US20120118985A1

US20120118985A1 - Control for air handler

Info

Publication number: US20120118985A1
Application number: US13/243,358
Authority: US
Inventors: Ernest E. Soderlund
Original assignee: Braeburn Systems LLC
Current assignee: Braeburn Systems LLC
Priority date: 2010-11-16
Filing date: 2011-09-23
Publication date: 2012-05-17
Also published as: CA2757609A1; MX2011012002A; CA2757609C

Abstract

The present invention provides for a control for activating and deactivating heating, cooling and fan recirculate modes having an interval timer switchable between a timer on (TON) state and a timer off (TOFF) state, both the TON and TOFF state durations are variable according to comparisons between room temperature and a set point temperature of the control and the control activating the fan recirculate mode when the room temperature deviates from the set point temperature of the control. An interval spacer is provided to prevent back to back fan on states.

Description

The present application claims priority to provisional Application No. 61/414,260 filed Nov. 16, 2010.

FIELD OF THE INVENTION

The present invention pertains to a control for an air handler and may comprise a portion of a thermostat. In an embodiment, the control is for an HVAC system and is used to monitor room temperature, allow for programming of desired functions and controlling heating, cooling and/or fan recirculation. The present control is focused, in particular, on controlling the operation of a fan when no call for heating or cooling is occurring.

BACKGROUND

Controls for air handlers such as, programmable thermostats, have increasingly more options and modes available to users, due to the use of fast microprocessors/microcontrollers. Careful programming of microprocessors provides for enhanced heating, cooling and fan control, operations previously unavailable. Thermostats that maximize the frequent circulation of air within a building improve cleanliness and keep the building more comfortable. If there are long off cycles for heating or cooling, air may stagnate and reduce cleanliness because filtration of the air is not occurring during these off cycles. This is because in typical systems, the fan is off between heating and cooling cycles and runs only during the heating or cooling cycle. Some systems include a fan-on mode, in which the fan runs constantly. While running the fan constantly reduces the stagnate air, such an operation may waste energy. Nevertheless, it is known that extending the fan cycle may increase thermal efficiency.
Some systems are known to provide for intermittent fan recirculation modes that are triggered by the end of the last operation of the fan during a heating or cooling cycle. Such a system has the disadvantage of not including a temperature contingent fan control variable and cannot prevent back to back fan on modes. The present invention overcomes the disadvantage of previous systems and provides for a system that increases occupant comfort, while providing efficient fan control.

