JP2882312B2 - Livestock heat combustion heating system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a regenerative combustion / heating apparatus which heats room air to warm air by combustion, and also heats and stores heat in a heat storage section to heat the heat storage section to warm air.

[0002]

2. Description of the Related Art Conventionally, this type of heat storage combustion heating apparatus is shown in FIG.
As shown in FIG. 1, a burner 2 in a main body casing 1 and a combustion cylinder 3 disposed so as to surround a combustion portion of the burner 2;
A burner fan 4 for supplying combustion air to the burner 2, a convection fan 5 for sucking and blowing indoor air, guides 6 and 6 'for regulating the flow direction of the air flow by the convection fan 5, and the guides 6, 6 ', A mixing section 7 of exhaust gas and air formed by
And a control unit 10 for controlling the operation of the combustion and convection fans.

When the combustion air is supplied by the burner fan 4 and the burner 2 is burned, the exhaust gas is discharged from the outlet of the combustion tube 3 and reaches the mixing section 7. On the other hand, the direction of flow of the air flow supplied from the convection fan 5 is regulated by the guides 6 and 6 ′, reaches the mixing section 7 and is mixed with the exhaust gas. The heat storage member 8 is heated by the mixed flow, and the mixed flow is then blown out as hot air from the hot air outlet 9. When the combustion stops, the convection fan 5
The supplied air flow receives heat from the heat storage unit 8 and continues to emit hot air for a certain period of time even after combustion.

[0004]

However, in the above-mentioned conventional structure, the high-temperature exhaust gas obtained by combustion is mixed with the low-temperature air flow supplied from the convection fan 5, and the heat storage unit 8 is heated after the temperature is lowered. Therefore, there has been a problem that the temperature of the heat storage unit 8 does not rise sufficiently, and thus the amount of heat storage also decreases. Further, an operation mode in which the high-temperature exhaust gas obtained by combustion does not give heat to the heat storage unit 8 and blows out all the heat as hot air is required, but it is configured to contact and pass through the heat storage unit 8. There was also a problem that it could not be done. Also, after the combustion is stopped, even in the thermal storage heating mode in which the stored thermal storage section 8 exchanges heat with the air flow supplied from the convection fan 5 and the warm air, the temperature is reduced by mixing with the supplied low-temperature air flow and the temperature is reduced. There was also a problem that it was difficult to obtain. Further, since the heat storage section 8 is not insulated and provided in an open state in the mixing section, there is also a problem that heat is released immediately after the combustion is stopped and cools down.

The present invention solves the above-mentioned problems. In the combustion heating mode, all the heat generated by combustion is used for heating without storing heat in the heat storage member. In the heat storage combustion mode, the heat storage section is heated to a high temperature by high-temperature combustion gas. It is a first object of the present invention to provide a heat storage combustion heating device in which the amount of heat storage is increased by heating, and in a heat storage heating mode, the warm feeling of warm air obtained from the heat storage unit is improved.

A second object is to simplify switching between a combustion heating mode, a heat storage combustion mode, and a heat storage heating mode.

A third object is to further simplify switching between the combustion heating mode, the heat storage combustion mode, and the heat storage heating mode.

A fourth object of the present invention is to provide a heat storage combustion heating device configured to be able to selectively control a heat storage radiation heating mode in which radiant heating is performed by the heat storage amount of the heat storage unit.

[0009]

Therefore, in order to achieve the first object, a heat storage combustion heating apparatus according to the present invention is provided between a heat storage part and a combustion tube to allow air from a blower to flow. By controlling an inflow opening, an outflow opening through which hot air flows out, an opening to the heat storage unit, and an air path switching cylinder having these opening and closing means, and an air path switching cylinder opening and closing means. Combustion / heating mode in which the hot air outflow opening is opened and the air that has flowed in through the air inflow opening is mixed with the combustion gas from the burner and blown out through the hot air outflow opening. The hot air outflow opening is closed. The indoor air that has flowed in through the opening for air inflow is mixed with the combustion gas of the burner and guided to the heat storage unit, and the heat storage combustion mode in which the heat is stored is stopped, the burner combustion is stopped, and the hot air outflow opening is closed. Air that flows in from the air inlet opening to the heat storage unit Can, in which the heat storage heating mode to heat exchange hot air thermal storage heat of the heat storage unit and a control unit for selectively controlling the structure provided with.

