Sizing Emergency Generators for Hospitals
Sizing Emergency Generators for Hospitals
(OP)
I have a question regarding sizing a standby, diesel generator for a hospital.
Typically, I total up the total KVA load connected to the generator, add 20% to the load (assuming no future capacity needed) and size the generator to the next larger KVA size. For example, if the total load on the generator is 468 KVA, add 20% is 561.6 KVA, so I might pick a 500 KW/625 KVA generator. The voltage is 480/277 volt, 3 phase 4 wire.
Now, I KNOW that the actual load the generator will "see" is less than the 468 KVa, because of diversity, motors not running fully loaded, receptacles not being used, etc.
So, here is my question: Assuming the 468 KVa load is 150 KVa of motors, 100 KVa of lighting and the balance (218 KVa) is receptacles, misc loads, etc. how would you aize the generator? (Assume we are not in California, where you have to size to connected load).
Thx.
Typically, I total up the total KVA load connected to the generator, add 20% to the load (assuming no future capacity needed) and size the generator to the next larger KVA size. For example, if the total load on the generator is 468 KVA, add 20% is 561.6 KVA, so I might pick a 500 KW/625 KVA generator. The voltage is 480/277 volt, 3 phase 4 wire.
Now, I KNOW that the actual load the generator will "see" is less than the 468 KVa, because of diversity, motors not running fully loaded, receptacles not being used, etc.
So, here is my question: Assuming the 468 KVa load is 150 KVa of motors, 100 KVa of lighting and the balance (218 KVa) is receptacles, misc loads, etc. how would you aize the generator? (Assume we are not in California, where you have to size to connected load).
Thx.






RE: Sizing Emergency Generators for Hospitals
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: Sizing Emergency Generators for Hospitals
RE: Sizing Emergency Generators for Hospitals
RE: Sizing Emergency Generators for Hospitals
RE: Sizing Emergency Generators for Hospitals
The largest load will be the DX cooling on 2 roof top units. There are 4 RTUs total, all with DX cooling. All RTUs will be on the generator, but only the cooling from 2 (that serve patient rooms) will be on the generator.
The largest motor HP will be approximately 30 HP.
Thanks for the feed back thus far.
RE: Sizing Emergency Generators for Hospitals
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: Sizing Emergency Generators for Hospitals
RE: Sizing Emergency Generators for Hospitals
But, none of these dictate exactly how you have to size it. For example, NFPA 99, 2005 ed, chapter 4 (elec systems), 4.4.1.1.9 says "The generator set(s) shall have sufficient capacity and peoper rating to meet the maximum actual demand likely to be produced by the connected load of the essential electrical system(s) at any one time".
I was just curious as to how other EEs design/size the gensets they specify for hospitals.
thx.
RE: Sizing Emergency Generators for Hospitals
RE: Sizing Emergency Generators for Hospitals
I hear ya! Thx.