasons) are fairly well defined in that section.
 
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