Can anyone explain what occurs differently between a fast startup and a normal startup for a John Brown Frame 5 unit with a diesel engine starting package?

 

It's impossible to say exactly what happens with the unit at your site without being able to look at the logic diagrams for the control system.

In general, there is 'fast start' and 'fast load start'. In a 'fast start', usually the diesel warm-up time is "bypassed", sometimes the purge time is shortened, and sometimes the acceleration rate is increased, all so that the unit will reach full speed-no load (FSNL) sooner than it would have otherwise. At that point, the operator will then synchronize and load the unit.

Generally, in a 'fast load start' the unit is started normally (normal diesel warm-up time, normal purge time, normal acceleration rate), but once the unit gets to FSNL it automatically synchronizes (without operator initiation), and then loads to Base Load *very* quickly, sometimes in as little as 1.5 minutes or even less.

Now, depending on the circumstances and requirements of the site when the unit was engineered and installed, some or all of the parameters involved (diesel warm-up time, purge time, acceleration rate, loading rate) can individally be adjusted to meet contractual or Customer requirements. That's why it's impossible to say for sure precisely what happens with the unit at your site. But, in general, the above are the parameters which in some combination will be affected by a fast start or fast load start.