If you are feeding a 3 Phase and Single Phase panel from a pad mounted transformer how many wires should you run between the transformer and the first means of disconnect. Also, how many from the First means of disconnect to each sub-panel in the building for both 3Phase and Single Phase.
3 Phase from transformer to first means of disconnect
- Thread starter mtaylor
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Four or five, depending on who owns the transformer, where you put the MBJ, what there is available for metalic paths - like a grounding grid.mtaylor said:
3phase - 4 wires (no line to neutral loads)mtaylor said:
1phase 4 wires
I confess I don't know why you would put in a 1ph panel. The way you phrased your question, you have one panel for 3ph only loads, and a separate panel for 1ph loads. Which leads me to believe you have a 208V system. If so why put in a 1ph panel for the 1ph loads? Guarantees an unbalanced system.
I'm surprised the drawings don't show this level of detail.
carl
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
coulter said:
Actually the OP probably has a 240/120 3 Phase 4 wire Delta service (a high/wild leg).
On these services, my preference is to install one 3-wire + g 3-phase 240V panel and a separate 3-wire +g 1-phase 120/240 panel.
What we have is a 3Phase pad mounted transformer (208/120v) that feeds a 3Phase 200A MB outside of the building by means of underground service. How many wires should be ran and what size should the wire be including the neutral and ground. From that point we are feeding a 200A 3P panel interior panel. what size wire and how many wires should I pull to this panel? I know on residential after the first means of disconnect it needs to be a 4 wire system to the inside panel, however, this is a commercial job and I noticed on some jobs they require a 5W system. Don't quite understand.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
I made a wrong assumption, what a way to start an afternoon.
4 wires (3 ungrounded and 1 grounded) need to be run from the utility transformer to the service disconnect point (your outdoor breaker). 5 wires (3 ungrounded, 1 grounded, and 1 grounding) need to be run from the service disconnect to any 3-phase distribution panel feeding 120V loads.
4 wires (3 ungrounded and 1 grounded) need to be run from the utility transformer to the service disconnect point (your outdoor breaker). 5 wires (3 ungrounded, 1 grounded, and 1 grounding) need to be run from the service disconnect to any 3-phase distribution panel feeding 120V loads.
Mtaylor, don't take me wrong, but these questions don't sound like questions that would be coming from an Estimator/Office Manager, they are very basic in nature for an Electrical Contractor
Isn't there someone in this office with a Journeyman or Masters license that can answer these questions?
Roger
Isn't there someone in this office with a Journeyman or Masters license that can answer these questions?
Roger
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