In order to achieve the second object, according to the present invention, there is provided an air path switching cylinder, wherein an inflow opening is always open, and when the air path switching cylinder is made vertical, an outflow opening is closed to open an opening to a heat storage section. A damper as an opening / closing means for closing the opening to the heat storage unit and opening the outflow opening when it is horizontal, the control unit burns the burner and controls the damper horizontally, It is possible to selectively control a heat storage combustion mode in which the burner is burned and the damper of the damper is controlled vertically, and a heat storage heating mode in which the combustion of the burner is stopped and the damper of the damper is controlled at an intermediate position between horizontal and vertical. .

In order to achieve the third object, the present invention provides an air path switching cylinder, wherein an opening for an inflow opening and an opening to a heat storage section are opened, and an opening and closing means for opening and closing an outflow opening. The control unit burns the burner, the control unit burns the burner, the combustion heating mode controls the damper to open, the burner burns, the heat storage combustion mode controls the damper to close, stops the burner combustion, and closes the damper. The heat storage heating mode to be controlled can be selectively controlled.

In order to achieve the fourth object, according to the present invention, the air flow path switching cylinder is configured such that the inflow opening is always open, and the air path switching cylinder is connected to the upper portion of the air path switching cylinder to advance upward and then downward. And a heat storage unit passage that joins with the outflow opening of the air path switching cylinder and is connected to the hot air outlet, and a device front side of a part that is turned down below the heat storage unit passage is formed of a heat storage unit. The control unit burns the burner and controls the damper of the air path switching cylinder to open the outflow opening. The combustion unit heats the burner and controls the damper of the air path switching cylinder to close the outflow opening. The heat storage combustion mode to be selected, the burner combustion and the blower are stopped, the damper of the air passage switching cylinder is controlled to close the outflow opening, and the heat storage radiant heating mode for performing radiant heating with the heat storage heat amount of the heat storage unit is selectively controlled. It is made possible.

[0013]

In the regenerative combustion heating apparatus according to the present invention, when the combustion heating mode is selected, the control unit closes the opening for the heat storage section of the air flow path switching cylinder and transfers the air that has flowed in from the air inflow opening to the combustion gas of the burner. When the heat storage combustion mode is selected, the hot air outflow opening is closed and the air that flows in through the air inflow opening is mixed with the combustion gas from the burner to store heat. When the heat storage and heating mode is selected by blowing out from the opening for
The combustion of the burner is stopped, and the air that has flowed in from the air inlet opening is blown out from the heat storage unit opening. In the combustion heating mode, all of the heat generated by combustion is used for heating without storing heat in the heat storage member. In the heat storage combustion mode, the amount of heat storage is increased. Can be improved.

When the combustion heating mode is selected, the control unit burns the burner, controls the damper of the air path switching cylinder horizontally to close the opening for the heat storage unit, and passes the air that has flowed in from the opening for air inflow to the burner. When the heat storage combustion mode is selected, the burner is burned, the damper is controlled vertically, the hot air outflow opening is closed, and the air inflow opening is mixed. Mixed with the combustion gas of the burner and blown out from the opening for the heat storage section,
When the heat storage heating mode is selected, combustion of the burner is stopped, and the damper is controlled to an intermediate position between the horizontal and vertical to blow out the air that has flowed in from the air inlet opening through the heat storage opening. And combustion heating mode, heat storage combustion mode,
Switching of the heat storage heating mode can be simplified.

When the control unit selects the combustion heating mode, the burner is burned, the damper is controlled to be open, and the air introduced from the air inflow opening is mixed with the combustion gas of the burner to make the hot air outflow opening. When the heat storage combustion mode is selected, the burner is burned, the damper is controlled to be closed, the hot air outflow opening is closed, and the air flowing in from the air inflow opening is mixed with the combustion gas of the burner. When the heat storage heating mode is selected, the burner stops burning, the damper is controlled to be closed, and the air that flows in from the air inlet opening is blown out from the heat storage opening. . Further, switching between the combustion heating mode, the heat storage combustion mode, and the heat storage heating mode can be further simplified.

