1. Field of the Invention
This invention relates generally to heating systems and more particularly to a heating system employing a dynamic thermal stabilizer for receiving, mixing, holding and outputting a circulating fluid received from both an input heat exchange unit and an output heat exchange unit. The system affords room air heating and domestic water heating by using heated water from the dynamic thermal stabilizer alone or in combination with the input heat exchange unit when additional heat input is required. The heating system is combined with an air conditioner or heat pump to afford a triple integrated, air cooling, air heating, and domestic hot water supply system.
2. Background
Over the years, housing apartment units and especially multi-family units have employed a wide variety of heating systems for both room air space heating and potable water heating. Multi-family units have often employed a central heat source such as a boiler or forced-air system using gas-fired or electric resistance furnaces for room air heating. Just as common is the use of individual heating devices (gas or oil furnace, electric heat pump, or electric resistance heating) in each unit. Domestic hot water is typically supplied from a central source although it is not uncommon to have individual electric or gas water heaters in each unit of a multi-family complex. Finally most dwelling units are air conditioned, either from a central chilled water source, window air conditioners, or by use of individual heat pumps that provide both heating and cooling.
Needless to say such configurations require considerable amounts of individual dwelling unit space or costly duct work and plumbing when central heating units, cooling units, and domestic water supplies are used. From a developer's point of view, either of these options is costly and a need exists to develop a single compact package that provides room air heating, domestic water heating, and air conditioning into a single efficient unit with minimum operating space and cost.
A wide variety of approaches have been made in an effort to solve these problems. In the area of potable water and room air heating, one approach has been the direct heating of a potable-water tank with the heated, potable water being used with a separate water-to-air exchanger for room heating. Typically these designs focus on improving the heat exchange from the combustion gases to the water tank, e.g., Marshall (U.S. Pat. No. 3,833,170), Sweat (U.S. Pat. No. 4,178,907), Jatana (U.S. Pat. No. 4,451,410 and U.S. Pat. No. 4,641,631), Moore Jr. (U.S. Pat. No. 4,925,093 and U.S. Pat. No. 5,074,464), Ripka (U.S. Pat. No. 5,076,494) and Noh (U.S. Pat. No. 5,415,133). As a second embodiment, Ripka (U.S. Pat. No. 5,076,494) uses an additional set of coils within the water tank to form a closed-loop, non-potable liquid, heat-exchange system for heat exchange between the room heating air exchanger and the potable-water tank Pernosky (U.S. Pat. No. 4,178,907) uses warm combustion gases from initial water-tank heating to further heat the potable water prior to its delivery to the room-heating air exchanger. Cashier (U.S. Pat. No. 4,640,458) and Ripka (U.S. Pat. No. 4,939,402) use the warm combustion gases from water-tank heating to preheat cold, potable water prior to entry into the water tank.
Because these approaches use the water tank as a single source of hot potable water for both the domestic hot water supply and room heating, the water tanks must be large in order to provide the needed hot water for both space heating and domestic use. Moreover, the arrangements tend to be complex as various heat exchange features are incorporated in or used with the water tank In a related approach, Handley (U.S. Pat. No. 2,833,267), Dalin (U.S. Pat. No. 2,822,136), Grooms, Jr. (U.S. Pat. No. 2,998,003), Ronan (U.S. Pat. No. 3,269,382) and Masrich (U.S. Pat. No. 3,563,225) use the combustion gases from heating the potable-water tank and the heat from the tank itself to heat room air. Eubanks (U.S. Pat. No. 3,236,228) uses an arrangement of multiple, coaxial, double heat-exchange tubes in which combustion gases in the inner coaxial tubes heat potable water flowing in the outer coaxial tubes which in turn heat room air flowing over the exterior of the outer coaxial tubes. The outer tubes and headers at each end of the outer tubes serve as the hot water storage tank. In such systems, the elaborate and intricate heat exchange paths increase fabrication costs and tend to be difficult to access and service.
In a second approach that emphasizes space heating, combustion gases from direct air heating or the resulting heated air itself are used to heat a potable-water tank. Doherty (U.S. Pat. No. 2,354,507) and Biggs (U.S. Pat. No. 5,361,751) use warm combustion gases from a space-heating, combustion-gas exchanger to further heat potable water in a water tank. In both cases, direct combustion gas heating of the tank is also provided. Because of the need for dual burners, one in the hot-air furnace and the other for the water tank design, such devices tend to be large in size as a result of the dual combustion gas, room air, and potable water heat-exchange requirements. Mariani (U.S. Pat. No. 4,971,025) uses a central combustion chamber to heat room air in an annular chamber surrounding the combustion chamber with heat from the hot room air also used to heat a potable-water tank. Such an arrangement tends to be somewhat inefficient for water heating especially when room heating is not required because of the double heat exchange from combustion gas, to air, to the hot-water container for potable water heating.
