Abstract: An air handling unit for a heating, ventilating and air conditioning system of a building has a plurality of exhaust fans. The exhaust fans are sequentially activated in response to the amount of air flowing into the air handling unit from outdoors. Thus the amount of air exhausted from the building approximates the amount of air drawn into the building through the air handling unit. This operation maintains the static air pressure within the building to acceptable levels.

Abstract: A system for circulating ventilating air in a space includes a supply air chamber configured for communication with a supply duct, a return air chamber configured for communication with a return air duct, and an outside air chamber configured to receive outside air from an outside air intake. The outside air chamber includes an outside air damper having a plurality of settings for varying outside air flow volume in the outside air chamber. The outside air damper establishes a predetermined relationship between each outside air damper setting and the outside air flow volume. The outside air damper establishes each setting in response to a damper control signal. The system further includes a mixed air plenum in communication with the return air chamber and the outside air chamber and a fan positioned between the mixed air plenum and the supply air chamber, the fan supplying a constant volume of air to the supply air chamber in response to a fan control signal.

Abstract: An apparatus and method indirectly determines the amount of outside air introduced into the ventilation system of a structure to control the indoor air quality in the structure. Test gas concentrations, preferably carbon dioxide concentrations, are measured for return air, outside air and mixed (supply) air. The flow rate of mixed air is measured. The volume of outside air introduced into the system is determined through use of the test gas concentration measurements without directly measuring the volume or flow rate of outside air. Preferably, a single sensor is utilized to measure each of the trace gas concentrations in the return air, outside air and supply air, and the various measurements sequentially multiplexed to a controller. Moreover, for calibrating the apparatus, a return air sensor is calibrated to the outside air and a mixed air sensor is calibrated to the outside air or the return air to eliminate inaccuracy due to sensor drift.

Abstract: A position actuator includes a motor driven low efficiency lead screw with a follower moving in parallel relation to a valve coupler of a valve shaft and a switch operator of a force/torque limit unit. A lever is pivotally coupled to the follower, coupler and the operator. The lever pivots about the operator to move the valve coupler at a valve limit. The coupler cannot move and the lever pivots about the coupler to move the operator and actuates a switch to signal an alarm and/or another controller. The limit unit includes an elongated coil spring having a low spring rate within a tubular housing having mounting plates for switches. The operator passes through the spring and has retainers abutting the spring ends and the housing to provide a factory spring calibration. The lever couplings include a lever opening with spaced knife-edges to provide low friction engagement. In a damper control, limit unit is mounted to a driven sector gear and a lever is secured to a damper shaft.

Abstract: A control valve includes a single diaphragm as a common wall between an input signal chamber having an input port and an output chamber having a central supply port and an exhaust orifice. The orifice has a seating face parallel to and spaced from the diaphragm. A spring-loaded ball valve unit in the supply passage is aligned with an operator moving with the diaphragm. An increasing input signal first moves the diaphragm to close the exhaust orifice and thereafter moves the operator to open the supply valve. Pressure builds in the output chamber, tending to return the diaphragm and close the supply valve until the output and pilot pressure are balanced. The supply valve then closes. As the exhaust is sealed off, this effectively seals the output chamber. If the signal decreases, the diaphragm uncovers the exhaust orifice until a new balanced state is created.

Abstract: A vacuum operated sewerage system includes a static pressure sensor establishing a trigger signal at selected first level in a standpipe. The sensor is connected upstream of a discharge control valve and actuates a timer at the selected sensed pressure. The timer is connected to actuate the discharge control valve after a suitable time delay to prevent transient signal actuation, and establish flow for a predetermined period. An air admission valve is connected in series with the sensor to the timer to actuate the timer if the system vacuum drops below a selected level in the same manner as an increased hydrostatic pressure. The sensor can be eliminated for separate air admission control directly in response to the vacuum condition of the line.

Abstract: A press control includes a pair of pushbuttons each operating a pneumatic pump means to form a pair of signal pulses and an integrated valve to form a pair of binary logic pressure signals. A press position sensor provides a binary pressure signal related to the press position. The pushbutton and sensor signals are connected to fluidic logic gate means to compare and detect the actuation of the pushbuttons as well as the status of such pushbuttons and the press cycle. The logic output is connected by a plurality of logic gates to actuate a flip-flop output unit to generate an extend output or a retract output. The flip-flop output unit has an input connected to a latch input control to provide automatic reset to the retract output if release of the button signal sources occurs during a hazardous portion of the extend cycle. Once the non-hazardous portion of the extend cycle is reached, the latch is complete for the terminal portion of the extend cycle.