When the control unit selects the combustion heating mode, the burner is burned, the damper is controlled to be open, and the air flowing in from the air inlet opening is mixed with the combustion gas of the burner to discharge the hot air outlet. When the regenerative combustion mode is selected, the burner is burned, the damper is controlled to close the outflow opening, and the air that has flowed in from the air inflow opening is mixed with the burner combustion gas to store the regenerative heat. When the heat storage heating mode is selected by blowing out from the storage opening, the burner and the blower are stopped, the damper is controlled to close the outflow opening, and radiant heating is performed by the heat storage heat amount of the storage unit. Then, radiant heating can be performed with the heat storage amount of the heat storage unit.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.

In FIG. 1, reference numeral 8a denotes a heat storage section, which stores heat by heating with the combustion gas of the burner 2 and radiates heat when combustion is stopped. Reference numeral 11 denotes an air path switching cylinder, which is provided between the upper portion of the combustion cylinder 3 and the heat storage section 8a, and has an inflow opening 12 through which air from the blower 5 flows, and an outflow opening through which hot air is discharged. It has a section 13, a heat storage section opening 14, and a means 15 for opening and closing these openings.

In the above configuration, when the control section 10a selects the combustion heating mode, the control section 10a closes the heat storage section opening 14 of the air path switching cylinder 11, and transfers the air flowing from the air inlet opening 12 to the combustion gas of the burner 2. Mixing with hot air outlet 1
3 and the heat storage combustion mode is selected, the hot air outflow opening 13 is closed, and the air flowing in from the air inflow opening 12 is mixed with the combustion gas of the burner 2 and the heat storage combustion opening 14 is opened. When the heat storage heating mode is selected, the hot air outflow opening 13 is closed, the combustion of the burner 2 is stopped, and the air flowing in from the air inflow opening 12 is blown out from the heat storage opening 14. In the combustion heating mode, all of the heat generated by combustion is used for heating without storing heat in the heat storage unit 8a. In the heat storage combustion mode, the amount of heat storage is increased. In the heat storage heating mode, the amount of hot air obtained from the heat storage unit 8a is reduced. Warm feeling can be improved.

Next, another embodiment of the present invention will be described with reference to FIG. In the air path switching cylinder 11, the inflow opening 12 is always open, and when it is vertical, the outflow opening 13 is closed to open the heat storage unit opening 14, and when it is horizontal, the heat storage unit opening 14 is closed. A damper is provided as an opening / closing means for opening the outflow opening 13 so that the control unit 106 can selectively control a combustion heating mode, a heat storage combustion mode, and a heat storage heating mode.

Reference numeral 16a denotes a damper, which is vertically closed to close the outflow opening 13 and open the heat storage opening 14;
When it is horizontal, the heat storage section opening 14 is closed and the outflow opening 13 is opened.

In this configuration, when the combustion heating mode is selected, the control unit 10b causes the burner 2 to burn and the air passage switching cylinder 1
The first damper 16a is horizontally controlled to open the heat storage section opening 14.
Is closed, the air introduced from the air inlet opening 12 is mixed with the combustion gas of the burner 2 and blown out from the hot air outlet opening 13. When the heat storage combustion mode is selected, the burner 2 is burned and the damper 16 a Is vertically controlled to close the hot air outflow opening 13, and the air introduced through the air inflow opening 12 is mixed with the combustion gas of the burner 2 to mix the heat storage opening 1.
4, when the heat storage heating mode is selected, the combustion of the burner 2 is stopped, and the damper 16a is controlled to an intermediate position between the horizontal and vertical directions to allow the air that has flowed in from the air inlet opening 12 to flow through the heat storage opening. Blow out from 14. And
Switching between the combustion heating mode, the heat storage combustion mode, and the heat storage heating mode can be simplified.

Next, another embodiment of the present invention will be described with reference to FIG. The air passage switching cylinder 11 opens the opening to the inflow opening 12 and the heat storage section 8a without providing a damper, and opens and closes the outflow opening 13 to the damper 1 as opening / closing means.
6b is provided, and the control unit 10c is capable of selectively controlling a combustion heating mode, a heat storage combustion mode, and a heat storage heating mode. 16b is a damper as opening / closing means for opening and closing the outflow opening 13.

