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Proportional control system for a motorRelated Patent Categories: Heat Exchange, With Timer, Programmer, Time Delay, Or Condition Responsive Control, Having Heating And Cooling Capability, Means To Control Fan Or Pump To Regulate Supply Air Flow Or Supply Water Flow, Responsive To TemperatureProportional control system for a motor description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060151165, Proportional control system for a motor. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] The present invention also provides a proportional control system for use in an HVAC unit within a ventilation system comprising a processing means programmed with an air exchange-defrost cycle. One or more sensing means are also positioned in the HVAC unit and operatively connected to the processing means and a damper mechanism positioned in the HVAC unit wherein the sensing means and the processing means determine the motor speed to be applied during the defrost cycle. FIELD OF THE INVENTION [0002] The present invention pertains to the field of control systems and more specifically to a proportional control system for a defrost cycle within an HVAC unit for a ventilation system. BACKGROUND [0003] The present invention generally relates to an apparatus for ventilation systems which have means for the transfer of sensible heat and/or water moisture between exhaust air (taken from inside a building) and exterior fresh air (drawn into the building). Such an apparatus may, for example, have means for the transfer of sensible heat and/or water moisture from warm exhaust air to cooler exterior fresh air, the systems using warm interior air as defrost air for defrosting the systems during cool weather. [0004] Sensible heat and/or water moisture recovery ventilation systems are known which function to draw fresh exterior air into a building and to exhaust stale interior air to the outside. The systems are provided with appropriate ducting, channels and the like which define a fresh air path and an exhaust air path whereby interior air of a building may be exchanged with exterior ambient air; during ventilation the air in one path is not normally allowed to mix with the air in the other path. [0005] A sensible heat and/or water moisture recovery ventilator device or apparatus, which may form part of a ventilation system, in addition to being provided with corresponding air paths may also be provided with one or more exchanger elements or cores, e.g. one or more rotary and/or stationary (i.e. non-rotary) exchanger elements or cores. Heat recovery ventilation devices may also have a housing or cabinet; such enclosures may for example be of sheet metal construction (e.g. the top, bottom, side walls and any door, etc. may be made from panels of sheet metal). The heat exchanging core(s), as well as other elements of the device such as, for example, channels or ducts which define air paths, filtration means, insulation and if desired one or more fans for moving air through the fresh air and exhaust air paths may be disposed in the enclosure. Such ventilation devices may be disposed on the outside of or within a building such as a house, commercial building or the like; appropriate insulation may be provided around any duct work needed to connect the device to the fresh air source and the interior air of the building. A stationary heat exchanger element(s) may, for example, take the form of the (air-to-air) heat exchanger element as shown in U.S. Pat. No. 5,002,118. Thus, the heat exchanger element(s) may have the form of a rectangular paraellpiped and may define a pair of air paths which are disposed at right angles to each other; these exchanger element(s) may be disposed such that the air paths are diagonally oriented so that they are self draining (i.e. with respect to any condensed or unfrozen water). [0006] During the winter season, the outside air is not only cool but it is also relatively dry. Accordingly, if cool dry outside air is brought into a building and the warm moist interior air of the building is merely exhausted to the outside, the air in the building may as a consequence become uncomfortably dry. A relatively comfortable level of humidity may be maintained in a building by inter alia exploiting an above mentioned desiccant type thermal wheel for transferring water from the stale outgoing air to the relatively dry fresh incoming air. During winter these types of heat exchangers may transfer up to 80% of the moisture contained in the exhaust air to the fresh supply air. Advantageously a rotary exchanger wheel may transfer both sensible and latent heat between fresh air and exhaust air; in this case the exhaust air stream as it is cooled may also be dried whereas the incoming fresh air may be warmed as well as humidified. However, a problem with such heat recovery ventilation equipment having a desiccant type heat exchanger wheel, is the production of frost or ice in the air permeable heat exchange matrix of the thermal wheel. [0007] During especially cold weather such as -10.degree. F. or lower (e.g. -25.degree. C. or lower), prior to expelling the relatively warm exhaust air, the equipment provides for the transfer of latent heat from the relatively warm moist exhaust air to the relatively cool dry (fresh) outside