The Emergency Generator:

The Emergency Generator is a stand-alone unit that sets on a concrete pad next to the Automatic Transfer Switch.   It runs on propane, supplied from a tank near G and H Buildings.

     The generator is fully automatic, turned on from a sensing circuit in the Automatic Transfer Switch.  When a MECO power failure is sensed, the generator will automatically start, then the transfer switch will disconnect the MECO electrical cables and connect the generator to the Control Panel.  When MECO power is restored, the transfer switch will disconnect the generator and reconnect the MECO power cables.  After a 2-5 minute cooldown cycle, the generator will automatically shut down.

    The generator has an “auto-exercise” function.  Once per week (initially set for Thursdays at 2 pm) the generator will automatically start up and run for about 15 minutes, then shut itself off.  The generator remains disconnected from the Control Panel during this exercise period.

Note:

 

Inside the Control Panel, this Lock-out Relay was added to the circuitry.

 

Because of the high starting current required by the SPS pumps, the generator capacity is limited to starting and running only one of the two pumps in the wetwell.  When a MECO power outage occurs, this relay opens, which disconnects the “second pump” float in the wetwell.  This, in turn, prevents the second pump from starting.

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Lock-out Relay