Parallel feeders single phase

[iwire]

Re: Parallel feeders single phase

Originally posted by milwaukeesteve:
In the case of running the underground installations as described in PVC, these raceways DO NOT enter a metal cabinet throug a knock out or with the use of a metal lockring. These installations are ONLY into open bottom switch gear.
That way you do not encircle the phase conductor with a metal circle.

Steve now you saying things that the NEC does not state.

300.3(B)(1)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).

So far we must use non-metallic raceways underground.

300.20(B) Individual Conductors. Where a single conductor carrying alternating current passes through metal with magnetic properties, the inductive effect shall be minimized by (1) cutting slots in the metal between the individual holes through which the individual conductors pass or (2) passing all the conductors in the circuit through an insulating wall sufficiently large for all of the conductors of the circuit.

We could bring the isolated phase conduits into a steel bottom enclosure if we just have to cut the slots.

We could also use brass or aluminum at the entry point. When we run single conductor MI we use cut a square out of the enclosure and use a brass plate over the hole to enter the MI cables through.

The few times I have brought in a service this way it was with open bottom gear.

 

[iwire]

Re: Parallel feeders single phase

Here is a good picture of single conductor MI cable entries.

 

[roger]

Re: Parallel feeders single phase

Jim,

Originally posted by james wuebker:
Roger, I read 300.3(B) then looked at 300.3(1). It does stay that you can run them like you explained if it is an underground run. I think he's running this somewhere inside the building which what you are staying doesn't apply now. If you can show me I'm wrong please let me know. A good learning process for this old guy.
Thanks!
Jim

I'm not sure of the installation in the Waynes original post either, my point is that it is allowed in PVC and underground per 300.3. It is actually much easier to keep conductors the same length as well as keeping the gear itself neat when you may be talking a Tri, Quad, or more raceway fed service or feeder.

I don't see an electrical or code reason that two or more of the same legs or phases and a neutral as described in the original post would be a problem if installed per the Exception of 300.3(B)(1).

Roger

 

[wayne123]

Re: Parallel feeders single phase

Hey Guys, sorry I haven't responded to all this ( been busy) but to clear the install up a little... The meter is a 320 Amp mounted on the outside of the building, the conductors are run thru 2 1/2 " PVC which comes out the bottom of the meter and then LB's thru a concrete block wall into the 400A panel. There is no underground feeders.I have not had a chance to return to the job for about 2 weeks but I did tell the job super that he needed to talk to the electrcian that did the work. I told him that I will make the changes but I think the person who did the work should be responsible. Heck, he might even learn something.

 

[charlie]

Re: Parallel feeders single phase

Why can't 300.3(B)(3) be used for this application?

Nonferrous Wiring Methods Conductors in wiring methods with a nonmetallic or other nonmagnetic sheath, where run in different raceways, auxiliary gutters, cable trays, trenches, cables, or cords, shall . . .

This infers that the isolated phase installations may be use in other than underground installations. In other words, why have the rules if you can't do it?

 

[milwaukeesteve]

Re: Parallel feeders single phase

Hey Bob,
I know what I had stated is not actually in the NEC (about running into an opened bottom cabinet).
What I am using is electrical knowledge. I know that electromagnitism needs to be avoided, else we will have chocking, heating, and damage to the insulation.

300.3(B)(1) states that the requirement to run all conductors (310.4) shall apply seperately to each portion of the paralleled installation.
Notice that it says paralleled installation, not pralleled phases or conductors.

We have to maintain the integrity of a single conductor while installing it as several conductors. That is why 310.4 is so detailed.

Now, for the U/G PVC installation. Granted, Bob, I did say ONLY. I didn't mean ONLY as far as what I had listed. I meant that we can ONLY install single phases like this if we install it in limited instances and with certain precautionary steps. They are listed in 300.20(B) None that are listed are standard knockout,locknut installations like we use in normal wiring.

 

[milwaukeesteve]

Re: Parallel feeders single phase

wayne123,
For this installation, parallel installations must follow 300.3(B)(1). This requires all phase conductors, neutrals and EGC to be within each raceway.
For the conductors themselves, they must comply with 310.4. They must be the same length, same material, same size, same insulation, and be terminated the same. They must be the same.