SUMMARY

The present invention provides for an air conditioning system comprising an air handler, a circulating fan and a control for activating and deactivating heating, cooling and fan recirculate modes. The control is operatively coupled to the air handler and the fan for controlling the air handler and the fan. The control has an interval timer switchable between a timer on (TON) state and a timer off (TOFF) state. Both the TON and. TOFF state durations are variable according to comparisons between room temperature and a set point temperature of the control. The control activates the fan recirculate mode when the following conditions are met:
a) the control is in the fan recirculate mode;
b) heating and cooling of the air conditioning system are not active;
c) the room temperature deviates from the set point temperature of the control.
In an embodiment, the air conditioning system may further comprise an interval spacing mechanism, wherein the room temperature is compared to the set point temperature, in order to avoid back to back fan on states and to allow activation of the fan when the interval timer is in the TON state. In an embodiment, the interval spacing comparison may be calculated according to the following formula, when the control has the heating mode activated:
T _s+0.3≧T _r ≧T _s+0.1
where T_sis the set point temperature and T_ris the room temperature.
In an embodiment, the interval spacing comparison may be calculated according to the following formula when the control has the cooling mode activated:
T _s−0.3≦T _r ≦T _s−0.1
where T_sis the set point temperature and T_ris the room temperature.
In an embodiment, the interval timer may be activated upon power-up of the control and following expiration of the TON state, the TOFF is activated until expiration and the interval timer operates in a continuous loop with TON and TOFF states sequentially running one after the other and the interval timer being independent of the interval spacing mechanism. In an embodiment, the interval timer TON duration is equal to a first value plus the absolute value of the difference between of the set room point temperature and the room temperature multiplied by a first scaling factor. In an embodiment, the first value is ten (10) minutes and the first scaling factor is 0.1. In an embodiment, the interval timer TOFF duration is equal to a second value plus the absolute value of the difference between the set point temperature and the room temperature multiplied by a second scaling factor. In an embodiment, second the value is twenty (20) minutes and the second scaling factor is 0.2.
In an embodiment, the control may be a thermostat. In an embodiment, the thermostat may include one of a mechanical fan switch for setting the fan to recirculate mode and a touchscreen input for setting the fan to recirculate mode.
The invention further provides for a method for activating recirculate mode comprising the steps of providing a control having an interval timer, the control operatively coupled to an air handler and a fan for activating and deactivating heating, cooling and fan recirculate modes, powering the control in order to the set the interval timer on (TON) state, varying the duration of the TON state by the interval timer to a first value by comparing room temperature with a set point temperature of the control, setting the interval timer to a timer off (TOFF) state, varying the duration of the TOFF state of the interval timer to a second value by comparing the room temperature and set point temperature of the control, setting the control fan recirculate mode, monitoring the control to confirm no heating or cooling of the air conditioning system is active and activating the fan recirculate mode when room temperature deviates from the set point temperature of the control.
In an embodiment, the fan recirculate mode may be activated when the interval timer is in the TON state only after an interval spacing mechanism is executed by comparing the room temperature to the set point temperature of the control. In an embodiment, the interval spacing mechanism value is not preselectable. in an embodiment, the interval spacing mechanism operates according to the following formula when the control has the heating mode activated:
T _s+0.3≧T _r ≧T _s+0.1
where T_sis the set point temperature and T_ris the room temperature.
In an embodiment, the TON spacing mechanism operates according to the following formula, when the control has the cooling activated:
T _s−0.3≦T _r ≦T _s−0.1
where T_sis the set point temperature and T_ris the room temperature.
In an embodiment, the method may further comprise the step of setting the TON duration that is equal to a first value plus the absolute of the difference of the set point temperature and the room temperature multiplied by a first scaling factor. In an embodiment, the TOFF state is not dependent from an end of the last operation of the fan. In an embodiment, the first and second value and first and second scaling factors are not user selectable.
In an embodiment, the method may further comprise the steps of activating the interval timer upon power-up of the control, activating the TON state until expiration, activating the TOFF state until expiration and operating the interval timer in a continuous loop with TON and TOFF states sequentially running, one after the other and the interval timer being independent of the interval spacing mechanism. In an embodiment, the control may simultaneously process the comparing, monitoring and activating steps. In an embodiment, the control may include a microprocessor for simultaneously processing the comparing, monitoring and activating steps. In an embodiment, the TON duration is between five (5) and fifteen (15) minutes. In an embodiment, the TON duration is approximately fifty-percent (50%) of the TOFF duration. In an embodiment, the TON and TOFF durations are not preselectable by a user. In an embodiment, a fan auto mode and a fan on mode are provided and further comprising the steps of monitoring the control to confirm no auto fan nor fan on mode are active. In an embodiment, the air handler may be a household HVAC system including an air filter and air ducts for circulating indoor and outdoor air.
The invention also provides for a control for activating and deactivating heating, cooling and fan recirculate comprising an interval timer switchable between a timer on (TON) state and timer off (TOFF) state, both the TON and TOFF state durations are variable according to comparisons between room temperature and a set point temperature of the control, and the control activating the fan recirculate mode when the room temperature deviates from the set point temperature of the control.
In an embodiment, the control may provide for an interval spacing mechanism, wherein the room temperature is compared to the set point temperature in order to avoid back to back fan on states and to allow activation of the fan when the interval timer is in the TON state. In an embodiment, the interval tinier is activated upon power-up of the control and following expiration of the TON state, the TOFF state is activated until expiration and the interval timer operates in a continuous loop with TON and TOFF states sequentially running one after the other and the interval timer being independent of the interval spacing mechanism. In an embodiment, the interval timer TON duration may be equal to a first value plus the absolute value of the difference between the set point temperature and the room temperature multiplied by a first scaling factor. In an embodiment, the interval timer TOFF may be equal to a second value plus the absolute value of the difference between the set point temperature and the room temperature multiplied by a second scaling factor.
In a further embodiment the invention provides for a control for activating and deactivating heating, cooling and fan recirculate modes comprising an interval timer switchable between a timer on (TON) state and a timer off (TOFF) state, an interval spacer to prevent back to back fan on states, the interval timer setting TON and TOFF state durations that are variable and are set independently from the operation of the interval spacer and the control activating the fan recirculate mode when the room temperature deviates from the set point temperature of the control following operation of the interval spacer. In an embodiment, the interval spacer may operates according to the following formula:
ABS (T _r −T _s)<Value A
where T_sis the set point temperature and T_ris the room temperature.
In an embodiment, the interval spacer may operate according to the following formula:
CALLON/(CALLON+CALLOFF)<A%.
In an embodiment, the interval spacer may operate according to the following formula:
CALLON/(CALLON+CALLOFF)<B%.
In an embodiment, the interval spacer may operate according to the following formula:
LASTOFF>Value A.
In an embodiment the interval spacer may operate by comparing the room temperature to the set point temperature of the control to allow activation of the fan when the interval timer is in the TON state. In an embodiment, the interval spacer may operate according to the following formula subsequent to a heating mode:
T _s+0.3≧T _r ≧T _s+0.1
where T_sis the set point temperature and T_ris the room temperature.
In an embodiment, the interval spacer may operate according to the following formula subsequent to a cooling mode:
T _s−0.3≦T _r ≦T _s−0.1
where T_sis the set point temperature and T_ris the room temperature.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of embodiments of the invention:

FIG. 1 is a plan view of the control of the present invention;

FIG. 2 is a partial circuit diagram of the control of the present invention;

FIG. 3 is a partial circuit diagram portion of the control of the present invention;

FIG. 4 is a partial circuit diagram portion of the control of the present invention;

FIG. 5 is a partial circuit diagram portion of the control of the present invention;

FIG. 6 is a flow diagram of a first embodiment of the control logic for the present invention;

FIG. 7 is a flow diagram of a second embodiment of the control logic for the present invention;

FIG. 8 is a flow diagram of a third embodiment of the control logic for the present invention;

FIG. 9 is a flow diagram of a fourth embodiment of the control logic for the present invention; and

FIG. 10 is a flow diagram of a fifth embodiment of the control logic for the present invention.

