AU2011100169A4 - Method and system for controlling humidity using an air conditioner - Google Patents

Description

Our Ref: 20807785 P/00/0 11 Regulation 3:2 AUSTRALIA Patents Act 1990 ORIGINAL COMPLETE SPECIFICATION INNOVATION PATENT Applicant(s): Actron Engineering Pty Limited 5 Irvine Place, Bella Vista, New South Wales 2153, Australia Address for Service: DAVIES COLLISON CAVE Patent & Trade Mark Attorneys 255 Elizabeth Street SYDNEY NSW 2000 Invention Title: "Method and system for controlling humidity using an air conditioner" The following statement is a full description of this invention, including the best method of performing it known to me: C:\NRPornb\DCC\AKW\3459910 L DOC-9/2/11 - 1 METHOD AND SYSTEM FOR CONTROLLING HUMIDITY USING AN AIR CONDITIONER 5 Technical Field [001] The present invention generally relates to the application of heating ventilation and air conditioning (HVAC), and more particularly, to a method and/or system for reducing humidity level in an enclosed space using an air conditioner. In one example, the method/system utilizes a variable capacity compressor (such as a digital scroll compressor, 10 variable speed compressor, etc.), a humidity sensor, and an adaptive variable speed indoor fan. Background [002] The level of comfort in an indoor space is associated with the combination of 15 temperature and humidity. Although there have been many directions investigated in employing temperature control in myriads of HVAC systems in the past, active humidity control is becoming ever more significant and various problems still persist. During steady state processing of an air conditioner, condensation on the cooling coils is the usual outcome when air flow has passed by the cooling coils; hence cooling or heating and 20 dehumidification of an indoor space. [003] Some currently known air conditioners have limited ability to manage the level of humidity within an indoor space as only a temperature difference is determined. Typical manufacturer's specifications include the net capacity of the equipment and the Sensible 25 Heat Ratio (SHR - the sensible heat or cooling load divided by the total heat or cooling load) at a specific design condition. The SHR provides a mechanism in understanding the design of the HVAC system. [004] Fixed capacity air conditioners usually have a constant SHR but variable capacity 30 systems (such as inverters and digital scroll) have varying SHR's proportional to the load within the space that is being cooled. A unique characteristic of these variable capacity systems is to match the heat load of a space to minimize overcooling which equates to better energy efficiency and occupant comfort. For dehumidification to occur, the cooling coil (i.e. the evaporator heat exchanger) surface temperature must be below the dew point -2 temperature of the air. However, in low-load operation where the temperature of the space is in proximity to the target temperature, the temperature of the cooling coil in variable capacity air conditioners approaches and exceeds the dew point of the air. Thus, the cooling coil is only then able to provide sensible cooling and no further dehumidification 5 can occur. [005] In these low-load conditions, as the air is cooled without any further dehumidification, the relative humidity of the air increases. This is problematic in high humid climate zones where mould is easily formed due to the high levels of relative 10 humidity. [006] Some known air conditioning systems presently incorporate a humidity sensor whilst having a fixed speed compressor engaged at full capacity. However, an increase in temperature swing of an indoor space, whereby the system is displaced, results; and in 15 addition the human comfort level is reduced. Other known air conditioning systems controlling the humidity level may include a desiccant wheel or down grade of a high capacity with electric heating, however the cost of implementation is relatively high. [007] For these and other reason, the Applicant has identified that existing methods and 20 systems that attempt to moderate or reduce the humidity level using an air conditioner, particularly when in a relatively high humidity environment, are not very effective. [008] There is a need for a method and/or system for reducing humidity level using an air conditioner which addresses or at least ameliorates one or more problems inherent in the 25 prior art. [009] The reference in this specification to any prior publication (or information derived from the prior publication), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that the prior 30 publication (or information derived from the prior publication) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

