Abstract:
An auxiliary or supplemental vehicle heating system that operates on natural gas or propane is provided for use with a vehicle engine having a liquid cooling/heating circuit. A propane- or natural gas-fired burner supplies heat during the operation or non-operation of the engine and the heat produced is used to supply heat to the engine, passenger compartment(s), mobile work areas, cargo containers and in the case of natural gas vehicles, provide heat to the on-board fuel system regulator. Thus, the auxiliary or supplemental heating system supplies heat independent of the engine&#39;s liquid cooling/heating circuit. In some embodiments, the cooling/heating circuit uses the heat produced from the natural gas or propane auxiliary heating system to supply heat to the engine via a heat exchanger.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority from U.S. Provisional Patent Application Ser. No. 61/915,929, filed Dec. 13, 2013, entitled “Vehicle Heating Apparatus and System and Method of Doing the Same,” the entire disclosure of which is hereby expressly incorporated by reference herein in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    Embodiments of the present invention generally relate to a device, system, and method for providing thermal energy to a motor vehicle. More specifically, embodiments of the invention relate to a supplemental heating device and system for natural gas- or propane-operated vehicles. 
       BACKGROUND OF THE INVENTION 
       [0003]    Some common cooling systems for motor vehicle combustion engines may also provide heat to occupant compartments of the vehicles. Existing systems often comprise a radiator, a fan that may be engine-driven, and a pump, that may be engine-driven, which circulates engine coolant from the engine to the radiator and back to the engine. Coolant heated by the running vehicle engine transfers heat to the radiator core through which the fan draws air to aid heat transfer from the core to the air. Thus, the air takes heat from the coolant to keep the engine cool. The warm air may then be used to heat occupant compartments of the vehicle. 
         [0004]    Certain motor vehicles, such as trucks, for example, have occupant compartments (cabs) that include at least a driver&#39;s compartment and sometimes a sleeper compartment behind the driver&#39;s compartment. One way to provide cold weather heating for an occupant compartment is by allowing the engine to idle while the vehicle is parked to keep the engine coolant sufficiently hot for adequate heating by an occupant compartment heater through which the coolant is circulated. This, however, is wasteful of fuel because it necessitates running the engine. 
         [0005]    An on-board auxiliary coolant heater can instead provide ample heating without running the engine (i.e., “no-idle” heating). One brand of commercially available heaters offers heaters with heat output ranges from 5.500 to 120,000 BTU/hr, heaters that operate on either 12 volts or 24 volts, and heaters that can run on the gasoline or diesel fuel carried by the vehicle. There are various types of auxiliary coolant heaters including those that use fuel carried by the vehicle, those that have electric heater elements, and generators. An auxiliary coolant heater may alternatively or additionally be used for engine pre-heating or supplemental heating. 
         [0006]    These supplemental heating systems, however, are not offered for use with natural gas or propane. Thus, some natural gas and propane vehicle manufactures have utilized a diesel- or gasoline-operated auxiliary heater, which does not use the same fuel type as the vehicle. Accordingly, the vehicle must have a separate fuel tank installed for the auxiliary heater&#39;s fuel. 
         [0007]    Compressed natural gas (also called CNG herein) engine cold starts below freezing temperature are problematic due to moisture freezing and/or oil found naturally in methane restricting fuel supply/injectors. Additionally the pressure regulator 3000 psi to engine supply pressure of 125 psi may also experience freezing and/or oil blockage of the supply gas to the engine. Current vehicle engines supply heated coolant to the high-pressure regulator, but only after the engine has warmed. 
         [0008]    Thus, natural gas- and propane-operated vehicles (such as trucks and school buses using gaseous fuels) have no means of providing “non-engine idling” pre-conditioning or pre-heating prior to vehicle use using the on-board fuel source. Likewise, during colder weather, supplemental heating during “engine on” is also unavailable in these natural gas and propane vehicles to boost heating to operator and/or passenger areas. Additionally, vehicles without an auxiliary or a supplemental heating source that are required to heat cargo, work, or passenger areas and/or to maintain operational temperatures in specific vehicle systems, such as the hydraulic systems and/or oil systems, may be rendered unoperational because the vehicles are not in a work-ready state. Current natural gas- and propane-operated vehicles typically use diesel supplemental heaters. Thus, the supplemental heater requires a second fuel tank, e.g., diesel, for use in the supplemental heater. Additional fuel tanks make these systems difficult to install and less convenient because the driver must refill two types of fuel. 
         [0009]    One known supplemental heater for a natural gas vehicle is available for large, transit buses (available in 24 VDC only). This supplemental heater, however, is impractical for a truck or school bus application because the heat output (between approximately 100,000 and 120,000 BTU/hr) grossly exceeds the needs of a truck or school bus, would not perform correctly on a truck, school bus, etc., would short cycle, and the temperature of the heating/cooling fluid would spike rapidly. Accordingly, an incorrectly-sized supplemental heater would not work properly. 
       SUMMARY OF THE INVENTION 
       [0010]    These and other needs are addressed by the various embodiments of the present invention. Embodiments of the present invention relate to natural gas- or propane-fueled vehicles that are over-the-road vehicles (i.e., Class 8), straight trucks (i.e., Classes 6 and 7), garbage trucks, trucks used to transport cargo, trucks used in the refuse industry, trucks used in the read-mix industry, and work trucks (service industry). In some embodiments, the heater operates on 12 VDC vehicles. An appropriately-sized propane or natural gas heater would have a heat cycle that produces more even heat than a larger, incorrectly-sized heater would produce. 
         [0011]    Embodiments of the present invention relates to a motor vehicle comprising a liquid-cooled combustion engine having ports for coolant to leave the engine and to return to the engine. Embodiments of the present invention relate to trucks, school buses, etc. running on natural gas or propane. In particular, various embodiments of the invention are directed to such trucks and school buses in which a heating system is provided by means of an internal combustion engine. 
         [0012]    Features of the present invention may be employed in a wide range of vehicles and applications. For example, many types of vehicles are used to move cargo or passengers or provide other work truck services, such as refuse, cement, etc., and are required to provide heating to passenger compartments, temporary living quarters, or temporary working quarters. These vehicles include self-propelled, over-the-road vehicles and other vehicles with internal combustion engines, such as so-called recreational vehicles, school busses, work trucks, garbage trucks, etc. Also, self-propelled vans have been used as mobile work spaces, such as for providing medical services at remote or movable locations in a city. Other self-propelled vehicles include boats in which internal combustion engines provide the primary power source. Non-self-propelled vehicles, such as trailers, have been used to provide shelter for temporary living, such as for vacation or recreation. Also, trailers are used to provide space for performing work, such as at construction sites or performing atmospheric sensing at remote locations. All of these vehicles are characterized by the need to provide heat to a space, in the form of at least a passenger compartment. 
         [0013]    Note that the term “supplemental” and “auxiliary” may be used interchangeably herein. The term “vehicle” is used herein to refer to all types of vehicles, whether or not self-propelled and whether an over-the-road or a water vehicle, so long as there is a space to be heated in the vehicle. The term “vehicle” also includes motor vehicles with a main power source, such as an internal combustion engine, that has the primary function of propelling the vehicle on land or water. 
         [0014]    The main power source of such vehicle is turned off when the vehicle arrives at the destination, and reliance is placed on a supplemental source of thermal energy. Such supplemental thermal energy sources include diesel-fired and gasoline-fired burners, such as those disclosed in U.S. Pat. Nos. 2,726,042 and 3,877,639, which are incorporated by reference herein in their entireties. 
         [0015]    Customarily, those main power sources are heated when not in operation, so that they will start readily when the vehicle is to be moved. The main power source of such vehicle is often turned off when the vehicle arrives at its destination and the vehicle relies on a supplemental source of thermal energy. Such supplemental thermal energy sources include diesel-fired and gasoline-fired burners, such as those disclosed in U.S. Pat. Nos. 2,726,042 and 3,877,639. 
         [0016]    An improved heating system for a vehicle is described in U.S. Pat. Nos. 5,025,985 and 5,067,652 to Enander, both of which are incorporated herein by reference in their entireties. However, improvements are desirable. For example, it would advantageous if the heating system were compact, so as not to take up valuable space in a vehicle than is necessary, similar to U.S. Pat. No. 6,572,026 to Enander, which is incorporated herein by reference in its entirety. It would be advantageous for the heating system to include an efficient control system and for the heating system to provide space heating as well as optional engine heating if desired. 
         [0017]    It is one aspect of embodiments of the present invention to provide a novel natural gas- or propane-operated heater for selectively distributing or fully distributing heat to the vehicle&#39;s occupant compartments and/or the vehicle&#39;s main engine. In some embodiments, supplemental heaters of the present invention use natural gas or propane, like the vehicle&#39;s main engine, which simplifies installation because an additional fuel tank does not need to be installed. Accordingly, heaters of embodiments of the present invention use existing on-board fuel. 
         [0018]    Another aspect of embodiments of the present invention is to provide a supplemental heater that uses a vehicle&#39;s existing engine, engine fuel, and engine battery. Additionally, the supplemental heater will consume a low amount of power from the battery in order to not interfere with a vehicle cold start at −20° F. 
         [0019]    It is one aspect of embodiments of the present invention to provide a supplemental heater that is reasonably compact and contains components necessary to heat and circulate engine coolant while the engine is off. Thus, the heater is compact and is packaged to utilize the space of the heater enclosure and to fit smaller vehicles (such as school buses and trucks). The heater is mounted efficiently, while still permitting access to the heater for servicing. The heater may provide heat at different selectable levels, and may be under the control of an associated control unit to maintain a set temperature. In one embodiment, when occupant compartment heating is required, a coolant pump starts circulating coolant. A supplemental heater heats the coolant as it circulates so that heated coolant flows out of the supplemental heater. 
         [0020]    It is one aspect of embodiments of the present invention to provide a supplemental heater sized to match the heat requirement of the vehicle. The heat requirement may be determined in multiple ways. One way is: 
         [0000]    
       
         
           
             
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         [0000]    The heat requirement may include the heat needed to preheat the engine, provide interior compartment heating, oil pan heating, fuel regulator heating, and/or hydraulic system heating. Additionally, a small percentage safety factor may be added to account for line losses in the lines that carry heat. 
         [0021]    It is another aspect of various embodiments of the present invention to provide occupant compartment heating while keeping the engine warm when the engine is shut off after having been running. 
         [0022]    It is yet another aspect of embodiments to provide engine pre-heating to a cold engine prior to starting the engine. 
         [0023]    It is one aspect of embodiments of the present invention to provide a supplemental or auxiliary heater for a vehicle that is accessible from the exterior of the vehicle. Additionally, no major disassembly is required to change main heater components such as the fuel solenoid, fan motor, fuel orifice, ignition, flame detection, etc. 
         [0024]    It is yet another aspect of various embodiments of the present invention to provide a heat source—preferably a natural gas or propane fuel-burning heat source—to heat the heat transfer medium (for example, coolant). In some embodiments, a tank agitation device may also be provided to provide efficient heat transfer to the heat transfer tank and/or fluid located within the tank. An optional heating loop may also be provided for engine preheating. 
         [0025]    It is another aspect of embodiments to provide the fuel gas in the fuel gas supply line with a negative pressure relative to atmospheric pressure and provide a valve or switch directly adjoining the fuel gas supply line. 
         [0026]    It is a further aspect of embodiments of the present invention to provide a system with a specific back pressure, which is not in other products on the market today. This specific back pressure holds the heat range and is an important part of the functionality of the system. 
         [0027]    It is one aspect of embodiments of the present invention to provide a supplemental heater for a vehicle that has reduced emissions. In one embodiment, emissions are reduced by mixing the air and fuel (e.g., natural gas or propane) before the air or fuel enters the burner air-mixing tube. 