DETAILED DESCRIPTION

FIG. 1 depicts a control, such as a thermostat 100 of the present invention. The control 100 includes a housing 110 for enclosing a printed circuit board and components therein and a display screen. 120. The control 100 includes a mechanical switch 130 for operating the control 100. The display screen 120 may be any well-known display, such as an LCD or LED type screen. The screen includes display areas for alpha numeric displays and touch sensitive areas for touch buttons. The embodiment of the invention of FIG. 1 alpha-numeric display area 151 displays the current room temperature. The control 100 includes a sensor within the housing 110 for sensing room temperature which has an output that provides for the display 151 as an alpha numeric representation. The room temperature display 151 in the embodiment depicted in FIG. 1, shows an alpha numeric display of “88”. This alpha numeric display is indicating that the current room temperature is currently 88° F.
A display area 153 is provided for displaying the day and time. The day and time alpha numeric display 153 may be programmed by the user of the control 100 via the touch buttons. The day and time display area 153 in the embodiment of FIG. 1 provides for an alpha numeric display of “M MORN 11:07am.” This indicates that it is Monday morning at 11:07 a.m.
The display screen 120 also includes a display area 155 for an alpha numeric display of the set point temperature. As depicted in FIG. 1, the set point temperature display area 155 includes an alpha numeric display of “SET AT 72”. This indicates that the user has input a temperature set point of 72° F.
The display screen 120 also provides for symbol displays or icons displays 157. For example, the icon 157 provides a graphical depiction of the blades of a fan. In the embodiment depicted in FIG. 1, when the icon 157 is present it indicates that the fan is currently running.
The display screen 120 also includes an alpha numeric or icon display for the current mode display area 158. As depicted in FIG. 1, the mode display area 158 includes “HEAT”. This mode display indicates that the system has been set to a heating mode. The display 120 also includes a fan mode display area 159. In the embodiment depicted in FIG. 1, the fan mode display area includes a “CIRC” icon. This fan mode display area 159 indicates that the fan mode has been set to the recirculate mode.
The display screen 120 also includes touch sensitive areas that provide for touch buttons each having a generally rectangular outline to identify the button. The display screen includes a system button 161, fan button 162, program button 163, hold button 164, day/time button 165, clean button 166 and configuration button 167. Each of these buttons has an operation that is described by U.S. pending application Ser. No.12/982,959 filed Dec. 31, 2010, which is incorporated herein by reference.
The fan button 162 operates the control with respect to the selection of multiple fan modes. In a preferred embodiment, the fan modes include an auto mode, an on mode and a recirculate mode. By sequentially depressing the fan button 162, a user may scroll through each of these three fan modes and the particular alpha numeric representation or icon for each mode will appear in the fan mode display area 159. As is depicted in the embodiment of FIG. 1, the recirculate mode has been selected and as evidence of that selection, the alpha numeric representation of “CIRC” is presented in the fan mode display area 159. The fan recircluate mode allows for the fan to run intermittently, when there is no call for heating or cooling. The fan auto mode provides for the running of the fan during a heating or cooling call. The fan on mode provides for the fan to run continuously during heating and cooling and, also, when there is no call for heating and cooling. The control 100 of the present invention includes circuitry for operating all parts of the: air conditioning system, including each of the three fan modes. The main focus of this application pertains to the operation of the fan recirculate mode.
FIG. 2 is a circuit diagram for the present invention. Such circuitry may be provided on a printed circuit board mounted within the housing 110 of the control 100 (FIG. 1). The control includes an electrical connector for connection with HVAC components including an air handler 190 such as a furnace or cooling unit or boiler, a fan, humidifier, dehumidifier or air filter. The fan 200 maybe connected through air ducts to an outside air damper. The circuit depicts micro-controller 201, which is connected to a fan relay 203 via a switching transistor 204. When the touch button 162 (discussed above in FIG. 1) is operated to place the system in recirculate mode 159, the micro-controller 201 will operate according to the specific flow diagram logic programmed therein and based on characteristics, such as room temperature and set point temperature, the micro-controller 201 will activate the fan relay 203. As depicted in FIG. 2, the fan relay 203 is currently shown de-energized as a result of the micro-controller 201 selecting a deactivate mode for the fan 200. As will be discussed in greater detail below, when the flow logic of the preferred embodiment determines appropriates conditions, the G terminal 208 will be energized in order to run the fan 200.
In the fan “on” mode, pole 207 connects fan terminal 208 to 24-volt power from RC terminal 209. In the fan auto and recirculate modes, fan 200 operation is controlled by a latching relay 203 shown with its contacts in the de-energized mode in FIG. 2. In the recirculate or auto modes, the fan 200 operation is controlled by the relay state, which is in turn controlled by the output of the microprocessor 201 through switch 204.
The control circuitry is illustrated in FIGS. 2-4. As depicted in FIG. 3 and FIG. 4 a 1P, 1T switch 210, 220 with poles 221, 222 provide an output to the input 231, 232 of the microprocessor 201 to tell the microprocessor the state of the fan relay 203 (FIG. 2). A gas-electric switch 210 shown in FIG. 3 provides an input to the microprocessor 201 so that the furnace logic and not the thermostat controls the fan 200 (FIG. 2) operation during the gas heating cycle.
FIG. 4 depicts a portion of the circuitry for selecting a heat pump or conventional system depicting the power input 232 for the microcontroller 201.
FIGS. 3-5 depict a portion of circuit diagrams for an embodiment where a mechanical switch is provided on the control 100 (FIG. 1) for setting the fan modes or gas, electric or heat pump configurations. Such configurations may also be accomplished via software by using an installer menu to input the settings using a display of the control 100 (FIG. 1). As depicted in FIG. 5, a 1P, 3T switch 240 includes a fan 200 (FIG. 2) on pole 241, a fan recirculate pole 243 and fan auto pole 245. Each pole 241, 243, 245 is selected by a mechanical button or switch on the thermostat 100 (FIG. 1). While in the fan auto mode, as depicted in FIG. 2, the fan terminal 208 is essentially controlled utilizing furnace logic or the microprocessor 201. That is, the fan terminal 208 is energized upon call for cooling and de-energized after the set point temperature is reached. When in the heating mode, fan terminal 207 may be energized upon call for heat, and de-energized when the call is satisfied in an electrical heat system.
