Testing of either individual automatic transfer

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each transfer switch will be wired in series to allow testing at either location. Testing of either individual automatic transfer switches or the entire essential electrical system will be possible. Each test switch will simulate a normal power source failure and automatically cause the engine generator sets to crank, attain rated frequency and voltage, and to transfer associated essential electrical system loads from the normal source to the emergency source. After 30 minutes of operation in the emergency mode, © J. Paul Guyer 2010 14
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essential electrical system loads being tested will again be automatically transferred back to the normal source. If for any reason the generator units experience difficulty while in the emergency mode, the load will immediately be transferred to the normal source automatically. During this test run, nonessential hospital loads will continue to be served from normal power supply without experiencing interruption. A manual override switch will be installed that can be actuated to keep essential hospital loads on the emergency source as long as desired. This switch will permit engine generator sets to operate indefinitely beyond the 30 minute automatic transfer restoration time. 3.9 Generator Set Operation . Generator sets will be designed to function essentially as follows: After 30 hertz (cycles) following an interruption of the normal power supply, each generator set will receive the starting signal simultaneously, whereupon each set will automatically crank and attain normal speed and voltage. Voltage for sensing devices to start generator sets will be taken from each phase of the incoming normal power terminal of each automatic transfer switch. The first generator sets to reach preset voltage and frequency conditions will be automatically connected to the emergency bus. System protection will be provided to prevent simultaneous connection of non-synchronized generators to the dead emergency bus. A priority selective device will be provided and programmed or preset to transfer the emergency system loads (life safety and 2 or more critical branches supported from separate ATSs) from the normal bus to the emergency bus within 10 seconds from time of NORMAL POWER interruption. The remaining unit will automatically synchronize with the emergency bus, close the respective generator breaker, and connect the units in parallel for normal operation. After this, the equipment system loads will be automatically transferred to the emergency bus by programmed or preset incremental steps. The equipment system loads will be completely transferred within 45 seconds, based on a priority sequence, after the generator sets are connected in parallel. Should one or more of the generator sets fail to crank or is shutdown for any reason during the operation, the remaining unit will be scheduled to serve only emergency system loads and, if possible, highest priority equipment system loads until the failed unit is energized and connected to the emergency bus. For such a condition, a programming device will shed all or part of the © J. Paul Guyer 2010 15
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equipment loads, to keep the remaining generator within its kw rating. If the automatic
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