Operating Instructions

Controlling Laboratory Air Flow
Siemens Building Technologies, Inc. 3-11
Example 1: Occupancy Schedule Combined with a Manual Switch
The occupancy schedule, combined with a manual switch approach, makes sense in cases
where the laboratory is primarily occupied according to a regular schedule, but must also be
available to workers at unscheduled times. Here, the schedule is the main source of
occupancy information. An operator sets up the schedule, using the Building Automation
System (BAS), so that it covers the normal working hours. When a laboratory worker wants to
use the laboratory outside the normal working schedule, that worker must flip a switch to "turn
on" the laboratory ventilation. This can be the same switch that turns on the lights, or a
separate switch. The worker will observe that the occupancy light in the room now indicates
that the ventilation system is operating in the occupied mode, and that it is safe to work there.
When the operator is finished working, the switch should be flipped again to "turn off" the
laboratory ventilation. If the schedule still indicates an unoccupied period, the LRC switches
to the unoccupied mode.
Example 2: Button on Thermostat Combined with Fume Hood Sash
Positions
In this case, the lab worker uses the push-button on the room temperature sensor to tell the
LRC to change the ventilation mode. Upon entering the laboratory, the employee must
observe the occupancy indicator. If the lower ventilation rate is in effect, then the employee
must press the button on the thermostat. Within a few seconds of this action, the room will
shift to the higher ventilation rate. The employee may notice the change at the occupancy
indicator light, or on the thermostat display screen. When the employee leaves, the button on
the thermostat should be pressed again to switch the room back to unoccupied mode. As an
additional safety, the LRC will operate at the higher ventilation rate whenever the fume hood
is open.
If the laboratory operator presses the button upon leaving and the fume hood sash is open,
the room will not switch to the lower ventilation rate. At this point, an informed worker may
realize that the fume hood has been left open. Closing the hood will switch the room to the
unoccupied mode.
Your local Siemens Building Technologies, Inc. office has the expertise to help design the
occupancy detection scheme best suited to the operation of your facility, and to implement
that system for you.