Mechanical Services



Pneumatic Building Control Systems – A Primer: This type of control system uses compressed air as a medium of control for HVAC systems vs. a low or line voltage control method.

Compressed air is carried via copper and plastic tubes from a controller to a control device, usually a damper or valve actuator. This control method relies on sensors and thermostats that bleed or retain the line pressure from the sensor to the control device and the actuator. Each sensor responds to changes in temperature, humidity, and static pressure as examples, to provide feedback in a control loop to open or close the actuator to meet the control set point. The actuators contain diaphragms and spring to function in sequence with the control signal.

The prevalence of 25PSI based Pneumatic Building Control Systems that have been installed over many decades remain as a substantial and valid methodology within ICI (Industrial, Commercial, Institutional) facilities and as such require a specialized skill set to properly service and maintain these vital infrastructure systems. Consideration to convert pneumatic control systems to a current state of the art BAS (Building Automation System) are often thwarted by the potentially significant capital cost which in many cases outweigh the net benefits…or at a minimum, the retrofit project under consideration cannot sufficiently meet the building owner’s ROI target mandate.

Smith & Long Mechanical has field technicians who are very well versed in this control systems methodology and can efficiently provide service, maintenance, inspections, relocation of devices, installation of new devices, recalibration services, optimized systems operation, etc.

As a mechanically dependent system of control, there are many components that require routine inspection and maintenance to ensure maximized systems reliability such as Air Compressors, Air Dryers, Sequencing Accumulator, Air Gauges, Control Valves, Isolation Valves, Solenoid Valves, and Pressure / Electric (P/E) Switches. Due to the relatively low air pressure channeled and ported through a myriad of tubing and sensitive mechanical controls, it requires extremely clean and dry air as a control source.