Sizing of Transformers for a new Shopping Center

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SCEngineer

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Fellow Engineers,
I am currently designing a shopping center with multiple buildings. The incoming power is 480/277V, and in most cases we have step down transformers for 208/120V tenant panels. My question is do I rate the transformers for 480V before the step down, or do I rate them at the highest possible demand of the 208V panels? Any help would be greatly appreciated. Thank you.
 
Welcome to the Forum.
I'm not a "fellow engineer" but I did stay at a Holiday Inn across the street from a shopping center :D so I will voice an opinion.

A vast majority of the shopping center I have inspected have transformers that match the main in the secondary panels they supply.
 
On what basis are you sizing anything in the first place? Since you don't know what is going to be there at present, I don't see how you can do a load calculation.
 
petersonra said:
On what basis are you sizing anything in the first place? Since you don't know what is going to be there at present, I don't see how you can do a load calculation.
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Future tenant spaces here in Fl for the type of construction I believe the OP is referring to usually get a 200A 3? panel.
 
chris kennedy said:
Future tenant spaces here in Fl for the type of construction I believe the OP is referring to usually get a 200A 3? panel.
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My inclination then would be to give them a feeder and xfmr that would be adequate for 200A.

But I don't know what might be customary in this kind of situation. It kind of seems like a shot in the dark.
 
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SCEngineer said:
Fellow Engineers,
I am currently designing a shopping center with multiple buildings. The incoming power is 480/277V, and in most cases we have step down transformers for 208/120V tenant panels. My question is do I rate the transformers for 480V before the step down, or do I rate them at the highest possible demand of the 208V panels? Any help would be greatly appreciated. Thank you.
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Maybe I'm not understanding the question, but VA is VA, which is how transformers are rated. 50 kVA is the same whether you're looking at the primary or secondary side.
 
George Stolz said:
Maybe I'm not understanding the question, but VA is VA, which is how transformers are rated. 50 kVA is the same whether you're looking at the primary or secondary side.
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That is a good question. When i read the OP, I somehow got the impression he was asking for sizing suggestions. One would think an engineer tasked with this kind of design would know that VA is VA. Maybe he just worded it wrong.
 
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