 

[roger]

Re: Parallel feeders single phase

Steve,

Originally posted by milwaukeesteve:
wayne123,
For this installation, parallel installations must follow 300.3(B)(1). This requires all phase conductors, neutrals and EGC to be within each raceway.

Wayne said PVC, read 300.3(B)(3) as Charlie pointed out.

Roger

[ May 24, 2005, 03:54 PM: Message edited by: roger ]

 

[milwaukeesteve]

Re: Parallel feeders single phase

Roger,
If you use a non ferrous wiring method, then it describes what steps to take at the cabinet opening or connection to minimize the effect of the electromagnitism.

Where are you going to cut notches into lockrings and the cabinet in a NEMA 3 box. There goes your weather proofing.

Besides, it says non ferrous wiring method. That metal locknut is still part of the wiring method.

300.3.b.3 is not all inclusive to include any PVC runs you make. It is specific as to what needs to be done in a certain installation. It states withtin close proximity of each other, due to the EM characteristics. Then it tells you how you can enter a cabinet.

This is not an installation that Wayne is installing. Not even close.


You don't need to go into INTENT to figure out what these parallel conductor/raceway codes are talking about. Again, any electrician should have learned the basics of electromagnitism, and should know why you would NOT put the same phase conductors together in a raceway without a cancelling phase to compliment it.
We don't do this in 1/2"EMT and a single conductor, nor do we do this in 8000A SE conductors paralleled 14 times.

 

[roger]

Re: Parallel feeders single phase

Steve, I for one am tickled that you know some basic electrical theory,

Again, any electrician should have learned the basics of electromagnitism, and should know why you would NOT put the same phase conductors together in a raceway without a cancelling phase to compliment it.

but you missed it there. In a PVC raceway all conductors of any one leg or phase will still cancel the EMF if run in close proximity with other PVC raceways carrying other legs or phases and the same thing if it might include a neutral.

The meter can could be aluminum, so no problem there.

The PVC raceways could enter the bottom of the NEMA 3 inclosure where we could cut slots ajoining the two openings, so we have solved your concern here.

The PVC could also terminate with alumunum lock nuts, so another of your concerns are out the window.

You'll have to do better in your argument, and no, "intent" is not part of it.

Read 300.3(B)(3) again.

Roger

[ May 25, 2005, 01:54 PM: Message edited by: roger ]

 

[shelco]

Re: Parallel feeders single phase

Why would you not run it with phase and neutral conductors in the same cond. to begin with, this eliminates all doubt. I for the life of me cannot see the reason to do it any other way.
If you have to pick apart the code to make it right, even if ultimately it is, why bother when there is a method that has no doubt.

 

[roger]

Re: Parallel feeders single phase

Shelco, why do you think this is picking apart the code?

In reality, what may seem strange to you is normal for others, for instance read 330.10(A)(13), this is one place we have used this type of installation in industrial applications, it is not even questioned.

Other reasons have already been touched on in this thread.

Roger

 

[milwaukeesteve]

Re: Parallel feeders single phase

What you are talking about Roger is very specific installations, with definite reasons as to why you would install it that way.

There should be absolutely no good reason for Waynes situation to happen. If you know what you are doing, you would not install all of one phase inside one raceway in this or any other normal instance.
You should not be arguing me on this in respect to Waynes post. The installation methods that you are citing are completely different. It is unfair to Wayne that he asks for our help, and we argue about something not pertinent.

Basic Electric Theory cannot allow us to install in a fashion that this thread was based on. If you do you are asking for the following:
-Impedance on the conductor at the point of the electromagnet (ie. locknut or metal cabinet)
-At minimum, lower efficiency due to wasted electricity.
-Heat generated by the impedance
-Vibration on the conductor at the point of impedance and the electromagnet
-Breakdown of insulation at point of choke due to impedance, heat and vibration.
-Terminations failing due to Heat and vibration on the conductor.


Do you want Wayne to leave this post confused because you are arguing something that does not pertain to him?

 

[roger]

Re: Parallel feeders single phase

Steve, Steve, Steve,

If you know what you are doing, you would not install all of one phase inside one raceway in this or any other normal instance.

I've already pointed out that is not true.

You should not be arguing me on this in respect to Waynes post. The installation methods that you are citing are completely different.

