1/2" plastic conduit

[pudgybear]

How many strands of #14 solid wire can be used in 1/2" conduit? Here's the scoop - power source on the west side of the garage and the entrance door on the east, i want to run power in the conduit from the source to the pair of switches by the door back up to the pair of lights, or would i be better off just using 3/4" conduit? one last question! going up the wall to the ceiling what kind of "elbow" do i use? The one idea is a long radius or would a fitting with the access door in it be better?

 

[pattenp]

Eleven #14 in 1/2". For a close fit to the corner you can use a 90 deg inside corner pull elbow. And use stranded wire in conduit, it's a lot easier to pull.

*

 

[Executive]

11 in a single conduit and those #14 are no longer good for 15 amps.

Chris

 

[theoldwizard1]

... or would i be better off just using 3/4" conduit?

Going 1 size up on conduit is ALWAYS a good idea unless it is cost prohibitive or there is just no space.

going up the wall to the ceiling what kind of "elbow" do i use? The one idea is a long radius or would a fitting with the access door in it be better?

The long radius pre-bent is often called a sweep. The elbow with the access cover on the outside is called a pulling elbow.

The one pattenp showed is also call a pulling elbow but the top comes off, making a much cleaner looking elbow when you are done.

For reference, if you are going through a wall you want a 90° LB

 

[alfredeneuman]

Because of derating, any more than 6 causes them to be rated less than 15 amps.

7-9 conductors needed to be derated to 70%, which in the case of #14, would be 14 amps.

You'd be able to upsize to #12, and put up to 20 in a single conduit (not 1/2" though) and it would rated at 15 amps.

 

[sberry]

This pretty much assumes he is trying to fill the pipe which may not be the case. Sounds like these are light circuits, no one likes to load them to the limit. A 1/2 pipe is ideal for this.

 

[pudgybear]

Sberry, you are correct, strickly light circuits, i plan on having 2 switches as i enter the garage throught the pedesrian door, so the wire from the source to the switches and back in the conduit up to the 2 lights,,,,, 1 floresent over the work bench and the other a 60 watt light to " lite up my way "

 

[Executive]

Because of derating, any more than 6 causes them to be rated less than 15 amps.

7-9 conductors needed to be derated to 70%, which in the case of #14, would be 14 amps.

You'd be able to upsize to #12, and put up to 20 in a single conduit (not 1/2" though) and it would rated at 15 amps.

This is accurate but it should be noted that the 20 conductors mentioned in the example would have to be #12 rated for 90*C (THHN) to be good for 15 amps. Table 310.15(B)(3)(a) gives a 50% derating factor for 20 conductors in a raceway and the 90* Column of 310.15(B)(16) can be used if the insulation is rated 90*. Also note that when applying the provisions of 310.15(B)(3)(a), we are talking about current carrying conductors. The grounded (neutral) of a 120 volt circuit is considered a current carrying conductor, but the grounded conductor of a multi-wire branch circuit is not. The grounding (Green) conductor is calculated for wire fill in conduit sizing but is not a current carrying conductor for derating purposes. This information may help the OP in designing his system. It may be to his advantage to use multi-wire branch circuits to help with derating.

Chris

 

[pattenp]

Ignore my pictured corner connector, I just realized you are using PVC conduit.

Eleven #14 in 1/2". For a close fit to the corner you can use a 90 deg inside corner pull elbow. And use stranded wire in conduit, it's a lot easier to pull.

*

 

[Charles (in GA)]

The grounded (neutral) of a 120 volt circuit is considered a current carrying conductor, but the grounded conductor of a multi-wire branch circuit is not.
Chris

Can you cite any reference for this. I am always in the learning mode and have never heard of this before. Would like to see where it comes from. Thanks.

Charles

 

[skiingman]

Can you cite any reference for this. I am always in the learning mode and have never heard of this before. Would like to see where it comes from. Thanks.

Charles

NEC 2011 310.15(B)5 and 6.

If you wire a multiwire circuit correctly, it shouldn't be possible for the current in the three conductors to total more than 2x that of a single conductor as the neutral currents from line are 180 degrees out of phase and cancel each other. (6) says EGCs don't count as current carrying conductors either.

 

[Executive]

NEC 2011 310.15(B)5 and 6.

