milwaukeesteve
Senior Member
- Location
- Milwaukee, WI
Re: Parallel feeders single phase
Thank you Roger.
Thank you Roger.
Parallel feeders single phase
- Thread starter wayne123
- Start date
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milwaukeesteve
Senior Member
- Location
- Milwaukee, WI
Re: Parallel feeders single phase
Don, I do have to disagree. Roger has talked about things, as I mentioned, that are correct wiring methods. I even commented on his picture and how the wiring is correct.
I have reservations with how cavalier he is with this being not that big a deal.
I also have a problem with him stating that PVC would be legal. He didn't quantify when and where PVC is legal, like the 300.3(1)exception does; underground. Nor did he go into detail about using PVC as a non metallic sheath that is ran inside another raceway(300.3(B)(3).
My main problem is in relation to the original topic of this thread. Roger has strayed from the path. This can confuse someone if they don't know what they are doing. When dealing with parallel conductors, phasing, Current Transformers, and electromagnitism, especially the effects of each, the installer needs to know what he is doing.
Again, Don, I disagree with you about all of Roger's view of what the code permits.
Read 300.3(B)(1) and (3) again and tell me if I am wrong about PVC used as a raceway.
What the guy did in Wayne's example is wrong. Period.
[ June 01, 2005, 01:10 PM: Message edited by: milwaukeesteve ]
Don, I do have to disagree. Roger has talked about things, as I mentioned, that are correct wiring methods. I even commented on his picture and how the wiring is correct.
I have reservations with how cavalier he is with this being not that big a deal.
I also have a problem with him stating that PVC would be legal. He didn't quantify when and where PVC is legal, like the 300.3(1)exception does; underground. Nor did he go into detail about using PVC as a non metallic sheath that is ran inside another raceway(300.3(B)(3).
My main problem is in relation to the original topic of this thread. Roger has strayed from the path. This can confuse someone if they don't know what they are doing. When dealing with parallel conductors, phasing, Current Transformers, and electromagnitism, especially the effects of each, the installer needs to know what he is doing.
Again, Don, I disagree with you about all of Roger's view of what the code permits.
Read 300.3(B)(1) and (3) again and tell me if I am wrong about PVC used as a raceway.
What the guy did in Wayne's example is wrong. Period.
[ June 01, 2005, 01:10 PM: Message edited by: milwaukeesteve ]
wayne123
Senior Member
- Location
- North Carolina
Re: Parallel feeders single phase
Steve, sorry to hear about your loss.
I have quietly kept up with the comments on this forum, trying to see everyones point on this. Roger, I respect your opinions because you have been around this forum for sometime and I definetly read every post from you when I see one because I know that I will probably learn something but I do believe that we have , as Steve and Shelco have said gotten off of the subject. I have read the code article on this and I believe that the installation was done incorrectly and I am sure the inspector will see it that way too. I really don't want to debate or argue with any of my forum IDOLS. I am just here to learn and read up on what everyone is up to.It's great that we have this forum that Mike Holt has created for us to learn from each other and I thouroughly enjoy all of the comments I get when I post a question. I have been a licensed elect. contractor for 13 years and have been in the business for about 17 yrs. I have seen alot of stuff and when I see something that I am not sure of I call upon my friends here for input, man did I get some input on this one. I will hopefully be able to talk with the inspector about this next week when he come to this job and I will let you know what his thoughts are. Thanks for the input guys! Keep up the good work!!!
Steve, sorry to hear about your loss.
I have quietly kept up with the comments on this forum, trying to see everyones point on this. Roger, I respect your opinions because you have been around this forum for sometime and I definetly read every post from you when I see one because I know that I will probably learn something but I do believe that we have , as Steve and Shelco have said gotten off of the subject. I have read the code article on this and I believe that the installation was done incorrectly and I am sure the inspector will see it that way too. I really don't want to debate or argue with any of my forum IDOLS. I am just here to learn and read up on what everyone is up to.It's great that we have this forum that Mike Holt has created for us to learn from each other and I thouroughly enjoy all of the comments I get when I post a question. I have been a licensed elect. contractor for 13 years and have been in the business for about 17 yrs. I have seen alot of stuff and when I see something that I am not sure of I call upon my friends here for input, man did I get some input on this one. I will hopefully be able to talk with the inspector about this next week when he come to this job and I will let you know what his thoughts are. Thanks for the input guys! Keep up the good work!!!
