120/240 Delta - A Phase Black - B Phase Orange - C Phase ????

nicknorth

Senior Member
All our Delta services out here from the POCO seem very old and everyone I've ever seen doesn't have any markings from the weather head to the panel. This is always troublesome because we don't even have much of it out here and it's not always your first guess of what they have by visual looking at a panel. One give away is a empty spot in the panel every 3rd space, but it seems that back when these where installed no one cared about labeling them. I've seen buildings with a 480/277 service and then step down transformer to 120/240 Delta with conduits and wires running everywhere with every voltage in a conduit using all blue conductors.
 

kwired

Electron manager
Location
NE Nebraska
All our Delta services out here from the POCO seem very old and everyone I've ever seen doesn't have any markings from the weather head to the panel. This is always troublesome because we don't even have much of it out here and it's not always your first guess of what they have by visual looking at a panel. One give away is a empty spot in the panel every 3rd space, but it seems that back when these where installed no one cared about labeling them. I've seen buildings with a 480/277 service and then step down transformer to 120/240 Delta with conduits and wires running everywhere with every voltage in a conduit using all blue conductors.
Two biggest indicators of a high leg without any measuring are every third space in a panel not used/ or not using single pole breakers anyway, and pole mounted transformer banks with only two pots in the bank. Careful though, just because there is three pots doesn't mean it can't be a full delta bank, but it doesn't take too much training to see and understand the secondary connections and determine if they are wye or delta connected.
 

Greg1707

Senior Member
Location
Alexandria, VA
Occupation
Business owner Electrical contractor
120/208

120/208

This discussion raises a question I have. When installing a three pole breaker in a 120/208 panel to supply a load or sub panel is the position of the breaker an issue? Does it matter if it is placed to supply: ABC, BCA or CBA?
 

texie

Senior Member
Location
Fort Collins, Colorado
Occupation
Electrician, Contractor, Inspector
This discussion raises a question I have. When installing a three pole breaker in a 120/208 panel to supply a load or sub panel is the position of the breaker an issue? Does it matter if it is placed to supply: ABC, BCA or CBA?
No, and that is one reason the NEC changed way back (in the 70's as I recall) to require the high leg on the "B" phase.
 

kwired

Electron manager
Location
NE Nebraska
No, and that is one reason the NEC changed way back (in the 70's as I recall) to require the high leg on the "B" phase.
I must disagree. 408.3(E) specifies phase arrangement of switchboard/panelboard buses, but I am not finding any such requirements for switches or breakers. The "high leg" can be in any position in a fused or non fused switch, motor controller, a circuit breaker, or other devices, but is supposed to be the "B" bus in a switchboard or panelboard.
 
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