         [0028]    Fuel-burning heaters often require some minimum cycle time in order to ignite, burn, and extinguish safely. This is called one burn cycle. The post-burn period must be long enough to clear any residual combustibles from the burn chamber before it tries to re-ignite in order to permit cool down of the heater components and to exhaust combustion byproducts from the combustion chamber. The burn time must be long enough for the burn chamber to get hot enough to clear itself of any unburned material such as fuel, smoke, or soot often caused during startup. Of course, heat is not delivered until the flame is ignited and has burned long enough to heat its immediate surroundings. This is why the burn cycle must be started earlier than non-combustion heat sources and must run for a minimum length of time without overheating before it is allowed to turn off. Thus, it is one aspect of embodiments of the present invention to provide a combination of sensors, sensor locations, and controls to achieve the desired results. 
         [0029]    It is another aspect of embodiments to provide a supplemental heater with a device to ensure all unburnt fuel is not released into the environment. It is also an aspect of embodiments of the present invention to reduce the emission of unburned hydrocarbons in mobile heating devices. Upon shutting down the burner, typically residual fuel is still present in the fuel supply and in an inlet region of the burner. Unconsumed fuel constituents can still be present in the region of the burner. In typical mobile heating devices, usually hydrocarbon compositions are used as fuel. Thus, the remaining residual fuel and the fuel constituents typically are hydrocarbons. When the burner is inoperative, these unburned hydrocarbons may evaporate in the heating device and pass to the exterior of the heating device via the combustion air supply and the exhaust gas outlet (potentially via sound absorbers which may be provided in some embodiments). 
         [0030]    One aspect of embodiments of the present invention is to provide a waste gas removal system, which can include a filter. To reliably prevent the discharge of waste gases via the waste gas removal system, the waste gas emission suppression arrangement associated with the waste gas removal system may comprise a closing arrangement closing a waste gas-carrying duct. Since the waste gases, on the other hand, and the waste gases being carried during the combustion operation flow through the waste gas removal system in the same direction, it is not possible, in principle, to use filter material in the waste gas removal system, because the combustion waste gases now flowing through such a filter material during the combustion operation would absorb the waste gas absorbed in the filter material and transport them to the outside into the environment. The provision of a closing arrangement rather ensures a state of the waste gas removal system that is also closed against the emission of waste gases, especially when the vehicle heating system is not in operation. To keep the volume being gradually filled with waste gases in the inoperative state as small as possible, the closing arrangement should be positioned as close to the waste gas discharge of the burner arrangement as possible. In one embodiment that can be embodied with an especially simple design, the closing arrangement may comprise a siphon unit, similar to U.S. Patent Publication No. 2014/0008449 to Eger et al., which is incorporated by reference herein in its entirety. The combustion waste gases leaving the combustion chamber can flow through this siphon unit at the pressure difference present during the combustion operation. However, since the waste gases escaping from unburned fuel cannot build up such a high pressure in the inoperative state, the siphon unit reliably ensures that waste gases cannot escape to the outside. 
         [0031]    It is yet another aspect of embodiments of the present invention to provide a supplemental heater for vehicles that efficiently and effectively introduce air and fuel to the supplemental heater&#39;s combustion chamber, performs the combustion, and provides heat to the vehicle&#39;s coolant system. 
         [0032]    It is another aspect of embodiments of the present invention to provide a heater that reduces wear and tear on the heater such that the heater lasts longer. Thus, the heater will maintain a constant run cycle (i.e., heat input to the vehicle), which provides even heating to the vehicle rather than a fast heat cycle, which creates a large heat input to the vehicle, followed by a quick cool down where little to no heat is provided to the vehicle. 
         [0033]    During a normal purge stage, which may be approximately one minute to 2.5 minutes, or more specifically 90 seconds, the burner chamber, the exhaust system, and the thin jacket or coil are subjected to thermal stresses from the repeated cooling of the structure. The thermal stresses decrease the operating life of the burner and the thin jacket. Thus, it is one aspect of embodiments of the present invention to provide a method and an apparatus to overcome the above-described rapid cycling of the supplemental burner without wasting the excess heat produced by the supplemental burner. 
         [0034]    It is another aspect of embodiments of the invention to provide quiet interior heating. Low-velocity heat exchangers provide quiet interior heating in one embodiment. Temperatures can be controlled in separate (one or more) heating areas independently. The supplemental heater can provide uniform, draft-free heating; no hot and cold air pockets. The heater provides safety features such as automatic shut-down in case of low voltage or overheat. The AC-powered electric heating element can provide heating and domestic hot water during low demand periods. The supplemental heater can use the vehicle&#39;s on-board natural gas or propane fuel, thus there is no need for propane or natural gas fuel to supply heat. The unit can provide low natural gas or propane fuel usage and low electrical DC power consumption. 
         [0035]    One aspect of embodiments of the invention is to provide sound absorbers adapted to absorb the above described noise at the combustion air supply and/or at the exhaust gas outlet in mobile heating devices. Usually, these sound absorbers are provided outside of the actual heating device in a combustion air supply pipe and/or in an exhaust gas outlet pipe. Sound absorbers of this kind can be formed as absorption-type sound absorbers absorbing the noise or as reflection-type sound absorbers multiply reflecting and refracting the noise. Realization as an absorption-type sound absorber enables space-saving accommodation of the sound absorber. Absorbers similar to the ones described in U.S. Patent Publication No. 2011/0114741 to Kaindl, which is incorporated by reference herein in its entirety, can be used. 
         [0036]    It is another aspect of embodiments to overcome the shortcomings of the prior art by providing a means for heating the interior of a motor vehicle having an independent electrical circuit and coolant pump that utilizes maximum latent heat usage from a shut down engine to conserve fuel. Weight sensors are provided in the seats to detect the presence of a passenger therein and activate said system once the engine is turned off. The secondary heating system of the present invention further can include a periodic shut down at preset intervals to extend battery usage. Canadian Patent No. CA 2796793A is incorporated by reference herein in its entirety. 
         [0037]    It is one aspect of embodiments of the present invention to provide an electric auxiliary heating unit that reliably avoids temperature overshoots of the heated air. To this end, the temperature of the air flowing into the heating is determined and converted into a heating power for controlling the heating elements. This is preferably done via a stored characteristic field via which a plurality of vehicle parameters, such as the vehicle speed, the opening condition of the convertible top, etc., can be taken into account. Also, the temperature of the incoming air can be derived from temperature values which are already available in the vehicle. A user-friendly electric heating can be realized very easily in this way. Temperature fluctuations in the heated air can be avoided reliably and easily even in the case of dynamically varying operating conditions of the motor vehicle. U.S. Pat. No. 8,660,747 to Bolender et al. is incorporated by reference herein in its entirety. 
         [0038]    In one embodiment of the present invention, a novel natural gas or propane fuel operated heater selectively distributes or fully distributes heat to the vehicle&#39;s occupant compartments and/or the vehicle&#39;s main engine. Some embodiments may also include optional added heat exchangers throughout the coolant system to distribute heated coolant from an on-board auxiliary coolant heater in a motor vehicle, such as a highway truck. In some embodiments, the heating medium (e.g., coolant) preferably contains an antifreeze, such as ethylene glycol, for example. 
         [0039]    Some embodiments provide engine pre-heating to a cold engine prior to starting the engine. The coolant circuit also allows engine-heated coolant and/or auxiliary heater heated coolant to heat the occupant compartment(s) when the engine is running. U.S. Pat. No. 7,793,856 to Hernandez et al. is incorporated by reference herein in its entirety to provide further description and support. 
         [0040]    In some embodiments, the coolant flow control system comprises flow paths, connecting the engine ports, the occupant compartment heater ports, and the auxiliary coolant heater ports. By selective operation of the valve assembly, the flow control system can be placed in a first state to divert the coolant flow from the auxiliary heater through the engine, and can be placed in a second state to cause the coolant to flow from the auxiliary heater outlet to the compartment heat exchangers. 
         [0041]    In some embodiments, a gas-fired heater may be used, such as the one described in German Patent Application No. 12336683, which is incorporated by reference herein in its entirety. Typically the gas fuel is supplied to the heater with a pressure that exceeds atmospheric pressure, so that a solenoid valve triggered by an electronic control device is essential to control the gas supply. 
         [0042]    In one embodiment, the system may also comprise a gas/fuel leak detector or gas analyzer. The leak detector should be sensitive such that it shall be able to detect a low limit of 1% LEL. 
         [0043]    In one embodiment, a hydrocarbon storing element comprises a structure capable of being flown through having a large surface in relation to its volume. In this case, it is reliably ensured that the hydrocarbon storing element comes into contact with the evaporating unburned hydrocarbons. Formation of a large surface in relation to the volume allows space-saving, efficient storing of hydrocarbon emissions. A remarkable amount of such emissions can be stored in small space. Realization can e.g. be accomplished by open-pored porous structures, such as e.g. sponge-like or foam-like structures, fabric structures, three-dimensional grid structures, and the like. A further advantage in this case is that the hydrocarbon storing element can simultaneously serve as a sound absorbing element of a sound absorber, such as e.g. of a combustion air sound absorber or exhaust gas sound absorber. Thus, sound absorption and emission reduction can be integrated in one component. 
         [0044]    In various embodiments, the supplementary heater may comprise a water jacket. One such water jacket is described in U.S. Pat. No. 4,300,720 to Baier et al., which is incorporated by reference herein in its entirety. The water jacket may be insulated to prevent or minimize heat from escaping the system. Further, the water jacket may be sized such that it provides for a clean burn and thus the heater&#39;s emissions a very low. In one embodiment, the water jacket may be approximately 5 to 10 inches in diameter. In a preferred embodiment, the water jacket may be approximately 6 to 9 inches in diameter. In a more preferred embodiment, the water jacket may be approximately 8 inches in diameter. Additionally, the tank within the water jacket (i.e., the tank that contains the hot gas from the combustion chamber), which may be called a heat exchanger tank herein, may be sized to further increase efficiency and reduce emissions. In one embodiment, the heat exchanger tank may be approximately 4 to 9 inches in diameter. In a preferred embodiment, the heat exchanger tank may be approximately 5 to 8 inches in diameter. In a more preferred embodiment, the heat exchanger tank may be approximately 7 inches in diameter. 
         [0045]    In one embodiment, the water jacket can withstands operating pressure 2 bar or twice operating pressure, whichever is greatest (EC Directive 70/156/EEC). Further, the heat exchanger may be painted to withstand operating temperatures (800° F.) and environment conditions during normal use, such as cleaning chemicals found in maintenance facilities, salt mist, etc. 
         [0046]    According to one embodiment, a valve or switch is actuated by means of a membrane that causes the fuel gas supply line to close when the fan stops or its rpm is very low. A switch of this type, configured with a membrane, can be manufactured economically. This embodiment is especially simple when the fuel gas at the fuel gas inlet opening has a negative pressure relative to atmospheric pressure of roughly 10 to 20 pa and when the membrane directly abuts the fuel gas inlet opening. 
         [0047]    In one embodiment, the air and fuel gas are mixed in a plenum before entering the combustion chamber. In another embodiment, preparation of the combustion air/fuel gas mixture is improved by the use of a diffuser or a partition wall for swirling the mixture between the fan and the combustion chamber and by the fact that the plenum is protected from the heat radiated rearward from the combustion chamber by a heat shield or refractory. For further support and enablement, see U.S. Pat. No. 5,738,506 to Mosig, which is incorporated by reference herein in its entirety. In an additional embodiment, the air and fuel may be further mixed by a screen mesh flame tube. 
         [0048]    In one embodiment, the fuel gas is made available in fuel gas supply line by repeatedly dropping the pressure by a pressure change Δp which is, preferably, 10-20 pa under atmospheric pressure. For this reason, when the fan stops or the fan rpm is very low, the membrane is automatically placed in front of the mouth of fuel gas supply line and blocks it. 
         [0049]    In various embodiments, the heating system includes controls for monitoring safe operation, monitoring main power for heating system, and monitoring auxiliary methods for supply input voltages. Additional input power may be supplied from the vehicle&#39;s power source or, alternatively, grid power, which is also known as shore power or line voltage. 
         [0050]    In some embodiments, the coolant system includes engine ports, various heat exchanger ports (in compartments such as cabs or work areas, for example), and fluid-to-fluid or fluid-to-air heat exchangers. 
         [0051]    In one embodiment of the present invention, an auxiliary heater comprises an inlet port through which coolant enters the auxiliary heater for heating and an outlet port through which heated coolant exits the auxiliary heater. 
