Abstract: A control system and method provide a multiple option select function in which an option select resistor acts as a selector. The control system determines the resistance value of the resistor and maps the resistance value to a data entry in an option select table. The index of the data entry is determined and used to reference option parameters in at least one option parameter table. The index allows the control system to select an option parameter from many possible option parameters in the option parameter table. Furthermore, additional option parameter tables may also be referenced to select multiple option parameters using a single select resistor. The control system is disclosed as controlling a water heater system, although such control systems may be used to control other systems, such as furnaces and hydronic heating and water systems. A calibrating circuit is used to measure a transient response of an RC circuit.

Abstract: A fully integrated electronic appliance controller for controlling the operation of a appliance (e.g., a gas-fired water heater or boiler). The controller includes an integrated intelligent control system; enhanced safety features including an igniter current proving circuit, a flame detection circuit, a safety limit string and an energy cut-out (ECO) control; an intelligent user interface including a display unit and a communications system; and an adaptive control feature. According to a preferred embodiment of the present invention, the controller is adapted to receive as many as four temperature probes (e.g., thermistors). The first probe senses the water temperature at the outlet of a water heater, the second probe senses the water temperature at the inlet of the water heater, the optional third probe senses the temperature at a first location in an associated remote water storage tank, and the optional fourth probe senses the temperature at a second location in the associated remote water storage tank.

Abstract: An apparatus and method for optical sensing of liquid level in cooking vessels are disclosed. The apparatus comprises: a first sensor (P1) for detecting a liquid and generating a first signal indicating a vessel level of the detected liquid above a desired liquid level (110) in the cooking vessel (102); a second sensor (P2) for detecting the liquid and generating a second signal indicating the vessel level of the detected liquid below the desired liquid level (110) in the cooking vessel (102); a third sensor (P3) for detecting the liquid and generating a third signal indicating the vessel level of the detected liquid (110) at the bottom of the cooking vessel (102); and a controller (108) for receiving the signals and for determining the vessel level in the cooking vessel (102).

Abstract: A heating and cooling system, particularly for water, provides advantages in safety, reliability and efficiency of temperature regulation systems for liquids. A temperature regulation unit is controlled by a controlling device. A sensing unit is relied upon to detect a particular liquid temperature and a safety unit enables the temperature regulation unit to be disabled. A reset device connectable to a power source via a transforming unit is adapted to lower the voltage level of the power source to a level safe for use by a user. The reset device is operable to reset the safety unit, thus enabling a controller unit to again operate the temperate regulation unit. In a preferred embodiment, the controller unit operates the temperature regulation unit through the safety unit, such that when the safety unit is activated, power cannot be transferred to the temperature regulation unit.

Abstract: This is a system for controlling the heating of water in the tank, water in tank adapted to be heated by a first heater and a second heater, the system comprises a timer adapted to keep time, and a sensor to monitor the temperature of the water in the tank at a first position and the temperature of the water in the tank at a second position. The system is adapted to set a first set point temperature at a specified time and the first set point temperature is varied by the system over time. The system is also being adapted to set a second set point temperature the second set point temperature also being varied by the system over time. The system has an activator to activate the first heater to maintain the temperature of water in the tank at the first position at about the first set point temperature at a specified time. The system has an activator to activate the second heater to maintain the temperature of water in the tank at the second position at about the second set temperature at a specified time.

Abstract: A priority control system is disclosed for controlling multiple secondary load devices, and one priority load device. The secondary load devices can be randomly controlled at any time, except when the priority load device is activated, in which case, all secondary load devices are deactivated. The priority control system has a first relay which relays power to a plurality of secondary relays corresponding to the secondary load devices. The first relay is biased such that it normally provides power to the secondary relays. The first relay also has a priority position which is the non-biased position, for providing power to the priority load device. The first relay is activated by a priority control device which switches system power from the secondary relays to the priority load device. A priority timer circuit is provided to limit the time the first relay is in the priority position, regardless of a possible malfunction in the priority control device.