-3 Brief Summary [010] In one form, the present invention seeks to provide a method and/or system for more efficient management or control of humidity in an indoor space using a variable capacity air conditioning system. Preferably, a variable speed indoor fan and/or 5 compressor are controlled for optimal performance. In one example embodiment, the method/system checks, determines or otherwise scrutinizes whether the humidity level in an indoor space is greater than a pre-defined humidity threshold, and if so restructures selected control parameters, such as the variable speed fan and compressor output. In a situation where the humidity level is less than the pre-defined humidity threshold, the 10 variable capacity compressor can be adjusted to maintain adequate cooling, for example based on a dry bulb temperature only. If the humidity level is greater than the pre-defined humidity threshold, the output of a variable capacity compressor can be set or locked at or near maximum (i.e. full) capacity, and, optionally or alternatively, a variable indoor fan speed can be limited to a pre-determined percentage of maximum speed or output. If the 15 humidity level remains above the pre-defined humidity threshold the indoor fan speed can be decreased, continuously or periodically, in pre-defined steps until the humidity level is reduced below the pre-defined humidity threshold. [011] In another example embodiment, the method/system checks, determines or 20 otherwise scrutinizes whether an air conditioning system or controller has verified if the air conditioning system is in heating or cooling mode. A pre-defined humidity value is incorporated in the system/controller as a pre-defined humidity threshold, and after the humidity has passed this threshold limit, humidity control is activated and the compressor is set to run at or near maximum (i.e. full or 100%) cooling capacity, or pulse width 25 modulation (PWM), to assist with additional removal of the moisture in the indoor space. Preferably, though not necessarily, PWM compressor control can be utilized to provide humidity control, however other example embodiments can utilize other types of communication within the air conditioning system components, such as, for example, variable speed control compressors, voltage level signals such as 0-1Ov, or other signals. 30 [012] In another example aspect, a secondary pre-caution is provided by the integration or inclusion of a second, lower, humidity threshold assigned for human comfort in which the system re-evaluates the necessity of humidity control. To maintain cooling and -4 dehumidification in the indoor space, such as a room, an indoor fan simultaneously operates along with the humidity control system/method. For relative humidity levels below the pre-defined threshold levels, the system/method maintains a set fan speed. When relative humidity has reached the second pre-defined threshold, a variable speed indoor fan 5 (i.e. evaporator fan) is limited to a specific value or output for a pre-defined period. Also the fan speed can be further reduced in pre-defined steps, continuously or periodically, if the relative humidity remains above the second pre-defined threshold limit. [013] In one aspect there is provided a method of controlling humidity in an indoor space 10 using an air conditioner in a cooling mode, including the steps of: obtaining a humidity level in the indoor space using at least one humidity sensor; determining if the humidity level is greater than a pre-defined humidity threshold; and if so, adjusting the output of a variable capacity compressor. 15 [014] Optionally, if the humidity level is less than the pre-defined humidity threshold, then a further determination is made if the humidity level is greater than or less than a second pre-defined humidity threshold, which is at least partially used to control operation of the variable capacity compressor. 20 [015] In another aspect there is provided a method of controlling humidity in an indoor space using an air conditioner in a heating mode, including the steps of: obtaining a humidity level in the indoor space using at least one humidity sensor; determining if the humidity level is greater than a pre-defined humidity threshold; and if so, adjusting the output of a variable speed indoor fan. 25 [016] In another aspect there is provided a system for controlling humidity in an indoor space using an air conditioner, including: at least one humidity sensor for obtaining a humidity level in the indoor space; at least one processor for determining if the humidity level is greater than a pre-defined humidity threshold; a variable capacity compressor, the 30 output of which can be adjusted if the humidity level is greater than the pre-defined humidity threshold; and, a variable speed indoor fan, the output of which can be adjusted if the humidity level is greater than the pre-defined humidity threshold.

