Energy reducing retrofit method for a constant volume HVAC system

• US 8,515,584 B2
• Filed: 08/20/2009
• Issued: 08/20/2013
• Est. Priority Date: 08/20/2009
• Status: Active Grant

• Current Assignee: Pro Star Energy Solutions LLC
• Original Assignee: Transformative Wave Technologies LLC (Performance Mechanical Group)
• Inventors: Miller, Danny, Sipe, Justin
• Primary Examiner(s): Ali, Mohammad
• Assistant Examiner(s): Norton, Jennifer L
• Application Number:
  US12/544,960
• Publication Number:
  US 20110046790A1
• Time in Patent Office: 1,461 Days
• Field of Search: 700/276, 700/295, 621/26, 621/86, 165/201, 236/49.3, 236/44.C, 236/44.R, 454/239, 454/256, 454/333
• US Class Current: 700/276
• CPC Class Codes: F24F 11/30 for purposes related to the operation of the system, e.g. for safety or monitoring
• CPC Class Codes: F24F 11/46 Improving electric energy efficiency or saving
• CPC Class Codes: F24F 11/58 using Internet communication
• CPC Class Codes: F24F 11/62 characterised by the type of control or by internal processing, e.g. using fuzzy logic, adaptive control or estimation of values
• CPC Class Codes: F24F 11/77 by controlling the speed of ventilators
• CPC Class Codes: F24F 2011/0006 using low temperature external supply air to assist cooling
• CPC Class Codes: F24F 2110/20 Humidity
• CPC Class Codes: F24F 2110/50 Air quality properties
• CPC Class Codes: F24F 2110/70 Carbon dioxide
• CPC Class Codes: G05B 19/042 using digital processors G05B19/05 takes precedence
• CPC Class Codes: G05B 19/05 Programmable logic controllers, e.g. simulating logic interconnections of signals according to ladder diagrams or function charts
• CPC Class Codes: G05B 2219/1133 Sensor actuator, asi, bus, network
• CPC Class Codes: G05B 2219/25289 Energy saving, brown out, standby, sleep, powerdown modus for microcomputer
• CPC Class Codes: G05B 2219/2614 HVAC, heating, ventillation, climate control
• CPC Class Codes: G05D 23/1919 characterised by the type of controller
• CPC Class Codes: G05D 7/0676 by action on flow sources G05D7/0688, G05D7/0694 take precedence
• CPC Class Codes: H04L 67/12 specially adapted for proprietary or special-purpose networking environments, e.g. medical networks, sensor networks, networks in vehicles or remote metering networks
• CPC Class Codes: H04L 67/125 involving control of end-device applications over a network
• CPC Class Codes: Y02B 30/54 Free-cooling systems
• CPC Class Codes: Y02B 30/70 Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating
• CPC Class Codes: Y02B 30/90 : Passive houses; Double facade technology

Abstract

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 for the reduction of fan speed in the heating and cooling modes. 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. The fan speed may be further reduced upon a reduction in sensed occupancy levels of the space, such as with a CO₂ sensor. Additionally, the fan speed may be reduced in the heating and/or cooling mode to further reduce energy consumption. The controller may also be programmed and equipped with sensors to allow simultaneous mechanical compressor cooling and economizer free cooling operation, for the operation of the economizer in response to the monitoring of outside air and return air to determine the preferred source for cooling operations, to keep the outside air damper closed during the unoccupied heating modes such as morning warm-up, and/or to provide fault detection. The retrofit method and apparatus may be employed in a stand-alone or networked version.

Claims

1. A method reducing energy consumption comprising:

retrofitting a single zone, constant volume HVAC system that provides one or more of the following;

heating, cooling, or ventilation to an indoor space within that single zone, the indoor space having at least partial occupancy, wherein the heating, cooling, or ventilation is based on preset conditions or on occupancy command and wherein the preexisting HVAC system consists of a fan assembly, including a fan and a fan motor;

a thermostatic device that references temperature of the indoor space served by the single zone, constant volume HVAC system; and

heating and/or cooling assembly having equipment control terminations;

providing a programmable logic controller that can receive input from the pre-existing thermostatic device and send heating, cooling, and ventilation instructions to the pre-existing fan assembly for ventilating the indoor space, and to a pre-existing heating assembly that can send heat to the indoor space, and to a pre-existing cooling assembly that can send cooling to the indoor space; and

operably connecting the programmable logic controller to the pre-existing equipment control terminations;

providing a variable frequency drive (VFD), controlled by the programmable logic controller, and operably connecting it to the pre-existing fan motor;

operating the HVAC system in a ventilation mode, a heating mode, and/or a cooling mode, all modes controlled by the programmable logic controller based on an input from a provided occupancy sensor;

operating the pre-existing fan motor 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 and/or current status switch, including detection of fan fault, heat/cool (temperature-based) fault, and energy consumption fault; and

the fan fault and heat/cool (temperature-based) fault are interconnected and the fan fault detection is run first and then the heat/cool (temperature-based) fault detection is run and the energy consumption fault is independent of the fan fault and the heat/cool (temperature-based) fault detection.