In this configuration, when the combustion heating mode is selected, the control unit 10c burns the burner 2 and the damper 16b
Is controlled to be open, the air introduced from the air inlet opening 12 is mixed with the combustion gas of the burner 2 and blown out from the hot air outlet opening 13. When the heat storage combustion mode is selected, the burner 2 is burned. By controlling the damper 16b to be closed, the hot air outflow opening 13 is closed, and the air that has flowed in through the air inflow opening 12 is mixed with the combustion gas of the burner 2 and blown out through the heat storage opening 14. When the heat storage heating mode is selected, the combustion of the burner 2 is stopped, the damper 16b is controlled to be closed, and the air flowing in from the air inlet opening 12 is blown out from the heat storage unit opening 14. Further, switching between the combustion heating mode, the heat storage combustion mode, and the heat storage heating mode can be further simplified.

Next, another embodiment will be described with reference to FIG. The air path switching cylinder 11 always opens the inflow opening 12, connects to the upper portion of the air path switching cylinder 11, proceeds upward, then turns downward, and further outflows the opening 13 of the air path switching cylinder 11. And a heat storage unit that forms a heat storage unit passage 17 connected to the hot air outlet 9 and a part that is turned back below the heat storage unit passage 17 by the heat storage unit. The mode and the heat storage / radiation heating mode can be selectively controlled.

Reference numeral 16c is a damper. Reference numeral 17 denotes a heat storage unit passage which is connected to an upper portion of the air passage switching cylinder 11 and travels upward.
Next, it turns downward, and further joins with the outflow opening 13 of the air path switching cylinder 11 to be connected to the hot air outlet 9. 8b
Denotes a heat storage unit, which constitutes a portion of the apparatus front side 18 that is folded back below the heat storage unit passage 17.

In this configuration, when the combustion heating mode is selected, the control unit 10d burns the burner 2 and the damper 16c
Is controlled to be open, the air introduced from the air inlet opening 12 is mixed with the combustion gas of the burner 2 and blown out from the hot air outlet opening 13. When the heat storage combustion mode is selected, the burner 2 is burned. , The damper 16 c is controlled to close the outflow opening 13, and the air introduced from the air inflow opening 12 is mixed with the combustion gas of the burner 2 to mix the heat storage opening 14.
When the heat storage heating mode is selected, the combustion of the burner 2 and the blower 5 are stopped, the damper 16c is controlled to close the outflow opening 13, and radiant heating is performed with the heat storage heat of the heat storage unit 8. Then, radiant heating can be performed with the heat storage amount of the heat storage unit 8.

Further, a reference example of the present invention will be described with reference to FIG. Provided between the heat storage unit 8a and the blower 5, when open, the room air contacts and passes through the heat storage unit 8a, and when closed, the room air passes around the combustion cylinder 3 without contacting the heat storage unit 10e. And a control unit 10e capable of selectively switching between the combustion heating mode, the heat storage combustion mode, and the heat storage heating mode.

A damper 16d is provided between the heat storage section 8a and the blower 5, and when opened, the indoor air is stored in the heat storage section 8a.
, And when closed, the indoor air operates so as to pass around the combustion cylinder 3 without contacting the heat storage section 8a.

In this configuration, when the combustion heating mode is selected, the control unit 10e causes the burner 2 to burn, and the damper 16d
Is controlled to be open, the air from the blower 5 mixes with the combustion gas of the burner 2 in the space above the combustion tube 3 and blows out as hot air. When the heat storage combustion mode is selected, the burner 2 is burned and the damper 16 d Is closed and the combustion gas of the burner 2 heats and stores the heat storage unit 8a, and then mixes with the room air from the blower 5 and blows out the hot air from the hot air outlet 9 as hot air,
When the heat storage heating mode is selected, the combustion of the burner 2 is stopped, the damper 16d is opened, and the indoor air from the blower 5 exchanges contact heat with the heat storage unit 8a, and is blown out from the hot air outlet 9 as hot air. In the switching between the combustion heating mode, the heat storage combustion mode, and the heat storage heating mode, the configuration can be simplified without providing the air path switching cylinder 11.