         [0052]    In another embodiment, an occupant or work compartment has an interior space that is heated by a compartment heater having an inlet port through which coolant enters and an outlet port through which coolant exits. 
         [0053]    In one embodiment, a pump may circulate the coolant from a return conduit or fluid path to a heat transfer coil. The coil receives thermal energy from the heat transfer liquid and heats the coolant. The coolant is pumped through the supply conduit to the engine where it is circulated within the engine to heat the engine to a desired temperature. When the engine is operating, the flow of coolant can be reversed to provide heated coolant to the coil for heating the liquid. 
         [0054]    Sensors may be placed throughout the systems of embodiments at various locations. In one embodiment, the fluid, e.g. the coolant, passes the first temperature sensor, passes through the first heat transfer device and exits the auxiliary heater at an outlet. This heated fluid can be used for any appropriate purpose. While the fluid is being heated in this matter, the first temperature sensor will sense the cooler temperature of the cold inlet fluid. This low sensed temperature will cause the compartment heat exchanger circuit to be temporarily deactivated (e.g., zone pumps will be turned off) so that all the heating is directed to the heating of this cold inlet fluid. This cold inlet fluid can draw down the temperature of the heating medium quickly, because the first heat transfer device located within the tank typically has a high heat transfer capacity and the tank typically has a low volume. For example, the first heat transfer device can be a water jacket or can be about 20-40 linear feet of coiled copper. It will be appreciated that any appropriate heat transfer device (e.g., tubular, plates, etc.) can be employed. Furthermore, the system may include an ambient air thermometer that prevents operation of the supplemental heater when the ambient temperature is above a predetermined value (e.g., 45° F.) to save fuel when the heater is not required. However, this may be overridden such that an operator can turn on the heater even when the ambient temperature is above the predetermined value. The system may also include a timer, as is known in the art. 
         [0055]    For example, a suitable temperature sensor is a mechanical snap disk manufactured by Elmwood Sensors. The mechanical snap disk is preset at a desired temperature, e.g., 120° F. When the temperature reaches or falls below the preset temperature, a disk pops out which electrically deactivates other heating circuits. For example, when the disk pops out, an electrical circuit can be broken thus turning off the zone pumps and the engine preheat pump. Other suitable deactivation devices and techniques can also be employed. 
         [0056]    In one embodiment, the heater may comprise an orifice that leads to the combustion chamber. To ignite the fuel-air mixture, an ignition electrode is provided and is supplied with electrical energy via an ignition spark generator, which is located outside of the housing part of the combustion chamber or the water jacket. An ignition electrode extends parallel to the outer wall of the combustion chamber, which is provided with openings. In one embodiment, the spark igniter may be a 10 kV igniter. The fuel gases leave the combustion chamber on the end opposite the gas entrance, where they are reversed and discharged from the heater via an exhaust gas channel and exhaust connection. In doing so, most of the thermal energy is extracted from the exhaust gases via the heat exchanger. For this reason, water flows through a water jacket which surrounds combustion chamber and may also surround the exhaust gas channel in a spiral in counterflow, entering heat exchanger via the inlet port and leaving the heater at the outlet port. 
         [0057]    Often in cold temperatures, the propane or natural gas engine will not start because the air intake butterfly valve freezes shut in the closed position. In various embodiments, a supplemental heater provides heat to the engine, fuel intake, manifold, and air intake valve such that the butterfly valve will defrost and open during engine start. Additionally, the engine of a vehicle may lose power while the vehicle is in route if the butterfly valve sticks due to cold temperatures. The supplemental heater eliminates this problem by providing heat to the engine, fuel intake, manifold, and air intake valve. 
         [0058]    If outside temperatures are very cold (e.g., below −20° F.), the engine may lose power while in use and while the vehicle is in transit because condensation on the exhaust freezes and blocks the exhaust. This is due to the air at the air intake having 100% relative humidity, low temperatures on the exhaust exterior, and the fuel having a very low temperature. In some embodiments, the supplemental heater may heat the engine in order to increase the engine temperature and possibly melt the condensation on the exhaust. 
         [0059]    In one embodiment, the associated electrical control system comprises an auxiliary heat control, a main HVAC control, a blower/temperature control, and an engine pre-heat control. The particular details of the blower/temperature control in any specific vehicle may depend on the specific vehicle. The main control may comprise controls that are available to the driver for the blower/temperature control when the vehicle is being driven, but that may also be effective in certain ways when the vehicle is not being driven and the engine is off. The auxiliary control may be either independent of or integrated with the main control. Either way, the auxiliary control may have control of the valve assembly and when the auxiliary control requests that the valve assembly be energized, the auxiliary control causes the valve assembly to be open. 
         [0060]    With the auxiliary control off, the main HVAC controls that are accessible to the driver control the blower system and temperature of air that is heated by the heater due to flow of engine-heated coolant through the heater. The flow of heated air is directed by an air distribution system that may take any of various forms for distributing the heater air inside a vehicle compartment. The air may be distributed for any one or more of windshield defrosting, driver&#39;s compartment heating, and sleeper compartment heating when the truck has a sleeper compartment. 
         [0061]    An over-temperature sensor may be provided for the burner and an over-temperature sensor may be provided for the electric heater. These two sensors will shut down the burner and electric heater, respectively, if an over-temperature is reached (e.g., 140° F., 190° F., or 240° F.). This provides a back-up safety feature to prevent overheating. A low-water cutoff switch may also be provided to shut down operation of the heater in the event that the heating medium falls below a minimum level. This is yet another safety feature. 
         [0062]    In some embodiments, to supply the thermal load of compartment (room air) heat exchangers, a vehicle is provided with the auxiliary heating system having a peak thermal output of about 40,000-50,000 BTU/hr. The auxiliary system may include a propane or natural gas-fired burner. In one embodiment, the burner is a burner manufactured by Webasto AG having a thermal output of approximately 45,000 BTU/hr. Such a burner is normally shipped with a combustion chamber in the form of a closed horizontal cylinder having an air/fuel inlet at one end and an exhaust pipe at the other end. 
         [0063]    In various embodiments, a propane-fuel supplemental heater is equipped with an AC electric heating element. The heater may provide both coolant heating and domestic water heating. The heater may include two or more thermostatic heating zones, two or more zone heating circulation loops, one or more cozy heat exchangers, bay heating, electronic controllers, over 50,000 BTU/hr output. The heater may use AC shore power for light-duty heating and hot water use. The heater may also use propane fuel for heating in colder temperatures and to provide continuous hot water. 
         [0064]    In one embodiment, a motor vehicle is provided comprising: fluid; an engine comprising a first port through which the fluid can leave the engine and a second port through which the fluid can return to the engine, wherein the engine is one of a propane-operated engine and a natural gas-operated engine; a first heat requirement that is heated by a compartment heater having an inlet port through which the fluid enters, an outlet port through which the fluid exits, and a heat exchanger; an auxiliary coolant heater system comprising: an inlet port through which the fluid enters the auxiliary coolant heater system for heating; an outlet port through which heated fluid exits the auxiliary coolant heater system; a blower; a combustion chamber comprising an igniter and a burner tube; a plenum; a heat transfer medium; and an exhaust; and a coolant flow control system comprising: a first flow path that connects the compartment heater inlet port, the compartment heater outlet port, the auxiliary coolant heater inlet port, and the auxiliary coolant heater outlet port such that the first flow path provides for the fluid to flow from the auxiliary coolant heater outlet port through the compartment heater and back to the auxiliary coolant heater inlet port; a second flow path that connects the engine first port, the engine second port, the auxiliary coolant heater inlet port, and the auxiliary coolant heater outlet port such that the second flow path provides for heated fluid to flow from the auxiliary coolant heater outlet port to the engine second port to heat the engine; and a fluid pump. In an additional embodiment, the auxiliary coolant heater system may operate on at least one of propane and natural gas. Furthermore, the heat transfer medium may be a tank that encases at least a portion of the fluid around the combustion chamber. Alternatively, the heat transfer medium may be copper tubing comprising the fluid, wherein the copper tubing is positioned proximate to the combustion chamber 
         [0065]    In one embodiment, a motor vehicle heating system is provided comprising: an engine comprising a first port through which a fluid leaves the engine and a second port through which the fluid returns to the engine, wherein the engine is one of a propane-operated engine and a natural gas-operated engine; a compartment heater having an inlet port through which the fluid enters, an outlet port through which the fluid exits, and a heat exchanger; an auxiliary coolant heater system comprising: an inlet port through which the fluid enters the auxiliary coolant heater system; an outlet port through which heated fluid exits the auxiliary coolant heater system; a blower; a combustion chamber comprising an igniter and a burner tube; a plenum; a heat transfer medium; and an exhaust port; and a coolant flow control system comprising: a first flow path that interconnects the compartment heater inlet port, the compartment heater outlet port, the auxiliary coolant heater inlet port, and the auxiliary coolant heater outlet port such that the first flow path provides for the coolant fluid to flow from the auxiliary coolant heater outlet port through the compartment heater and back to the auxiliary coolant heater inlet port; a second flow path that connects the engine first port, the engine second port, the auxiliary coolant heater inlet port, and the auxiliary coolant heater outlet port such that the second flow path provides for heated coolant fluid to flow from the auxiliary coolant heater outlet port to the engine second port to heat the engine; and a fluid pump. In some embodiments, the first flow path is in fluid communication with the compartment heater inlet port, the compartment heater outlet port, the auxiliary coolant heater inlet port, and the auxiliary coolant heater outlet port and the second flow path is in fluid communication with the engine first port, the engine second port, the auxiliary coolant heater inlet port, and the auxiliary coolant heater outlet port. 
         [0066]    In some embodiments, the coolant flow control system may further comprise a valve assembly having a first state and a second state. Additionally, the vehicle engine may be a liquid-cooled combustion engine. In alternative embodiments, the coolant fluid may be a mixture of water and coolant. 
         [0067]    In one embodiment, an auxiliary coolant heater system for a vehicle is provided comprising: coolant fluid; an inlet port through which the coolant fluid enters the auxiliary coolant heater system for heating; an outlet port through which heated coolant fluid exits the auxiliary coolant heater system; a blower; a combustion chamber comprising an igniter and a burner tube; a plenum; a water jacket; an exhaust; a first flow path for the heated coolant fluid that connects the outlet port to an inlet port of at least one of a vehicle engine, a compartment heat exchanger, a hydraulics heat exchanger, a fuel regulator, and an oil pan heat exchanger, a second flow path for the heated coolant fluid, wherein the second flow path connects the outlet port to an in-line heater, and wherein the in-line heater is interconnected to the vehicle engine; and a fluid pump. 
         [0068]    In some embodiments, the water jacket surrounds a heat exchanger tank, wherein the heat exchanger tank surrounds the combustion chamber, and wherein coolant fluid is positioned between the water jacket and the heat exchanger tank such that the coolant fluid is in a heat transfer relationship with the heat exchanger tank and the water jacket. 
         [0069]    In one embodiment, a method of heating a vehicle engine is provided comprising: providing coolant fluid; providing an engine comprising a first port through which the coolant fluid can leave the engine and a second port through which the coolant fluid can return to the engine, wherein the engine is one of a propane-operated engine and a natural gas-operated engine; providing a first heat requirement that is heated by a compartment heater having an inlet port through which the coolant fluid enters, an outlet port through which the coolant fluid exits, and a heat exchanger; providing an auxiliary coolant heater system comprising: an inlet port through which the coolant fluid enters the auxiliary coolant heater system for heating; an outlet port through which heated coolant fluid exits the auxiliary coolant heater system; a combustion chamber comprising an igniter and a burner tube; a heat transfer medium; and an exhaust; providing one or more flow paths; burning a mixture of air and at least one of propane fuel and natural gas fuel in the combustion chamber; transferring heat from the combustion air-fuel mixture to the heat transfer medium; transferring heat from the heat transfer medium to at least one of the engine, a compartment, a hydraulic system, an oil pan, and a fuel regulator. 