- Location
- Illinois
- Occupation
- retired electrician
Re: Parallel feeders single phase
Steve,
It is my opinion that PVC conduit is a wiring method with a nonmetallic sheath and that the exception to 300.3(B)(1) is not needed as 300.3(B)(3) permits this type of installations in all locations, not just underground.
Don
Steve,
It is my opinion that PVC conduit is a wiring method with a nonmetallic sheath and that the exception to 300.3(B)(1) is not needed as 300.3(B)(3) permits this type of installations in all locations, not just underground.
Don
Re: Parallel feeders single phase
The fact that pvc is used is not enough to be code compliant. All of Rogers situations and methods are correct, but all of the criteria as rogers has metioned must be met. And it is because we do understand the theory of electricity is why we are able to debate this and know full well what is right and what is not. Most situations would require rhat A phase B phase and neutral be in the same conduit.
The fact that pvc is used is not enough to be code compliant. All of Rogers situations and methods are correct, but all of the criteria as rogers has metioned must be met. And it is because we do understand the theory of electricity is why we are able to debate this and know full well what is right and what is not. Most situations would require rhat A phase B phase and neutral be in the same conduit.
milwaukeesteve
Senior Member
- Location
- Milwaukee, WI
Re: Parallel feeders single phase
Don,
300.3(b)(3) does not simply allow PVC. If you read it again, it says a nonmetallic sheath that is ran in another raceway. That sheath has to be a wiring method like it says, and has to be a nonmetallic and nonmagnetic. The raceway can be anything that is a legal raceway.
Again, 300.3(b)(3) does not give us permission to use PVC as just a raceway alone.
Don,
300.3(b)(3) does not simply allow PVC. If you read it again, it says a nonmetallic sheath that is ran in another raceway. That sheath has to be a wiring method like it says, and has to be a nonmetallic and nonmagnetic. The raceway can be anything that is a legal raceway.
Again, 300.3(b)(3) does not give us permission to use PVC as just a raceway alone.
- Location
- Illinois
- Occupation
- retired electrician
Re: Parallel feeders single phase
Steve,
So based on your reading of the section, I could use a ferrous raceways with all of A phase in one conduit and all of B phase in another conduit as long as the conductors had an overall nonmetallic sheath. That would be a problem. The section clearly permits the use of multiple raceways, and the only way that can work is if the raceways are nonferrous.
Don
Steve,
So based on your reading of the section, I could use a ferrous raceways with all of A phase in one conduit and all of B phase in another conduit as long as the conductors had an overall nonmetallic sheath. That would be a problem. The section clearly permits the use of multiple raceways, and the only way that can work is if the raceways are nonferrous.
Don
Re: Parallel feeders single phase
Back to the original question?
?I thought that with parallel feeders A@B run together. Am I correct??
No, not always, there are exceptions.
Until Wayne gives us all the information, we will not know if THIS PARTICULAR installation is OK.
What we have here is a failure to communicate.
Back to the original question?
?I thought that with parallel feeders A@B run together. Am I correct??
No, not always, there are exceptions.
Until Wayne gives us all the information, we will not know if THIS PARTICULAR installation is OK.
What we have here is a failure to communicate.
karl riley
Senior Member
Re: Parallel feeders single phase
Maybe at this point we can relax for a moment and look at a wider picture, aside from what the 2005 Code does or does not allow.
The effects of uncancelled magnetic fields is fairly new to the consciousness of most electricians. In the NEC it is treated in relation to the inductive heating of ferrous metals and the degradation of insulation. And this is dealt with in relation to the specific electrical hardware involved.
