Does anyone know if I can use SEU cable (2 insulated and 1 ground) to power a 3 phase 240 volt, center phase grounded system, Roof top unit. Or do I need SER cable witch is (3 insulated ans 1 ground)
Even though you have a grounded phase, it can not be used as an equipment grounding conductor. You would need a grounding conductor in addition to your 3 phase conductors.
Sorry, I made my previous post before I saw this. Yes, it appears that you have a corner grounded system, sometimes called a grounded B phase. But you still need 3 insulated conductors and an EGC. I must say though that a NM cable wiring method is a little unusual in any place that has a corner grounded system.I have always called it center phase ground, but corner ground may also be the term for it. It is a 3 phase delta 240 volt system where phase to phase is 240 volt, phase to ground is 240 volt with the exception of the center phase witch is 0 volts to ground
Sorry, I made my previous post before I saw this. Yes, it appears that you have a corner grounded system, sometimes called a grounded B phase. But you still need 3 insulated conductors and an EGC. I must say though that a NM cable wiring method is a little unusual in any place that has a corner grounded system.
That is wild. What are they used for?Here in Baltimore city there are many of these systems still being used and many of the services are in SEU cable. The bare conductor will loop through the main ground lug and land on the center pole of the main breaker. At first glance it can look like a single phase service.
I don't understand how this could be fine. A bare conductor also used as a phase conductor. Even though it is grounded there is current between phases so how could this not be dangerous? Sorry dense as usual.
I don't understand how this could be fine. A bare conductor also used as a phase conductor. Even though it is grounded there is current between phases so how could this not be dangerous? Sorry dense as usual.
He said it would work fine, but then said it would be a code violation. It is in most ways no different than a single phase feeder that uses the neutral for equipment grounding. It does work, but there are associated hazards and is a code violation.
I know what he said and I know it will work. My point was from the very beginning the op was asked whether it was a corner grounded or something else. Why does it matter if it is non-compliant anyway? That was my confusion
That is wild. What are they used for?
I believe these services were added to existing very old single phase services in commercial buildings when 3 phase power became available in the city for large equiptment that maybe used 3 phase motors.