         [0070]    In one embodiment, a method of manufacture is provided. The method comprises: placing combustion tubes on the fixture and installing the alignment plug, placing the fins in the fixture, tacking the top side of fins in place, removing the alignment plug and combustion tube assembly from the fixture, rotating the combustion tube assembly and attacking the bottom side of the fins in place followed by each slot in the fin, welding the fins into the tube, tacking the end cap onto the tube assembly, and welding the end cap onto the tube assembly. The method may further include tacking a coupler to the exhaust tube, welding the coupler to the exhaust tube, tacking the exhaust tube assembly to the combustion tube assembly, welding the exhaust tube assembly to the combustion tube assembly, performing a first leak check, and performing a second leak check. The method may also include tacking the combustion chamber tube to the flange, welding the flame tube flange stud holes closed, and welding the combustion chamber tube to the flange. In one embodiment, the method includes tacking a helix to the heat exchanger tube, removing a exhaust tab from the water jacket tube, installing the heat exchanger tank in the water jacket, tacking the exhaust steam, tacking the exhaust tab to the water jacket tube, welding the exhaust tab seams, welding the exhaust port seam, placing mounting feet in the fixture, placing the end cap in the fixture, placing the water jacket assembly in the fixture, placing a mounting flange in the fixture, and tacking the mounting feet to the heat exchanger and water jacket assembly. In some embodiments the method includes tacking an end cap on the water jacket tube, tacking a mounting flange on the heat exchanger tank and water jacket assembly, welding studs to the flange, welding an end cap onto the water jacket tube, welding a mounting flange on to the heat exchanger tank and water jacket assembly, welding the backside of the mounting flange to the water jacket assembly, taking an inlet and an outlet ports to the water jacket, welding the inlet and outlet ports to the water jacket, welding a thermostat mount to the water jacket, and removing all excess spatter from the assembly. The water jacket may further be manufactured by installing test fittings, doing a first leak check, performing a second leak check, removing the test fittings, cleaning the heat exchanger tank, masking the heat exchanger tank, painting the heat exchanger tank, and removing the mask from the heat exchanger assembly. The electronics may be manufactured and assembled into the system through the steps of: inserting control thermostat terminal in one or more connector and install a wedgelock, installing control thermostats, crimping terminals, inserting hi-limit thermostat terminal and installing a wedgelock, installing hi-limit thermostats, installing a first combustion chamber gasket, installing the combustion chamber inside the heat exchanger, and installing a second combustion chamber gasket. The method may also include installing an over inlet hose, installing grommets, installing an inlet formed hose, installing clamps on the inlet formed hose, installing pump suction hoses, fastening grounds and a ground strap to a ground stud, and fastening an amphenol connector to the enclosure wall. The method may include fastening a harness and a ground trap to the enclosure, placing the water jacket assembly in the enclosure base, riveting the water jacket to the enclosure, installing clamps, installing an outlet hose, installing a dust cover on the pump, and inserting pump wire terminals in a connector. The method may include manufacturing the plenum by tacking and welding components together, such as the baffle, the plenum front half, the plenum back half, the mixing tube, the flame tube, the burner, the burner mount flange, and the igniter mount block. Further, various components of the system may be tested for functionality. In some embodiments, wires, valves, connectors, and compression fittings may be installed. The heater or burner may be manufactured by fastening a burner premix head to a burner mount flange, installing a refractory igniter insulation element, fastening a flame sensor to a burner mount flange assembly, setting the flame sensor spacing, fastening a flame igniter to the burner mounting flange, installing a small hose barb in the plenum, installing a gas orifice fitting in an orifice holder, and applying a thin layer of grease to the orifice holder flange. Further, the method may include fastening a orifice holder flange to the plenum, drilling and taping a hole in the blower or fan casing, installing a small hose barb in the blower casing, installing studs in the blower mounting flange, fasting air shutter to the blower mounting flange, and fastening the blower to the air shutter assembly bracket. Then air shutter assembly may then be fastened to the plenum. The method of manufacture may include installing clamps, suction hoses, and other items on the pump. Additionally, the bottom pressure switch may be fastened to the enclosure wall and connecting tube may be installed. In one embodiment, a switch and an electrical component box is fastened to the enclosure wall and the igniter is interconnected to an igniter cable. In some embodiments, a timer is installed and a low voltage disconnect is installed in the system. Additional inlet ports, outlet ports, and tubing may also be installed in some embodiments. Domestic hot water heaters and other heat exchangers may be installed in the system in further embodiments. In one embodiment, a regulator is installed and a nipple is stalled in the nipple regulator. The method may also include installing a gas valve into the system. 
         [0071]    The phrases “at least one”, “one or more”, and “and/or”, as used herein, are open-ended expressions that are both conjunctive and disjunctive in operation. For example, each of the expressions “at least one of A, B and C”, “at least one of A, B, or C”, “one or more of A, B, and C”, “one or more of A, B, or C” and “A, B, and/or C” means A alone, B alone, C alone, A and B together, A and C together, B and C together, or A, B and C together. 
         [0072]    Unless otherwise indicated, all numbers expressing quantities, dimensions, conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term “about”. 
         [0073]    The term “a” or “an” entity, as used herein, refers to one or more of that entity. As such, the terms “a” (or “an”), “one or more” and “at least one” can be used interchangeably herein. 
         [0074]    The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Accordingly, the terms “including,” “comprising,” or “having” and variations thereof can be used interchangeably herein. 
         [0075]    It shall be understood that the term “means” as used herein shall be given its broadest possible interpretation in accordance with 35 U.S.C., Section 112, Paragraph 6. Accordingly, a claim incorporating the term “means” shall cover all structures, materials, or acts set forth herein, and all of the equivalents thereof. Further, the structures, materials, or acts and the equivalents thereof shall include all those described in the summary of the invention, brief description of the drawings, detailed description, abstract, and claims themselves. 
         [0076]    The Summary of the Invention is neither intended nor should it be construed as being representative of the full extent and scope of the present invention. Moreover, references made herein to “the present invention” or aspects thereof should be understood to mean certain embodiments of the present invention and should not necessarily be construed as limiting all embodiments to a particular description. The present invention is set forth in various levels of detail in the Summary of the Invention as well as in the attached drawings and the Detailed Description and no limitation as to the scope of the present invention is intended by either the inclusion or non-inclusion of elements, components, etc. in this Summary of the Invention. Additional aspects of the present invention will become more readily apparent from the Detailed Description, particularly when taken together with the drawings. 
         [0077]    These and other advantages will be apparent from the disclosure of the invention(s) contained herein. The above-described embodiments, objectives, and configurations are neither complete nor exhaustive. As will be appreciated, other embodiments of the invention are possible using, alone or in combination, one or more of the features set forth above or described in detail below. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0078]    Those of skill in the art will recognize that the following description is merely illustrative of the principles of the present invention, which may be applied in various ways to provide many different alternative embodiments. This description is made for illustrating the general principles of the teachings of this invention and is not meant to limit the inventive concepts disclosed herein. 
           [0079]    The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and together with the general description of the invention given above and the detailed description of the drawings given below, serve to explain the principles of the invention. 
           [0080]      FIG. 1A  is a flow diagram showing one embodiment of a vehicle engine&#39;s cooling system; 
           [0081]      FIG. 1B  is an alternate embodiment of a section of the flow diagram of  FIG. 1A ; 
           [0082]      FIG. 2  is a flow diagram showing a second embodiment of the vehicle engine&#39;s cooling system; 
           [0083]      FIG. 3  shows the heat transfer options in an embodiment of a heat exchanger; 
           [0084]      FIG. 4  shows an embodiment of the electrical, controlling, and monitoring of the vehicle heater and associated systems; 
           [0085]      FIG. 5  is perspective view of a vehicle provided with a heating apparatus for providing supplemental thermal energy for occupant compartment air and main engine heating; 
           [0086]      FIG. 6A  is a front elevation view of an embodiment of a supplemental heater; 
           [0087]      FIG. 6B  is a cross-sectional view of the supplemental heater of  FIG. 6A  taken at cut A-A; 
           [0088]      FIG. 7A  is a front elevation view of a second embodiment of a supplemental heater; 
           [0089]      FIG. 7B  is a perspective view of section B-B of the supplemental heater of  FIG. 7A ; 
           [0090]      FIG. 7C  is a front elevation view of a third embodiment of a supplemental heater; 
           [0091]      FIG. 7D  is a perspective view of section D-D of the supplemental heater of  FIG. 7C ; 
           [0092]      FIG. 8  is an embodiment of a vehicle heating system that includes a supplemental heater and one or more heat exchangers; 
           [0093]      FIG. 9  is an embodiment of a compartment heat exchanger system; 
           [0094]      FIG. 10A  shows a single closed-circuit supplemental heater; 
           [0095]      FIG. 10B  shows a single closed-circuit supplemental heater interconnected to a vehicle engine; 
           [0096]      FIG. 11  is a front right perspective view of a fourth embodiment of a supplemental heater; 
           [0097]      FIG. 12  is a front left perspective view of the supplemental heater of  FIG. 11 ; 
           [0098]      FIG. 13  is a front right perspective view of the supplemental heater of  FIG. 11  shown without the water jacket; 
           [0099]      FIG. 14  is a top plan view of the supplemental heater of  FIG. 11 ; 
           [0100]      FIG. 15  is a bottom plan view of the supplemental heater of  FIG. 11 ; 
           [0101]      FIG. 16  is a front right perspective view of the supplemental heater of  FIG. 11  with an enclosure; 
           [0102]      FIG. 17  is a rear left perspective view of the supplemental heater of  FIG. 16 ; 
           [0103]      FIG. 18  is a front elevation view of a fifth embodiment of a supplemental heater with an exhaust pipe; 
           [0104]      FIG. 19A  is a perspective view of one embodiment of a heater; 
           [0105]      FIG. 19B  is a perspective view of a second embodiment of a heater; 
           [0106]      FIG. 20  is a top perspective view of one embodiment of a multi-circuit supplemental heating system; 
           [0107]      FIG. 21  is an exploded perspective view of an embodiment of a single-circuit supplemental heater; 
           [0108]      FIG. 22  is an exploded perspective view of an embodiment of a triple-circuit supplemental heater; 
           [0109]      FIG. 23  is a flow chart of the operation of a supplemental heater according to one embodiment; 
           [0110]      FIG. 24  is a chart showing the cycling of a supplemental heater according to one embodiment; 
           [0111]      FIG. 25  is a flow chart of a vehicle&#39;s coolant system without a supplementary heater; 
           [0112]      FIG. 26  is a flow chart of a vehicle&#39;s coolant system with a supplementary heater; 
           [0113]      FIG. 27A  shows a dual closed-circuit supplemental heater; 
           [0114]      FIG. 27B  shows a dual closed-circuit supplemental heater interconnected to a vehicle engine; 
           [0115]      FIG. 28A  shows a triple closed-circuit supplemental heater; and 
           [0116]      FIG. 28B  shows a triple closed-circuit supplemental heater interconnected to a vehicle engine. 