A first embodiment of the control logic of the invention is depicted by the flowchart in FIG. 6. The unit starts the ON-OFF interval timer (loop B) at power-on or reset 310 and then (loop A) checks the fan mode 320. The first interval timer (loop B), is the timer ON (TON) state of the timer 410, 420. The length of the TON state is a first value, Value A assigned to TON. Following expiration of TON 420, additional TON duration is calculated at step 430 by the absolute value of the difference between the set point temperature and the room temperature, multiplied by a first scaling factor, Factor 1. When the ON state interval expires 440, the timer OFF state interval (TOFF) starts 450. The length of TOFF state is a second value, Value B. assigned to TOFF. Following expiration of the TOFF 460, additional TOFF duration is calculated at step 470 by the absolute value of the difference between the set point temperature and the room temperature, multiplied by a second scaling factor, Factor 2. When the TOFF state interval expires 480, the timer begins the TON state interval again 410.
During operation of loop A, if the fan 200 (FIG. 2) is in the AUTO mode, the control of the fan mode is determined solely by heating, cooling, humidification or dehumidification calls 321 (e.g., Normal Fan Control). If the fan 200 (FIG. 2) is in the constant ON mode, the fan 200 (FIG. 2) is on constantly 321 (e.g., Normal Fan Control). If the fan 200 (FIG. 2) is in the recirculate mode 320, and there is no heating, cooling, humidification or dehumidification call 330, the fan mode is activated and deactivated via step 380, according to the interval timer loop B. If the fan 200 (FIG. 2) is in the recirculate mode, and there is a heating, cooling, humidification or dehumidification call 330, control of fan mode is determined according to the requirements of the call type 340 (e.g. Normal Fan Control), 350. At the end of the call 360, the room temperature is compared to the set point, and if they are not within a fixed value, Value C, of each other, fan mode control again passes to the timer until the next call, or until the fan 200 (FIG. 2) is moved from the recirculate mode 320.
As a example of the control described by the above method, if the thermostat 100 first has power applied in the heating mode with the fan 200 (FIG. 2) in the recirculate mode, and is set at 50 degrees, but the room temperature is steady at 75 degrees, there is no heating call because the room temperature is greater than the set point temperature 330. Fan 200 (FIG. 2) control is therefore passed to the ON-OFF interval timer 380 (loop B). If Value A is programmed to be 10 minutes, and Factor 1 is programmed to be 0.1, then the length of the first fan 200 (FIG. 2) ON cycle will be ten minutes plus the absolute value of 75 minus 50, multiplied by 0.1 minutes. Expressed as an equation, this would be 10+ABS (75−50)×0.1 in minutes, or 12.5 minutes 430. If Value B is programmed to be 20 minutes, and Factor 2 is programmed to be 0.2, then the length of the first OFF cycle would be 20 minutes plus the absolute value of 75 minus 50, multiplied by 0.2 minutes. Expressed as an equation, this would be 20+ABS(75−50)×0.2 in minutes, or 25 minutes 470.
As a further example of the control described by the above method, if the room temperature drops to 45 degrees, there will be a heating call because the room temperature is less than the set point temperature 330. Fan 200 (FIG. 2) control is therefore determined by the thermostat 100 to match the type of heating system being used 340. When the heating call is completed 350, 360, the room temperature is subtracted from the set point temperature and the absolute value is compared to Value C 370 to provide an interval spacing mechanism/interval spacer to prevent back to back fan 200 (FIG. 2) on states. Immediately after the call is completed, the room temperature will match the set point temperature, so that the difference between the two will be close to zero. If Value C 370 is programmed to be 0.1 deg., the fan 200 (FIG. 2) will remain off 350 until the temperature drifts further from the set point temperature. If the temperature drifts lower to 49.8, then fan 200 (FIG. 2) control passes to the interval timer 380 (loop B) at whatever state it is in at that point, because the condition of 370 “is ABS (Room Temperature—Set Point Temperature<0.1?” would be met.
A second embodiment of the control logic of the invention is depicted in FIG. 7. The unit starts the ON-OFF interval timer (loop B) at power-up or reset 510 and then (loop A) checks the fan mode 520. The first interval timer (loop B), is the ON state of the timer 610, 620. The length of the ON state is a first value, 10 minutes assigned to TON. Following expiration of the TON timer, an additional duration for TON 630 is calculated by the absolute value of the difference between the set point temperature and the room temperature, multiplied by a first scaling factor (i.e., 0.1 or by dividing by 10). When the ON state interval expires 640, the TOFF state interval starts 650. The length of TOFF state is a second value, 20 minutes, assigned to TOFF. Following expiration of the TOFF timer, an additional duration for TOFF 670 is calculated by the absolute value of the difference between the set point temperature and the room temperature, multiplied by a second scaling factor (i.e., 0.2 or by dividing by 5). When the OFF state interval expires 680, the timer begins the ON state interval again 610.
If the fan 200 (FIG. 2) is in the AUTO mode, the control 100 is determined by loop A, solely by heating, cooling, humidification or dehumidification calls 521 (e.g., Normal Fan Control). If the fan 200 (FIG. 2) is in the constant ON mode, the fan 200 (FIG. 2) is on constantly 521 (e.g., Normal Fan Control). if the fan 200 (FIG. 2) is in the recirculate mode 520, and there is no heating, cooling, humidification or dehumidification call 530, the fan mode is activated and deactivated according to the interval timer 580 (loop B). If the fan 200 (FIG. 2) is in the recirculate mode, and there is a heating, cooling, humidification or dehumidification call 530, control of fan relay 203 (FIG. 2) is determined according to the requirements of the call type 540 (e.g. Normal Fan Control) 550. At the end of the call 560, the room temperature is compared to the set point temperature 570, and if there is a deviation, fan relay 203 again passes to the interval timer until the next call, or until the fan 200 (FIG. 2) is moved from the recirculate mode 520. The interval timer (loop B) operates independent of the other operations (loop A).