If you wire a multiwire circuit correctly, it shouldn't be possible for the current in the three conductors to total more than 2x that of a single conductor as the neutral currents from line are 180 degrees out of phase and cancel each other. (6) says EGCs don't count as current carrying conductors either.

Well done! This gentleman knows his NEC!

Chris

 

[sberry]

Its a big advantage in some cases, even though the ground isn't counted for current carry it can contribute to pipe fill.

We did a change out a while back where it was original wired single circuits,,, its really not loaded but,,, we tie a black to a white and add a circuit, in the end it was the same number of wires but removed 1 current carrying conductor .

 

[PRH44]

NEC 2011 310.15(B)5 and 6.

If you wire a multiwire circuit correctly, it shouldn't be possible for the current in the three conductors to total more than 2x that of a single conductor as the neutral currents from line are 180 degrees out of phase and cancel each other. (6) says EGCs don't count as current carrying conductors either.

Harmonics confuse this a bit: the neutral has to carry the "triplen harmonic" current of the load. We are permitted some leeway, but when the major portion of the load is non-linear, the neutral is no longer considered to carry only unbalanced current from the other conductors, and thus must be counted.
Odd multiples of the third harmonic: 3rd, 9th, 15th, etc. do not cancel, but add together in the neutral conductor. In systems with many single-phase, nonlinear loads, the neutral current can actually exceed the phase current. The danger here is overheating because, there are no circuit breakers in the neutral conductor to limit the current.
examples of nonlinear loads are battery chargers, electronic ballasts, variable frequency drives, and switching mode power supplies.

 

[pattenp]

To me your statement is worded a little misleading. The neutral is a current carrying conductor, period. Being in a multibranch circuit does not make it a noncurrent carrying conductor. It's just not counted when making adjustments per 310.15(B)(3)(a). Not being considered and not being counted are two different things. That may be why Charles was questioning this.

This is accurate but it should be noted that the 20 conductors mentioned in the example would have to be #12 rated for 90*C (THHN) to be good for 15 amps. Table 310.15(B)(3)(a) gives a 50% derating factor for 20 conductors in a raceway and the 90* Column of 310.15(B)(16) can be used if the insulation is rated 90*. Also note that when applying the provisions of 310.15(B)(3)(a), we are talking about current carrying conductors. The grounded (neutral) of a 120 volt circuit is considered a current carrying conductor, but the grounded conductor of a multi-wire branch circuit is not. The grounding (Green) conductor is calculated for wire fill in conduit sizing but is not a current carrying conductor for derating purposes. This information may help the OP in designing his system. It may be to his advantage to use multi-wire branch circuits to help with derating.

Chris

 

[Executive]

The neutral is NOT always a current carrying conductor. In theory current is there, but in practice the current is cancelled by the opposing current of the "companion" part of the circuit in a multi-wire branch circuit.

The grounded conductor in a multi-wire branch circuit (MWBC) only carries the imbalance of the two (a MWBC in a three phase system will always have some current) ungrounded conductors and as such is not considered a current carrying conductor for the purposes of derating. In fact, in a perfectly balanced MWBC, (rare) the grounded conductor carries zero amps. This is a fact and is confirmed by Article 310.15, circuit theory, and common practice.

PRH44 raises an interesting twist to this in that harmonic currents, multiples of the fundamental 60hz frequency of our power system, can add to the overall current of a grounded conductor when the non-linear loads he mentioned are present. In this case, consideration must be taken for the added current in the grounded conductor. This consideration usually takes the form of an oversized grounded conductor, (sometimes called "Superneutral") and according to 310.15, under such conditions, that grounded conductor must also be calculated as current carrying for the purposes of derating. This phenomenon has no bearing on the presence or absence of a MWBC.

Chris

 

[pattenp]

I'm just saying by definition the neutral conductor is intended to carry current under normal conditions. Whether or not it's physically carrying current does not change its definition.

 

[Executive]

I'm just saying by definition the neutral conductor is intended to carry current under normal conditions. Whether or not it's physically carrying current does not change its definition.

Please share that definition.
And while you are looking it up, research why we all (incorrectly) call the grounded conductor a neutral. This will help you understand my point.


Chris

 

[pattenp]

NEC Article 100 definitions.

Please share that definition.
And while you are looking it up, research why we all (incorrectly) call the grounded conductor a neutral. This will help you understand my point.