       
    
    
       [0117]    To assist in the understanding of the embodiments of the present invention the following list of components and associated numbering found in the drawings is provided herein: 
         [0118]    Item Name
         1  Exhaust     2  Vehicle     3  Supply Conduit     4  Return Conduit     5  Heater Conduit     6  Heated Fluid Outlet Port     7  Fuel Valve and Pressure Regulator     8  Blower     9  Air Inlet     10  Coolant Path to Engine     11  Flame Tube     12  Coolant Path Engine Outlet to Fuel Regulator     13  Outlet     14  Coolant Outlet Port     15  Fuel Entry     16  Vehicle Engine     17  Zone     18  Compartment Heat Exchanger     19  (First) Heat Load     20  Coolant Path to Engine     21  Secondary Fuel/Air Mixing     22  Coolant Inlet Port     23  Coolant Return Path from Fuel Regulator     24  Coolant Path in Fuel Regulator     25  (Heated) First Outlet Port     26  Conduit or Heated Fluid Path     27  Inlet Port (of the Heat Exchanger)     28  Coolant Solenoid Valve     29  Inlet     30  Fuel Tank (Propane/Natural Gas)     31  Coolant Pump Inlet Port     31 A Coolant Outlet     31 B Coolant Outlet     31 C Coolant Outlet     32  Engine Coolant Pump     32  Engine Coolant Pump Inlet     33  Heater (Coolant) Outlet Port     34  Air Delivery Location     35  Exiting Port     36  Auxiliary Power     37  Fuel-Air Mixture Delivery Point     38  Conduit or Heated Fluid Path     39  Inlet     40  Heat Load     41  Outlet     42  Fluid Outlet     43  Coolant Reservoir (Fluid Tank); Water Jacket     44  Fuel Regulator     45  Coolant Fill Point     46  Point (Regulated Fuel Supply for Engine)     47  Charging Source     48  Engine Coolant Outlet Port     49  Return Coolant Port     50  Voltage Source     51 A Heated Fluid Circuit     51 B Heated Load Circuit     52  Fuel Solenoid Valve     53  Monitoring     54  Directional Flow Valve     55  Coolant Pump     56  Electric Heating Element     57  Inlet Port     58  Outlet Port     59  Heat Exchanger Tank     60  (Auxiliary) Heater (Coolant) Inlet Port     61  Combustion Flame Area     62  Fuel Solenoid     63  Coolant Pump     64  Engine Coolant Inlet Port     65  (Internal) Coils     66  Inlet     67  Fluid Pump     68  Fuel Delivery     69  Fuel Solenoid     70  Tube     71  (Fluid-to-Fluid or Fluid-to-Gas) Fuel Heat Exchanger     72  Coolant Pump     73  Coolant (Circulation) Pump     74  Combustion/Exhaust Path     75  (Heated Fluid) Inlet Port     76  Return Coolant Path(s)     77  Engine (Coolant) Outlet Port     78  Exiting Port     79  Spark Igniter     80  (Heated Fluid) Outlet Port     81  First Flow Control Solenoid Valve     82  (Natural Gas- or Propane-Operated) (Supplemental or Auxiliary) Heater     83  Entering Port     84  Engine (Coolant) Outlet Port     85  Point (Regulated Fuel Supply for Heater)     86  Heated Load Circuit Outlet     87  Second Flow Control Solenoid Valve     88  Primary Fuel/Air Mixing Location     89  Spiral     90  Plenum     91  Entering Port     92  System Controls     93  End Piece     94  Fuel Orifice     95  Donut (Refractory)     96  Fins     97  Fuel Connection     98  Thermostat     99  Coolant or Fluid     100  Fluid to Fluid Heat Exchanger     100 A Heated Fluid Flow/Circuit     100 B Heated Load Circuit     101  Combustion Chamber     102  Outlet     103  On Signal     104  Flame Sensor     105  Partition     106  Enclosure     107  Pressure Sensor     108  Voltage Monitor     109  Maintenance Switch     110  First Heat Zone Outlet     112  Second Heat Zone Outlet     114  First Heat Zone Inlet     116  Second Heat Zone Inlet     118  Engine Preheat Inlet     120  Engine Preheat Outlet     122  Engine Preheat Circulation Pump     124  Control Thermostat     200  Burner Assembly     202  Exhaust     204  Gas Regulator     206  On/Off/Time 3-Position Switch     208  7-Day Timer     210  Engine Preheating     212  Oil Pan     214  Fuel Pressure Regulator     216  Hydraulics Reservoir     218  Operator Cabin Exchanger     220  Heat Zone Outlet 1     222  Heat Zone Outlet 2     224  Heat Zone 1 Return     226  Heat Zone 2 Return     227  Engine Preheat Circulation Pump     228  Engine Preheat Inlet     230  Engine Preheat Outlet     232  Zone Circulation Pumps     234  Fuel Inlet Outlet     236  Burn Chamber     238  Electric Heating Element     240  Thermal Storage Tank     242  Cold Water In     244  Cold Water Out     246  Water Tempering Valve     250  Cargo/Work Box     252  Water/Fluid Tank       
 
         [0270]    It should be understood that the drawings are not necessarily to scale, and various dimensions may be altered. In certain instances, details that are not necessary for an understanding of the invention or that render other details difficult to perceive may have been omitted. It should be understood, of course, that the invention is not necessarily limited to the particular embodiments illustrated herein. 
       DETAILED DESCRIPTION 
       [0271]    Although the following text sets forth a detailed description of numerous different embodiments, it should be understood that the legal scope of the description is defined by the words of the claims set forth at the end of this disclosure. The detailed description is to be construed as exemplary only and does not describe every possible embodiment since describing every possible embodiment would be impractical, if not impossible. Numerous alternative embodiments could be implemented, using either current technology or technology developed after the filing date of this patent, which would still fall within the scope of the claims. 
         [0272]      FIG. 1A  is a flow diagram showing one embodiment of a vehicle engine cooling system. More specifically,  FIG. 1A  shows the fluid flow circuits of a vehicle engine cooling system. Note that the fluid flow circuits may also be referred to as “systems” and “circuits” herein. In some embodiments, the vehicle engine cooling system comprises multiple fluid flow circuits, for example: a vehicle compartment heat exchanger circuit, a natural gas circuit, an engine coolant circuit, etc. The vehicle engine cooling system of  FIG. 1A  comprises an engine  16 , a compartment (also called a “cab” herein) heat exchanger  18  for compartment heating, a coolant path  12 ,  23  for heating a fuel regulator  44 , and a natural gas- or propane-operated supplemental heater  82 . 
         [0273]    The compartment heat exchanger  18  may be a heat exchanger through which fluid is circulated and have a blower system for moving air across the liquid-to-air heat exchanger to deliver heated air to the occupant compartment. The compartment heat exchanger  18  may also provide heat for the driver&#39;s compartment, for the sleeper compartment, or for both, depending on the particular vehicle model. In some embodiments, the compartment heat exchanger  18  comprises a coolant inlet port  22  through which coolant enters the compartment heat exchanger  18 , a coolant outlet port  14  through which coolant exits the compartment heat exchanger  18 , and a coolant path  10  from the compartment heat exchanger  18  to the engine  16 . A coolant solenoid valve  28  may also be placed between the first engine outlet port  48  and the inlet port  22  of the compartment heat exchanger  18  to shut off flow if, for example, the air conditioner is on. 
         [0274]    In some embodiments, the inlets and outlets may be ¼ inch i.d. hoses. Alternatively, the inlets and outlets may be ½ inch i.d. hoses. In a further embodiment, the inlets and outlets may be any combination of ¼ inch i.d. hoses and ½ inch i.d. hose. 
         [0275]    The engine  16  has two ports—a first engine coolant outlet port  48  and an engine coolant inlet port  64 —that provide for the vehicle compartment heat exchanger  18  to associate with the engine  16 . The first engine coolant outlet port  48  is at an engine coolant supply (pressure) side of the engine  16  and delivers heated coolant to the rest of the system. The engine coolant inlet port  64  is at an engine coolant return (suction) side of the engine  16 , where coolant returns to the engine  16 . The engine  16  may have an engine coolant pump  32  associated with the engine coolant inlet port  64  to create the suction needed to circulate the coolant. 
         [0276]    In some embodiments, the engine  16  cooling/heating system also comprises a fuel (e.g., natural gas) regulator  44 , a coolant path  24  in the fuel regulator  44 , a coolant return path  23  from the fuel regulator  44 , and a coolant path  12  to the fuel regulator  44  from a second engine outlet port  84 . The engine  16  (or supplemental heater  82 , in some embodiments) provides heat to the fuel regulator  44  to manage the fuel regulator  44  temperature at the point where the pressure of the fuel drops from a high pressure to a low pressure for engine  16  use (i.e., fuel source). Without a heating system, the drop in pressure across the regulator  44  is so significant that it would cause some fuel types to freeze and prevent operations (e.g., LPG, CNG, LNG). Thus, the engine  16  also has two ports associated with the fuel (e.g., natural gas or propane) circuit: the second engine coolant outlet port  84  and an engine coolant inlet port  64 . These ports  84 ,  64  provide heated coolant to a natural gas regulator  44 . The second engine coolant outlet port  84  is at an engine coolant supply (pressure) side of the engine  16 , which delivers heated coolant to the regulator  44  by flowing through the coolant path  12  from the second engine outlet port  84  to the regulator  44  and through the coolant path  24  in the fuel regulator  44 . The other port  32  is at an engine coolant return (suction) side where coolant returns to the engine  16 . 
         [0277]    A fuel tank  30  is interconnected to the regulator  44  so that as the fuel leaves the fuel tank  30 , the pressure of the fuel is reduced to a pressure that the system can handle. The fuel then flows through a fuel solenoid valve  52 , which opens when the ignition is on, thus providing fuel for the engine. At point  46  the fuel supply is now regulated for the engine  16  and flows toward the engine  16 . 
         [0278]    If the vehicle is used in a location with an extremely cold climate, then a fluid-to-fluid or fluid-to-gas fuel heat exchanger  71  may be included between the fuel solenoid and the engine  16  to heat the fuel prior to entry into the engine  16 . The fuel heat exchanger  71  may be located in series with the engine cooling system or in a branch circuit (shown in  FIG. 1A ). In some embodiments, the fuel heat exchanger  71  may be interconnected to the engine  16  for heating. Thus, the regulated fuel would enter the fuel heat exchanger  71  at inlet port  57  and exit the fuel heat exchanger  71  through an outlet port  58 . No other auxiliary or supplemental heater on the market heats the fuel (e.g., natural gas or propane) prior to the fuel entering the engine. One such heat exchanger  71  known in the art is the Arctic Fox natural gas and alternative fuel heat exchanger (http://www.arctic-fox.com/fuel-fluid-warming-products/alternative-fuel-warming), which is incorporated by reference herein. 
         [0279]    When the engine  16  is running, it can supply engine-heated coolant to the compartment heat exchanger  18  and a coolant path  24  in the natural gas regulator  44 . When the engine  16  is not running, or if the engine is running but is operating in extremely cold temperatures, an auxiliary or supplemental heater  82  is available for supplying heated coolant to the engine  16 , fuel regulator  44 , and/or compartment heat exchanger  18 . Note that the heater  82  may be called an “auxiliary heater,” a “supplemental heater,” or a “heater” herein. The heater  82  may comprise a pump  73  for circulating engine coolant when the engine  16  is not running and/or when the heater  82  is switched on. The pump  73  may be a self-contained pump and have a pump inlet port  31 . The pumps  73 ,  32  circulate the engine coolant throughout the system. In one embodiment, the coolant pump  73  to the heater outlet port  33  location, which achieves the same result for flow through the heater  82  and the fuel regulator  44 . Coolant enters the auxiliary heater  82  through a heater inlet port  60  and exits the heater  82  through a heater outlet port  33 . The engine also  16  has two ports  77 ,  64  that are associated with the heater  82 : a third engine coolant outlet port  77  and an engine coolant inlet port  64 . The third engine coolant outlet port  77  is at an engine coolant supply (pressure) side that delivers coolant to the heater  82 . The engine coolant inlet port  64  is at an engine coolant return (suction) side where coolant returns to the engine  16  from the heater  82  through a coolant path  20 . The heater  82  provides heated coolant output priority to the engine  16 , because the hottest fluid is supplied to the engine  16 . 
         [0280]    Vehicle heating priority or simultaneous heating to the compartment heat exchanger  18  and the fuel regulator  44  may further be controlled by the heater  82  location and may interconnect to the compartment heat exchanger  18  or the fuel regulator  44  through the connection from a coolant outlet  31 A,  31 B or  31 C to the pump inlet port  31  or from the heater outlet port  33  to the coolant outlet  31 B. Some embodiments may also include a flow directional valve or check valve  54  in line with any of the previous mentioned circuits or flow paths to ensure correct coolant flow direction in through the coolant path  24  in the fuel regulator  44 . 
         [0281]    When the engine  16  is off and the heater  82  is on, coolant flow is started by pump  73 . Coolant is heated through coolant path  20  and through the engine  16 , then coolant exits engine  16  via coolant path  12 . Next, heated coolant heats fuel regulator  44  by flowing through the coolant path  24  and then returns to the heater  82  via the coolant outlet  31 C and coolant pump inlet  31  to establish a full circuit of heated fluid. The flow directional valve  54  ensures flow through this flow path and prevents fluid flow through coolant path  23 . 
