Patent Application
20060123812
This invention relates to environmental control systems and more particularly to a system for controlling the humidity of a space.
Humidity in a space such as the space defined by a room or enclosure of a building is an ongoing problem. Excessive moisture or humidity in the air of the building enclosure can cause several problems. The moist air encounters cooler surfaces such as windows, ceilings or outdoor walls causing the air to cool and water to condense out of the cool air. The condensed water becomes a haven for fungus, mold and mildew which can contain potentially dangerous bio-toxins. Furthermore, humid air is uncomfortable for anyone in the enclosure. In addition, gaps in the ceiling or walls of the enclosure provide openings for humid air to access building structural members. Condensation can cause water deposits to accumulate on structural members. These deposits, unseen for years, can accelerate the deterioration of the structure.
Air conditioning systems, while effective to maintain the temperature of an enclosure at a comfortable level, in general are not effective in reducing humidity. In an effort to improve the ability of a typical air conditioning system to decrease the humidity of an enclosure, it has been proposed to selectively vary the speed of the system blower and, specifically, to selectively slow down the system blower whereby to cause the system evaporator coil to become cooler and increase the condensation at the coil. However, the resulting reduction in the airflow in the enclosure causes stratification, lazy air and dead air, especially close to the floor where mold often begins.
This invention is directed to the provision of an enclosure air conditioning system providing excellent humidity control in the enclosure.
The invention relates to an air conditioning system for a space or enclosure, the system including an air circulating blower and an evaporator coil positioned in the path of the circulating air.
According to an important feature of the invention methodology, the blower is operated at a substantially constant speed to provide a substantially constant air turn over rate in the system; the humidity and temperature of the space air is monitored as well as the temperature of the evaporator coil; upon the detection of a space air humidity value in excess of a predetermined set point value, a bypass damper is opened to allow circulating air to bypass the evaporator coil whereby to lower the temperature of the evaporator coil; and upon the temperature of the evaporator coil dropping to a predetermined value proximate but in excess of freezing, the damper is at least partially closed to maintain the evaporator coil temperature just above freezing.
According to a further feature of the invention methodology, the system further includes a compressor in a cooling loop with the evaporator coil and the compressor is energized upon the detection of a space air humidity in excess of the predetermined set point value.
According to a further feature of the invention methodology, the system further includes a space heater and the method includes the further steps of, upon a drop in space air temperature to a predetermined value below a predetermined set point value, de-energizing the compressor and energizing the space heater until the space air temperature returns to its set point value and thereafter, if the humidity value has not dropped to the set point value, de-energizing the space heater and re-energizing the compressor to resume dehumidification.
According to a further feature of the invention methodology, in response to a call for cooling, the bypass damper is closed.
According to a further feature of the invention methodology, the system further includes a controller; the damper is controlled by a damper motor; and the motor is selectively actuated by the controller to modulate the damper and modulate the volume of air bypassing the evaporator coil. This arrangement allows the volume of bypass air to be selectively modulated to selectively control the temperature of the evaporator coil and thereby selectively control the condensation occurring at the evaporator coil.
According to a further feature of the invention methodology, the space heater comprises an electric heating element interposed in the path of the circulating air.
According to a further feature of the invention methodology, the controller functions to control the space heater and the bypass damper in a manner to never allow the space air temperature to vary by more than approximately 2° F. irrespective of the mode of operation.
In overview, the invention methodology provides effective humidity control without reducing the speed of the blower with consequent stratification and mold formation problems.
According to an important feature of the invention air conditioning system apparatus, the system comprises ducting extending from an entry end opening in the space to an exit end opening in the space; a blower operative to move air through the ducting from the entry end to the exit end; a cooling loop including an evaporator coil positioned in the path of the air moving through the ducting and a compressor; bypass ducting extending around the evaporator coil; and a controller receiving signals indicative of the temperature of the air in the space, the humidity of the air in the space, and the temperature of the evaporator coil and operative in response to the received signals to selectively open and close the bypass ducting and selectively energize and de-energize the compressor.
According to a further feature of the invention apparatus, the controller is further operative to operate the blower at a substantially constant speed irrespective of the mode of operation of the system.
According to a further feature of the invention apparatus, the system further includes a heating element positioned in the ducting and the controller is further operative to selectively energize and de-energize the heating element.
The invention also provides a method of retrofitting an air conditioning system for a space to improve the ability of the system to control moisture and thereby mold in the space, the system including a controller, ducting extending from an entry end opening into the space to an exit end opening into the space, a cooling loop including a compressor and an evaporator coil positioned in the ducting, a heating element positioned in the ducting, and a blower operative to move air through the ducting from the entry end to the exit end with the circulating air passing over the evaporator coil and over the heating device.
According to the retrofit methodology of the invention, a bypass duct is provided extending around the evaporator coil; a coil temperature probe is installed proximate the liquid inlet of the evaporator coil; and the controller is modified to be operative in response to signals from the coil temperature probe as well as signals indicative of the temperature and humidity of the air in the space to selectively modulate the volume of air moving through the bypass duct and selectively energize and de-energize the compressor and the heating element.
Other applications of the present invention will become apparent to those skilled in the art when the following description of the best mode contemplated for practicing the invention is read in conjunction with the accompanying drawings.