-5 [017] In one further example form there is provided a method of controlling an air conditioner, the air conditioner measuring or otherwise determining a humidity level in an indoor space, the method comprising the steps of: determining if the humidity level in the indoor space is greater than a pre-defined humidity threshold; and if so, adjusting the 5 output of a variable capacity (or speed) compressor and a variable speed fan. [018] According to another example aspect, the pre-defined or otherwise pre-set humidity threshold is adjustable by an operator using a wall mounted control, but is not limited to a wall mounted control, such as other remote access devices. 10 [019] According to another example aspect, if the humidity level inside the indoor space reaches a maximum pre-defined threshold, the variable capacity compressor operate at or near maximum capacity. 15 [020] According to another example aspect, the variable indoor fan speed remains set on its previous setting until the humidity level inside the indoor space is less than the pre defined threshold. [021] According to another example aspect, if the humidity level is below the maximum 20 pre-defined threshold but is greater than the second pre-defined humidity threshold, the variable capacity compressor may or may not operate at or near maximum capacity, for example depending on if the active relative humidity mode is turned on, whereby instead of targeting an indoor set temperature targeting is to remove as much moisture as possible. 25 [022] According to another example aspect, if the humidity level is less than the second humidity threshold, the system targets a set temperature whereby the compressor is free to operate at any given capacity required. [023] According to another example aspect, a cooling differential equates to the 30 temperature difference between the indoor space and a set point temperature plus a perceived temperature offset.

-6 [024] In another example form there is provided a method of controlling an air conditioner, the air conditioner measuring or otherwise determining a variable speed indoor fan and a duration to maintain a humidity level, the method comprising the steps of: determining if the humidity level in an indoor space is greater than a pre-defined humidity 5 level; and if so, adjusting an output of the variable speed indoor fan. [025] According to another example aspect, if the humidity level inside the indoor space is less than the pre-defined threshold, the variable speed indoor fan remains set on its 10 previous setting. [026] According to another example aspect, if the humidity level inside the indoor space is greater than the a second pre-defined threshold but is less than a maximum humidity threshold, the variable speed indoor fan is adjusted and locked to a pre-determined fan 15 capacity. [027] According to another example aspect, if the humidity level inside the indoor space is greater than the second pre-defined threshold whilst the fan capacity is greater than the pre-determined indoor fan capacity defined, then the indoor fan capacity remains set for a 20 pre-defined time period. [028] According to another example aspect, the indoor fan capacity can be reduced by a pre-defined percentage for a selected period. 25 [029] According to another example aspect, if a pre-defined minimum indoor coil temperature is reached due to low air flow and high compressor capacity, then the compressor capacity is periodically reduced in steps until the indoor coil temperature increases to a pre-defined value. 30 Brief Description Of Figures [030] Example embodiments should become apparent from the following description, which is given by way of example only, of at least one preferred but non-limiting embodiment, described in connection with the accompanying figures.

-7 [031] FIG. 1 is a diagrammatic representation of an example air conditioner; [032] FIG. 2 illustrates a flow diagram of an example method of relative humidity 5 control; [033] FIG. 3 illustrates a flow diagram of an example method of adaptive fan control; [034] FIG. 4 is an illustrative diagram highlighting an example system control; 10 [035] FIG. 5 illustrates a functional block diagram of an example processing system that can be utilised to embody or give effect to a particular embodiment. Preferred Embodiments 15 [036] The following modes, given by way of example only, are described in order to provide a more precise understanding of the subject matter of a preferred embodiment or embodiments. The following detailed description should be read with the reference to the drawings. The drawings, which are not necessarily to scale, depict illustrative embodiments and are not intended to limit the scope of the invention. In the figures, 20 incorporated to illustrate features of an example embodiment, like reference numerals are used to identify like parts throughout the figures. [037] FIG. 1 shows a diagrammatic schematic view of an example split air conditioner system 100 having humidity control providing a method and/or system for controlling a 25 humidity level in an indoor space. In the illustrative example embodiment, one or more thermostat 110 and at least one Relative Humidity (RH) sensor 120 provide direct feedback to the indoor controller 130. The thermostats 110 read two inputs, a user's set point and a dry bulb sensor, which are both integrated. A typical currently known system is limited to only temperature control in the thermostat, whilst embodiments of the present 30 invention incorporate the additional RH sensor 120, to communicate back to the indoor controller 130 in order to calculate a Perceived Temperature (PT) and relevant system information. Data, gathered from the inputs and sensors are tabulated and computed, and sent from the indoor controller 130 to the indoor fan 140 and the outdoor controller 150.