         [0282]    When the engine  16  is on and the heater  82  is on or off, the system has increased power/flow due to the engine coolant pump  3 . Thus, the same flow as described above with the engine  16  off is applicable except that the coolant path  23  will begin to flow fluid and coolant path  31 C will flow in the reverse direction due to the increased power of the engine coolant pump  32 . Coolant path  12  will continue to see coolant flow due to the low fluid flow restriction. 
         [0283]      FIG. 1B  is an alternate embodiment of a section of the flow diagram of  FIG. 1A . In  FIG. 1B , the fuel exits the fuel tank  30  and enters a fuel solenoid valve  62 , which may be the vehicle&#39;s existing fuel solenoid valve. In various embodiments, the fuel solenoid valve  62  may be positioned either before or after the fuel regulator  44 . When the heater  82  or engine  16  calls for fuel, the fuel solenoid valve  62  will open such that fuel may flow to the heater  82  or engine  16 . In some embodiments, the fuel solenoid valve  62  may be integrated into the vehicle fuel distribution box. The fuel then flows through the fuel regulator  44  before reaching a fuel connection  97 , which is a safety point. At the fuel connection  97 , the fuel may flow to a first fuel solenoid valve  52  and then to the engine  16  through point  46  or the fuel may flow to a second fuel solenoid valve  69  and then to the heater  85  through point  85  where the fuel is regulated to approximately 125 psi. 
         [0284]      FIG. 2  is a flow diagram showing a second embodiment of the vehicle engine&#39;s cooling system, which includes a coolant reservoir or fluid tank  43 , which may also be called a water jacket. The engine&#39;s cooling system may comprise an optional heater  82  with a fuel-operated heat exchanger in a coolant reservoir  43 . The coolant reservoir  43  may be insulated (not shown) in some embodiments to increase the efficiency of the heater system. The additional coolant reservoir  43  provides heat to the various fluid circuits and systems such that the fluid circuits may be heated together or heated in isolation from one another. In another embodiment, the heater  82  is outfitted with a larger heat exchanger  59 , which is also referred to as a heat exchanger tank or a tank. The heat exchanger tank  59  may be a cylindrical shape or any other shape, such as square or rectangular. This embodiment provides isolation from direct contact to the existing vehicle systems. Further, the heater  82  may further be constructed to facilitate several fluid inlets  23 ,  49 ,  45  and several fluid outlets  25 ,  6 . The vehicle engine&#39;s cooling system may function with the above description of the heater  82  (shown in  FIGS. 1A ,  2 , and  3 ), standalone without the reservoir  43 , or with a heat exchanger tank  59  around the heater  82  heat exchanger. The coolant reservoir  43  may also comprise a coolant fill point  45 , with or without a pressure cap. The coolant reservoir  43  may also be integrated into the various circuits. 
         [0285]    In each fluid circuit, fluid flow control is accomplished by the circuit&#39;s coolant pump  73 ,  55 ,  72 ,  63 ,  57 ,  67  by either a switch-on for heating or a switch-off for no heating. This circuit zone control utilizes the heaters&#39;  82  heated fluid for the preference or priority circuit to heat. 
         [0286]      FIG. 2  illustrates the separation of the engine&#39;s primary coolant circuit by means of a fluid-to-fluid heat exchanger  100 A,  100 B and separation by fluid-to-fluid heat for an engine heating/cooling circuit and a heater circuit. Thus, there may be one path  38  for heated fluid flow  100 A for the heater circuit and a separate path  100 B for the engine heating/cooling circuit. The engine  16  may comprise a coolant outlet  31 A for providing heated coolant to an inlet port  27  of the heat exchanger  100 A,B. The heat exchanger  100 A,B also has an outlet port  86  interconnected to the engine  16  through a flow path  15 . The engine heating/cooling circuit may be associated and/or interconnected to a compartment heating circuit comprising a compartment heat exchanger  18  and a coolant solenoid valve  28  positioned between a first engine outlet port  48  and the compartment heat exchanger  18  to shut off flow of heated coolant if, for example, the air conditioner is on. 
         [0287]    The heater circuit may comprise a path  38  for heated fluid flow  100 A through a heat exchanger  100 A,B, a heat load  40 , a pump  55 , a heated fluid inlet port  75  on the heat exchanger  100 A,B, a heated fluid outlet port  80  on the heat exchanger  100 A,B, a return coolant port  49  on the heater  82  or on the tank  59 , and a heated fluid outlet port  6  on the heater  82  or tank  59 . 
         [0288]    A heat load circuit is a glycol-based fluid system that has a first heat load  19  and a conduit or fluid path  26  exiting the coolant reservoir  43  at a first outlet port  25 . The heat load circuit feeds heat exchanger  51 A,  51 B comprising an entering port  91  and an exiting port  35 . The fluid then returns to the heater  82  via a heater inlet port  60 . The heat exchanger  51 A,B may be a fluid-to-fluid heat exchanger or a plate-to-plate heater exchanger. Advantages of a plate-to-plate heat exchanger are that the fluid for one system or circuit (e.g., zone  17 ) is not required to be the same type of fluid as the fluid in the other system or circuit (e.g., the heat load circuit). Fluid in a zone  17  enters a heater exchanger  51 A,B by movement of the fluid from the activation of a pump  67 . The fluid enters the heat exchanger  51 A,B through an inlet port  83  and exits through an outlet port  78 . The fluid in zone  17  may be hydraulic fluid, domestic-potable or non-potable water, oil, etc. In some embodiments, the hydraulic fluid warmers may need about 4,000 to 10,000 BTU/hr to operate. Examples of hydraulic tank warmers include those made by Arctic Fox. Cab heat exchangers may need about 6,000 to 8,000 BTU/hr to operate. Thus, in some embodiments, a domestic hot water heat exchanger is provided for heating domestic water. Furthermore, the pump  67  would exchange with the requirements of the necessary flow and fluid requirements of zone  17 . A first flow control solenoid valve  81  is shown in heat load circuit to ensure the heated fluid ends in the heat exchanger  51 A,B. The first flow control solenoid valve  81  may be closed, for example, in summer months to ensure no heated coolant flows to heat the hydraulic fluid, if zone  17  is the hydraulic circuit. A second flow control solenoid  87  provides protection in zone  17  in the event zone  17  requires isolation from the heat exchanger  51 A,B. 
         [0289]      FIG. 2  illustrates two heat loads  19 ,  40  for design purposes, only. Other embodiments may include a system with numerous different heat loads (also called heat requirements). Heat loads may include, are not limited to, liquid-to-air heat exchangers, fluid-to-fluid heat exchangers, radiant heaters, and emersion heaters, to name a few. 
         [0290]    In additional embodiments, one or more different heat transfer mediums as previously described may be installed. Further, the inlet ports and outlet ports are not limited to the specific number shown and may also be reduced or increased. 
         [0291]      FIG. 3  shows the heat transfer options in an embodiment of a heat exchanger. Further, the heater  82  may further be constructed to facilitate several fluid inlets  20 ,  39 ,  66  and several fluid outlets  13 ,  41 ,  102 . 
         [0292]      FIG. 3  expands on the innovative solutions for isolating the vehicle heating requirement systems. Thus, the heater  82  is outfitted with a larger heat exchanger tank  59 , thereby providing a novel method of containing the heat exchangers inside the tank  59  to heat the heated fluid or coolant in the coolant reservoir. The heated fluid in the tank  59  may transfer heat to internal coils  65  wrapped around the hot portion of the heater  82 , or may transfer heat to a tube  70  or coil  65  passing through the tank  59 . Fluid entering the tank  59  through the inlet  66  is mixed and heated in the tank  59 . The heated fluid is driven by a fluid pump  73  when it exits the tank  59  through the outlet  41  to return heated fluid to a system or circuit. Fluid entering the inlet  66  and exiting the outlet  41  is not by means of a tube, but rather the tank  59  is part of an isolated system from the tube  70  and coils  65 . The coils  65  are secured, such as by brazing, in a serpentine path or in a circular path to the outer side of the heater  82  so that the fluid in the coil  65  is in heat transfer relationship with the liquid in the tank  59 . Fluid enters the coils  65  through an inlet  29  and exit the coils  65  through an outlet  102 . Fluid in a tube  70  enters the heater  82  or heat exchanger through inlet  39  and exits the heater  82  or heat exchanger through outlet  13 . 
         [0293]      FIG. 4  shows an embodiment of the electrical, controlling, and monitoring of the vehicle heater and associated systems. The diagram also illustrates an added heat source  82  connected to the water jacket or reservoir  43 . Fluid to be heated enters the heater  82  at inlets  76  and heated fluid exits the heater at outlets  42 . The system may also include pumps  73  to circulate the fluid. The system of  FIG. 4  may include a charging source  47  (such as a vehicle alternator or inverter 110/220 VAC to 12 or 24 VDC), a voltage source  50  (12 VDC or 24 VDC), an on signal  103  (which may include controls such as a timer, switches, an ambient thermostat, etc. to activate the heater  82 ), monitoring  53  for the safe starting, operation, and shutdown of the system, system controls  92  to control components outside of the heater enclosure (e.g., coolant pumps, status lights, blower, heat exchanger, coolant solenoid valves, fuel solenoid valves, etc.), and auxiliary power  36  for supplying voltage for electrical heating elements. 
         [0294]      FIG. 5  is perspective view of a vehicle  2  provided with a heating apparatus for providing supplemental thermal energy for occupant compartment air and main engine heating. When assembled, a fluid-tight system is provided for the engine coolant or other heating/cooling fluid. The vehicle  20  may be propelled by an engine  16 . As described above, the vehicle  20  may also be in the form of a boat, in which event the engine  16  propels the boat on the water. The vehicle  2  may also be a trailer that is towed by another self-propelled vehicle. 
         [0295]    The engine  16  may be an internal combustion engine or other type of engine having a liquid coolant system for maintaining the engine  16  at a desired operating temperature. Preferably, when the vehicle  2  is being propelled by the engine  16 , thermal energy is supplied via a conduit  3  that carriers heated engine coolant to a compartment heat exchanger  18  and/or to an auxiliary heater  82 . Cooled coolant is returned to the engine  16  via a return conduit  4 . When the engine  16  is not operating, the engine  16  can optionally be maintained at a desired temperature by supplying heated engine coolant from the auxiliary heater  82  to the engine  16  via the return conduit  4 . Additionally, heated coolant may be provided to a zone  17  to heat additional requirements, such as oil, domestic water, hydraulics, etc. 
         [0296]    In the various forms of the vehicles, separate spaces or rooms can be provided for various living or working activities. In each room, at least one liquid-to-air heat exchanger  18  is provided for heating the room air to a desired temperature. These heat exchangers  18  may be of a standard type known as fan convectors. Heat transfer liquid is supplied to the heat exchangers  18  from the engine  16  (or heater  82  in alternate embodiments) by supply conduit  3  and is returned to the heater by heater conduit  5 . 
         [0297]      FIG. 6A  is a front elevation view of an embodiment of a supplemental heater.  FIG. 6B  is a cross-sectional view of the supplemental heater of  FIG. 6A  taken at cut A-A. The heater  82  may comprise a blower  8  to blow air from an air inlet (not shown) into a plenum  90  at an air delivery location  34  where the air mixes with the fuel at a primary fuel/air mixing location  88 . In one embodiment, the plenum volume is between about 94.5 and 115.5 cubic inches (which may also be the primary air/fuel mixing controlled volume). In a preferred embodiment, the plenum volume is about 105 cubic inches. In one embodiment, the air may enter the plenum  90  at about 50 to 60 CFM. In another embodiment, the combustion air may enter the plenum  90  at between about 10 and 20 CFM. In a first preferred embodiment, the combustion air enters the plenum  90  at between about 12 and 17 CFM (for example, for a propane heater). In a first more preferred embodiment, the combustion air enters the plenum  90  at between about 14 and 16 CFM (for example, for a propane heater). In a second preferred embodiment, the combustion air enters the plenum  90  at between about 11 and 16 CFM (for example, for a natural gas heater). In a second more preferred embodiment, the combustion air enters the plenum  90  at between about 12 and 15 CFM (for example, for a natural gas heater). 