Chris

 

[Executive]

Excellent. You have a code book. I don't have mine right here with me, but if I recall correctly, the NEC definition says something about carrying current under "normal conditions". A MWBC is not a "normal condition" and as such, Article 310.15(B)(5)(a) tells us that a neutral that only carries unbalanced current , such as on a MWBC, is not counted when calculating the derating required by Table 310.15(B)(3)(a), which is how this discussion got started in the first place. Look it up. I'm going from memory here.

Here's another thing to look at: a good explanation of how a MWBC works. http://www.nachi.org/forum/f19/explaining-multiwire-circuits-fun-3038/

Good discussion!

Chris

 

[pattenp]

I'm not disagreeing with you in this respect. I'm saying the neutral in a MWBC is still identified as a grounded current carrying conductor, but as you pointed out it is not counted when derating is required. I think we're getting our wires crossed over semantics. It's like all rectangles are squares, but not all squares are rectangles.

Excellent. You have a code book. I don't have mine right here with me, but if I recall correctly, the NEC definition says something about carrying current under "normal conditions". A MWBC is not a "normal condition" and as such, Article 310.15(B)(5)(a) tells us that a neutral that only carries unbalanced current , such as on a MWBC, is not counted when calculating the derating required by Table 310.15(B)(3)(a), which is how this discussion got started in the first place. Look it up. I'm going from memory here.

Here's another thing to look at: a good explanation of how a MWBC works. http://www.nachi.org/forum/f19/explaining-multiwire-circuits-fun-3038/

Good discussion!

Chris

 

[dledinger]

And while you are looking it up, research why we all (incorrectly) call the grounded conductor a neutral.

Chris

The NEC defines the common point of a wye system, or the midpoint of a 3 wire system as the Neutral Point.

Neutral conductor is defined as the conductor connected to the neutral point of a system.

For the purposes of the discussions on this forum, the Neutral is the grounded conductor 99% of the time and there's nothing incorrect about it.

 

[Executive]

The NEC defines the common point of a wye system, or the midpoint of a 3 wire system as the Neutral Point.

Neutral conductor is defined as the conductor connected to the neutral point of a system.

For the purposes of the discussions on this forum, the Neutral is the grounded conductor 99% of the time and there's nothing incorrect about it.

First: all neutrals are grounded conductors but not all grounded conductors are neutrals. (We can leave the ungrounded secondary of a separately derived system out of this for the sake of clarity, and it is very unlikely that someone on this board is working with a corner grounded delta.)

The main discussion here in this thread is that the grounded conductor of a multi-wire branch circuit is NOT required to be counted as a current carrying conductor for purposes of amp acuity adjustment for more than three current carrying conductors in a raceway. That's it.

Chris

 

[dledinger]

OK, I can play like that:

FIRST: A neutral conductor is NOT, by definition, a grounded conductor.

SECOND: A grounded conductor is NOT, by definition, a neutral.

Like I said above, for the purpose of most discussions on this forum, there is nothing at all incorrect about calling the grounded conductor a neutral.

We can get back on topic if you want, but this was a good opportunity to help others understand this.

 

[Executive]

OK, I can play like that:

FIRST: A neutral conductor is NOT, by definition, a grounded conductor.

SECOND: A grounded conductor is NOT, by definition, a neutral.

Like I said above, for the purpose of most discussions on this forum, there is nothing at all incorrect about calling the grounded conductor a neutral.

We can get back on topic if you want, but this was a good opportunity to help others understand this.

You are incorrect.

Chris

 

[dledinger]

Lets see what the NEC says:

2014 NEC..

Grounded Conductor: A system or circuit conductor that is intentionally grounded.

Neutral Conductor: The conductor connected to the neutral point of a system that is intended to carry current under normal conditions.

2011: Same

2008: Same

I believe that you are confused on these definitions due to a lack of understanding of both the NEC definitions and article 250, which requires that systems that can obtain 150V or less to ground by grounding, be grounded. That doesn't change the definition of neutral, though.

The main discussion here in this thread is that the grounded conductor of a multi-wire branch circuit is NOT required to be counted as a current carrying conductor for purposes of amp acuity adjustment for more than three current carrying conductors in a raceway.

This is also incorrect and an oversimplification of 310.15, as a grounded conductor that is part of multiwire branch circuit from a 3 phase wye WOULD require derating.

