PLC hard wiring

[rsdoran]

Darn it, I always forget about that Delta high leg.
Article 215.8 Means of Identifying Conductor with the Higher Voltage to Ground
On a 4 wire, delta connected secondary where the midpoint of one phase winding is grounded to supply lighting and similar loads, the phase conductor shall be identified by an outer finish that is orange in color or by tagging or other effective means.

I knew this too, its one of my main marked pages.

 

[kamenges]

Originally posted by Rick Densing:

You need the same insulation rating in case your higher voltage wire is damaged. If you have a paritially exposed 480V wire lying next to a 300V insulated wire, you are going to have a breakdown. Things can go boom. Like Ron said, NEC is to prevent fire and injury, not for nice clean I/O signals.

I know I risk winding some people up by continuing with a topic that is only loosely related to the original post, but in for a penny in for a pound, I always say.
Wouldn't you get that same boom factor if the bared 480 volt wire touched the grounded conduit it was running in? I guess that's my original point, which I DIDN'T express initially (sorry). What makes the grounded conduit so special that it isn't a concern for stray voltage but the other wires in the conduit are a concern?
I'm not trying to rock the boat (too much). Just trying to get a handle on the mindset of a document that is WAY too big and has too many exceptions.

Keith

 

[tom_stalcup]

Well, say for example that you have a wire bundle that has a bunch of 24vdc wires in it, and also has a 240vac wire in it. If something happens to the insulation on the two wires, the poor bast--- that is disconnecting a prox expecting 24vdc gets hit with a 240v jolt....


(happened here last weekend..... gonna be doing some re-wiring on 7 different machines in the near future)

 

[leitmotif]

I reviewed the whole thread.
FIRST can you put signal (or control or whtever you want to call it) wire in the same conduit as power conductors.
ANSWER It is a free world you can do what ever you like -- if you can live with the consequences.

SECOND would I do it ?? Resounding NO
I am just a maintenance electrician - the good thing about this is you learn how other people screw up cause you get to fix it. It is hard enough to pull in multi wire when they are the same type and size. Now you are going to mix in other type conductors or multi conductor cable??
WHY NOT ?? What will happen is the softer coverings will get more chafe. NOW you may get into a deal where you can have a fault in a power conductor that can cross over to the signal. I have heard the horror story of a phone guy who cut a phone cable that 13 kV on it.
THE OTHER REASON is of course the fields from the power conductors fouling up the signal in you signal conductors.
BUT it is your system and us maintenance guys need the work so go ahead if you want.

COLOR CODES
1. I agree with Ron Doran and Tark that the five colors white gray, green or green yellow trace and orange are the only ones required by NEC. The thing to remember is NEC is basically a life safety code and is not written to ensure a good job. YOu can wire to NEC and have a job that is not worth the powder to blow it to hell.

2. Ron thank you for BOY (Brown Orange Yellow) I always get confused on the common used colors for 3 phase 240 and 480. But then way back when in the Navy we were taught black white red ABC 123 for three phase DIFFERENT system because of no grounded neutral on ships. WHY oh WHY can I remember that and not the other and NOT confuse the two.
3. Yeah you are supposed mark the hi leg on delta when you center tap one phase and ground it for a neutral. That is orange. This circuit I think is falling by the wayside -- havent seen it in recent construction.

Dan Bentler

 

[Rick Densing]

Wouldn't you get that same boom factor if the bared 480 volt wire touched the grounded conduit it was running in?

Not necessarily, it may just blow a fuse. (Proper design- it will blow a fuse) The conduit should have a much higher ampacity than the original wire. If you short to another wire, the completion path may be through a device that can't handle the current.

 

[stasis]

3. Yeah you are supposed mark the hi leg on delta when you center tap one phase and ground it for a neutral. That is orange. This circuit I think is falling by the wayside -- havent seen it in recent construction.

Dan Bentler

no...the high leg is the one carrying a higher voltage (used to be called a '******* leg') than the other two conductors in the circuit. As stated, grounded (or neutral) is gray (high volt) or white (low volt) and green/bare is for grounding (ground). The high leg is quite common with Georgia Power, at least furthert away from the city. They like it because you can get away with less transformers on the poles.

 

[leitmotif]

I mentioned the neutral connection to ensure everyone knew what I was talking about. The high leg would not be the neutral since the neut is grounded and at ground potential which I hope would not be that of a high leg.

Are they using 4 wire delta in Ga for commercial only? Here in Seattle for small stuff service seems to be 4 wire wye or 3 wire Edison and 3 wire Edison for residential of course.

Dan Bentler

 

[stasis]

well, it's mostly seen in light industrial, like warehouses & the like. But, most of these warehouses end up with machinery installed in them so the owner doesn't have to make an addition to his building...the cheapskates.

 

[leitmotif]

Well that was the whole idea of 4 wire delta - you get your lites and receptacles off the center tapped phase and you have the 3 phase for motors. Saw a fair amount in older school districts.

Dan Bentler

 

[Tark]

In the end, you really need to check your local city ordinances, they are the authority having jurisdiction.

NEC 90.4 – The authority having jurisdiction may waive specific requirements in this Code or permit alternate methods….

Case in point – A city near me does NOT use orange to mark the high leg on a delta, I think they use orange for one of the conductors on a 480 Y.

Always check with the city you are working in to find out if they have any alterations or exceptions to the NEC

 

[rubber ken]

I have run 120v descrete I/O in the same conduit with 3 phase motor feeders with no problems. I would not recommend using the same conduit space for 3 phase feeders and 24vdc or analog I/O.