         [0298]    In some embodiments, the fuel enters the plenum  90  through a fuel entry  15  and a fuel orifice (also called a nozzle herein)  94 . In one embodiment, the fuel may enter the plenum  90  at a pressure between about 3 and 5 inches water column. In a preferred embodiment, the fuel may enter the plenum  90  at a pressure of about 4 in. w.c. (approximately 0.145 psi), which results in the fuel entering the plenum  90  at about 0.94 cubic feet per minute. In an alternate embodiment, the fuel may enter the plenum  90  at a pressure between about 8 in. w.c. and 13 in. w.c. In one embodiment, the fuel content volume is between approximately 20 and 26 cu.ft. and the fuel content quality is between about 2,000 and 3,000 BTU cu.ft. (for example, for a propane heater). In a preferred embodiment, the fuel content volume is between approximately 20.5 and 25.5 cu.ft. (for example, for a propane heater). In a more preferred embodiment, the fuel content volume is about 22 cu.ft. and the fuel content quality is approximately 2,516 BTU cu.ft. (for example, for a propane heater). In a second embodiment, the fuel content volume is between approximately 45 and 65 cu.ft. (for example, for a natural gas heater). In a preferred embodiment, the fuel content volume is between approximately 50 and 60 cu.ft. (for example, for a natural gas heater). In a more preferred embodiment, the fuel content volume is about 56 cu.ft. and the fuel content quality is between about 900 and 1,100 BTU cu.ft. (for example, for a natural gas heater). 
         [0299]    The plenum  90  has a partition  105  to route the fuel-air mixture toward the combustion chamber  101  and to further encourage mixing at the primary fuel/air mixing location  88 . In one embodiment, the air and fuel mix within the plenum  90  at a pressure between about 0.25 and 0.65 in. w.c. and the pressure within the combustion chamber  101  is between approximately 0.25 and 0.6 in. w.c., which creates a back pressure at the entrance of the combustion chamber  101  (for example, for a propane heater). In a preferred embodiment, the air and fuel mix within the plenum  90  at a pressure between about 0.55 and 0.6 in. w.c. and the pressure within the combustion chamber  101  is between approximately 0.3 and 0.4 in. w.c., which creates a back pressure at the entrance of the combustion chamber  101 . In a second embodiment, for example, for a natural gas heater, the air and fuel mix within the plenum  90  at a pressure between about 0.25 and 0.60 in. w.c. and the pressure within the combustion chamber  101  is between approximately 0.15 and 0.5 in. w.c., which creates a back pressure at the entrance of the combustion chamber  101 . In a second preferred embodiment, the air and fuel mix within the plenum  90  at a pressure between about 0.35 and 0.45 in. w.c. and the pressure within the combustion chamber  101  is between approximately 0.2 and 0.3 in. w.c., which creates a back pressure at the entrance of the combustion chamber  101 . 
         [0300]    In one embodiment, the minimum air to fuel concentration percentage that permits ignition is between about 4.4% and 5.1%. In one embodiment, the maximum air to fuel concentration percentage that permits ignition is between about 15% and 17%. In a preferred embodiment, the air to fuel concentration percentage should be between approximately 5.1% and 15%. The air-fuel mixture then enters a flame tube  11  within a combustion chamber  101  where secondary fuel/air mixing  21  occurs. In one embodiment, the flame tube  11  is between approximately 6.5 and 8.5 inches long, as measured from the point of interconnection to the water jacket  43  to the end of the flame tube  11  within the combustion chamber  101 . In a preferred embodiment, the flame tube  11  is between approximately 7 and 8 inches long. In a more preferred embodiment, the flame tube  11  is approximately 7.5 inches long. The majority of the flame tube  11  may be a mesh material to further promote the mixing of the fuel and the air. However, parts of the flame tube  11  may be solid. One example of a mesh-like flame tube is the Worgas TEXI premix burner. An igniter  79 , which may be an electronic spark igniter, sparks a flame in the combustion flame area  61  such that the air-fuel mixture burns in the flame tube  11 . In embodiments using natural gas, the igniter is often a spark igniter. In embodiments using propane, the igniter is often a hot surface igniter. A donut or refractory  95  is positioned behind the spark igniter  79  to prevent the gases from flowing backwards within the combustion chamber  101 . The refractory  95  is a solid tube that removes gas from behind the igniter  79  tip. This makes the area behind the source of the ignition (e.g., spark igniter  79 ) flat and sealed, which stabilizes the pressure and the gas flow and removes turbulence at the ignition source  79  tip. The hot gases exit the combustion flame area  61  along the combustion/exhaust path  74 , which is between the combustion chamber  101  and a heat exchanger tank  59 , and then out the exhaust  1 . In one embodiment, the volume of the heat exchanger tank  59  is between about 390 and 470 cubic inches. In a preferred embodiment, the volume of the heat exchanger tank  59  is about 430 cubic inches. In one embodiment of the present invention, the heating system performance can be improved increasing the surface area of the heat exchanger tank  59 . Thus, the heat exchanger tank  59  may have fins  96  to increase the speed and amount of heat transfer to the fluid  99  contained between the heat exchanger tank  59  and the coolant reservoir  43  (i.e., fluid tank). The fins may be painted white to scrub heat off of the gas. The fins  96  increase the surface area of the tank, which increases heat transfer. The combustion chamber  101  transfers the heat of the flame and combustion to the fluid in the coolant reservoir  43 . The coolant reservoir  43  may have an end piece  93  interconnected to the structure of the coolant reservoir  43 . If the coolant reservoir  43  is cylindrical, then the end piece  93  will be circular to fit the coolant reservoir  43  shape. When assembled, a fluid-tight tank (i.e., the coolant reservoir  43 ) is provided for the coolant. Additionally, a control thermostat  124  on the water jacket  43  may be provided to measure the temperature of the water jacket  43 . The control thermostat  124  may include a bimetal switch in some embodiments. In some embodiments, the thermostat may be puck spot welded to the top of the water jacket  43 . 
         [0301]      FIG. 7A  is a front elevation view of a second embodiment of a supplemental heater and  FIG. 7B  is a perspective view of section B-B of the supplemental heater of  FIG. 7A . The numbering used in  FIG. 7B  correlates to the numbering used in  FIG. 6B . Additional arrows are shown in  FIG. 7B  to indicate the direction of the gas flow. Additionally, the flame tube  11  promotes further mixture of the fuel and air by using a mesh screen in some embodiments. Thus, the fuel-air mixture is delivered to the combustion chamber  101  at delivery points  37 . Furthermore, the exhaust  1  may include threads to interconnect or detachably secure an exhaust pipe (not shown) to the exhaust  1 . 
         [0302]      FIG. 7C  is a front elevation view of a third embodiment of a supplemental heater and  FIG. 7D  is a perspective view of section D-D of the supplemental heater of  FIG. 7C . The numbering used in  FIG. 7D  correlates to the numbering used in  FIGS. 6B and 7B . However, the embodiment shown in  FIG. 7D  is slightly different from the embodiment shown in  FIG. 7B . For example, the refractory  95  in  FIG. 7D  is thicker/wider than the refractory in  FIG. 7B . The larger refractory  95  of  FIG. 7D  removes more gas from behind the igniter  79  tip than the smaller refractory  95  of  FIG. 7B . This makes the area behind the ignition source  79  flatter and the pressure and gas flow at the ignition source  79  tip more stable than the thinner refractory  95 . In one embodiment, the combustion chamber  101  has a volume of between about 240 and 280 cubic inches. In a preferred embodiment, the combustion chamber  101  has a volume of between about 255 and 265 cubic inches. In a more preferred embodiment, the combustion chamber  101  has a volume of about 262 cubic inches. 
         [0303]      FIG. 8  is an embodiment of a vehicle heating system that includes a supplemental heater  82  interconnected to one or more compartment heat exchangers  18 A,  18 B,  18 C. In the embodiment shown, heated coolant flows out of the heater  82  through a heated outlet port  33  and into a first compartment heat exchanger  18 A through a first coolant inlet port  22 A. The coolant then exits the first compartment heat exchanger  18 A through a first coolant outlet port  14 A and enters a second compartment heat exchanger  18 B through a second coolant inlet port  22 B. The coolant then exits the second compartment heat exchanger  18 B through a second coolant outlet port  14 B and enters a third compartment heat exchanger  18 C through a third coolant inlet port  22 C. After the coolant exits the third compartment heat exchanger  18 C through a third coolant outlet port  14 C, the cooled coolant returns to the heater  82  through a heater inlet port  60 . The heat exchangers  18 A-C may be any type of heat exchanger, but are preferably fluid-to-air heat exchangers such that heated engine coolant or other liquid may circulate through the heat exchangers  18 A-C and heat from the fluid can be transferred to air blowing across the heated fluid and blow into a compartment of the vehicle. 
         [0304]      FIG. 9  is an embodiment of a compartment heat exchanger system. In the embodiment shown, the compartment heat exchanger  18  is interconnected to a voltage source  18 , which may be the vehicle battery. A thermostat  98  is positioned between the compartment heat exchanger  18  and the voltage source  50  such that a switch within the thermostat  98  may allow the compartment heat exchanger  18  to receive power from the voltage source  50  when the ambient temperature is below a predetermined minimum and the thermostat  98  may not allow the compartment heat exchanger  18  to receive power from the voltage source  50  when the ambient temperature is above a predetermined maximum. 
         [0305]      FIG. 10A  shows a single closed-circuit supplemental heater comprising a burner assembly  200 , and exhaust  202 , a gas regulator  204 , a 3-position switch (on/off/time)  206 , a 7-day timer  208 , a coolant outlet  31 A, and a coolant inlet  22 .  FIG. 10B  shows the single closed-circuit supplemental heater interconnected to a vehicle engine. The system comprises engine preheating  200 , an oil pan  212 , a fuel pressure regulator  214 , a hydraulics reservoir  216 , and an operator cabin exchanger  218 . The heater provides heat to the engine, oil pan  212 , fuel pressure regulator  214 , hydraulics reservoir  216 , and operator cabin exchanger  218 . 
         [0306]      FIG. 11  is a front right perspective view of a fourth embodiment of a supplemental heater  82 . The heater  82  and heater system may include a coolant reservoir  43  to provide a medium for one or more coolant paths and devices to be heated. The coolant reservoir  43  has an end piece  93 , a coolant outlet port  33  where coolant heated by the combustion chamber (not shown) exits the heater  82 , and a coolant inlet port  60  where coolant to be heated enters the heater  82 . In some embodiments, the inlet port  60  is located on the bottom or lower side of the coolant reservoir  43  and the outlet port  33  is located on the top or upper side of the coolant reservoir  43  because heated coolant rises and because gas or air bubbles rise and move the liquid with bubbles. The heater also has a control thermostat  124  on the water jacket  43  to measure the temperature of the water jacket  43  or the fluid within the water jacket  43 . In some embodiments, the coolant reservoir  43  may be encased or encircled in insulation to increase the efficiency of the heater and reduce heat loss to the environment. The heater  82  also comprises a flame sensor  104  (only the end is shown) and a spark igniter  79  (only the end is shown). The igniter  79  may be a two-wire electrode or other igniter known in the art, including a hot surface igniter. In one embodiment, the positions of the flame sensor  104  and the spark igniter  79  are switched. The heater  82  further comprises a regulator  44  to reduce the pressure of the fuel from 125 psi to 0.5 psi, a redundant fuel valve and pressure regulator  7  to reduce the pressure from 0.5 psi to 4 inch w.c. (water column), a fuel entry  15  into a plenum  90 , and a blower  8  to blow air into the plenum  90  and to blow the fuel-air mixture into the combustion chamber. In other embodiments, the redundant fuel valve and pressure regulator  7  may reduce the pressure from 0.5 psi to between 8 and 13 in. w.c. 
