Two Pole Service Panels on 208

Status
Not open for further replies.
B

bellington

Senior Member
Location
Hahira, GA
Occupation
Consultant
On an island with 5 buildings, 29 service panels, solar, battery, and diesel generator, providing 480 3-phase, and at least (3) 480/208 step-down transformers, are we saving a significant amount of money on equipment and wire by running 9 service panels on just 2 legs of 208?

For each of the (9) 2-leg 208 panel, what is the acceptable engineering terminology for labeling? They are functioning as single-phase, similar to 240. Should the drawings simply call them 120/240, 1 phase, 2 pole, 3 wire? Or, should they be labeled 120/208, 2 phase, 2 pole, 3 wire, even though the 2 phases functions as 1?

Are 208/480 step-up transformers a new fad? For a small island, wouldn't another set of 480 3-phase feed lines be significantly cheaper and more efficient than running 208 lines large enough to handle a 175 KVA step-up transformer and the cost of the transformer?

Thanks for any input you may provide.
 
bellington said:
For each of the (9) 2-leg 208 panel, what is the acceptable engineering terminology for labeling? They are functioning as single-phase, similar to 240. Should the drawings simply call them 120/240, 1 phase, 2 pole, 3 wire? Or, should they be labeled 120/208, 2 phase, 2 pole, 3 wire, even though the 2 phases functions as 1?
Click to expand...
Certainly not 2 phase. If they're 1Ø from a 3Ø source then IMO it should be: 1Ø, 3-wire, 120/208. You could even leave out the 3-wire part.

You're thread title says "service panels" it doesn't sound like these are actual services.
 
infinity said:
Certainly not 2 phase. If they're 1Ø from a 3Ø source then IMO it should be: 1Ø, 3-wire, 120/208. You could even leave out the 3-wire part.

You're thread title says "service panels" it doesn't sound like these are actual services.
Click to expand...
I apologize; I should have noted that some are sub-panels.
 
bellington said:
I apologize; I should have noted that some are sub-panels.
Click to expand...

Is your primary power source a utility ??

In regard to the OP. I would agree, if you have 480 available, it makes no sense to install a 208v feeder and then a step-up transformer. Higher install cost + energy loss of the transformer.
 
electrofelon said:
Depending on details, you could use single phase 480-120/240 transformers.
Click to expand...
I wanted to limit the number of transformers needed. I was hoping if everyone knew the panels were 208 (not labeled 120/240), then nobody would specify equipment that would not function efficiently on 208.
 
Thank you for the input. Primary power sources are (1) diesel generator, (1) one large battery pack and inverters, and roof solar with inverters, with transfer switch for backup power from neighboring island.
 
bellington said:
On an island with 5 buildings, 29 service panels, solar, battery, and diesel generator, providing 480 3-phase, and at least (3) 480/208 step-down transformers, are we saving a significant amount of money on equipment and wire by running 9 service panels on just 2 legs of 208?

...
Are 208/480 step-up transformers a new fad? For a small island, wouldn't another set of 480 3-phase feed lines be significantly cheaper and more efficient than running 208 lines large enough to handle a 175 KVA step-up transformer and the cost of the transformer?
Click to expand...

Doesn't it depend on the distances from your sources to your buildings? As anywhere else, the cost and labor of transformers is justified by what's saved in between them.

If the distances are short, there is certainly nothing wrong with running 3-wire 120/208 to the panels. This is frequently done for each apartment in multi-unit buildings served by 208/120 3-phase.

For each of the (9) 2-leg 208 panel, what is the acceptable engineering terminology for labeling? They are functioning as single-phase, similar to 240. Should the drawings simply call them 120/240, 1 phase, 2 pole, 3 wire? Or, should they be labeled 120/208, 2 phase, 2 pole, 3 wire, even though the 2 phases functions as 1?
Click to expand...

I would label them 120/208, 1-phase, 3-wire.
 
jaggedben said:
Doesn't it depend on the distances from your sources to your buildings? As anywhere else, the cost and labor of transformers is justified by what's saved in between them.

If the distances are short, there is certainly nothing wrong with running 3-wire 120/208 to the panels. This is frequently done for each apartment in multi-unit buildings served by 208/120 3-phase.



I would label them 120/208, 1-phase, 3-
Click to expand...
I was talking about using 208 to feed a 208 to 480 step-up transformer. Seems like distance would not matter, other than the greater the distance, the more problems there would be using 208 to feed 175 KVA through a transformer.
 
bellington said:
I was talking about using 208 to feed a 208 to 480 step-up transformer. Seems like distance would not matter, other than the greater the distance, the more problems there would be using 208 to feed 175 KVA through a transformer.
Click to expand...

Now I'm confused, I thought you said the sources provide 480. So why would you step down to 208 and then back up to 480?

(I thought your question was about whether to feed several buildings with different legs from one 208V secondary, or to run 480 to individual step downs at each building. In the latter case your step-downs could be to 240V.)

More info or clarification needed.
 
What is the output from the PV inverters (voltage and phases)?
 
jaggedben said:
Now I'm confused, I thought you said the sources provide 480. So why would you step down to 208 and then back up to 480?

(I thought your question was about whether to feed several buildings with different legs from one 208V secondary, or to run 480 to individual step downs at each building. In the latter case your step-downs could be to 240V.)

More info or clarification needed.
Click to expand...
Yes, the part about stepping down and back up again is my issue. The part about stepping down and back up again was the reason for this original 2 questions:
...
Are 208/480 step-up transformers a new fad? For a small island, wouldn't another set of 480 3-phase feed lines be significantly cheaper and more efficient than running 208 lines large enough to handle a 175 KVA step-up transformer and the cost of the transformer?
 
bellington said:
I don't think so. What island is that?
Click to expand...

It is referencing the TV series Lost (2004 - 2010). :)

On a more helpful note for you, can you tell us more about the generator? It may be possible to reconfigure the windings, even to something like 416/240 that could be more helpful here. Cutting out the initial step up transformer would make a big difference and if the inverters will match any voltage, that is a plus.

What are the approximate distances for the service runs?
 
I thought of one other radical idea, depending on the capacity of the inverters and your flexibility to amend that infrastructure. You could, in theory, rectify the generator output and use the existing inverters to obtain your 480 V output (think of it as online UPS conversion).
 
Status
Not open for further replies.
Top