Abstract: A method for gas supply pressure control is disclosed. Gas is supplied to a gas burner at a gas supply pressure which is higher than an ignition pressure, and after the ignition of the gas burner, the gas supply pressure increases during a predetermined time until fluid to be heated reaches a target temperature. The increase of the gas supply pressure is performed gradually according to a predetermined number of pressure levels set between the ignition pressure and maximum gas supply pressure of the gas boiler. If the fluid reaches the target temperature, the gas is supplied according to a corresponding to the target pressure temperature. Since the time that the gas is supplied at the maximum gas supply pressure is reduced during the time of initial operation of the gas boiler and during the operation of the gas boiler, the noise resulting from combustion is reduced.

Abstract: In a fluid heating apparatus having a fluid tank, a combustion chamber communicating with the fluid tank for heat exchange, and a combustible fluid delivery system coupled to the combustion chamber, a plurality of valves are individually configured in either an off-state or an on-state for delivering combustible fluid to the combustion chamber. Depending on the configuration of the multiple valves, the rate at which combustible fluid is supplied to the combustion chamber may be varied in response to a heat demand signal. Individual valve signals are generated for each of the multiple valves in response to the heat demand signal to place the multiple valves in a configuration to supply combustible fluid at predetermined rates. The demand signal is calculated in response to reading temperature at an inlet temperature probe and an outlet temperature probe, wherein the outlet temperature probe is located nearer a fluid outlet from the fluid tank than is the inlet temperature probe.

Abstract: A water heating system for a number of apartments or offices 10 each having a water store 15 for receiving hot water from a common boiler 12. The system includes a temperature sensor S2 for sensing the temperature of incoming water from the boiler, with a valve V1 between the temperature sensor S2 and the water store 15. A further temperature sensor S1 senses the temperature of water within the store 15. An electronic controller 30 controls the flow of water via valves V1, V2 dependent on the temperature detected by both the first and second sensors to prevent water being received by the store when the temperature differential is too small. This avoids the risk of reduction of the water temperature within the store 15, and meter 21 will not register utilization under these circumstances as valve V2 allows the return of the water other than via store 15.

Abstract: A water heater control modifies a temperature differential setting in a hot water heater according to elapsed time between calls for heat. This allows the temperature setting of the hot water heater to remain low, which reduces the risk of scalding, yet allows the hot water heater to deliver hot water consistently. For example, a hot water heater temperature setting is 120.degree. F. and the temperature differential is normally set to 20.degree. F. After six hours without a call for heat, during which time period the water in the tank has destratified, the water heater control could set the differential to 15.degree. F., which would cause a call for heat when the water temperature drops to 105.degree. F. Once a call for heat is generated, the temperature differential can be set back to 20.degree. F.

Abstract: A system for controlling a water heating system senses the temperature of new (unheated) water and uses any drop in that temperature as an early, quantitative measure of the demand for hot water within the system. The heater itself is turned "on" and "off" with respect to a control set point temperature (T.sub.C) which increases with decreasing inlet water temperature. Thus, the control set point is increased above a baseline by an amount related to the amount of unheated water drawn into the heater to replenish the heated water being used. In a preferred embodiment, a calculated demand value proportional to the drop in inlet water temperature (T.sub.I) is summed over time to reflect the time during which a given demand condition continues. When the heater is ultimately turned "off", signifying that the hot water supply temperature (T.sub.S) is substantially higher than the control temperature (T.sub.C), the control temperature is reset to its baseline value.

Abstract: A boiler controller for hydronic heating systems that reduces the standby heat losses from boiler to a minimum and activates the boiler automatically when hot water or/and space heating demand are present.

Abstract: A system and method for controlling operation of a water heater provides generating a heating demand signal which a minimum level corresponds to a required heat input for maintaining water temperature in the water tank in case of no exogenous demand for water. Responsive to the heating demand signal, air flow from the forced draft blower and flow of combustible fluid from the combustible fluid delivery system are varied to produce combustion product over a minimum 15 to 1 ratio. This allows water heating to be varied to meet maximum expected exogenous demand or to maintain water temperature with no exogenous demand.