As an example of the control described by the above method, if the thermostat 100 first has power-on applied in the heating mode with the fan 200 (FIG. 2) in the recirculate mode, and is set at 50 degrees, but the room temperature is steady at 75 degrees, there is no heating call because the room temperature is greater than the set point temperature 530. Fan 200 (FIG. 2) control is therefore passed via 580 to the ON-OFF interval timer 610 (loop B). The first fan timer ON (TON) cycle will be ten minutes. Following expiration of TON 420 additional TON duration is calculated at step 630 by the absolute value of 75 minus 50, divided by 10 minutes. Expressed as an equation, this would be ABS(75−50)/10 minutes, or 2.5 additional TON minutes. The first fan timer OFF (TOFF) cycle 650 is 20 minutes. Following expiration of TOFF 460, additional TOFF duration is calculated at step 670 by the absolute value of 75 minus 50, divided by 5 minutes. Expressed as an equation, this would be ABS(75−50)/5 minutes, or 5 additional TOFF minutes. In an embodiment, the initial TON and TOFF durations are input at the factory at the time the microcontroller is programmed.
As a further example of the control described by the above'method, if the room temperature drops to 45 degrees, there will be a heating call at step 540 because the room temperature is less than the set point temperature. Fan 200 (FIG. 2) control is therefore determined by the thermostat 100 to match the type of heating system being used (e.g. Normal Fan Control). When the heating call is completed 550, 560, the room temperature is compared to the set point temperature at 570, using the following formulas to provide an interval spacing mechanism to prevent back to back fan 200 (FIG. 2) on states:
T _s+0.3≧T _r ≧T _s+0.1 (subsequent to a heating mode)
T _s−0.3≦T _r ≦T _s−0.1 (subsequent to a cooling mode)
where T_sis the set point temperature, and T_ris the room temperature. Immediately after the call is completed, the room temperature will match the set point temperature, so that the difference between the two will be close to zero, so no call to the interval timer (loop B) is made and there will again be a determination at step 550 as to whether there is a call for cooling, heating, humidification or dehumidification. The fan 200 (FIG. 2) will remain off 560, until the temperature drifts further from the set point temperature. The room temperature is again compared to the set point temperature at 570, using the following formula to provide an interval spacing mechanism to prevent back to back fan 200 (FIG. 2) on states:
T _s+0.3≧T _r ≧T _s+0.1 (subsequent to a heating mode)
T _s−0.3≦T _r ≦T _s−0.1 (subsequent to a cooling mode)
where T_sis the set point temperature and T_ris the room temperature. Once the temperature drifts lower, for example, to 49.8, then according to 580, a fan 200 (FIG. 2) on state may occur based on the interval timer (loop B) at whatever state it is in at that point, because the condition of 570 would be met.
A third embodiment of the control logic of the invention is depicted by the flowchart in FIG. 8. The unit starts the ON-OFF interval timer at power-up or reset 710 and then checks the fan switch mode 720. The first interval, is the ON state of the timer. The length of the ON state is a first value, value A, assigned to TON 810. When the ON state interval expires, the OFF state interval starts 820. The length of OFF state is a second value, value B, assigned to TOFF 830. When the OFF state interval expires, the timer begins the ON state interval 840 again.
During operation of loop A, if the fan 200 (FIG. 2) is in the AUTO mode, the control of fan mode is determined solely by heating, cooling, humidification or dehumidification calls 721 (e.g., Normal Fan Control). if the fan 200 (FIG. 2) is in the constant ON mode, the fan 200 (FIG. 2) is on constantly 721. If the fan 200 (FIG. 2) is in the recirculate mode 720, and there is no heating, cooling, humidification or dehumidification call 730, the fan mode is activated and deactivated according to the interval timer 780. If the fan 200 (FIG. 2) is in the recirculate mode 720, and there is a heating, cooling, humidification or dehumidification call 730, control of fan mode is determined according to the requirements of the call type 740. At the end of the call 750, the fan relay 203 is turned off 760 and the room temperature is compared to the set point temperature, and if they are not within a fixed value, Value C, of each other 770, the fan mode control again passes to the timer 780 until the next call, or until the fan 200 (FIG. 2) is moved from the recirculate mode.
As an example of the control described by the above method, if the thermostat 100 first has power-on applied in the heating mode with the fan 200 (FIG. 2) in the recirculate mode, and is set at 50 degrees, but the room temperature is steady at 75 degrees, there is no heating call because the room temperature is greater than the set point temperature. Fan 200 (FIG. 2) control is, therefore, passed to the ON-OFF interval timer 780. If Value A is programmed to be 10 minutes, then the length of the fan 200 (FIG. 2) ON cycle will be ten minutes 810. If Value B is programmed to be 20 minutes, and then the length of the OFF cycle would be 20 minutes 840.
As a further example of the control described by the above method, if the room temperature drops to 45 degrees, there will be a heating call because the room temperature is less than the set point temperature. Fan 200 (FIG. 2) control is therefore determined by the thermostat to match the type of heating system being used 740 (e.g., Normal Fan Control). When the heating call is completed 750, 760, the room temperature is subtracted from the set temperature and the absolute value is compared to Value C 770 to provide an interval spacing mechanism to prevent back to back fan 200 (FIG. 2) on states. Immediately after the call is completed, the room temperature will match the set temperature, so that the difference between the two will be close to zero. If Value C is programmed to be 0.1 deg., the fan 200 (FIG. 2) will remain off until the temperature drifts further from the set point temperature 760. If the temperature drifts lower to 49.8, then fan 200 (FIG. 2) control, according to 780, passes to the interval timer at whatever state it is in at that point, because the condition of 770 “is ABS (Room Temperature−Setpoint Temperature<0.1 ?” would be met.
A fourth embodiment of the control logic of the invention is depicted by the flowchart in FIG. 9. The unit starts the ON-OFF interval timer at power-on or reset 910 and then checks the fan mode 920. The first interval, is the ON state of the timer 1010. The length of the ON state is a first value, Value A, assigned to TON. When the ON state interval expires 1020, the OFF state interval starts 1030. The length of TOFF state is a second value, Value B, assigned to TOFF. When the OFF state interval expires 1040, the timer begins the ON state interval 1010 again.