air by the use of a suitable desiccant type heat exchange wheel. However, the cooling of the relatively moist interior air by the cold exterior air can result in the formation of ice (crystals). An uncontrolled buildup of ice within the matrix of a rotary exchanger wheel can result in decreased heat transfer, and even outright blockage not only of the exhaust air path but the (cold) fresh air path as well. Accordingly a means of periodically defrosting such a system is advantageous in order to maintain the system's efficiency. [0008] A defrost mechanism has been suggested wherein the fresh air intake is periodically blocked off by a damper and warm interior air is injected, via a separate defrost air conduit, into the fresh air inlet side of the fresh air path of the ventilation apparatus. However, during the defrost cycle, the stale inside air is still exhausted to the outside via the exhaust air path; this is disadvantageous since by blocking only the fresh air inlet and continuing to exhaust interior air to the outside, a negative air pressure can be built up in the interior of a building relative to the exterior atmosphere. Such a negative pressure may induce uncontrolled entry of air through any cracks and cranies in the structure of the building; the negative pressure may, in particular, produce a backdraft effect, for oil and gas type beating systems, whereby exterior air may be pulled into the chimney leading to the accumulation of gaseous combustion products in the building. [0009] An alternate system has been suggested wherein both the fresh air inlet and exhaust air outlet are both blocked off such that warm interior air is circulated through the fresh air side of the heat exchanger element as well as through the exhaust air side of the heat exchanger element and is sent back into the building; see for example U.S. Pat. No. 5,193,610. [0010] Another problem with respect to ventilation systems comprising a heat exchanger element or core relates to the installation of an exchanger device in a building such as for example a house or other type of building. In order for the system to operate efficiently and effectively the outgoing exhaust air flow preferably at least substantially equals the incoming fresh air flow; i.e. the exhaust and fresh air flows are preferably balanced so as to minimize or eliminate under-pressure or over-pressure in the house relative to the outside atmospheric pressure; a certain degree of overpressure may, however, be tolerated. [0011] Presently, such ventilation systems are balanced by means of balancing dampers and removeable flowmeters such as, for example, a pitot tube type flow measuring device comprising a manometer to measure pressure difference; these elements must usually be installed by the balancing technician at appropriate places in the duct work connected to the ventilation device. [0012] Given the above, it would be advantageous to have a control system in order to defrost a ventilation system which does not require the use of motors at full speed during the defrost operation or the addition of a number of additional components to the ventilation system. It would also be advantageous to have a ventilation system with a defrost system that is controlled by the outside temperature and the speed of the motors. [0013] It would also be advantageous to have a defrostable ventilation apparatus which is of simple construction. [0014] This background information is provided for the purpose of making known information believed by the applicant to be of possible relevance to the present invention. No admission is necessarily intended, nor should be construed, that any of the preceding information constitutes prior art against the present invention. SUMMARY OF THE INVENTION [0015] An object of the present invention is to provide a proportional control system for use in an HVAC unit within a ventilation system comprising a processing means programmed with an air exchange-defrost cycle. One or more motor speed sensing means are also positioned in the HVAC unit and operatively connected to the processing means and one or more temperature sensing means are positioned in the HVAC unit and operatively connected to the processing means wherein the temperature and motor speed sensors determine the motor speed to be applied during the defrost cycle. [0016] Another object of the present invention is to provide a proportional control system for use in an HVAC unit within a ventilation system comprising a processing means programmed with an air exchange-defrost cycle. One or more sensing means are also positioned in the HVAC unit and operatively connected to the processing means and a damper mechanism positioned in the HVAC unit wherein the sensing means and the processing means determine the motor speed to be applied during the defrost cycle. BRIEF DESCRIPTION OF THE FIGURES [0017] FIG. 1 is a side perspective of one embodiment of the present invention. [0018] FIG. 2 is a side perspective of a heat exchanger. [0019] FIG. 3 is a perspective, broken away enlarged and partially schematic view of a portion of the heat exchanger shown in FIG. 2. [0020] FIG. 4 is a side perspective of one embodiment of the present invention. Continue reading about Proportional control system for a motor... 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