But let's for a moment look at the reality beyond these limitations. Steve mentioned a dog's chain, which was easy to treat with humor, but any metal object in proximity would be heated and carry electrical current. Many electronic devices would be affected because of the induced currents and voltages. (The NEC does not address electronic interference). Non-ferrous metals such as aluminum will also heat due to induced current. Are we forgetting that transformers induce currents in non-ferrous copper, and that copper heats also?
Imagine a Code compliant PVC carrying a single conductor with 2000A under a floor in a building. It could be done in a Code compliant way. A computer monitor would have to be 1300 feet away from it to be free from flickering (at 10 mG). A person within 1 meter of the conductor would be in a 4000 milligauss magnetic field. Childhood leukemia doubles at 4 mG exposure (WHO, IARC research review).
So aside from whether one can cut the right slots to satisfy the exceptions, remember that the NEC is not the authority to go to for the full story on the effects of high magnetic fields.
Karl
Maybe at this point we can relax for a moment and look at a wider picture, aside from what the 2005 Code does or does not allow.
The effects of uncancelled magnetic fields is fairly new to the consciousness of most electricians. In the NEC it is treated in relation to the inductive heating of ferrous metals and the degradation of insulation. And this is dealt with in relation to the specific electrical hardware involved.
But let's for a moment look at the reality beyond these limitations. Steve mentioned a dog's chain, which was easy to treat with humor, but any metal object in proximity would be heated and carry electrical current. Many electronic devices would be affected because of the induced currents and voltages. (The NEC does not address electronic interference). Non-ferrous metals such as aluminum will also heat due to induced current. Are we forgetting that transformers induce currents in non-ferrous copper, and that copper heats also?
Imagine a Code compliant PVC carrying a single conductor with 2000A under a floor in a building. It could be done in a Code compliant way. A computer monitor would have to be 1300 feet away from it to be free from flickering (at 10 mG). A person within 1 meter of the conductor would be in a 4000 milligauss magnetic field. Childhood leukemia doubles at 4 mG exposure (WHO, IARC research review).
So aside from whether one can cut the right slots to satisfy the exceptions, remember that the NEC is not the authority to go to for the full story on the effects of high magnetic fields.
Karl
- Location
- Massachusetts
Re: Parallel feeders single phase
Karl I agree with you there is a difference between what is required and what is a good idea.
I do have a question for you.
Part of the requirements for running isolated phases is "The raceways shall be installed in close proximity"
Will there still be EMF issues if this rule is followed?
Karl I agree with you there is a difference between what is required and what is a good idea.
I do have a question for you.
Part of the requirements for running isolated phases is "The raceways shall be installed in close proximity"
Will there still be EMF issues if this rule is followed?
Re: Parallel feeders single phase
Karl, I will point out the same code requirement as Bob,
You have said more than once in the past that EMF and PQ issues can most times be traced back to code violations, this would be no different.
I'll say again to those who don't understand the theory behind, or are scared of this method, don't use it.
Wayne, thanks for the kind words.
Roger
Karl, I will point out the same code requirement as Bob,
and if done this way there would not be a problem, i.e. magnetic field elimination due to current cancellation.
You have said more than once in the past that EMF and PQ issues can most times be traced back to code violations, this would be no different.
I'll say again to those who don't understand the theory behind, or are scared of this method, don't use it.
Wayne, thanks for the kind words.
Roger
karl riley
Senior Member
Re: Parallel feeders single phase
Right,if the separated conduits are grouped together closely, cancellation would occur. How they are grouped would be important. There has been a huge amount of study by EPRI on the best ways to group conductors on power lines to reduce the magnetic field.
Reverse phasing works best when they have to be spread out due to high voltage. This could also be used when paralleling, by having two layers of conduits carrying ABC over CBA for 3 phase, or AB over BA for single phase, with neutrals running with each.
Undergrounding (for power lines)is best if grouped together closely or in the same cable.
Sooner or later there will be max magnetic field specs for installations, but those will probably show up in the specs before the NEC adopts them, well into the future. Because of the lack of these specs I have had a lot of business dealing with the consequences in office buildings.