If the fan 200 (FIG. 2) is in the AUTO mode, control of fan mode is determined solely by heating, cooling, humidification or dehumidification calls 921. If the fan 200 (FIG. 2) is in the constant ON mode, the fan 200 (FIG. 2) is on constantly 921 (e.g., Normal Fan Control). If the fan switch is in the recirculate mode 920, and there is no heating, cooling, humidification or dehumidification call 930, the fan mode is activated and deactivated according to the interval timer 950. If the fan switch is in the recirculate mode 920, and there is a heating, cooling, humidification or dehumidification call 930, control of fan mode is determined according to the requirements of the call type 940 (e.g., Normal Fan Control). At the end of the call, fan mode control again passes to the timer 950 at whatever state it is in until the next call, or until the fan 200 (FIG. 2) is moved from the recirculate mode 920.
As an example of the control described by the above method, if the thermostat first has power applied in the heating mode with the fan 200 (FIG. 2) in the recirculate mode, and is set at 50 degrees, but the room temperature is steady at 75 degrees, there is no heating call because the room temperature is greater than the set point temperature 930. Fan 200 (FIG. 2) control is therefore passed to the ON-OFF interval timer 950. If Value A is programmed to be 10 minutes, then the length of the fan 200 (FIG. 2) ON cycle will be ten minutes 1010. If Value B is programmed to be 20 minutes, and then the length of the OFF cycle would be 20 minutes 1030.
As a further example of the control described by the above method, if the room temperature drops to 45 degrees, there will be a heating call because the room temperature is greater than the set point temperature 930. Fan 200 (FIG. 2) control is, therefore, determined by the thermostat to match the type of heating system being used 940. When .the heating call is completed, the fan 200 (FIG. 2) control passes to the interval timer at whatever state it is in at that point 950.
A fifth embodiment of the control logic of the invention is depicted by the flowchart in FIG. 10. The unit starts the ON-OFF interval timer at power-on or reset 1110 and then checks the fan mode 1120. The first interval, is the ON state of the timer 1310. The length of the ON state is a first value, Value A, assigned to TON. When the ON state interval expires, the OFF state interval starts 1320. The length of TOFF state is a second value, Value B, assigned to TOFF 1330. When the OFF state interval expires, the timer begins the ON state interval again 1340.
If the fan 200 (FIG. 2) is in the AUTO mode, the control of fan mode is determined solely by heating, cooling, humidification or dehumidification calls 1121 (e.g. Normal Fan Control). If the fan 200 (FIG. 2) is in the constant ON mode, the fan 200 (FIG. 2) is on constantly 1121 (e.g., Normal Fan Control). If the fan 200 (FIG. 2) is in the recirculate mode 1120, and there is no heating, cooling, humidification, or dehumidification call 1130, the fan mode is activated and deactivated at 1260 according to the interval timer loop B. If the fan 200 (FIG. 2) is in the recirculate mode 1120, and there is a heating, cooling, humidification or dehumidification call 1130, a CALLON timer is started 1140, and control of fan mode is determined according to the requirements of the call type 1150 (e.g., Normal Fan Control). When the call ends 1160, the CALLON timer is stopped 1170, and a CALLOFF tinier is started, along with a LASTOFF timer. When the percentage of time that the fan 200 (FIG. 2) has been running, since of the last call started, is less than a first percentage value, Percentage A 1180, the fan 200 (FIG. 2) will start 1190 to provide an interval spacing mechanism to prevent back to back fan 200 (FIG. 2) on states so long as there is no heating or cooling call 1200. When the percentage of time that the fan 200 (FIG. 2) has been running, since the last call started, exceeds a second percentage value, Percentage B 1210, so long as there is no heating or cooling call 1220, the fan 200 (FIG. 2) stops 1230. This process repeats unless a heating, cooling, humidification or dehumidification call 1210, 1220 occurs, or unless the period of time fan has not run exceeds a third value, Value C 1250, in which case all timers are reset, and the process repeats 1180. The LASTOFF timer is initialized and started at step 1240
As an example of the control described by the above method, if the thermostat first has power-on applied in the heating mode with the fan 200 (FIG. 2) in the recirculate mode 1120, and is set at 50 degrees, but the room temperature is steady at 75 degrees, there is no heating call because the room temperature is greater than the set point temperature 1130. Fan 200 (FIG. 2) control is therefore passed to the ON-OFF interval timer 1260. If Value A is programmed to be 10 minutes, then the length of the fan 200 (FIG. 2) ON cycle will be ten minutes 1310. If Value B is programmed to be 20 minutes, and then the length of the OFF cycle would be 20 minutes 1330.
As a further example of the control described by the above method, if the room temperature drops to 45 degrees, there will be a heating call because the room temperature is less than the set point temperature 1130. Fan 200 (FIG. 2) control is therefore determined by the thermostat 100 to match the type of heating system being used 1150, and the CALLON timer is started 1140. If, after the call starts, it takes 15 minutes for the system to bring the room temperature to the set point temperature 1160, the value of CALLON is stopped at 15 minutes 1170, and CALLOFF begins incrementing from zero. If there are no further heating calls for 36 minutes step 1180 is taken to provide an interval spacing mechanism to prevent back to back fan 200 (FIG. 2) on states when. If Percentage A is set to 30%, the calculation of CALLON/(CALLON+CALLOFF) becomes less than 0.3, so the fan 200 (FIG. 2) is activated 1180. CALLON begins incrementing from its last value, 15 minutes. If there are no further heating calls, and Percentage B is set to 40%, CALLON / (CALLON+CALLOFF) exceeds 0.4 after 9additional minutes of fan 200 (FIG. 2) run time, and the fan 200 (FIG. 2) is deactivated 1210. Any heating call will cause timers CALLON and CALLOFF to reset 1220, 1230, 1240. If Value C is set to 60 minutes, any time the fan 200 (FIG. 2) has been off for a period of time greater than 60 minutes 1250, then passes to the interval timer described above, at whatever state it is in 1260.
The previous description of the disclosed embodiments is provided to enable a person, skilled in the art to use the present invention. There is modifications to these embodiments would be readily apparent to those skilled in the art, and the generic principle applied herein may be applied to other embodiments within departing from the spirit or the scope of the invention. Thus, the present invention does not intend to be limited to the embodiments shown herein, but is to be accorded to the widest scope consistent with the principles and novel features disclosed herein and as defined by the following claims.

