Connecting Fuel Cells to Distribution System
Calculated load is 2500 amps at 480 volts. To leave room for future growth, I pick a 2500 KVA transformer and a 4000 amp main switchboard. Newly manufactured fuel cells will be tested at this facility. The intent is to use the building’s distribution system, instead of a separate load bank, as the load for the fuel cells. At maximum capacity, the fuel cells can supply up to 1500 amps. If I connect this energy source to the main switchboard (i.e., in parallel with the utility), do I have to upsize it to 5000 amps?
One viewpoint is that the main switchboard woud have two energy sources, one rated at 3000 amps and the other at 1500 amps, and therefore the bus must be rated for at least that much current. The other viewpoint is that any current supplied by the fuel cells is simply current that is not supplied by the transformer, and the total current supplied will never be higher than the calculated demand load, and therefore the 4000 amp board is adequate.
Last edited by charlie b; 10-26-12 at 10:16 AM.
Charles E. Beck, P.E., Seattle
Comments based on 2008 NEC unless otherwise noted.