Frank,
You're wise to be careful with your fire panel. During any work on the sprinkler system, the flow switches (or in some buildings, pressure switches) will activate when water flow is sensed. Sometimes, the wrong valve is closed, so that when draining is begun, the flow switch for the riser alarms the fire panel, causing your local evacuation signals to be activated. Some Simplex panels have a simple method to put the system into a test or bypass mode, so that normal alarm functions do not happen. When the sprinkler zone is refilled, you would then also have a flow alarm, if you are not in the bypass mode. Most of the flow switches have built in pneumatic or diaphragm type timers to prevent normal small pressure changes from activating the alarm.
If you have specific questions about your panel, you may want to contact the Simplex technician who works on your panel, for further info. I have caused fire trucks to roll on several occasions!
Good luck,
Homer