Claims

1. An air conditioning system comprising:

an air handler;

a circulating fan;

a control for activating and deactivating heating, cooling and fan recirculate modes, the control operatively coupled to the air handler and the fan for controlling the air handler and the fan, the control having an interval timer;

the interval timer switchable between a timer on (TON) state and a timer off (TOFF) state, both the TON and TOFF state durations are variable according to comparisons between room temperature and a set point temperature of the control; the control activating the fan recirculate mode when the following conditions are met:

a) the control is in fan recirculate mode;

b) heating and cooling of the air conditioning system are not active; and

c) the room temperature deviates from the set point temperature of the control.

2. The air conditioning system of claim 1, further comprising an interval spacing mechanism, wherein:

d) the room temperature is compared to the set point temperature in order to avoid back to back fan on states and to allow activation of the fan when the interval timer is in the TON state.

3. The air conditioning system of claim 2, wherein the interval spacing comparison is made according to the following formula subsequent to a heating mode:

T _s+0.3≧T _r ≧T _s+0.1

where T_sis the set point temperature and T_ris the room temperature.

4. The air conditioning system of claim 2, wherein the interval spacing comparison is made according to the following formula subsequent to a cooling mode:

T _s−0.3≦T _r ≦T _s−0.1

where T_sis the set point temperature and T_ris the room temperature.

5. The air conditioning system of claim 2, wherein the interval spacing comparison is made according to the following formula:

ABS(T _r −T _s)<Value C

where T_sis the set point temperature and T_ris the room temperature.

6. The air conditioning system of claim 2, wherein the interval spacing comparison is made according to the following formula:

CALLON/(CALLON+CALLOFF)<A%.

7. The air conditioning system of claim 2, wherein the interval spacing comparison is made according to the following formula:

CALLON/(CALLON+CALLOFF)<B%.

8. The air conditioning system of claim 2, wherein the interval spacing comparison is made according to the following formula:

LASTOFF>Value C.

9. The air conditioning system of claim 2, wherein the interval timer is activated upon power-up of the control and following expiration of the TON state, the TOFF state is activated until expiration and the interval timer operates in a continuous loop with TON and TOFF states sequentially running one after the other and the interval timer being independent of the interval spacing mechanism.

10. The air conditioning system of claim 1, wherein the interval timer TON duration is equal to a first value plus the absolute value of the difference between the set point temperature and the room temperature multiplied by a first scaling factor.

11. . The air conditioning system of claim 10, wherein the first value is 10 minutes and the first scaling factor is 0.1.

12. The air conditioning system of claim 10, wherein the interval timer TOFF duration is equal to a second value plus the absolute value of the difference between the set point temperature and the room temperature multiplied by a second scaling factor.

13. The air conditioning system of claim 12, wherein the second value is 20 minutes and the second scaling factor is 0.2.

14. The air conditioning system of the claim 1, wherein the control is a thermostat.

15. The air conditioning system of claim 14, wherein the thermostat includes one of a mechanical fan switch for setting the fan to recirculate mode and a touchscreen input for setting the fan to recirculate mode.

16. A method for activating a fan recirculate mode of an air conditioning system comprising the steps of:

providing a control having an interval timer, the control operatively coupled to an air handler and a fan for activating and deactivating heating, cooling and fan recirculate modes;

powering the control in order to set the interval timer to a timer on (TON) state;

varying the duration of the TON state by the interval timer to a first value by comparing room temperature with a set point temperature of the control;

setting the interval timer to a timer off (TOFF) state;

varying the duration of the TOFF state of the interval timer to a second value by comparing the room temperature and the set point temperature of the control;

setting the control to fan recirculate mode;

monitoring the control to confirm no heating or cooling of the air conditioning system is active; and

activating the fan recirculate mode when the room temperature deviates from the set point temperature of the control.

17. The fan activation method of claim 16, wherein the fan recirculate mode is activated when the interval timer is in TON state only after an interval spacing mechanism is executed by comparing the room temperature to the set point temperature of the control.

18. The fan activation method of claim 17, wherein the interval spacing mechanism value is not preselectable.

19. The fan activation method of claim 17, wherein the interval spacing mechanism operates according to the following formula subsequent to a heating mode:

T _s+0.3≧T _r ≧T _s+0.1

where T_sis the set point temperature and T_ris the room temperature.

