Abstract:
An air heating and cooling system includes (1) a heat pump, illustratively devoid of auxiliary electric resistance type air heating structure, operative to provide refrigerant-based heating or cooling of air being delivered to a conditioned space, (2) a fuel-fired modular blower selectively operable to generate combustion heat, and (3) a control system associated with the heat pump and the modular blower. The control system has a heat pump thermostat electrically connected to a modular blower control and operative to transmit to the modular blower a first signal indicative of heating operation of the heat pump, and a second signal indicative of a need for alternative heat during a heating demand cycle. The modular blower is operative, in response to receiving both signals, to provide combustion-based air heating in place of refrigerant-based heat pump air heating.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims priority to and is a continuation of U.S. patent application Ser. No. 14/200,938, filed Mar. 7, 2014, which claims priority to and the benefit of the filing date of provisional U.S. Patent Application 61/775,916 filed Mar. 11, 2013. The entire disclosures of both priority applications are hereby incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    It is known in the space heating art to provide both heating and cooling to a building interior using a reversible circuit electric heat pump that operates to either pump indoor ambient heat out of the building (during the heat pump&#39;s cooling cycle) or, with its refrigerant circuit reversed by operation of a reversible valve in the circuit, pump ambient outdoor air heat into the building (during the heat pump&#39;s heating cycle). Particularly in cold northern climates, winter temperatures commonly reach low temperatures that make it difficult if not impossible to wring sufficient heat out of the frigid outside air to sufficiently heat the building interior using only the heat pump. Because of this it has been common practice to add to the heat pump auxiliary heating in the form of electric resistance strip heaters that supplement the refrigerant heating capacity of the heat pump when heating conditions warrant. 
         [0003]    While this meets the comfort requirements of the building, it also substantially increases the yearly heating bill due the normally much higher cost of electric resistance heating compared to the refrigerant-based heating provided by a heat pump. As an alternate to this resistance heat add-on technique, various proposals have been made to supplement the refrigerant heating capacity of a reversible heat pump with a fuel-fired supplemental heating source used in place of the heat pump during high heating demand periods when the heat pump cannot provide sufficient heat by itself. However, a common shortcoming of such proposals has been their tendency to lessen the overall resulting efficiency of the heat pump/fuel-fired hybrid heating system to an undesirable degree. Accordingly, a need exists for a heat pump/fuel-fired hybrid heating system that strikes a more desirable balance between efficiency and operating costs, while restricting the user from overriding the heat pump. It is to this need that the present invention is primarily directed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]      FIG. 1  is a schematic diagram of the components in the heat pump/non-condensing type fuel-fired modular blower system; 
           [0005]      FIG. 2  is a simplified schematic wiring diagram for the  FIG. 1  system; 
           [0006]      FIG. 3  is an alternate embodiment of the  FIG. 2  simplified schematic wiring diagram; 
           [0007]      FIG. 4  is a control logic flow chart for the modified fuel-fired modular blower control portion of the  FIG. 1  system; and 
           [0008]      FIG. 5  is an alternate control logic flow chart portion which may be added to the  FIG. 4  flow chart. 
       
    
    
     DETAILED DESCRIPTION 
       [0009]    Referring initially to  FIG. 1 , in a representatively illustrated embodiment thereof the present invention provides a specially designed reversible circuit heat pump-based system  10  comprising an indoor heat pump coil unit  12  (representatively, as denoted in  FIG. 1 , having no electric resistance type of secondary heating structure), an outdoor heat pump unit  14 , and a fuel-fired supplemental heating source which is representatively a non-condensing type gas-fired modular blower  16 . Illustratively, the indoor heat pump coil unit  12  rests atop the modular blower  16  which has the schematically depicted blower and heating sections  18  and  20 , the heating section  20  being supplied with gas (or another type of fuel) via a fuel supply line  22 . The indoor heat pump coil unit  12  has an indoor refrigerant coil  24  which, via refrigerant lines  26  and  28 , is operatively coupled to an outdoor coil and associated circuit components (not shown) within the outdoor unit  14 . 
         [0010]    Three control components are associated with the system  10 —a heat pump thermostat  30  representatively mounted external to the indoor heat pump unit  12  on a wall  32 , a specially designed modified modular blower control  34  representatively associated with the blower section  18  of the modular blower  16 , and a heat pump controller  36  representatively mounted on the outdoor heat pump unit  14 . The heat pump thermostat  30  is electrically coupled to the modular blower controller  34 , as schematically depicted by the numeral  38 , and to the heat pump controller  36 , as schematically depicted by the numeral  40 . 
         [0011]    During cooling operation of the heat pump system  10 , the blower section  18  of the non-condensing fuel-fired modular blower  16  sequentially flows system return air  42  upwardly through the modular blower heating section  20  (which is unfired during heat pump cooling cycles), and then upwardly across the indoor refrigerant coil  24  which cools the air  42  so that it exits the heat pump  12  as conditioned (i.e., cooled) air  42   a.  Alternatively, the heat pump coil unit  12  may be a downflow or horizontal unit if desired. 
         [0012]    During normal heating operation of the heat pump system  10 , the blower section  18  of the non-condensing fuel-fired modular blower  16  sequentially flows system return air  42  upwardly through the unfired modular blower heating section  20 , and then upwardly across the indoor refrigerant coil  24  which heats the air  42  so that it exits the indoor heat pump coil unit  12  as conditioned (i.e., heated) air  42   b.  Using a specially designed overall control technique for the system  10 , as subsequently described herein, in a heating cycle thereof the system  10  normally produces the heated discharge air  42   b  using only the refrigerant heat from the indoor coil  24  but if its heating output is detected as being insufficient to meet a particular heat demand, the overall system control automatically terminates heat pump operation and initiates firing of the modular blower heating section  20  to replace the refrigerant-based heating of the indoor coil  24  with combustion heat and thereby raise the temperature of the heated supply air  42   b  being discharged from the heat pump  12 . When the overall system control detects that the replacement combustion heat from the modular blower heating section  20  is no longer required, such combustion heat is terminated and the heat pump coil unit  12  is re-activated until the heat demand is met by the indoor refrigerant coil  24 . 