Meanwhile, it wouldn't hurt, even as a curiosity measure, to carry a gaussmeter in your box and check out the reading after paralelling.
Karl
Right,if the separated conduits are grouped together closely, cancellation would occur. How they are grouped would be important. There has been a huge amount of study by EPRI on the best ways to group conductors on power lines to reduce the magnetic field.
Reverse phasing works best when they have to be spread out due to high voltage. This could also be used when paralleling, by having two layers of conduits carrying ABC over CBA for 3 phase, or AB over BA for single phase, with neutrals running with each.
Undergrounding (for power lines)is best if grouped together closely or in the same cable.
Sooner or later there will be max magnetic field specs for installations, but those will probably show up in the specs before the NEC adopts them, well into the future. Because of the lack of these specs I have had a lot of business dealing with the consequences in office buildings.
Meanwhile, it wouldn't hurt, even as a curiosity measure, to carry a gaussmeter in your box and check out the reading after paralelling.
Karl
pierre
Senior Member
- Location
- Westchester County, New York
Re: Parallel feeders single phase
With Karl's vast knowledge on the "effects" that may occur, it helps with a different perspective towards possible health affects and electronic interference considerations.
But back to the NEC for a minute.
Steve keeps mentioning "sheath", I do not see where sheath is mentioned. Maybe someone could point this out to me.
"300.3 Conductors.
(A) Single Conductors. Single conductors specified in Table 310.13 shall only be installed where part of a recognized wiring method of Chapter 3.
(B) Conductors of the Same Circuit. All conductors of the same circuit and, where used, the grounded conductor and all equipment grounding conductors and bonding conductors
shall be contained within the same raceway, auxiliary gutter, cable tray, cablebus assembly, trench, cable, or cord, unless otherwise permitted in accordance with 300.3(B)(1) through (4).
(1) Paralleled Installations. Conductors shall be permitted to be run in parallel in accordance with the provisions of 310.4. The requirement to run all circuit conductors within the same raceway, auxiliary gutter, cable tray, trench, cable, or cord shall apply separately to each portion of the paralleled installation, and the equipment grounding conductors shall comply with the provisions of 250.122.
Parallel runs in cable tray shall comply with the provisions of 392.8(D).
Exception: Conductors installed in nonmetallic raceways run underground shall be permitted to be arranged as isolated phase installations. The raceways shall be installed in close proximity, and the conductors shall comply with the
provisions of 300.20(B).
Concentrating on the exception seems to spell this out, that a PVC raceway is permitted.
I know this is usually installed in an open bottom switchgear, I have in the past been involved in a large IBM building where there were 20 sets of PVC raceways entering the building with isolated phases, making the termination a whole lot easier and a lot neater - especially because our company did the PM in this building/complex as well.
I agree with Roger that this may not be an everyday occurrance in our industry, but it can be installed this way, and if installed properly would be a safe installation.
This is also one of the reasons I love this industry: we have to constantly be aware of what we are doing and have new challenges everyday
With Karl's vast knowledge on the "effects" that may occur, it helps with a different perspective towards possible health affects and electronic interference considerations.
But back to the NEC for a minute.
Steve keeps mentioning "sheath", I do not see where sheath is mentioned. Maybe someone could point this out to me.
"300.3 Conductors.
(A) Single Conductors. Single conductors specified in Table 310.13 shall only be installed where part of a recognized wiring method of Chapter 3.
(B) Conductors of the Same Circuit. All conductors of the same circuit and, where used, the grounded conductor and all equipment grounding conductors and bonding conductors
shall be contained within the same raceway, auxiliary gutter, cable tray, cablebus assembly, trench, cable, or cord, unless otherwise permitted in accordance with 300.3(B)(1) through (4).
(1) Paralleled Installations. Conductors shall be permitted to be run in parallel in accordance with the provisions of 310.4. The requirement to run all circuit conductors within the same raceway, auxiliary gutter, cable tray, trench, cable, or cord shall apply separately to each portion of the paralleled installation, and the equipment grounding conductors shall comply with the provisions of 250.122.