         [0307]      FIGS. 12-19B  show different views of the heater  82  shown in  FIG. 11 . The components shown and/or numbered in  FIGS. 12-19B  correlate to the components shown and/or numbered in previous figures. In the interest of brevity, the component names and numbers will not be repeated for  FIGS. 12-19B .  FIG. 12  is a front left perspective view of the heater  82 . The air inlet  9  in the blower  8  can be seen in this view. Additionally, a control thermostat  124  on the water jacket  43  measures the temperature of the liquid in the water jacket  43  in one embodiment and the control thermostat  124  measures the temperature of the water jacket  43  itself in another embodiment. In alternative embodiments, the control thermostat  124  measures either the fluid entering the water jacket  43 , the fluid exiting the water jacket  43 , or both. As is discussed below in  FIG. 24 , the burner (i.e., flame tube, combustion chamber, burner, etc.) of the heater  82  cycles on and off depending on the temperature measured by the control thermostat  124 . 
         [0308]      FIG. 13  is a front right perspective view of the heater  82  shown without the water jacket  43 . In one embodiment of the present invention, the heating system performance can be improved by agitating the water in the water jacket  43  to enhance heat transfer. A fin or spiral  89  on the outside of the heat exchanger tank  59  induces helical flow of the fluid around the heat exchanger tank  59  so that more heat will transfer from the combustion chamber and heat exchanger tank  59  to the coolant or fluid flowing around the tank  59  within the water jacket  43 . The fins or spiral  89  are secured to the heat exchanger tank  59 , for example by brazing, in a serpentine path or in a circular path within the water jacket  43  so that the water or coolant in the water jacket  43  is in heat transfer relationship with the heat exchanger tank  59 . In another embodiment, the spiral  89  may be a helix spot-welded. In additional embodiments, the spiral  89  may be tighter wound such that it encircles the tank  59  more times, the spiral  89  may be looser wound, or the tank  59  may comprise more than one spiral  59 . Additionally, the controls  92  are shown in  FIG. 13 . The controls  92  are contained within an enclosure to protect the circuitry of the controls  92 . The controls  92  control the heater  82  operation. 
         [0309]      FIG. 14  is a top plan view of the heater  82 . The heater  82  further comprises a pressure sensor  107 , which is connected by a small tube to the combustion air and/or the blower motor. The pressure sensor  107  is detecting a pressure between approximately 0.10 inch w.c. and 0.18 inch w.c. In one embodiment, the pressure sensor  107  detects a pressure of about 0.14 inch w.c. The pressure sensor  107  is a safety that ensures the blower  8  is operational prior to permitting gas to enter the combustion chamber. A back pressure switch may also be incorporated into the pressure sensor  107 . The heater  82  may also comprise a voltage monitor  108 , which can be set between approximately 9.5 and 11.5 VDC or it can be set in a “no monitor” position. The voltage monitor  108  includes a low voltage disconnect such that if the voltage drops below the set point, the heater will switch off to protect the vehicle&#39;s battery from draining. The heater also comprises a coolant circulation pump  73  and an on/off maintenance switch  109  mounted to the heater  82  enclosure (not shown). 
         [0310]      FIG. 15  is a bottom plan view of the heater  82 .  FIG. 16  is a front right perspective view of the heater  82  with an enclosure  106 . The enclosure  106  may include insulation, panels, or covers (e.g., an access cover) (not shown). 
         [0311]      FIG. 17  is a rear left perspective view of the heater  82 .  FIG. 18  is a front elevation view of a fifth embodiment of a heater  82  with an exhaust pipe interconnected to the exhaust  1 . Thus, the combustion products from the combustion chamber can be exhausted through an exhaust pipe. In one embodiment, a portion of the exhaust pipe passes through the coolant or through a heat exchanger in order to extract waste heat from the exhaust. 
         [0312]      FIG. 19A  is a perspective view of one embodiment of the burner components of a heater and  FIG. 19B  is a perspective view of a second embodiment the burner components of a heater. The burner may include an igniter  79  and a flame sensor  104 .  FIG. 19B  is similar to  FIG. 7D  in that it has a larger or wider refractory  95  than the embodiment of  FIGS. 19A and 7B . 
         [0313]      FIG. 20  is a top perspective view of one embodiment of a multi-circuit supplemental heating system. Specifically, the embodiment shown is a triple-circuit supplemental heater  182  comprising circulation pumps  73 , a blower  8 , a plenum  90 , a fuel valve and pressure regulator  7 , a fuel entry  15 , a spark igniter  79 , and coils  65  (which may be copper) encircling the combustion area, flame, and flame tube  11 . The heat transfer coil  65  provides thermal energy to preheat a vehicle engine in one mode of operation and provides a source of heat to other heat loads (e.g., a hydraulic reservoir, an oil pan, a fuel pressure regulator, a compartment heater or heat exchanger, a cargo box, a water tank, etc.) when needed and/or when the engine does not need to be preheated. The tank or case may be surrounded by various insulation panels and covers (e.g., an access cover). When assembled, a fluid-tight system is provided for the coolant. The heater  182  comprises a first heat zone inlet  114 , a second heat zone inlet  116 , and an engine preheat inlet  116 . The heater  182  further comprises a first heat zone outlet  110  where heated fluid exits the heater  182  to heat a first zone in the engine heating/cooling system, a second heat zone outlet  112  where heated fluid exits the heater  182  to heat a second zone in the engine heating/cooling system, and an engine preheat outlet  120 . The engine preheat circuit has an engine preheat circulation pump  122 . 
         [0314]      FIG. 21  is an exploded perspective view of an embodiment of a single-circuit supplemental heater  82 . The components shown and/or numbered in  FIG. 21  correlate to the components shown and/or numbered in previous figures showing single-circuit heaters. 
         [0315]      FIG. 22  is an exploded perspective view of an embodiment of a triple-circuit supplemental heater  182  with an enclosure  106 . The components shown and/or numbered in  FIG. 22  correlate to the components shown and/or numbered in  FIG. 20  showing a triple-circuit heater  182 . 
         [0316]      FIG. 23  is a flow chart of the operation of a supplemental heater according to one embodiment. In step  230 , an on signal may be provided by a user and received by the heater controls. In a pre-purge step  232 , the coolant pump, control thermostat, blower, and external gas solenoid are turned on. The heater attempts to ignite in step  234 . Thus, the gas valve opens and the igniter switches on. Once the heater is lit, the burn cycle  236  begins. During the burn cycle step  236 , the igniter turns off once the flame is lit, the flame sensor is on, and coolant is heated to a predetermined maximum temperature. Once the coolant reaches the predetermined maximum temperature, a control pause begins in step  238 . A post-purge step  240  follows where the control thermostat is turned off, the gas valve is closed, and the flame sensor is off. Once the post-purge step  240  is complete, the blower is turned off in step  242 . With the heater turned off, the coolant reaches a predetermined minimum temperature in step  244 . The temperature of the coolant may be measured anywhere in the system. In preferred embodiments, the temperature of the coolant is measured somewhere on or in the water jacket or copper coils. After the temperature reaches a predetermined minimum temperature and if heat is still required, the cycle repeats itself starting at step  234 . 
         [0317]      FIG. 24  is a chart showing the cycling of a supplemental heater according to one embodiment. In this embodiment, the heater system includes a thermostat or heat sensor that is designed to turn on the supplemental heater and/or electric heater when the temperature of the heating medium (e.g., coolant) falls below a predetermined minimum temperature (e.g., 120° F. or 122° F. for the coolant heated by the heater) and to shut off the heater and electric heater when the temperature of the heating medium rises above a predetermined maximum temperature (e.g., 140° F. for the coolant heated by the heater). 
         [0318]      FIG. 25  is a flow chart of a vehicle&#39;s coolant system without a supplementary heater. Plug-ins may provide additional heat to some items, e.g., the oil pan and engine block. No supplemental heater is provided in the system of  FIG. 25 . Therefore, the regulator, fuel intake manifold, and air intake butterfly valve had to wait for the engine to heat up in order to receive heat from the engine coolant. 
         [0319]      FIG. 26  is a flow chart of a vehicle&#39;s coolant system with a supplementary heater. Fuel flows through the system along the path represented by solid, thick lines. Coolant flows through the system along the paths represented by dashed lines (circuit  1 ) and thin, solid lines (circuit  2 ). The fuel (e.g., CNG or compressed natural gas) is held within a tank at approximately 3000 psi, or whatever other pressure the vehicle&#39;s fuel tank is designed to withstand. The pressure of the fuel is then reduced through a regulator and the temperature of the fuel drops from about −40° F. to about −100° F. as the fuel&#39;s pressure drops. Accordingly, heat at the regulator is desired. The fuel then flows through a filter, through an in-line heater, and then to a junction point where the fuel may either go into the fuel intake/manifold on the engine, into the supplemental heater, or to both the engine and the heater where the fuel is burned. 
         [0320]    The supplemental heater (e.g., Work Ready heater in  FIG. 26 ) may heat coolant and provide heated coolant to the regulator. When the supplemental heater is in operation, the fuel flow and heat exchangers are warmed. The supplemental heater may also provide heated coolant to heat the filter, either in line with the regulator or in series with the regulator. The heated coolant then flows to the engine to provide heat to the engine if needed in very cold temperatures and/or to avoid a thermo shock to the engine prior to starting. The heater may heat circuit  1  when the engine is either on or off. In some embodiments, the heater may provide heated coolant to the in-line fuel heater through a second circuit in order to heat the fuel before it enters the fuel intake/manifold on the engine and/or heat the fuel before it enters the supplemental heater. This second circuit is only used when the engine is on and it is often not needed in summer months or on warm days. Thus, the second circuit is separate from the first circuit such that the second circuit may be turned off if it is not needed. Circuit  2  is in parallel with circuit  1  as connected to the supplemental heater. Circuit  2  will operate if the ignition signal is present and the in-line heater thermostat is closed. The fuel intake/manifold and air intake valve may also be heated by hot air coming off of the engine. 
         [0321]      FIG. 27A  shows a dual closed-circuit supplemental heater comprising a heat zone 1 outlet  220 , a heat zone 2 outlet  222 , a heat zone 1 return  224 , a heat zone 2 return  226 , an engine preheat inlet  228 , an engine preheat outlet  230 , zone circulation pumps  232 , a fuel inlet outlet  234 , a burner chamber  236 , an electric heating element  238 , and a thermal storage tank  240 .  FIG. 27B  shows the dual closed-circuit supplemental heater interconnected to a vehicle engine. The system comprises engine preheating  200 , an oil pan  212 , a fuel pressure regulator  214 , a hydraulics reservoir  216 , an operator cabin exchanger  218 , and a cargo/work box  250 . The heater provides heat to the engine, oil pan  212 , fuel pressure regulator  214 , hydraulics reservoir  216 , operator cabin exchanger  218 , and cargo/work box  250 . 
         [0322]      FIG. 28A  shows a triple closed-circuit supplemental heater comprising a heat zone 1 outlet  220 , a heat zone 2 outlet  222 , a heat zone 1 return  224 , a heat zone 2 return  226 , an engine preheat circulation pump  227 , an engine preheat inlet  228 , an engine preheat outlet  230 , zone circulation pumps  232 , a fuel inlet outlet  234 , a burner chamber  236 , an electric heating element  238 , a thermal storage tank  240 , a cold water inlet  242 , a hot water outlet  244 , and a water tempering valve  246 .  FIG. 28B  shows a triple closed-circuit supplemental heater interconnected to a vehicle engine. The system comprises engine preheating  200 , an oil pan  212 , a fuel pressure regulator  214 , a hydraulics reservoir  216 , an operator cabin exchanger  218 , a cargo/work box  250 , and a water/fluid tank  252 . The heater provides heat to the engine, oil pan  212 , fuel pressure regulator  214 , hydraulics reservoir  216 , operator cabin exchanger  218 , cargo/work box  250 , and water/fluid tank  252 . 
         [0323]    While various embodiments of the present invention have been described in detail, it is apparent that modifications and alterations of those embodiments will occur to those skilled in the art. However, it is to be expressly understood that such modifications and alterations are within the scope and spirit of the present invention, as set forth in the following claims. Further, the invention(s) described herein is capable of other embodiments and of being practiced or of being carried out in various ways. In addition, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.