Hi Guys (and ladies, of course): I need a little learnin' here. A church in this area is undergoing a service upgrade. There are four separate raceways being installed to provide a three phase service. Each one, equipped with weatherhead, travels along the back side of the church building for a distance of about 50 feet before elbowing through the wall into a switchgear room. So far, the conductors for the three hot legs (color-coded black, red and blue - three conductors per leg) have been pulled into the conduits. However, unlike what I've read, and seen discussed here previously, all three black legs are in one conduit, all three reds in another, and all three blues in the third (instead of one of each appearing in each conduit). The fourth conduit is empty at present - I assume that the "neutral" is supposed to go here.

I thought that this was strictly a NO-NO, and serious problems could result from this. Can y'all elaborate on this for me?

Mike (mamills)

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[This message has been edited by iwire (edited 08-12-2003).]

I have done similar installations underground but I do not believe you can do this aboveground look at the one exception for Paralleled Installations.

[quote]300.3 Conductors.

(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).

Bob

Mike,
What are raceways made of?
Don

Don;
They appear to be rigid steel pipe with threaded fittings. I'm guessing they are about 3 1/2 - 4" diameter.

Mike (mamills

Don would you be able to apply 300.3(B)(3) to a paralleled installation.


Bob

I haven't personally seen an installation like this, but someone I know told me of a serious heat problem caused by the situation you described. Perhaps someone can elaborate on possible complications.

Bob

I would say based on 300.3(B)(1)exception, that the above installation is a violation, and it will definitely cause a heating of the conduit problem. Possibly causing a fire.
300.3(B)(3) does not pertain to paralleled installations.
Even if they had run PVC above grade, that is a violation.
I understand why some like to install a parallel service this way, it makes working with the conductors easier.

Pierre

All i can say is stand back when they throw the main. Due to the magnetic field produced from the flow of electrons, you DO NOT want to install all the same phase conductors in there own pipe. I know a company that did that on a Kwickset factory not far from me. Blew the concrete wall off the back of the building. That was their first and last big job.

[This message has been edited by arseegee (edited 08-12-2003).]

Bob,
In my opinion 300.3(B)(3)would permit this installtion if the raceways were nonferous. Note that you would have to comply with 300.20(B) where the conductors enter the panel. If these are ferous raceways, then the installation is a code violation and will fail very quickly when any load is applied.

Pierre,
I see nothing in 300.3(B)(3) that says you can't use the section for parallel installations.

Don

Don

I agree with you that 300.3(B)(3) does not restrict this type of installation.

300.3(B)(1)exception restricts parallel installations of nonmetallic raceways to underground installations.

Pierre

Many years ago I was called to an office building where there were strange noises coming from the ceiling cavity. I heard the noise and got a look into the area and there were four GRS conduits containing the service conductors with a phase and neutral each in separate conduits. Some of the u-bolts securing the conduit to the steel trusses had broken and I actually witnessed the conduit moving and they were HOT! I called the owner, fire department, POCO, and the local inspector. The building was condemned until changes were made to correct the problem. The wire size was adequate but the separate conduits were the culprit.
Rowdy

See 300.5(i), Exception No. 2

A second instance was at a shopping mall in El Paso, TX. The large chillers were connected with three GRS raceways with a phase per conduit. One chiller was down due to charred wire and chiller 2 & 3 conduits were so hot only a quick touch prevented skin burn. The original EC was working on chiller #1 at the time I made the survey. #2 & #3 were immediately shut down.
Rowdy