# Odb



## macmikeman (Jan 23, 2007)

It's common to the Bay Area. Those are TRANSformers.


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## Arrow3030 (Mar 12, 2014)

They don't have em on the islands?


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## chicken steve (Mar 22, 2011)

Arrow3030 said:


> If I see two transformers on a utility pole dropping to a rural residence how safe is it to assume it's an open delta bank?
> 
> I see it all the time out here and I'm pretty sure the reason for it is the wells are three phase and the house is of course single.


I'll give that a 9 outta possible 10 Arrow

:vs_cool:
~CS~


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## macmikeman (Jan 23, 2007)

I just couldn't resist that answer that I gave you...... sorry:vs_laugh:


Yes your'e guess was right, dual services - separate rates for pumps , ac's, Etc. We see it for cliff side mansions, although they run it down the pole and underground to the CT cans. Never overhead for the wealthy wealthy.


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## Arrow3030 (Mar 12, 2014)

chicken steve said:


> I'll give that a 9 outta possible 10 Arrow
> 
> 
> 
> ...


Yeah. I always look at them as I'm driving down the little highway. It makes me smile a bit.


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## splatz (May 23, 2015)

I think if the wiring at the transformer jives with open delta its pretty much a sure thing.


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## Arrow3030 (Mar 12, 2014)

What's the factor for an old dirty bastard? Isn't something like 75% as efficient?

I meant ODB LOL. That's how I remember the acronym.


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## chicken steve (Mar 22, 2011)

So do they have panels with every 3rd slot plugged up out there? :surprise:~CS~:glasses:


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## chicken steve (Mar 22, 2011)

Arrow3030 said:


> What's the factor for an old dirty bastard? Isn't something like 75% as efficient?
> 
> .


I could ask the wife......:vs_OMG:~CS~:vs_laugh:


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## Arrow3030 (Mar 12, 2014)

chicken steve said:


> So do they have panels with every 3rd slot plugged up out there?
> 
> 
> 
> ...


Nah. They drop to a customer pole first. Only SP goes to the house. Three phase goes wherever the pumps are.


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## splatz (May 23, 2015)

Arrow3030 said:


> What's the factor for an old dirty bastard? Isn't something like 75% as efficient?
> 
> I meant ODB LOL. That's how I remember the acronym.


The capacity is worse than you'd guess, it's less than two thirds the capacity of a closed delta.


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## Arrow3030 (Mar 12, 2014)

Arrow3030 said:


> Nah. They drop to a customer pole first. Only SP goes to the house. Three phase goes wherever the pumps are.


Let me clean this up...ahem. Usually three phase goes to an agricultural meter. The house gets a regular old SP service.


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## Arrow3030 (Mar 12, 2014)

splatz said:


> The capacity is worse than you'd guess, it's less than two thirds the capacity of a closed delta.


I thought that if a delta feed motor lost a phase it would still work but only at xx%. 

Isn't an ODB a similar concept?


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## splatz (May 23, 2015)

Arrow3030 said:


> I thought that if a delta feed motor lost a phase it would still work but only at xx%.
> 
> Isn't an ODB a similar concept?


Yes I had to look it up but it's sqrt(3)/3 = 57.7% which is the same factor for a delta connected motor losing a phase.


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## Arrow3030 (Mar 12, 2014)

Thanks for looking it up!

I'm not sure that's the whole story out here though...

There's usually a large transformer for the split phase plus the ag stuff and a much smaller transformer just for the third phase of the ag.


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## frenchelectrican (Mar 15, 2007)

Arrow3030 said:


> Thanks for looking it up!
> 
> I'm not sure that's the whole story out here though...
> 
> There's usually a large transformer for the split phase plus the ag stuff and a much smaller transformer just for the third phase of the ag.


It is common for overhead transfomer cans to be sized differentally ., however padmounted transfomers ., that is a game of it own.,, some will use two pads.,

but with large two single phase transformer then ya got a pretty good load there. 

But with open delta connection it always 57% rating of closed delta (or full delta). 

I know couple farms in wisconsin only used one meter a simple three phase delta meter or use the CT's so the single phase service is typically go to the house while three phase load useally go to water pump or other loads that need three phase system. 

Here in Philippines we do use two meters but open delta is not super common around here.


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## Arrow3030 (Mar 12, 2014)

I thought I read on this site a while ago that ODB is super rare. It's pretty much all I see out here in wine country.


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## frenchelectrican (Mar 15, 2007)

Arrow3030 said:


> I thought I read on this site a while ago that ODB is super rare. It's pretty much all I see out here in wine country.


For resdential useage yes the open delta is pretty rare nowdays. 

way back in 70's era yes it was pretty common but there still alot of handydolts dont understand the open delta system and they make good smoke making event if they dont heed the warning. 

commercal/ industrail side not really it kinda still common in few locations.


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