The description herein makes reference to the accompanying drawings wherein like reference numerals refer to like parts throughout the several views, and wherein:
The invention method and apparatus are seen schematically in
The apparatus of the invention includes ducting 12 extending from an entry or return air end 12a opening in the space to an exit end 12b opening in the space; a heater device 14 positioned in the ducting; a cooling loop including a compressor 16, an evaporator coil 18 positioned in the ducting, a condenser coil 20, and a expansion valve 22; a blower 24 positioned in the ducting and operative to move air through the ducting from the entry end 12a to the exit end 12b with the circulating air passing over the evaporator coil and over the heating device; bypass ducting 25 extending around the evaporator coil and including an entry end 25a and a discharge end 25b; a damper 26 positioned in the bypass ducting entry end 25a and controlling the movement of circulating air through the bypass ducting; an electric motor 28 controlling the damper; tubing 30, 32, 34 and 36 interconnecting the various components of the cooling loop; a temperature probe 38 positioned on the tubing 36 proximate the entry to the evaporator coil 18; a thermometer 40 sensing the temperature of the air in the enclosure 10; a humidity meter 42 sensing the humidity of the air in the enclosure 10; and a controller 44.
Leads 46, 48 and 50 interconnect probe 38, thermometer 40 and humidity lead 42 to controller 44, whereby the controller receives temperature and humidity signals; a further lead 52 connects the damper motor 28 and the controller; a further lead 54 connects the heating element 14 and the controller; a further lead 56 connects the compressor and the controller; and a further lead 58 connects the blower and the controller.
The system, in general, may comprise a five ton, 2,000 cfm system. The cooling loop functions in known manner with the compressor 16 receiving low pressure gas from the evaporator coil 18 via the conduit 30; the condenser 20 receiving high pressure gas via the conduit 32 from the compressor; the expansion valve 22 receiving liquid refrigerant from the condenser via a conduit 34; and the evaporator coil 18 receiving liquid refrigerant from the expansion valve 22 via the conduit 36.
The heating element 14 may be a resistive wire element of the type typically utilized in HVAC systems where the primary requirement of the HVAC system is to provide cooling and the secondary requirement is to provide heat only on an as needed basis during occasional cold spells.
Controller 44 may comprise a microprocessor and may include for example a temperature selection knob 44a, a humidity selection knob 44b, and further controls 44c, 44d, to select operational levels of the various components.
The size of bypass duct 25 will of course vary depending upon the size of the overall system. For example, for a system having a capacity of between 4.5 and 6 tons, the bypass conduit 25 may have a diameter of 14 inches.
Bypass damper 26 is moveable between a fully closed position and a fully open position and may be positioned in various modulated positions between the fully open and the fully closed positions. The primary and bypass ducting may be sized such that, with the damper 26 in the fully open position, approximately 1,000 cfm will pass through the primary ducting 12 and over the evaporator coil 18 and approximately 1,000 cfm will pass through the bypass duct 25 around the evaporator coil.
On a call for dehumidification, the controller functions to energize the compressor and the blower as well as the damper 26. Specifically, the damper 26 is opened to allow air to flow through the bypass ducting and bypass the evaporator coil. This causes the coil temperatures to drop until it reaches a set point temperature slightly above freezing, such for example as 35° F. When the evaporator coil temperature reaches the 35° F. setting, the controller re-energizes the bypass damper motor 28 to allow the damper to move to a fully or partially closed position to maintain a coil temperature just above freezing. This has the effect of causing the air conditioning system to maximize its latent capacity while minimizing its sensible capacity. If the temperature of the air in the space 10 drops 2° F., the compressor is de-energized and the space heating device 14 is energized to bring the space temperature back to its set point which also adds to the reduction of relative humidity. If the relative humidity set point has not been satisfied at this point, the space heating device is de-energized and the compressor is re-energized and dehumidification is resumed. If during a call for dehumidification a call for cooling is made, the bypass damper is closed which causes the air conditioning system to maximize its sensible capacity to maintain the cooling set point. Importantly, the controller functions to maintain the blower 24 at a constant speed irrespective of the operational mode of the system so that the system functions to maintain constant air turnover rate throughout the space in the heating cooling and dehumidification modes whereby to avoid the formation of stratified air, lazy air, or dead air within the space.
The apparatus and methodology of the invention also lend themselves readily to retrofit applications. Specifically, for an existing HVAC system including a controller, ducting extending from an entry end opening into the space to an exit end opening into the space, a cooling loop including a compressor and an evaporator coil positioned in the ducting, a heating element positioned in the ducting, and a blower operative to move air through the ducting from the entry end to the exit end with the circulating air passing over the evaporator coil and over the heating device, the retrofit methodology consists simply in providing the bypass ducting 25 extending around the evaporator coil, providing the modulated motor control damper 26 at the entry 25a of the bypass ducting controlled by the controller, installing the probe 38 proximate the liquid inlet of the evaporator coil as sensed by the controller, and modifying the programming of the controller to be operative in response to signals from the coil temperature probe as well as signals indicative of the temperature and humidity of the air in the space to selectively modulate the volume of air moving through the bypass ducting via modulation of the damper 26 and selectively energize and de-energize the compressor and the heating element.
As previously noted, the principal application of the invention apparatus and methodology is with respect to HVAC systems in regions of relatively high temperature and relatively high humidity where the heating function is only occasional and incidental. As explained, the retrofitting of these systems to carry out the methodology of the invention may be performed simply and inexpensively by installation of ducting 25, provision of the damper 26 in the ducting entry 25a, provision of the evaporator coil inlet temperature probe 38, and appropriate modification of the software of the controller to enable the system to carry out the invention methodology.
The invention will be seen to provide an improved apparatus and methodology for inhibiting the formation of mold in a space or enclosure controlled by an HVAC system. Further, the invention will be seen to provide a ready and inexpensive means of retrofitting existing HVAC air conditioning systems to provide the mold inhibiting capacity of the invention.
While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiments but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, which scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures as is permitted under the law. For example, and as seen in