A third approach to potable-water heating involves direct heat exchange from the combustion gases to the potable water without use of a water tank. Such devices are typically referred to as instantaneous, hot water units. Saylor (U.S. Pat. No. 2,840,101) illustrates an early design directed only to water heating. Tsutsui (U.S. Pat. No. 4,819,587) illustrates a gas burner ignition device while Ito et al. (U.S. Pat. No. 4,627,416) illustrates a burner diaphragm valve responsive to a vacuum produced by water flowing through the heat exchanger. Woodin (U.S. Pat. No. 4,848,416) and Wolter (U.S. Pat. No. 5,039,007) illustrate an instantaneous heat exchanger that provides hot, potable water that is also used for air heating. Clawson (U.S. Pat. No. 5,046,478) uses a high dew-point, combustion gas heat exchanger for heating potable water that is used for air heating and stored in a water tank for domestic use. In the Clawson design, water from the room heat exchanger is returned directly to the combustion gas heat exchanger. A diverter valve and a flow control valve regulates the flow of hot water from the combustion gas heat exchanger to either the room-air heat exchanger or to the water tank.
In a variation of the combustion-gas/potable-water heat exchanger system design, the hot, potable water is stored in a hot-water tank but the hot water is not used for space heating. Rather, room air heating is carried out with a room air/combustion-gas exchanger. Sherman (U.S. Pat. No. 2,294,579), Thomas (U.S. Pat. No. 5,529,977), and McCracken (U.S. Pat. No. 3,181,793) are illustrative of this design. Typically such units tend to be large in size because of the additional air/combustion gas exchanger requirements and complex with attendant high fabrication, installation and service costs as a result of the integration of the combustion gas/air and liquid exchangers. Such units tend to be inefficient as a result of high heat loss after the heat demand it met. Because of high on/off cycling, exchanger corrosion tends to be high and component controls, valves, ignitors, etc. are subject to high rates of wear.
In a fourth approach to potable water and room air heating, Vrij (U.S. Pat. No. 4,748,968), Loeffler (U.S. Pat. No. 4,823,770) and Martensson (U.S. Pat. No. 5,470,019) heat a non-potable liquid in a tank and use the resulting hot liquid to heat room air with an air/non-potable liquid exchanger. Potable water is heated with an exchange coil placed inside of the non-potable liquid tank. Borking et al. (U.S. Pat. No. 4,415,119) uses a combination of tanks, or heat exchangers, or both within the non-potable water tank for the hot, potable water supply. As with potable-water tanks, the tanks must be large and the location of heat-exchangers within the tank increases with manufacturing and service costs. Regan (U.S. Pat. No. 4,340,174) combines a heated potable water tank and a heated non-potable water tank (for space heating) into a single device where the combustion gases from non-potable tank heating augment potable water tank heating.
Finally, the last approach to room air and potable-water heating involves the use of combustion gas to heat a non-potable liquid using a heat exchanger. As seen in Casier (U.S. Pat. No. 4,638,943), Gerstmann et al. (U.S. Pat. No. 4,798,240), Farina (U.S. Pat. No. 4,805,590), Stapensea (U.S. Pat. No. 4,671,459), Jensen (U.S. Pat. No. 5,248,085) and the GlowCore products (Cleveland, Ohio; GlowCore Engineering/Design Manual, 1992), the hot, non-potable liquid from the combustion-gas exchanger is then used to 1) heat room air using an air/non- potable liquid heat exchanger or 2) to heat potable water in a potable-water tank using a potable-water/non-potable liquid heat exchanger. Gerstmann et al., in an alternative embodiment, directs hot, non-potable liquid to a non-potable liquid tank where it is used to heat potable water with a potable-water heat exchanger. In each of these "parallel processing" systems, one or more valves divert hot, non-potable liquid either to the air heating or to potable-water heating function. In all cases, the non-potable water from either the room air heat exchanger or the potable water exchanger is returned directly to the combustion gas/non-potable liquid exchanger. Sharff (U.S. Pat. No. 2,573,364) uses a closed-loop, "sequential processing" arrangement of the following components: 1) a combustion gas/non-potable liquid exchanger, 2) a non-potable liquid/air exchanger, and 3) a non-potable liquid tank with potable water exchange coil. Because the combustion gas/liquid heat exchanger must be operating for either hot-liquid or air heating, an undue load is placed on the combustion-gas exchanger causing excessive on/off cycling, high corrosion rates, and undue wear and tear on system switching components such as valves and switching devices and ignition systems. Moreover the combustion gas exchanger is mismatched with regard to the air and potable water heating requirements.