Parallel runs in cable tray shall comply with the provisions of 392.8(D).
Exception: Conductors installed in nonmetallic raceways run underground shall be permitted to be arranged as isolated phase installations. The raceways shall be installed in close proximity, and the conductors shall comply with the
provisions of 300.20(B).
Concentrating on the exception seems to spell this out, that a PVC raceway is permitted.
I know this is usually installed in an open bottom switchgear, I have in the past been involved in a large IBM building where there were 20 sets of PVC raceways entering the building with isolated phases, making the termination a whole lot easier and a lot neater - especially because our company did the PM in this building/complex as well.
I agree with Roger that this may not be an everyday occurrance in our industry, but it can be installed this way, and if installed properly would be a safe installation.
This is also one of the reasons I love this industry: we have to constantly be aware of what we are doing and have new challenges everyday
Re: Parallel feeders single phase
Roger , you are unbelievable. I take great offence to your inference that people on this board are not as smart as you. ( those that don't understand or are afraid.)most of us understand full well the "theory behind this and fear has nothing to do with it. Probably 80% or better of parallel feeders would require the conventional method. We as contractors need to do our work the most efficient way possible to turn a profit, and to spend the time making sure all of these criteria are met and cutting slots etc. is just pain economically foolish. We can have these discussions with out resorting to insults.
[ June 04, 2005, 06:10 PM: Message edited by: shelco ]
Roger , you are unbelievable. I take great offence to your inference that people on this board are not as smart as you. ( those that don't understand or are afraid.)most of us understand full well the "theory behind this and fear has nothing to do with it. Probably 80% or better of parallel feeders would require the conventional method. We as contractors need to do our work the most efficient way possible to turn a profit, and to spend the time making sure all of these criteria are met and cutting slots etc. is just pain economically foolish. We can have these discussions with out resorting to insults.
[ June 04, 2005, 06:10 PM: Message edited by: shelco ]
- Location
- Massachusetts
Re: Parallel feeders single phase
Shelco
It seems that you just do not like this type of installation.
Fine don't do it, we are each entitled to work how we want within the confines of the NEC.
Isolated phase installations be done safely, efficiently and code compliantly.
The few times I have used that exception it saved labor and money. And I did not have to cut any slots.
Shelco
It seems that you just do not like this type of installation.
Fine don't do it, we are each entitled to work how we want within the confines of the NEC.
Isolated phase installations be done safely, efficiently and code compliantly.
The few times I have used that exception it saved labor and money. And I did not have to cut any slots.
Re: Parallel feeders single phase
iwire
You are correct I don't like this method ,just personal preference, but I don't begrudge any one from using it. I do take offence that if we don't use it we are some how less informed or educated. I don't use methods just to show my level of knowledge I use the most effective and efficient methods for the application. Nothing more nothing less. Nothing personal.
Shelco
iwire
You are correct I don't like this method ,just personal preference, but I don't begrudge any one from using it. I do take offence that if we don't use it we are some how less informed or educated. I don't use methods just to show my level of knowledge I use the most effective and efficient methods for the application. Nothing more nothing less. Nothing personal.
Shelco
Re: Parallel feeders single phase
Shelco, my statement has nothing to do with me thinking I'm smarter than you or any one else.
I don't do many installations that would come under chapter 8, so admittedly I'm not up on these methods and would not try to use them with out researching the chapter. This does not mean the people who do use this chapter regularly are smarter than me, it's just that they use these methods and are comfortable with them.
Hop on the HD and cool off.
BTW, why did you think I was aiming my statement towards you?
Roger
Shelco, my statement has nothing to do with me thinking I'm smarter than you or any one else.
I don't do many installations that would come under chapter 8, so admittedly I'm not up on these methods and would not try to use them with out researching the chapter. This does not mean the people who do use this chapter regularly are smarter than me, it's just that they use these methods and are comfortable with them.
Hop on the HD and cool off.
BTW, why did you think I was aiming my statement towards you?
Roger
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