208Y/120 Volt 3 Phase, 4- Wire Service

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208Y/120 Volt 3 Phase, 4- Wire Service

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jtedesco
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Posted: Jun 11, 2004 3:38 PM       Post Subject:

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When inspecting multifamily dwellings the Home Inspector should become familiar with a 208Y/120 volt, 3 phase 4 wire service, just to have some idea of how the 3-wire feeders are run to each unit panelboard so they will be balanced (evenly proportioned).

Use the following as a guide so it will be clearer to the Home Inspector:

Since there are 3 phases, and a common grounded conductor the best way for me to explain it would be as follows:
************************************************************

    A = Black Phase 1
    B = Red Phase 2
    C = Blue Phase 3
    N = White Grounded Conductor


AB/N CA/N BC/N AB/N CA/N BC/N AB/N .. etc.

Sure hope I got this right! I tried to make it very easy for you.

Quote:
If anyone else who collects "Big Brass Balls" can add to this discussion, that would be really nice and it would be appreciated, and if you have any problems with this explanation feel free to call me so we can talk about the problems that you create in your mind when you don't understand the issue!


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Joe Tedesco, NEC Consultant

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Shawn Rowe

HomeFirst Inspection Services, LLC
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Posted: Jun 11, 2004 8:31 PM       Post Subject:
I don't have Big Brass ones but would like more info on the 3 phase electrical for multi-family.

Do you have any photos of "good panels" and "bads"? Where can I check these out?

THANKS JOE!!!
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tallen
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Posted: Jun 11, 2004 8:35 PM       Post Subject:

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Remember if there is no pretty Red or Blue tape.

It should go .
A,B,C
Font to back
Top to bottom
Left to right

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Ryan Jackson
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Posted: Jun 11, 2004 10:12 PM       Post Subject:

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tallen wrote:
Remember if there is no pretty Red or Blue tape.

It should go .
A,B,C
Font to back
Top to bottom
Left to right


What do you mean left to right? In the panel? It should go
black black
red red
blue blue

From left to right. Or is this not what you are talking about?

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Ryan Jackson, Salt Lake City

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tallen
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Posted: Jun 11, 2004 10:18 PM       Post Subject:

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In a 3 phase panel don't the phases
A, black
B, red
C, blue

Going from A to C
From the front of the panel to the back
From the left of the panel to the right
or From the top of the panel to the bottom

Depending on the configuration of the lugs?

I am talking about the feeders.

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where , however, it now sits, making rude remarks.

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jtedesco
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Posted: Jun 12, 2004 5:37 AM       Post Subject:

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Todd and Ryan:

Quote:
Phase Arrangement.

The phase arrangement on 3-phase buses (busbars) is A, B, C from front to back, top to bottom, or left to right, as viewed from the front of the switchboard or panelboard.


This is the specific requirement for the supply into any 3 phase equipment.

My example is showing how the feeders that supply each dwelling unit are installed from the main service equipment on the board where all of the electric utility meters are installed, and where there are main disconnects that are not 3-pole but instead 2-pole.

When the electrician connects the wires they will be connected so that the 3 phases will land into each individual meter and main circuit breaker:

The identification can be 1, 2, 3 or a, b , c or black, red, blue


Black & Red | Blue & Black | Red & Blue | and so on .....

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Joe Tedesco, NEC Consultant

www.nachi.org/tedescobook.htm

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Bob Badger
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Posted: Jun 12, 2004 9:24 AM       Post Subject:

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Where are we getting the colors from?

These ungrounded conductors can be all black, only the grounding and grounded conductors must be marked.
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jtedesco
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Posted: Jun 12, 2004 9:31 AM       Post Subject:

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Bob:

The colors were provided here for a clearer explanation.

As I said they can be 1, 2, 3, or a, b, c

If anyone tried to use the all black (and we know that is what the color of the typical wire is) they could be in trouble for sure.

Thank you for reminding us about the required colors of conductors, which was not the subject of this informational subject.

I was talking about balancing the load. Can you add any other suggestions or field experience here?

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Joe Tedesco, NEC Consultant

www.nachi.org/tedescobook.htm

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jtedesco
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Posted: Jun 12, 2004 9:38 AM       Post Subject:

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Shawn:

Here is a 3 phase house panel used in an apartment building in San Diego:

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Joe Tedesco, NEC Consultant

www.nachi.org/tedescobook.htm

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Shawn Rowe

HomeFirst Inspection Services, LLC
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Posted: Jun 12, 2004 9:42 AM       Post Subject:
Thanks Joe! That is what I was looking for.
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Bob Badger
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Posted: Jun 12, 2004 9:46 AM       Post Subject:

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Double post sorry
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Bob Badger
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Posted: Jun 12, 2004 9:56 AM       Post Subject:

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Balancing the load is straight forward, do not put all loads on one phase.

Most times partially in a dwelling unit simple filling the panel will result in a balanced load.

If I have a few 2 pole loads from a 3 phase panel I will need to think about the breaker placement.
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jtedesco
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Posted: Jun 12, 2004 10:11 AM       Post Subject:

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Bob:

Understood, and in the panelboard we should also be aware of the following:

Quote:
Load Evenly Proportioned Among Branch Circuits.

Where the load is computed on a volt-amperes/square meter or square foot basis, the wiring system up to and including the branch-circuit panelboard(s) shall be provided to serve not less than the calculated load.

This load are required be evenly proportioned among multioutlet branch circuits within the panelboard(s).

Branch-circuit overcurrent devices and circuits are only required to be installed to serve the connected load.


Picture 40 separate dwelling units with 3 wire feeders, run to each unit off of the 3 phase 4 wire system and at the meters, and for all of the feeders and for their proper termination, it would be necessary to identify the "hot legs" and the neutral.

Why even one nick, two nicks in the wires for identification to the main lugs would work too.

Any house 3 phase loads would come from the house panel.

I will try to find a diagram that will show it in a clearer manner.

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Joe Tedesco, NEC Consultant

www.nachi.org/tedescobook.htm

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jtedesco
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Posted: Jun 12, 2004 12:19 PM       Post Subject:

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Joe Tedesco, NEC Consultant

www.nachi.org/tedescobook.htm

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Ryan Jackson
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Posted: Jun 12, 2004 7:32 PM       Post Subject:

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Todd, I thought you were refering to the breaker layout, not the lug layout.

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Ryan Jackson, Salt Lake City

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tallen
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Posted: Jun 12, 2004 8:25 PM       Post Subject:

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I know Ryan. I was not very specific. My bad.

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I have put the past behind me,
where , however, it now sits, making rude remarks.

www.whiteglovehomeinspections.net

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