         [0013]    In the depicted representative embodiment of the present invention, the use of a non-condensing gas-fired modular blower  16  as an alternative to electric resistive elements for back-up heat is uniquely coupled with the specially designed modified modular blower control  34  in a manner assuring that the modular blower  16  is only utilized for secondary heat when the heat pump portion  12 , 14  of the system  10  cannot provide adequate heat (e.g., at extremely low outdoor ambient temperature conditions or if the heat pump portion  12 , 14  has failed). 
         [0014]    A simplified wiring diagram for the system  10  is shown in  FIG. 2  and indicates the arrangement of the connection terminals, and the electrical wires interconnecting them, for the heat pump (HP) thermostat  30 , the modified non-condensing gas-fired modular blower (MB) electronic control  36 , and the outdoor heat pump (HP) control  36 . 
         [0015]    With the following exceptions relating to the modular blower control  34 , the thermostat  30  and the controls  34  and  36  may be of conventional construction and configurations. First, the modified modular blower control  34  is provided with a new connection terminal “B” that indicates when a call for heat pump heating operation is requested from the heat pump thermostat  30  (via its connection terminal “B”), for example, when the heat pump reversing valve has been switched to its heating orientation. Second, the modified modular blower control  34  is provided with a new input connection terminal “E” indicating when a call for secondary heat operation is requested from the heat pump thermostat  30  (via its connection terminal “E”), such request being indicative of a call for emergency heat during a heat pump heating cycle. The new terminal “E” of the modular blower control  34  may be the former “W” input terminal from a conventional control used in a non-condensing gas furnace. Third, the software algorithms in the modular blower control  34  are modified to prevent utilization of the non-condensing gas-fired modular blower  16  except under secondary conditions (i.e., when the “E” input to the modular blower control  34  is active). 
         [0016]    An alternate embodiment of the  FIG. 2  simplified control wiring diagram is depicted in  FIG. 3 . The  FIG. 3  wiring diagram is identical to the  FIG. 2  wiring diagram with the exception that in the  FIG. 3  electrical wiring circuit an outside air temperature lockout portion  44  is incorporated therein. The lockout portion  44  has an outside air temperature (OAT) sensor portion  46  and functions to limit when the modular blower (MB)  16  can be used for back-up heat. 
         [0017]    A logic flow diagram  48  is shown in  FIG. 4  and illustrates the operation of the modified modular blower control  34  in controlling the use of combustion heat from the modular blower  16  to replace the refrigerant-based heat provided by the heat pump portions  12 , 14  (see  FIG. 1 ) during a space heating demand cycle. Subsequent to a suitable starting step  50 , a query is made at step  52  as to whether a heat pump thermostat output signal “B” is being input to the modular blower control  34 . If it is not, the system loops back to step  52 . If the step  52  query answer is “yes” a transfer is made from step  52  to step  54  at which a query is made as to whether the heat pump thermostat output signal “E” is being input to the modular blower control  34 . If it is not, the system loops back to step  52 . If the step  54  query answer is “yes”, a transfer is made from step  54  to step  56 . 
         [0018]    At step  56  the heat pump is turned off and the modular blower heating section  20  (see  FIG. 1 ) is energized to replace the refrigerant-based heat previously being generated by the now idle heat pump indoor refrigerant coil  24  (see  FIG. 1 ). A transfer is then made from step  56  to step  58  at which a query is made as to whether the signal “E” transmitted to the modular blower control  34  has terminated. If it has not, the system loops through steps  56  and  58 , continuing to provide replacement combustion heat from the modular blower until the answer to the step  58  query becomes “yes”. When this occurs, a transfer is made from step  58  to step  60  at which the heating of the modular blower section  20  is terminated, heat pump operation is re-enabled, and a transfer is made from  60  back to step  52 . 
         [0019]    When the previously described outside air temperature lockout circuit portion  44  (see  FIG. 3 ) is utilized, the  FIG. 4  logic flow diagram is modified, as shown in  FIG. 5 , by interposing an additional step  62  between the previously described steps  50  and  52 . At the additional step  62  shown in  FIG. 5 , a query is made as to whether the outside ambient temperature is less than a predetermined magnitude. If it is not, the system pauses at step  62  until the query answer becomes “yes” at which point a transfer is made from the additional step  62  to the previously described step  52  in the logic flow diagram of  FIG. 4 . 
         [0020]    As can be seen from the foregoing, in an illustrated representative embodiment of the present invention, combustion heat from a fuel-fired modular blower, preferably a non-condensing type fuel-fired modular blower, is used to replace the refrigerant-based heating capacity of a reversible circuit heat pump only when the heat pump refrigerant heat is insufficient to meet a heat pump heating demand as evidenced by the receipt by a modular blower control from a heat pump thermostat of both a first signal indicative of a call for heat pump heat (by, for example, the heat pump reversing valve having been set to its heating orientation), and a second signal indicative of a call for emergency heat during a heat pump heating cycle. Additionally, this is done in a manner desirably restricting the user from overriding the heat pump. 
         [0021]    The foregoing detailed description is to be clearly understood as being given by way of illustration and example only, the spirit and scope of the present invention being limited solely by the appended claims.