Phase cond. marking and polarity issue

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patc

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I've got a job that has a 3 phase 3w 240v corner grounded delta service. This service takes care of two air cond loads. On site there is a 3 phase 4w 120/240 genset and xfer switch. If I install a seperate xfer switch fed from the same genset, is there any way to comply with the code and feed the 3 phase 3w corner grounded load with the 120/240 3 phase 4w generator? I know that the A/C equipment will run but how would the grounded/ungrounded phase be marked to identify which system its running on. Also would this installation not comply with 200.11 ?

Thanks
 
This would be my approach to this situation. In our area, three phase corner grounded delta systems are normally used with 2-pole overcurrent protective devices (safety switches or circuit breakers), so we need to start at the load and work backwards. To maintain the same disconnecting means and overcurrent protective devices, why not feed a delta - delta isolation transformer from the 120/240 volt three phase 4-wire system and create a three phase 3-wire system, ground one phase, and go from there?
 
It seems to me that the generator's center-tap bond (if there is one) should be able to be opened, so a corner can be bonded.

First, I'd make sure exactly how the generator is presently configured. Don't assume it's like a 120/240 4-wire high-leg Delta.
 
The transformer set up would work and has been suggested. The genset is not a high leg and is presently being used for other loads too. My question is really whether or not the grounded conductor of the incoming system can be reidentified to indicate while its on generator power, showing that it is no longer grounded and also would this setup conflict with 200.11.
The system would have a grounded center phase while on utility power but it would have voltage on the center leg while on generator power.
Thanks
 
Landing the grounded corner of the xfmr on the center phase of the breaker makes it that way. Back to the question though, is there a way to codify changing the premise wiring from having a grounded phase conductor while on utility, to having that same conductor l(oad side of the transfer switch) be an ungrounded (hot) phase while on generator?

How do ya get drawings to post on the board...it may be easier to explain.
 
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patc said:
The system would have a grounded center phase while on utility power . . .
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I took this to mean a grounded-center-tap, not that the center terminal is grounded.

Okay, let me ask: what exactly is the fourth wire coming from the generator?
 
patc said:
Back to the question though, is there a way to codify changing the premise wiring from having a grounded phase conductor while on utility, to having that same conductor l(oad side of the transfer switch) be an ungrounded (hot) phase while on generator?
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Beyond the main-disco bonding, the grounded conductor is treated like ungrounded ones, other than the white coloring. If the genny's output is floating, there's no reason you can't simply choose one to ground, and use it as you would the utility. I'd still like to know what the fourth wire from the genny is before going on.
 
LarryFine said:
...I'd still like to know what the fourth wire from the genny is before going on.
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Sounds to me like there is a 240/120 3? 4W (Delta High Leg) system already being fed by the genset, and he wants to "tap" the genset output a feed a second xfer switch. If this is the case...

It can't be done electrically, i.e. regardless of color-coding, if there is a possibility of both systems being concurrently transferred to genset power... without adding an isolation xfmr, that is.
 
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