20. The fan activation method of claim 17, wherein the interval spacing mechanism operates according to the following formula subsequent to a cooling mode:

T _s−0.3≦T _r ≦T _s−0.1

where T_sis the set point temperature and T_ris the room temperature.

21. The fan activation method of claim 16, further comprising the step of setting the TON duration that is equal to a first value plus the absolute value of the difference between the set point temperature and the room temperature multiplied by a first scaling factor.

22. The fan activation method of claim 21, wherein the first value is 10 minutes and the first scaling factor is 0.1.

23. The fan activation method of claim 21, further comprising the step of setting the TOFF duration that is equal to a second value plus the absolute value of the difference between the set point temperature and the room temperature multiplied by a second scaling factor.

24. The fan activation method of claim 22, wherein the second value is 20 minutes and the second scaling factor is 0.2.

25. The fan activation method of claim 22, wherein the TOFF state is not dependent from an end of a last operation of the fan.

26. The fan activation method of claim 22, wherein the first and second value and first and second scaling factors are not user selectable.

27. The fan activation method of claim 16, further comprising the steps of:

activating the interval timer upon power-up of the control;

activating the TON state until expiration;

activating the TOFF state until expiration; and

operating the interval timer in a continuous loop with TON and TOFF states sequentially running one after the other and the interval timer being independent of the interval spacing mechanism.

28. The fan activation method of claim 16, wherein the control simultaneously processes the comparing, monitoring and activating steps.

29. The fan activation method of claim 16, wherein the control includes a microprocessor for simultaneously processing the comparing, monitoring and activating steps.

30. The fan activation method of claim 16, wherein the TON duration is between 5 and 15 minutes.

31. The fan activation method of claim 16, wherein the TON duration is approximately 50% TOFF.

32. The fan activation method of claim 16, wherein the interval timer TON and TOFF durations are not preselectable by a user.

33. The fan activation method of claim 16; wherein a fan auto mode and fan on mode are provided and further comprising the steps of monitoring the control to confirm no auto fan mode or fan on mode are active.

34. The fan activation method of claim 16, wherein the air handler is a HVAC system, including an air filter assembly and air ducts for circulating indoor and outdoor air.

35. The fan activation method of claim 16 further comprising the steps of:

depressing a fan button of the control;

selecting the recirculate mode by scrolling through multiple fan modes; and

upon selection of the fan recirculate mode providing an indication of the mode selected.

36. The fan activation method of claim 35, wherein the control includes a display having an LCD display having touch sensitive areas including a touch button for the fan button.

37. The fan activation method of claim 36, wherein the icon is an alpha numeric presented in a fan mode display area.

38. The fan activation method of claim 36, wherein the icon is a graphical representation of a fan presented on the display.

39. The fan activation method of claim 35, wherein the fan button is a mechanical switch.

40. The fan activation method of claim 16, were in the activation of the fan occurs when a microcontroller of the control energizes a fan terminal in order to power the fan.

41. A control for activating and deactivating heating, cooling and fan recirculate modes comprising:

an interval timer switchable between a timer on (TON) state and a timer off (TOFF) state, both the TON and TOFF state durations are variable according to comparisons between room temperature and a set point temperature of the control and the control activating the fan recirculate mode when the room temperature deviates from the set point temperature of the control.

42. The control of claim 41, further comprising an interval spacing mechanism, wherein the room temperature is compared to the set point temperature in order to avoid back to back fan on states and to allow activation of the fan when the interval timer is in the TON state.

43. The control of claim 42, wherein the interval timer is activated upon power-up of the control and following expiration of the TON state, the TOFF state is activated until expiration and the interval timer operates in a continuous loop with TON and TOFF states sequentially running one after the other and the interval timer being independent of the interval spacing mechanism.

44. The control of claim 41, wherein the interval timer TON duration is equal to a first value plus the absolute value of the difference between the set point temperature and the room temperature multiplied by a first scaling factor.

45. The control of claim 41, wherein the interval timer TOFF duration is equal to a second value plus the absolute value of the difference between the set point temperature and the room temperature multiplied by a second scaling factor.

46. A control for activating and deactivating heating, cooling and fan recirculate modes comprising:

an interval timer switchable between a timer on (TON) state and a timer off (TOFF) state;

an interval spacer to prevent back to back fan on states;

the interval timer setting TON and TOFF state durations that are variable and are set independently from the operation of the interval spacer; and

the control activating the fan recirculate mode when the room temperature deviates from the set point temperature of the control following operation of the interval spacer.

47. The control of claim 46, wherein the interval spacer operates according to the following formula:

ABS(T _r −T _s)<Value A

where T_sis the set point temperature and T_ris the room temperature.

48. The control of claim 46, wherein the interval spacer operates according to the following formula:

CALLON/(CALLON+CALLOFF)<A%.

49. The control of claim 46, wherein the interval spacer operates according to the following formula:

CALLON/(CALLON+CALLOFF)<B%.

50. The control of claim 46, wherein the interval spacer operates according to the following formula:

LASTOFF>Value A.

51. The control of claim 46, wherein the interval spacer operates by comparing the room temperature to the set point temperature of the control to allow activation of the fan when the interval timer is in the TON state.

52. The control of claim 51, wherein the interval spacer operates according to the following formula subsequent to a heating mode:

T _s+0.3≧T _r ≧T _s+0.1

where T_sis the set point temperature and T_ris the room temperature.

53. The control of claim 51 wherein the interval spacer operates according to the following formula subsequent to a cooling mode:

T _s−0.3≦T _r ≦T _s−0.1

where T_sis the set point temperature and T_ris the room temperature.