Abstract: A real time remote sensing pressure control system is provided which uses periodically sampled remote sensors to generate a bias signal that modifies the base setpoint of a proportional-integral controller that controls variable speed pumps. This control scheme saves energy by slowing the rotational speed of the variable-speed secondary pumps during periods of light system demand. The system can be provided with more than one zone of system loads (such as chilled or hot water coils) and a remote pressure sensor (gauge or differential) can be provided at each of those zones. In addition, a local pressure sensor (gauge or differential) is provided at the primary and secondary pumps. The process variable signals detected by the remote pressure sensors is communicated by a building automation system or other type of data highway, which inherently delays the real time nature of those sensed signals and only periodically provides an update of those signals.

Abstract: A primary-secondary circuit hydraulic interface is disclosed for use in chilled water and hot water systems in which a suction manifold header is used to tie in the secondary return water, the primary supply water, and the suction side of the primary and secondary pumps. The hydraulic interface is installed within the suction manifold at the location where the secondary return water enters the suction manifold. The hydraulic interface allows the bypass water (which is excess primary supply water) and the secondary return water to easily enter the hydraulic interface into a downstream portion of the manifold through large openings and forces the two streams of water to collide together, thereby ensuring a turbulent mixing to take place. The hydraulic interface forces the mixed water to exit the hydraulic interface through much smaller openings into a downstream portion of the manifold, thereby ensuring that the bypass water and secondary return water are thoroughly blended together as they exit.

Abstract: A primary-secondary circuit hydraulic interface is disclosed for use in chilled water and hot water systems in which a suction manifold header is used to tie in the secondary return water, the primary supply water, and the suction side of the primary and secondary pumps. The hydraulic interface is installed within the suction manifold at the location where the secondary return water enters the suction manifold. The hydraulic interface allows the bypass water (which is excess primary supply water) and the secondary return water to easily enter the hydraulic interface into a downstream portion of the manifold through large openings and forces the two streams of water to collide together, thereby ensuring a turbulent mixing to take place. The hydraulic interface forces the mixed water to exit the hydraulic interface through much smaller openings into a downstream portion of the manifold, thereby ensuring that the bypass water and secondary return water are thoroughly blended together as they exit.

Abstract: A circuit for simulating a slide wire device includes a pair of resistors connected electrically in series with a reference voltage source. Switching means are provided for alternately shorting the resistors in a duty cycle fashion such that when one of the resistors is shorted, the other resistor is unshorted. By adjusting this duty cycle, the output provided by the circuit is adjusted and a slide wire device simulated.