-8 The outdoor controller 150 feeds a signal to the outdoor fan 160 and sends a specific PWM value or 0-1OV signal to the variable capacity compressor 170. [038] FIG. 2 is a flow chart showing an example method 200 for adjusting a control 5 parameter (e.g. compressor PWM) for an air conditioner. The flow chart is entered at circle "Start", and control is passed to decision step "Unit in Cooling". The block "Unit in Cooling" observes the active mode of the air conditioner, whether the system is in cooling or heating. If the observed active mode is in cooling, control determines the level of humidity located in the return air of the indoor unit via the RH sensor. A decision step "o > 10 oe" follows, which compares the RH level to a first pre-defined humidity level oe. If the observed RH returns true with greater than the first pre-defined humidity level ee, control is passed to block "Set RH mode". Block "Set RH mode" indicates to the system control to switch on the Active Relative Humidity Control. The RH sensor takes a reading every pre defined time and average out over a pre-selected time period, as a non-limiting example 15 every 2 seconds and averaged over a 30 second period. Block "Set Compressor Capacity at 100%" locks the compressor control parameter at 100% compressor capacity, or alternatively near maximum capacity, or PWM in an attempt to reduce the humidity level in the indoor space and returns control to block "Start" where the control continuously and reiteratively scans the system. 20 [039] In other example embodiments, additional control steps are executed, as further illustrated in FIG. 2. For example decision step "o > oe" may return a false, a second decision step follows "o > ec". This secondary control compares the RH level to a second pre-defined humidity level oc, where oc is less than ee. At certain periods within the 25 system, the level of humidity may return a true for an "o > oc". In such instances, decision step "In RH mode?" follows to review the status of the RH level in the indoor room. After the control parameter is adjusted by "Set Compressor Capacity at 100%" and returns subsequent call for cooling, a time delay is observed. For example, after the decision "o > oe" has been observed, "Set RH mode" can be activated which consequently switches the 30 "Set Compressor Capacity at 100%". At this later time period, the "o > oc" may be activated. Since the "Set RH mode" is running, the secondary decision step "In RH mode?" is required. If Active Relative Humidity Control is already engaged then block "Set Compressor Capacity at 100%" continues. In instances where the decision step "In -9 RH mode" returns a false, block "Clear RH Mode" follows. Cooling temperature difference is calculated, determining the difference between the dry bulb temperature sensor and the set point of the user plus the Perceived Temperature Offset. It follows, the system continues to target the set temperature, and as a result the compressor is free to 5 operate at any given percentage of PWM that is necessary. This ends the cycle in block "return" and returns to the block "Start" for the subsequent scanning and adjustment. [040] In some example embodiments, the observed active mode may be in heating mode as illustrated in FIG. 2. Presently the humidity level is not activated and the temperature 10 differential between the indoor space and the set point is determined. The system adjusts its parameter to target the set temperature by which the compressor is free to run at any given percentage of PWM. [041] The bottom half of the example embodiments shown in FIG. 2 show how the 15 control logic provides a preventative mechanism to stop the coil freezing. Whether the unit is in heating or cooling, the system evaluates the temperature of the indoor coil as denoted by the decision step "Tic < Ta" where Tic stands for temperature of the indoor coil and Ta represents a predefined temperature value. At certain periods within the system, the temperature level may return a true for "Tic < Ta" then block "Set AF mode" is activated. 20 In such instances, decision step "Tic < Tc" follows where Tc is greater than Ta. If block "Tic < Tc" returns true, the block "reduces compressor PWM by P% every D seconds" follows, a mechanism for preventing the system from cooling too quickly as such causing the indoor coil to freeze. However, in situations where the "Tic < Tc" returns a false, another decision steps follows "Tic > Td" where Td is greater than Tc. If block "Tic > Td" 25 returns true, then the compressor needs to increase its capacity to maintain optimal condition of the indoor space with block "Increase compressor PWM by D% every D seconds". If "Tic > Td" returns false then the system's logic loops back to the start for an additional re-evaluation. It should be noted that if block "Tic < Ta" returns false then another decision step follows "Tic <Tb" where Tb is greater than Td. When the indoor coil 30 temperature is lower than the Tb, the system needs to determine if the decision step "in AF mode" is activated. If after a certain period the system returns true for "in AF mode" then the logic follows path of checking if the indoor coil temperature has fallen