2. The method according to claim 1 wherein the fan motor is operated at a reduced speed during the heating and/or cooling mode.

3. The method according to claim 1 wherein the fan speed is reduced in the range of 10% to 90% in the ventilation mode.

4. The method according to claim 2 wherein the fan speed is reduced in the range of 1%-30% in the heating and/or cooling mode.

5. The method according to claim 1 wherein the occupancy sensor to determine occupancy levels within the building indoor space and sending the sensed occupancy level to the programmable logic controller;

and operating the fan motor at a reduced speed during the ventilation mode when the occupancy level requires less than maximum ventilation.

6. The method according to claim 5 wherein the fan speed is reduced in the range of 10% to 90% in the ventilation mode in response to the sensed occupancy needs.

7. The method according to claim 1 wherein the programmable logic controller and VFD are incorporated into a single unit.

8. The method according to claim 1 further comprising providing a central processor and an interconnection in order to network one or more programmable logic controllers.

9. The method according to claim 8 wherein the interconnection is wireless.

20. The method according to claim 1 wherein the energy consumption fault is run continuously.

10. A method reducing energy consumption comprising:

retrofitting a single zone, constant volume HVAC system that provides heating, cooling, and/or ventilation to an indoor space within that single zone, the indoor space having at least partial occupancy, wherein the heating, cooling, and/or ventilation is based on preset conditions or on occupancy command and wherein the preexisting HVAC system consists of a fan assembly, including a fan and a fan motor, a thermostatic device that references temperature of the indoor space served by the single zone, constant volume HVAC system;

heating and/or cooling assembly having equipment control terminations; and

an economizer comprised of at least one outside air damper and one return air damper with an associated damper actuator;

providing a programmable logic controller that can receive input from the preexisting thermostatic device and send heating, cooling, and ventilation instructions to the preexisting fan assembly for ventilating the building space in a ventilation mode, and to the preexisting heating assembly that can send heat to the building space in a heating mode, and to the preexisting cooling assembly that can send cooling to the building space in a cooling mode, and to the system economizer in an economizer mode; and

operably connecting the programmable logic controller to the 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 motor;

providing an occupancy sensor to determine occupancy levels within the indoor space and sending the sensed occupancy level to the programmable logic controller for at least the ventilation mode, the heating mode, and/or the cooling mode;

providing an input sensor and an output sensor to sense respective outside air condition and return economizer air and that the sensors communicate their sensed conditions to the programmable logic controller;

operating the fan motor at a reduced speed during the ventilation mode when the occupancy level requires less than maximum ventilation;

operating the fan motor at a reduced speed during the heating and/or cooling mode; and

operating the HVAC system in the ventilation mode, the heat and/or cooling mode, and the economizer mode, wherein all modes are controlled by the programmable logic controller based on an input from the provided occupancy sensor;

providing a discharge air sensor and/or a current status switch, including detection of fan fault, heat/cool (temperature-based) fault, and energy consumption fault in order to provide fault detection to the HVAC system; and

the fan fault and heat/cool (temperature-based) fault are interconnected and the fan fault detection is run first and then the heat/cool (temperature-based) fault detection is run and the energy consumption fault is independent of the fan fault and the heat/cool (temperature-based) fault detection.

11. The method according to claim 10 wherein further energy savings are gained by the operation of the economizer in response to the monitoring of outside air and return air to determine the preferred source for cooling operations.

12. The method according to claim 10 wherein further energy savings are gained by closing the at least one outside air damper during the unoccupied heating modes.

13. The method according to claim 10 wherein further energy savings are gained by integrating the economizer and cooling operations.

14. The method according to claim 10 wherein the fan speed is reduced in the range of 10% to 90% in the ventilation mode.

15. The method according to claim 10 wherein the fan speed is reduced in the range of 1%-30% in the heating and/or cooling mode.

16. The method according to claim 10 wherein the programmable logic controller senses one of the following:

temperature, enthalpy, or dew point in the economizer mode.

17. The method according to claim 10 wherein the programmable logic controller and VFD are incorporated into a single unit.

18. The method according to claim 10 further comprising providing a central processor and an interconnection in order to network one or more programmable logic controllers.

19. The method according to claim 18 wherein the interconnection is wireless.

21. The method according to claim 10 wherein the energy consumption fault is run continuously.