HVAC system relay autotuning and verification

#Proportional-integral (PI) feedback control can be used to regulate disturbances and achieve desired setpoints in HVAC systems. One example of a component in an HVAC system that can use such PI feedback control is a fan coil unit (FCU), which can regulate fan speed, cooling/heating medium flow, and/or other variables to meet desired temperature of a zone. The PI parameters, proportional gain and integral time can, however, be difficult to determine and pre-set, prior to commissioning of the HVAC system. Further, when implemented, such HVAC systems and components can be affected by a variety of time-dependent variables that often make a single set of PI parameters unsuitable for indefinite use. As a result, PI parameter re-tuning is often desired, allowing the controller to respond to changes in the characteristics of the system.

#To provide such dynamic system control, the HVAC system controllers may be re-tuned while online. Tuning may be manual, proceeding by trial-and-error, or may be automatic. Manual tuning is often time consuming and can lead to sub-optimal results, for example, by introducing human error. Further, automatic tuning or “autotuning” is frequently inaccurate and/or unreliable. If a process disturbance occurs during such autotuning, the controller can erroneously set the PI parameters as if the transitory disturbance was part of the system cause-effect response. Further, system models, often used to estimate the tuning parameters from information measured in the system, can be difficult to identify online.

#What is needed are systems and methods for autotuning an HVAC system controller.

#The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate aspects of the present teachings and together with the description, serve to explain principles of the present teachings. In the figures:

#FIG. 1 illustrates a schematic view of an exemplary HVAC system, according to an embodiment.

#FIG. 2 illustrates an exemplary block diagram of a control feedback loop with a PI controller, according to an embodiment.

#Reference will now be made in detail to various embodiments of the present teachings, an example of which is illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

#In the following description, reference is made to the accompanying drawings that form a part thereof, and in which is shown by way of illustration specific implementations in which may be practiced. These implementations are described in sufficient detail to enable those skilled in the art to practice these implementations and it is to be understood that other implementations may be utilized and that changes may be made without departing from the scope of the present teachings. The following description is, therefore, merely exemplary.

#FIG. 1 illustrates a schematic view of an exemplary HVAC system 100, according to an embodiment. The HVAC system 100 is configured to chill and/or heat air supplied to a volume or “zone” 101, which may be a facility, room, or portion thereof. In an exemplary embodiment, the HVAC system 100 includes a fan coil unit (FCU) 102, a controller 104, and a sensor 106. It will be appreciated that a variety of other HVAC systems 100 may be employed, without departing from the scope of the present disclosure. Further, in the illustrated embodiment, the FCU 102 may include a fan 108 and a coil 110. The fan 108 may be any suitable axial, radial, or centrifugal fan or blower, and the coil 110 may be any suitable heat exchanger, such as a heat exchange coil. Further, the coil 110 may form part of a heat pump or other refrigerant cycle so as to heat or cool air pushed across the coil 110 by the fan 108. The FCU 102 may be configured to supply air to the zone 101 via a duct 112, which may be any suitable size and shape and may have one or more inlets and/or one or more outlets, so as to distribute air flow in the zone 101 and/or to direct air to other zones (not shown).