500 KVA outdoor transformer

[lilsparky]

The cost difference between a 500kVA and say a 750kVA transformer, when you include installation cost is minimal. Upgrading in the future will be a huge cost. IMO you should always go big when there is any doubt, will be cheaper in the long run.

I know what you are saying but the issue is between using an existing 500KVA transformer vs purchasing a new 750KVA transformer.

 

[kwired]

I'm glad you mentioned that. I have been asked to put in diversity factors for the loads. I have identified when certain pieces of equipment works by themselves and/or with other pieces of equipment to try to come up with a diversity factor. For examplefor some reason I can't attach my spreadsheet or pictures to this forum I'll just give a brief synopis) All loads are 480V


40 Hp Air compressor w/1/20 hp dryer (one unit)
15 Hp VFD for Rotation Dollies
75 KVA Transformer
AHU #1 7.5 Hp
AHU #2 2 Hp


So when work is being done on the Rotation Dolly, the air compressor is being used, and the AHUs are on. Which means the 50T crane and trolley aren't being used, nor will the hydraulic units be used. So I'm trying to come up with some diversity factor for these scenarios. Any suggestions?

The thing about listing 40 hp compressor, 15 hp dollies, 7.5 hp AHU, and even 75kVA transformer is knowing how much actual load is, and/or what peak demand is and for how long. Does the 40 HP compressor ever actually draw 40 hp of demand, it can if needed but likely maybe only peaks at 30 or 35 hp and maybe only for short periods of time. The 15 HP VFD - does it run full load at full speed very often or maybe it never does. If that 15 HP motor only runs at 2/3 full speed most of the time it likely does not draw any more than 10 hp of load.

You need to use the nameplates when calculating branch circuits just in case of temporary high loading, but when considering feeders and services and supply sources if you use nameplate vs actual demand info you will have larger capacity than what is normally demanded by the equipment.

 

[zog]

I know what you are saying but the issue is between using an existing 500KVA transformer vs purchasing a new 750KVA transformer.

Oh, disregard then