What is wrong here

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ggunn said:
Why? Is the HVAC three phase? What else would use the high leg? Why not transform it down to 208 so that the load can be balanced?

Caveat: I am an engineer, not an electrician. Be gentle with me. :D
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We don't have place for pad mounted, utility xfrmrrer
delta -4w it is
only 3-ph elevator, load
voltage supplies from the city is 4wire, delta overhead
 
Toros said:
We don't have place for pad mounted, utility xfrmrrer
...
voltage supplies from the city is 4wire, delta overhead
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No place for pad mount has nothing to do with it. I do realize consumers are stuck with whatever the utility says they will make available, but seems strange they will not supply 208/120V 3? 4W.

Never heard of 4-wire delta transmission lines... only 3-wire. 4-wire is always wye, to my knowledge.
 
Smart $ said:
Perhaps service transformers are open delta with large lighter, small stinger. 3? balancing would actually create a problem.

Service conductor sizes for neutral and high leg could possibly be reduced to match maximum unbalanced load for neutral and load/OCPD-rating for high leg.
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We ran into that situation designing and installing a PV system in San Antonio. We ignored the high leg and built it as a 3W 240V split phase interconnect.
 
Smart $ said:
No place for pad mount has nothing to do with it. I do realize consumers are stuck with whatever the utility says they will make available, but seems strange they will not supply 208/120V 3? 4W.

Never heard of 4-wire delta transmission lines... only 3-wire. 4-wire is always wye, to my knowledge.
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Nots that he said supply, not primary.
The service wiring from two or three pole mounted pots is four wire high leg.
 
Smart $ said:
No place for pad mount has nothing to do with it. I do realize consumers are stuck with whatever the utility says they will make available, but seems strange they will not supply 208/120V 3? 4W.

Never heard of 4-wire delta transmission lines... only 3-wire. 4-wire is always wye, to my knowledge.
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The transmission line might be two phase legs only. Then the poco can give you 3-phase with an open-wye, open-delta arrangement of 2 transformers. One clue would be when you see the service coming off of two different size transformers on a pole. I don't think you can get a grounded wye secondary in this case.
 
GoldDigger said:
Nots that he said supply, not primary.
The service wiring from two or three pole mounted pots is four wire high leg.
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JoeStillman said:
The transmission line might be two phase legs only. Then the poco can give you 3-phase with an open-wye, open-delta arrangement of 2 transformers. One clue would be when you see the service coming off of two different size transformers on a pole. I don't think you can get a grounded wye secondary in this case.
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Both good points and likely they be... ;)
 
Smart $ said:
Yeah, but they usually keep track of several such open deltas on their primary and rotate the phases to balance their primary.
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As well as all the single phase services they supply need to be balanced across the primary lines - for their benefit.
 
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