single phase transformer

[billsnuff]

4 hand dryers @ 12.5a * 120v = 1500va * 4 = 6kVA

7.5 kVA 480/240 - 120 xformer

480v buss plug - 15A (FRS-R) 12AWG THHN to primary <25'

65A @ 75C - 6AWG THHN to panel <10'

100A main in panel w/4 - 20A branch circuits w/ 12AWG THHN.

Industrial setting...........good design? it's what's in the shop...:roll:

 

[BryanMD]

Using equipment that suits the available power is another option;
from the Excel website:

 

[jim dungar]

4 hand dryers @ 12.5a * 120v = 1500va * 4 = 6kVA

7.5 kVA 480/240 - 120 xformer

480v buss plug - 15A (FRS-R) 12AWG THHN to primary <25'

65A @ 75C - 6AWG THHN to panel <10'

100A main in panel w/4 - 20A branch circuits w/ 12AWG THHN.

Industrial setting...........good design? it's what's in the shop...:roll:

Your primary fuse can be as large as 20A.

Are you wiring the transformer as 120V only or 120/240V?
If you have a single voltage then the secondary conductors can be protected by the primary device, and your 15A fuse could protect your 65A conductors. the main in the panel is immaterial.
If you are using 120/240 (how are you creating a 120V only panel?) your secondary conductors would need to be compatible with the panelboard main.

FWIW, I would use 20A primary fuses, wire the transformer for 120/240V output, and backeed a 40A breaker in my panel.

 

[billsnuff]

Thanks Jim.

Got a call, boss what to replace cloth towel machines with blow dryers.

Facility 100k + sq ft. 20 lighting panels. Just so happens that in this particular area, both panels are full. He wanted a quick and dirty answer on cost to install dryers. so in this case material cost = zero. Post was to make sure I didn't miss something. panel would be 240v/120v single ph.
15 or 20 amp primary protection only.

Will sit down today and check buss load, see if I can sell an upgrade.

Thanks again.......