Model selection：

Room Pressure Controller：TSI Sureflow™ Model 8681/8682 Offset Controller;

Face Velocity Controller for Fumehood：TSI Model FHC50-02 Fume Hood Controller;

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 FHC50-02 fume hood controller uses a sash sensors continuously measure the fume hood sash opening, and through a VAV venturi valve to control the exhaust volume of the fume hood to achieve rapidly-stable face velocity. Meanwhile, the pressure-independent venturi valve itself mechanically compensates static-pressure changes from ductwork system without any action on the valve. If the sash openning become larger, the controller will increase the exhaust volume to maintain the face velocity stable at the pre-set value. If the sash openning become smaller,  the controller will reduce the exhaust volume to maintain the face velocity stable at the pre-set value. When unoccupied,the controller will maintain face velocity in "standby" status setting.

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 room controller continuously maintains a constant flow offset between supply and exhaust volumes. 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. 

Temperature Control Sequence of Operation

The room controller continuously measures the room temperature. If the room temperature rises above setpoint, the room controller closes the reheat valve and then opens the supply air valve until either the room temperature achieves setpoint or the supply air volume reaches its cooling maximum setpoint. If the room temperature falls below setpoint, the room controller reduces the supply air volume to its minimum ventilation or room balance flow and then opens the reheat valve until room temperature achieves setpoint.