[0031]

As described above, according to the present invention, an air passage switching cylinder having an inflow opening, an outflow opening, an opening for a heat storage unit, and means for opening and closing these openings between the heat storage unit and the combustion tube. Is established,
When the combustion heating mode is selected by controlling the opening / closing means of the air passage switching cylinder and providing a control unit for selecting and controlling the combustion heating mode, the heat storage combustion mode, and the heat storage heating mode, the control unit When the heat storage opening of the path switching cylinder is closed, the air introduced from the air inflow opening is mixed with the combustion gas of the burner and blown out from the hot air outflow opening. Close the outflow opening, mix the air that has flowed in through the air inflow opening with the combustion gas from the burner and blow it out through the heat storage opening, and close the hot air outflow opening when the heat storage heating mode is selected. Then, the combustion of the burner is stopped, and the air that has flowed in from the air inlet opening is blown out from the heat storage unit opening. In the combustion heating mode, all of the heat generated by combustion is used for heating without storing heat in the heat storage member. In the heat storage combustion mode, the amount of heat storage is increased. Can be improved.

Next, according to the present invention, in the air path switching tube, the inflow opening is always open, the outflow opening is closed and the heat storage opening is opened when it is vertical, and the heat storage opening is open when it is horizontal. A damper as an opening / closing means for closing the opening and opening the outflow opening is provided, and the control unit is configured to selectively control the combustion heating mode, the heat storage combustion mode, and the heat storage heating mode. When the mode is selected, the burner is burned, the damper of the air path switching cylinder is controlled horizontally to close the opening for the heat storage section, and the air introduced from the opening for air inflow is mixed with the combustion gas of the burner to warm up. When the heat storage combustion mode is selected by blowing out from the wind outlet, the burner is burned, the damper is controlled vertically, and the warm air outlet is closed.
The air introduced from the air inlet opening is mixed with the burner combustion gas and blown out from the heat storage opening, and when the heat storage heating mode is selected, the burner combustion is stopped and the damper is moved to the middle position between the horizontal and vertical positions. And the air that has flowed in from the air inlet opening is blown out from the heat storage unit opening.
Further, switching between the combustion heating mode, the heat storage combustion mode, and the heat storage heating mode can be simplified.

Next, according to the present invention, the air path switching cylinder is provided with a damper as opening / closing means for opening the inflow opening and the opening to the heat storage section without providing a damper, and opening and closing the outflow opening. The control unit is configured to be able to select and control the combustion heating mode, the heat storage combustion mode, and the heat storage heating mode.When the combustion heating mode is selected, the control unit burns the burner, controls the damper to open, and air inflows When the heat storage combustion mode is selected, the burner is burned and the damper is closed to control the air flow from the hot air outflow opening. Close the opening, mix the air that has flowed in from the air inflow opening with the combustion gas of the burner and blow it out from the opening for the heat storage section.If the heat storage heating mode is selected, stop the burner combustion and close the damper Control The air that has flowed from the air inlet opening to blown from the heat storage unit opening Te. Further, switching between the combustion heating mode, the heat storage combustion mode, and the heat storage heating mode can be further simplified.

Next, according to the present invention, the air flow path switching cylinder has an inflow opening which is always open, is connected to the upper part of the air path switching cylinder, proceeds upward, then returns downward, and further turns the air path switching cylinder. A heat storage unit passage that merges with the outflow opening and is connected to the hot air outlet and a front side of the device that is folded back below the heat storage unit passage are formed by a heat storage unit. Mode, the heat storage radiant heating mode can be selected and controlled.When the combustion heating mode is selected, the control unit burns the burner, controls the damper to open, and controls the air that flows in from the air inflow opening. When mixed with the combustion gas from the burner and blown out from the hot air outflow opening, when the heat storage combustion mode is selected, the burner is burned, the damper is controlled to close the outflow opening, and the air flows in from the air inflow opening Combined air with burner combustion gas When the heat storage heating mode is selected, the combustion of the burner and the blower are stopped, the damper is controlled to close the outflow opening, and radiant heating is performed using the heat storage heat of the heat storage unit. Let it. And
Radiant heating can be performed with the amount of heat stored in the heat storage unit.

[Brief description of the drawings]

FIG. 1 is a sectional view of a heat storage combustion heating apparatus according to an embodiment of the present invention.