 

[Executive]

Lets see what the NEC says:

2014 NEC..

Grounded Conductor: A system or circuit conductor that is intentionally grounded.

Neutral Conductor: The conductor connected to the neutral point of a system that is intended to carry current under normal conditions.

2011: Same

2008: Same

I believe that you are confused on these definitions due to a lack of understanding of both the NEC definitions and article 250, which requires that systems that can obtain 150V or less to ground by grounding, be grounded. That doesn't change the definition of neutral, though.



This is also incorrect and an oversimplification of 310.15, as a grounded conductor that is part of multiwire branch circuit from a 3 phase wye WOULD require derating.

I'm pretty sure I have a good understanding of the Code. I've been teaching it for over 20 years and have over 300 students licensed through my program.

You need to read all of my posts in this thread, particularly #16 which references three phase MWBCs.

"...systems that can obtain 150V or less to ground by grounding, be grounded..."

What?

Unless connected to an ungrounded secondary of a separately derived system, a neutral is always grounded.

A grounded conductor can be a corner grounded delta, but you knew that since you read my post #23 above.

The NEC has only recently in the past few cycles adopted the term neutral more globally. The more correct term is grounded conductor. Article 200 for example refers to identification of grounded conductors not neutrals.

None of this changes my original premise that the OP consider using multi wire branch circuits for his job so that he does not have to count his grounded (ok neutral) conductor in his ampacity adjustment calculation for his single phase loads.

Chris

 

[dledinger]

I teach code too, but I also know that doing something for a long time does not make one right. There are plenty of people that do wrong their whole lives. I don't spout off credentials to use as a crutch when I know I am wwwwwwwrrr. Ah hell, I can't even say it.

Regarding, "What"? I'm not typing the code out again because you have a hard time reading it. Check out 250.20 regarding systems 50-1000 volts, which says exactly what I said in code language.

You're adding "unless" to your definition of neutral now, in apparent effort to make yourself more correct.

Calling a conductor connected to the neutral point of a system a neutral is not in any way less correct than calling it a grounded conductor. That is just silly. It's either a neutral or it's not. The NEC defines it as a neutral, and has for years.

I understood your original purpose, but when you oversimplified it you made it wrong. Not everyone may read the whole thread and they could be misled by your error.

 

[dledinger]

None of this changes my original premise that the OP consider using multi wire branch circuits for his job so that he does not have to count his grounded (ok neutral) conductor in his ampacity adjustment calculation for his single phase loads.

Think about this, too, while you're getting frustrated...

The referenced conductor as part of a MWBC is carrying only imbalanced current because it's the neutral, not because it's grounded. Even the NEC in this case calls it a neutral.

So is "neutral" conductor really less correct than grounded conductor?

I think in this case it's far MORE correct.

 

[sberry]

I'm pretty sure I have a good understanding of the Code. I've been teaching it for over 20 years and have over 300 students licensed through my program.

You need to read all of my posts in this thread, particularly #16 which references three phase MWBCs.

"...systems that can obtain 150V or less to ground by grounding, be grounded..."

What?

Unless connected to an ungrounded secondary of a separately derived system, a neutral is always grounded.

A grounded conductor can be a corner grounded delta, but you knew that since you read my post #23 above.

The NEC has only recently in the past few cycles adopted the term neutral more globally. The more correct term is grounded conductor. Article 200 for example refers to identification of grounded conductors not neutrals.

None of this changes my original premise that the OP consider using multi wire branch circuits for his job so that he does not have to count his grounded (ok neutral) conductor in his ampacity adjustment calculation for his single phase loads.

Chris

The guy wants to switch a couple lights, does he need a mwbc? Makes one wonder about a couple 20 yr teachers cant even get a simple switch loop in a 15 a circuit right, doesn't even need a white wire in it. Probably runs 200 watts of lights.

 

[Executive]

The guy wants to switch a couple lights, does he need a mwbc? Makes one wonder about a couple 20 yr teachers cant even get a simple switch loop in a 15 a circuit right, doesn't even need a white wire in it. Probably runs 200 watts of lights.

Actually 404.2(C) requires a GROUNDED CONDUCTOR where switches are present for lighting loads.

(Unless, of course, the circuit is in a raceway as in the case of the OP)

Chris