below Tc. However if either the decision step of "Tic < Tb" or "In AF mode" returns false, then the -10 block "clear AF mode" is activate as the indoor coil temperature is above the temperature threshold whereby freezing occurs. [042] FIG. 4 is a flow chart showing a supplementary example method 400 for adjusting 5 the indoor fan control parameters for an air conditioning system. This flow chart for the Indoor Fan Control is operated simultaneously with the Active Relative Humidity Control shown in FIG. 3. The flow chart shown in FIG. 3 illustrates example method 300 and is entered at block "Start" and control is passed to decision step "Heating/Cooling Mode". If the decision block "Heating/Cooling Mode" is set to cooling mode, humidity level of the 10 indoor space is observed and control is passed to decision block "o > oe". Incidence where block "o > oe" returns a false, the control follows the block "Keep Indoor Fan Capacity". The indoor fan controlled by a defined percentage of PWM can remain unchanged at the current status, which accordingly presets the required fan speed to either low, medium or high depending on what setting it was previously on. During the cycle of the control, the 15 RH may have been changed at a later period which requires the corporation of the block "Check Required Fan Capacity". The indoor controller has an integrated fan speed controller in which the system adjusts the required indoor fan PWM setting to match this specific value at this specific time. The control follows to block "Return" which cycle back to block "Start". 20 [043] In another example embodiment, if the observed humidity, in block "o > oe", returns true, a secondarily pre-defined humidity level is required, in block "o > oh". If the humidity level is below oh, the control adjusts the percentage of the PWM from where it was set prior to now a. This is followed by the block "Check Required Fan Capacity" and 25 returns to the initiation of the control cycle. [044] For certain example embodiments, the block "o > oh" may return true and the Active Relative Humidity Control is activated in the "In RH Mode". If block "In RH mode" returns false, the "Check Required Fan Capacity" needs to be triggered which is 30 follow by a reiteration of the control cycle. If the block "In RH mode" returns true, an additional step is required before the reiteration. This involves the decision step "Fan Capacity > a%". For a scenario where the indoor fan PWM percentage is greater than a, the indoor fan speed is forced to remain fixed at percentage a for a period of p minutes before the control cycle in block "Set Fan Capacity = a% Load P min timer". For a specific predicament whereby the decision step 'Fan Capacity > a%" returns false, a secondary decision step is required to verify if the control cycle is already in the period of P with indoor fan speed PWM percentage of a. If the command returns false the system cycles, 5 however when P minutes in the period whereby the indoor fan PWM percentage is a returns true, the indoor fan PWM percentage is reduced by a specific percentage of 6 in block "Reduced Fan Capacity by 8%" to ensure humidity is reduced in the indoor space. To ensure moisture and cooling have been removed and maintained in servicing the indoor room, a time relay is set defined by block "Reload 1 min Fan Capacity Check timer" 10 before the control command reiterates. [045] A further particular embodiment of the present invention can be realised using a processing system, which can be provided as at least part of an indoor controller, outdoor controller, or thermostat or humidity sensor, an example of which is shown in FIG. 5. In 15 particular, the processing system 500 generally includes at least one processor 502, or processing unit or plurality of processors, memory 504, at least one input device 506 and at least one output device 508, coupled together via a bus or group of buses 510. In certain embodiments, input device 506 and output device 508 could be the same device, port or interface. An interface 512 might also be provided for coupling the processing system 500 20 to one or more peripheral devices, for example interface 512. At least one storage device or memory 514 which houses at least one database 516, or at least data, might also be provided. The memory 504 can be any form of memory device, for example, volatile or non-volatile memory, solid state storage devices, magnetic devices, etc. The processor 502 could include more than one distinct processing device, for example to handle different 25 functions within the processing system 500. [046] Input device 506 receives input data 518, for example temperature or humidity signals, and could be an interface, port, data receiver, antenna or wireless data adaptor, data acquisition card, etc. Input data 518 could come from different sources. Output 30 device 508 produces or generates output data 520, for example component control signals, etc. Output data 520 could be derived from different output devices and might include data transmitted to a network. In one form, a user or technician could view data output, or an interpretation of the data output, on, for example, a monitor or via a network.

