# Sizing a stepdown transformer 277 to 220 single phase



## cl1chicago (Jul 4, 2014)

Could not edit message, had one other question. Transformer will be outside, should I put it in NEMA 4 Hoffman enclosure or are there outside transformers available such as from places like Automation Direct? Thanks again!


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## Bad Electrician (May 20, 2014)

cl1chicago said:


> I was trying out a few online calculators to size a step down transformer and it asked for line to line voltage which I assumed meant the final voltage.
> 
> I need to step down from 277 single phase VAC to 220.
> 
> ...


Line voltageIMO should be the Primary/input voltage, Though to could be taken either way.

Of you have 277 why not go with a 480 Primary? 

Assuming you secondary load is 20 amps X 120 = 2400 VA or 2.4 KVA you can but should not IMO load this transformer to 100% so 2400 x 1.25= 3000 VA 3KVA you will most likely get a 5 KVA and ask the supplier but it should come NEMA 3R, many though not all small transformers are rated for outdoor use.


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## Norcal (Mar 22, 2007)

There are smaller X-formers w/ a 277V pri & 120/240V sec.


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## Bad Electrician (May 20, 2014)

Norcal said:


> There are smaller X-formers w/ a 277V pri & 120/240V sec.



Smaller than want? what he needs or 5kva?


There are 480/120's in a multitude of smaller sizes.


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## triden (Jun 13, 2012)

20 amps @ 120v = 2.4KVA


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## cl1chicago (Jul 4, 2014)

Perfect, thanks gentlemen!


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