Transformer Sizing

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southman

Member
Location
jacksonville, fl
I have 16 temp office trailers coming in. They each have two (2) 125 amp panels with 120/240 single phase service. What size 3-phase transformer should I spec out?
 

tw1156

Senior Member
Location
Texas
I have 16 temp office trailers coming in. They each have two (2) 125 amp panels with 120/240 single phase service. What size 3-phase transformer should I spec out?

Do you mean 120/208V single phase service to each trailer instead of 120/240V?
 

jumper

Senior Member
The trailer spec provided has "120/240 single phase", but you're right it has to be 120/208. The HVAC is 6.0 ton unit with 20kw heat strip.

Unless you want to spec an insanely large service like I joked about earlier, you need a load calc for each trailer before you can even think about what service size is need.

HVAC, receptacles, lights, various equipment, kitchens if applicable, and such.
 

topgone

Senior Member
Load calc! We don’t need no stinkin’ load calc!

Just total it all up. It only comes out to ~1.5 MW. :blink:

No problem.:D

Demand factors and all that stuff is too much trouble.

Yep. That could suffice.
Maybe, a 1,000 kVA could perhaps do it also (full-load amps = 2,775A, maximum amps per phase for 16 trailers @250A is 2,600A).
 

jumper

Senior Member
Randomly guessing, barely paying attention, and cheating like all get out I get something somewhere like maybe a 300 kVA tranny and 800A main gear.

Haphazard calculation at best when flying blind.:)
 

Ingenieur

Senior Member
Location
Earth
ac 10 kva per trailer
ht 20 kva
in FL chances are all AC will run at the same time 100% demand 160 kva
figure 75% for htg 225 kva

10 kva max ltg/recept per trailer 160 kva

350 kva sounds close
 

junkhound

Senior Member
Location
Renton, WA
Occupation
EE, power electronics specialty
I have 16 temp office trailers coming in. They each have two (2) 125 amp panels with 120/240 single phase service. What size 3-phase transformer should I spec out?

Typically the POCO will size the number and size of the trannies.

Depending on how spread out the trailers are, I'm guessing they will just put in 3 separate 120/240 1 phase, 25 kVA and call it good unless you fry one of them soon.
 
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