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Thread: Adding additional load onto and existing hotel building , need help

  1. #1
    Join Date
    Mar 2017
    Location
    Alberta
    Posts
    2

    Adding additional load onto and existing hotel building , need help

    My question is ,

    I need to add load to a 45kva transformer and I am wondering if it will handle the additional load.
    480v bus duct feeds transformer
    Delta to wye transformer
    120/208 out put
    100 amp primary fused
    3 phase

    So I primary = 45000va / (480v x 1.732) = 54 amp primary
    I secondary = 45000va / (208v x 1.732) = 125 amp secondary .

    So does that mean I have 125 amps on phase A,B&C . Or 125amps split between the 3 phases.

    120 Power is supplied once every three floors via a 45kva transformer and 100 amp disconnect off the 480v bus duct.


    The load that I am adding is one 20 amp circuit per room per floor of hotel. So worst case scenario 16 amp x 120v =1920w , 1920w x 16 rooms per floor =30,720w , 30,720w x 3 floors = 92,160w . This is assuming everyone would be using the extra load to its full potential all at the same time .

    What I am asking is if I add 3 subpanels to bring 120v power to each floor, 100 amp panels 3 phase , all running off existing 120v 3 phase 125amp panel fed by the 45kva transformer , would I be overloading the existing installation.

    Any help would be greatly appreciated .

  2. #2
    Join Date
    Jun 2016
    Location
    Tampa, FL, USA
    Posts
    372
    What is the new circuit being used for? If it's something dedicated like a heating unit, it will probably have a much higher utilization factor than if it's a convenience outlet on a deck for the occasional laptop/phone charger.

  3. #3
    Join Date
    Jul 2005
    Location
    LA basin, CA
    Posts
    1,402
    Room additions will require section 220 load calcs based on total square footage, etc..

    If permitted, some renovations may use 220.87 alternate load calcs, based on historical peak demand.

    Check with your building department, planning office.
    Roger Ramjet NoFixNoPay

  4. #4
    Join Date
    Mar 2017
    Location
    Alberta
    Posts
    2
    The plugs are for a unit comprised of mini frodge coffe maler and a small microwave

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