Even though this may be true, how have you come to that conclusion? Are you sure the meter can, panel, and PVC attachment is in a magnetic material? (yes it probably is)

Basic Electric Theory cannot allow us to install in a fashion that this thread was based on.

Same as above.

BTW, I,m pointing out methods and code, you seem to be arguing.

Roger

[ May 25, 2005, 04:48 PM: Message edited by: roger ]

 

[milwaukeesteve]

Re: Parallel feeders single phase

Roger, you are pointing out code articles that don't pertain.
Again, do you not realize what harm can be done by installing this way. The installations that you mention, that follow the code rules you cite, are very specific installations, done by someone that knows what they are doing.
If he has a NEMA 3 rated 400Amp Meter Socket that is non ferrous, and lock nuts that is non ferrous, and 2 interior panels that are non ferrous, and again 2 lock nuts that are non ferrous... then you could make the arguement that this installation fits within these code rules.

However, God forbid that the homeowner ties the dogs chain around one of the incoming raceways. That chain would become too hot to even remove it by hand.

Is this what you would call a good installation, just because you could do it per this code rule?

 

[roger]

Re: Parallel feeders single phase

Steve,

The installations that you mention, that follow the code rules you cite, are very specific installations,

you keep saying this, the code sections I have mentioned are Chapter 3 General wiring methods.

If I were quoting from chapter 5 through 8 you may have a point, but the truth is there is nothing special about this method except to those unfamiliar with it.

Give Wayne credit to understand my posts, he has been around here for quite awhile, and if he is unsure he'll ask more questions.

If the code is followed here (as well as in other areas) all your basic AC concerns you keep bringing up will not be an issue and Rover will be safe.

Roger

 

[iwire]

Re: Parallel feeders single phase

Originally posted by milwaukeesteve:
Where are you going to cut notches into lockrings and the cabinet in a NEMA 3 box. There goes your weather proofing.

Besides, it says non ferrous wiring method. That metal locknut is still part of the wiring method.

How about a die-cast lock ring?

Non-ferris is not the same as non-metallic.

The fact is isolated phase installations are safe and can be code complaint.

Most MI cable installations are isolated phase.

[ May 25, 2005, 08:24 PM: Message edited by: iwire ]

 

[shelco]

Re: Parallel feeders single phase

Roger
Perhaps I used the wrong terminology when I said pick the code apart. What I meant was if you are running two parallel conduits and you are pulling parallel feeders why would you not use the method that would never come under question VS. one that you would have to hunt down one or more code sections, articles and exceptions to insure its legality? I see no reason why you would want to put yourself in a situation where you have to debate the AHJ. The other method has to meet so many criteria to be legal that it would not be worth it, when you may be forced to re do it. I agree that people do things differently but why make it more difficult than it needs to be?
Just my thought and opinion, nothing more.

 

[milwaukeesteve]

Re: Parallel feeders single phase

I know that there are circumstances that allow this. I have a stage here where I'm at. The power for band equipment is single conductor 'cords' with ends on them for connectability, with 400A available. Each conductor is a separate run. This is a very specific installation.

This style of wiring that you are arguing is not general wiring, as you mentioned. It has specifics steps to take within the code rule itself, that is not 'general'.

Iwire,
You neglected to read all the reply. It is not just the locknut. It is any ferrous material that forms a circle around the conductor. That includes the cabinet, and like I mentioned, what if the dog's chain got tied around the pipe. As soon as it forms a circle, you have an electromagnet.

Would you use one conductor of a 14/2 romex to bring power to a box if a neutral already exists. NO. You would bring the neutral with the hot conductor. Same principle. You don't want to have one phase without an opposite. (either another phase or a neutral).

Why would you guys even be arguing this? Like Shelco said, do it the proper way. Leave this type of installation for where you absolutely need it. (this is not one of those times)

 

[inspector 102]

Re: Parallel feeders single phase

"That includes the cabinet, and like I mentioned, what if the dog's chain got tied around the pipe. As soon as it forms a circle, you have an electromagnet."
I just had a visual of my dog running around the yard and suddenly have the metal dog dish fly and stick to the riser of an electrical service. Thanks for the mental laugh. Others in the office are just looking at me and shaking their heads.