# The elusive closed Delta 120/240 overhead service



## MTW (Aug 28, 2013)

If it has a neutral, it has a high leg. Are you even an electrician? :confused1:


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## Southeast Power (Jan 18, 2009)

MTW said:


> If it has a neutral, it has a high leg. Are you even an electrician? :confused1:


What are you babbling about?
Explain yourself!!


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## frenchelectrican (Mar 15, 2007)

Southeast Power said:


> I thought it was a typical wye system and looked a bit closer and saw it was terminated as Delta with the bigger transformer split to create a neutral.
> I suspect they increased the capacity by adding a transformer on the open side.
> We see thousands of open delta services. This is the only one I can remember that added the third one:


Ahhh oui .,,, 

very simple with closed delta they can have much higher capacity rating compared to open delta system is and it about 57% more larger of capacity over conventail open delta system is. 

I used to live in Wisconsin before and it is common as dirt to see close delta system especially over 75Kva size 

But once a while I will run into both delta and wye service out of the POCO transfomers. ( little tricky to do this but it done a bit )


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## CoolWill (Jan 5, 2019)

I only see closed deltas. Rarely have I seen an open delta. I see them at lift stations from time to time. But for the most part, if I see a delta, it is closed.


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## 460 Delta (May 9, 2018)

Around here a closed Delta is really all you’ll see, I have about a dozen plants I attend to with full Delta banks. The only time I see open Deltas are when they are in open Star on the primary, where they wanted to save a buck on a conductor. 
It seems that convenience stores are the user of open banks around here, a big lighter and a small kicker, I presume they want three phase for the pumps only.


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## Southeast Power (Jan 18, 2009)

We always seem to see a wye system when they set three transformers.
I would have to assume the customer desperately needed 240 volts if they setup a closed delta service.


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## frenchelectrican (Mar 15, 2007)

Southeast Power said:


> We always seem to see a wye system when they set three transformers.
> I would have to assume the customer desperately needed 240 volts if they setup a closed delta service.


If the customer do have large motor load it may warrant to use the close delta system but smaller motors it not too bad but the other drawback is the short circuit rating it do go higher on close delta so just be aware of it.


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## drsparky (Nov 13, 2008)

Southeast Power said:


> I thought it was a typical wye system and looked a bit closer and saw it was terminated as Delta with the bigger transformer split to create a neutral.
> I suspect they increased the capacity by adding a transformer on the open side.
> We see thousands of open delta services. This is the only one I can remember that added the third one:
> 
> ...


We don't normally see horizontally mounted poles here, must be a southeastern thing.


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## CoolWill (Jan 5, 2019)

drsparky said:


> We don't normally see horizontally mounted poles here, must be a southeastern thing.


It's Florida. The whole place is sideways.


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## MTW (Aug 28, 2013)

My poco does not offer open or closed deltas and has not for a long time now. They want all existing deltas switched to wye but can't force the issue unless the service is upgraded.


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## CoolWill (Jan 5, 2019)

MTW said:


> My poco does not offer open or closed deltas and has not for a long time now. They want all existing deltas switched to wye but can't force the issue unless the service is upgraded.


That's because engineers like that are stupid.


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## MTW (Aug 28, 2013)

CoolWill said:


> That's because engineers like that are stupid.



Agreed. And lineman are even dumber, so the poco likes to keep it as basic as possible.


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## MTW (Aug 28, 2013)

Southeast Power said:


> What are you babbling about?
> Explain yourself!!


A 240 delta service with a neutral has a high leg.


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## B-Nabs (Jun 4, 2014)

MTW said:


> My poco does not offer open or closed deltas and has not for a long time now. They want all existing deltas switched to wye but can't force the issue unless the service is upgraded.


Same around here. The only deltas you'll see are very old. Most of them are ungrounded deltas, found at old industrial buildings. Usually there will be a small single phase service for lighting & receptacles. When these places get renovated nowadays, they'll get a zigzag transformer and a ground fault detection system, unless they are adding much load, then BC hydro makes them upgrade to 208Y120.

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