Originally Posted By: jtedesco This post was automatically imported from our archived forum.
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.
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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!
Originally Posted By: jtedesco This post was automatically imported from our archived forum.
Todd and Ryan:
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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 .....
Originally Posted By: jtedesco This post was automatically imported from our archived forum.
Bob:
Understood, and in the panelboard we should also be aware of the following:
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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.
