Demo. Laboratory Space Pressurization------Flow Tracking Control Supply and Exhaust Dampers

Laboratory design parameters:

Laboratory size(volume) = 5m*4.4m*3m=66m3

1500 bench-mounted fumehoods(2sets)=230CMHmin*-1150CFM max*

Flow offset =230CMH

Minimum ventilation flow= 660CMH* (ACPH = 10t/h)

Cooling flow = 660CMH*(ACPH = 10t/h)

Design pressure: Slightly negtive pressure

Design temperature= 25℃

Model selection：

Room Pressure Controller：TSI Sureflow™ Model 8682 Offset Controller;

Face Velocity Controller for Fumehood：TSI Model FHC50-01 Fume Hood Controller with Flow Station;

Static Pressure Controller for Exhaust Fan and MAU：TSI Sureflow™ Model 8635-ST Static Pressure Controller.

Controlsequence of Face Velocity Controller for Fumehoods:

The Model FHC50-01-FS fume hood controller with flow station uses a sidewall sensor and a flow station continuously monitoring and controlling the average face velocity and the actual exhaust volume of the fume hood. The controller maintains the face velocity stable at pre-set value by adjusting the variable airflow volume damper, meanswhile, the flow station ensure the exhaust volume of the fumehood above the minimun value all the time. 

Controlsequence of Static Pressure Controller for Fans and MAUs:

The Model Sureflow 8635-ST Controller use a static-pressure sensor to maintain static pressure of exhaust fans and MAUs stable at a pre-set value. If the measured value is higher than the setpoint, the controller will reduce the exhaust fans or MAUs drive speed back to the set-value. If the measured value is lower than the setpoint, the controller increases the exhaust fans or MAUs drive speed back to the set-value. When unoccupied, the controller will maintain static pressure value in "standby" status setting.

General Sequence of Operation

The TSI Sureflow™ Model 8681/8682 Room Pressure Controller  simultaneously controls room balance, ventilation and temperature in the laboratory. 

Room Balance Control Sequence of Operation(The sum of minimum exhaust volume of both fumehoods greater than that of ventilation required, so we do not set general exhaust)

The room controller continuously maintains a constant flow offset between supply and exhaust volumes(the flow stations continuously measure exhaust volume of each fumehood). If the offset becomes too large, indicating that the room balance is too negative, the room controller closes the general exhaust and then opens the supply to its maximum setpoint. If the offset becomes too small, indicating that the room balance is not negative enough, the room controller closes the supply to its minimum ventilation or cooling flow and then opens the general exhaust. 

Ventilation Control Sequence of Operation

The room controller maintains the supply air volume at or above its minimum setpoint through the flow stations.