-12 [047] In use, the processing system 500 is adapted to allow data or information to be stored in and/or retrieved from, via wired or wireless communication means, the at least one database 516 or memory. The interface 512, if provided, may allow wired and/or 5 wireless communication between the processing unit 502 and peripheral components that may serve a specialised purpose. It should be appreciated that the processing system 500 may be any form of specialised hardware or the like. The processing system 500 may be a part of a networked communications system. Processing system 500 could connect to network, for example the Internet, WAN or LAN. Input data 518 and output data 520 10 could be communicated to other devices via a network. [048] Optional embodiments of the present invention may also be said to broadly consist in the parts, elements and features referred to or indicated herein, individually or collectively, in any or all combinations of two or more of the parts, elements or features, 15 and wherein specific integers are mentioned herein which have known equivalents in the art to which the invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth. [049] Although a preferred embodiment has been described in detail, it should be 20 understood that many modifications, changes, substitutions or alterations will be apparent to those skilled in the art without departing from the scope of the present invention. [050] The present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, firmware, or an embodiment combining software and 25 hardware aspects.

Claims (5)

1. A method of controlling humidity in an indoor space using an air conditioner in a cooling mode, including the steps of: 5 obtaining a humidity level in the indoor space using at least one humidity sensor; determining if the humidity level is greater than a pre-defined humidity threshold; and if so, adjusting the output of a variable capacity compressor to operate at or near maximum capacity. 10

2. The method as claimed in claim 1, wherein if the humidity level is less than the pre-defined humidity threshold, then a further determination is made if the humidity level is greater than a second pre-defined humidity threshold, which is at least partially used to control operation of the variable capacity compressor. 15

3. A method of controlling humidity in an indoor space using an air conditioner in a cooling mode, including the steps of: obtaining a humidity level in the indoor space using at least one humidity sensor; determining if the humidity level is greater than a pre-defined humidity threshold; 20 and if so, adjusting the output of a variable speed indoor fan to a pre-defined lower speed.

4. The method as claimed in claim 3, wherein if the humidity level is greater than the pre-defined humidity threshold, then a further determination is made whether to reduce the 25 speed of the fan, continuously or periodically, if the humidity level remains greater than a second pre-defined threshold.

5. A system for controlling humidity in an indoor space using an air conditioner, including: 30 at least one humidity sensor for obtaining a humidity level in the indoor space; at least one processor for determining if the humidity level is greater than a pre defined humidity threshold; - 14 a variable capacity compressor, the output of which can be adjusted if the humidity level is greater than the pre-defined humidity threshold; and, a variable speed indoor fan, the output of which can be adjusted if the humidity level is greater than the pre-defined humidity threshold.