FIG. 2 is a sectional view of a heat storage combustion heating apparatus according to another embodiment of the present invention.

FIG. 3 is a sectional view of a heat storage combustion heating apparatus according to another embodiment of the present invention.

FIG. 4 is a sectional view of a heat storage combustion heating device according to another embodiment of the present invention.

FIG. 5 is a sectional view of a heat storage combustion heating apparatus according to a reference example of the present invention.

FIG. 6 is a sectional view of a conventional heat storage combustion heating device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main body casing 2 Burner 3 Combustion cylinder 5 Blower 8a Heat storage part 9 Hot air outlet 10a, 10b, 10c, 10d Control part 11 Air path switching cylinder 12 Inflow opening 13 Outflow opening 14 Heat storage part opening 15 Opening / closing Means 16a, 16b, 16c Damper 17 Heat storage unit passage 18 Front side of device

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) F24H 7/02 602 F24H 7/02 603 F24H 3/04 301

Claims (4)

(57) [Claims] 1. A blower for taking in and blowing out indoor air, a burner, a combustion cylinder equipped with the burner, and a heating cylinder provided at an upper portion of the combustion cylinder. Is a heat storage unit for dissipating heat, an inlet opening provided between the heat storage unit and the combustion tube, and for inflow of air from the blower, an outlet for outlet of hot air, and the heat storage unit. An air passage switching cylinder having an opening to the section and an opening / closing means for opening and closing the opening, a warm air blow-out port from which a room air turned into warm air in the air passage switching cylinder or the heat storage section blows out from the device, and By controlling the opening / closing means of the path switching cylinder, the opening for the hot air outflow is opened, and the room air introduced from the air inflow opening is mixed with the combustion gas of the burner and blown out from the hot air outflow opening. Combustion heating mode, hot air outflow opening The indoor air that has been closed and flowed in from the air inlet opening is mixed with the combustion gas of the burner and guided to the heat storage unit.The heat storage combustion mode in which the heat is stored is stopped, the burner combustion is stopped, and the hot air outflow opening is opened. And a control unit for selectively controlling a heat storage heating mode in which the indoor air that has been closed and introduced from the air inlet opening is introduced into the heat storage unit and heat is exchanged for warm air with the heat storage amount of the heat storage unit. Heating system. 2. The air path switching cylinder, wherein the inflow opening is always open, the outflow opening is closed and the opening to the heat storage section is opened when it is vertical, and the opening to the heat storage section is opened when it is horizontal. A damper is provided as an opening / closing means for closing the opening and opening the outflow opening, the control unit burns the burner, the combustion heating mode in which the damper is horizontally controlled, and the heat storage combustion in which the burner is burned and the damper is vertically controlled. 2. The heat storage combustion heating apparatus according to claim 1, wherein the mode and the burner combustion are stopped, and the heat storage heating mode in which the damper is controlled to an intermediate position between the horizontal and vertical can be selectively controlled. 3. The air path switching cylinder is provided with a damper as opening / closing means for opening an inlet opening and an opening to a heat storage unit and opening and closing an outlet opening, and a control unit burns a burner. ,
The combustion heating mode in which the damper is opened, the heat storage combustion mode in which the burner is burned and the damper is closed, and the heat storage heating mode in which the burner is stopped and the damper is closed can be selectively controlled. 2. The heat storage combustion heating device according to 1. 4. The air path switching cylinder has an inflow opening which is always open, is connected to an upper portion of the air path switching cylinder, proceeds upward, then turns downward, and further has an outflow opening of the air path switching cylinder. And a heat storage section that is connected to the hot air outlet and a heat storage section that forms the front side of the device that is folded back below the heat storage section passage.The control section burns the burner and controls the air path switching cylinder. The combustion heating mode in which the damper is controlled to open the outflow opening, the heat storage combustion mode in which the burner is burned and the damper of the air path switching cylinder is controlled to close the outflow opening, the burner combustion and the blower are stopped. The heat storage combustion according to claim 1, wherein the heat storage combustion is configured to control the damper of the air passage switching cylinder to close the outflow opening, and to selectively control a heat storage radiant heating mode in which radiant heating is performed by the heat storage amount of the heat storage unit. Heating system.