Operating Instructions

Laboratory Room Controller Owner's Manual
3-2 Siemens Building Technologies, Inc.
The LRC selects flow set points that drive this calculated flow difference to the selected
value, VOL DIF STPT. Ventilating the room means keeping the value of SUP AIR VOL above
the specified minimum value, SUP MIN. To control room temperature, the LRC drives SUP
AIR VOL to a value calculated in the temperature control algorithm, TEMP CTL VOL. The
supply flow only follows this value when it is consistent with the other goals.
Generally, the airflow control system follows two dynamic inputs: the flow through the fume
hood(s), HOOD VOL, and the need for supply airflow to control the room temperature, TEMP
CTL VOL. (It is also possible for the minimum and maximum flow limits to change with
occupancy, but these values can generally be viewed as constant). When the controller
receives these inputs, the flow control algorithm calculates how much supply flow is
necessary to meet all the goals. The controller will then calculate the corresponding general
exhaust flow set point and apply the maximum and minimum limits. The supply flow set point
is then calculated to maintain the correct flow difference. If that value is above the supply
maximum, then the set point goes to the maximum.
The Pressure Report, which is available through CIS, is the most convenient way to observe
the operation of the ventilation and pressurization system. Table 3-1 describes its contents.