In summary, efforts to use conventional direct-fired, potable water or non-potable liquid tanks as a source of hot water from a room-air heater require large potable-water or non-potable liquid storage tanks in order to provide the needed hot water or liquid for both space heating and domestic, hot-water purposes. Instantaneous heaters, that is, combustion gas/liquid heat exchangers used for both space and domestic water heating tend to be inefficient as a result of the large amount of heat loss after the heating demand has been met. Further, instantaneous-type systems experience a high rate of on/off cycling tending to incur high rates of corrosion and fatigue with an undue burden on switching components, ignition systems and valves. In addition, both the potable water and non-potable liquid/combustion gas exchanger systems require large combustion gas/liquid exchangers to meet high, hot, potable-water loads such as with twenty-minute shower use. As a result, such designs produce a combustion-gas/liquid exchanger mismatch between the space heating and potable water heating needs of the typical user.
Turning to the field of combined potable-water heating, air heating, and air conditioning units, the following approaches have been taken. Davidson (U.S. Pat. No. 3,749,157) uses a blower assembly with a rotating diverter to direct room air through either a cooling compartment or heating compartment of an integrated unit which also includes a separate hot water tank for domestic water purposes. Lodge (U.S. Pat. No. 4,072,187) is directed to a modular air cooling and heating device using individual blowers for each function The unit is mountable in-wall but does not provide for domestic-water heating. A preference for avoiding circulating fluids for space heating also is noted. Akin, Jr. (U.S. Pat. No. 4,828,171) is directed to an in-wall cabinet for housing a through-the-wall, gas-fired water tank and air heating unit along with an electric air conditioning unit. Gerstmann et al. (U.S. Pat. No. 4,798,240) provides a through-the-wall cabinet for an integrated water tank and room-air heat exchanger which are heated with a condensing combustion gas/non-potable liquid heat exchanger. The combustion gas/non-potable liquid exchanger uses a three-way valve assembly for heating either the potable water tank or the room-air exchanger. In either case, the liquid is returned directly to the combustion gas exchanger. The use of a condensing combustion gas/liquid exchanger requires a condensation drain tending to cause icing problems at the terminal vent under cold ambient conditions. The use of an open reservoir in the non-potable liquid system is subject to evaporation of the liquid with resulting maintenance problems. The hot water storage tank is large (thirty gallons) and the arrangement and accessibility of components within the housing present access problems when maintenance is required.
Finally in using some of the various prior art devices, it is desirable to mount the device through an exterior wall in order to minimize air and combustion gas handling vent and duct work, e.g., Gerstmann et al. (U.S. Pat. No. 4,798,240) and Akin, Jr. (U.S. Pat. No. 4,828,171). Of particular interest has been a combined combustion air/combustion gas design to supply combustion air from an outside source and exhaust combustion gases in a closed system. To this end, Baker et al. (U.S. Pat. No. 3,428,040) and Jackson (U.S. Pat. No. 3,662,735) use a coaxial tube arrangement in which the inner exhaust tube is aligned with a hole in the gas heater fire box. Henault (U.S. Pat. No. 4,651,710) uses a support plate having wing tabs that align with slots in angle iron fittings attached to the heating unit to align the heating unit with a through-the-wall coaxial exhaust and combustion air system. The match of the tab and slot arrangement, especially for larger units in confined spaces is time-consuming and increases the installation costs of the heating unit. Further, the exposure of hot exhaust pipes, especially at low elevational levels, can burn or scorch objects that contact the exhaust outlet.
It is an object of the present invention to simplify individual component construction of an integrated hot combustion product/liquid exchanger for space-heating or liquid heating or both.
It is an object present invention to reduce thermal loss encountered with instantaneous combustion gas/liquid heating devices.
It is an object of the present invention to reduce the size of tank components with liquid tank/combustion product devices used for both air and liquid heating.
It is an object of the present invention to reduce cycling wear on valves, ignitors, and electrical components associated especially with combustion product/liquid heat exchangers.
It is an object of the present invention to reduce overall system complexity of an integrated combustion product/liquid exchanger and air or liquid heating unit.
It is an object of the present invention to integrate a hot combustion product/liquid heat exchanger for liquid and air heating purposes with an air cooling device.
It is an object of the present invention to provide a through-the-wall combustion air and exhaust system that is easy to install and connect to a heating unit assembly.
It is an object of the present invention to more evenly match air and liquid heating needs with the heating capacity of a combustion product/liquid heat exchanger.
It is an object of the present invention to reduce air handling duct work and gas and liquid piping requirements.
It is an object of the present invention to provide a warm heat as is beneficial in daily living and especially in assisted care facilities.
It is an object of the present invention to provide a cool surface at the point where the exhaust gas is vented to the outdoors.
It is an object of the present invention to provide a safe and simple electrical control system.