Energy reducing retrofit method and apparatus for a constant volume HVAC system

摘要

An energy-reducing method and apparatus for retrofitting a constant volume HVAC system, with or without an economizer, that provides heating, cooling, and ventilation to occupants within a building space. The present invention includes the introduction of a programmable logic controller and variable frequency drive (VFD) that takes control of the existing fan, heating, cooling, and optional economizer operation. The controller is programmed fault detection of fan fault, heat/cool (temperature-based) fault, and energy consumption fault. The reduction of the fan speed in the ventilation mode when the 100% operation is not needed saves significant energy of the existing constant volume HVAC system where the fan motor is designed to run 100% of the time.

主权项

1. A method of reducing energy consumption by retrofitting a preexisting single zone constant volume HVAC system that provides one or more of the following: heating, cooling, or ventilation to an indoor space within a single zone of a building that has periodic occupancy, wherein the heating, cooling, or ventilation is initiated based upon preset conditions or on occupancy command and wherein the preexisting HVAC system includes a fan assembly configured to operate between no operation and a maximum ventilation with a range of operation from 0 to 100%, a thermostatic device, heating and/or cooling equipment having preexisting equipment control terminations, the energy reducing method comprising:
providing a programmable logic controller that can receive input from the thermostatic device and send heating, cooling, and ventilation instructions to a preexisting fan assembly for ventilating an indoor space within a single zone of a building, and to a preexisting heating assembly that can send heat to the same indoor space, and to a preexisting cooling assembly that can send cooling to the same indoor space; and operably connecting the programmable logic controller to preexisting equipment control terminations; providing a variable frequency drive (VFD), controlled by the programmable logic controller, and operably connecting the VFD to the preexisting fan assembly; operating the preexisting HVAC system in a ventilation mode, a heating mode, and/or a cooling mode, controlled by the programmable logic controller; operating the preexisting fan assembly at a reduced speed during the ventilation mode when the less than maximum ventilation is required; and providing fault detection via a discharge air sensor or current status switch.