Abstract: Gas is supplied to a gas flow modulator having a tubular member with a gas flow passage extending through the tubular member. A slide member in the gas flow passage is axially slidable longitudinally along the passage. Springs within the tubular member in opposite directions on the slide member so as to resiliently bias the slide member towards a predetermined position in the gas flow passage. A flow constrictor means is fixedly positioned within the gas flow passage for constricting gas flow along the gas flow passage, the slide member and the flow constrictor means being shaped to cease the flow of gas along the gas flow passage upon displacement of the slide member in a first direction from the predetermined position by means of an electromagnetic induction coil extending around the exterior of the tubular member and in cooperation with a magnetic material forming at least part of the slide member or secured thereto.

Abstract: A liquid immersible electronic aquastat in which a temperature responsive element and substantially all associated electronic circuitry are arranged on a circuit board within a tubular capsule of liquid impervious material closed at one end and having a external diameter not exceeding 3/8ths of an inch so as to be interchangeable with industry standard aquastat temperature sensor mounting hardware and fittings.

Abstract: A computerized control system for use in a deep fat fryer is provided for controlling a heating device and a temperature probe added to the deep fat fryer whereby both the heating device and temperature probe are located in proximity to the bottom zone of the cooking vessel of the fryer. The computerized control system thereafter regulates the temperature of the portion of the cooking substance located in proximity to the bottom zone of the vessel to a predetermined target temperature range. By doing so, moisture found within any cracklings located within the bottom zone of the vessel is minimized and the cooking substance therefore will not boil over the sides of the vessel.

Abstract: An apparatus and method for providing a hot water supply for a building such as a mobile home, house, or business. A hot water storage tank is positioned within the building. A gas-fueled burner is positioned outside the building adjacent a heat exchanger which is connected in fluid communication with the indoor water storage tank. A pump circulates water from the tank through the heat exchanger and back into the tank responsive to a thermostat in the tank. The heat exchanger includes a thermostat for sensing the temperature of water therein to activate the pump and circulate relatively warm water from the tank through the heat exchanger to prevent freezing of water within the heat exchanger, such as during winter months when the ambient temperature falls below freezing. The gas heater may be used to convert a conventional electric water heater to operate from gas which is combusted outside of the building.

Abstract: A water heater includes a tank for receiving cold water and dispensing heated water. A thermostat is associated with the tank and detects the temperature of water held therein. A gas burner including a hot surface igniter receives fuel to be combusted via a fuel line when a valve on the fuel line is opened. A controller is responsive to the thermostat and opens the valve and operates the igniter to ignite the fuel when the temperature of the water held in the tank falls below a first predetermined level. A vent including a flue passes through the tank and allows combustion gases and heat of combustion to be vented from the water heater. The vent includes a blower responsive to the controller which mixes ambient air with combustion gases prior to venting the combustion gases to the atmosphere. The controller initiates the blower when the water temperature falls below the first predetermined level to establish at least a predetermined pressure in the flue before the valve and igniter are operated.

Abstract: A water heater controller including hot water supply temperature sensor, a return water temperature sensor, a cold water flow sensor, a recirculation loop ambient temperature sensor, and a processor and control unit for controlling the heating of water and the circulation of water.

Abstract: A heat feeding apparatus employable for an internal combustion engine having a supercharger attached thereto, the apparatus including a compressed air bypass passage opening/closing valve disposed midway of a compressed air bypass passage by way of which the outlet of a blower is communicated with the inlet of a turbine in the supercharger and combustion means installed in an inlet region of the turbine, wherein opening or closing of the compressed air bypass passage opening/closing valve and combustion in the combustion means are initiated in dependence on the temperature of a specific kind of medium for which heat exchanging is effected in a heat exchanger, whereby a heat involved in the exhaust gas is transmitted to the heat exchanger in dependence on the demand required by the medium.

Abstract: A rapid recovery gas water heating system having a water storage tank, a gas water heater separate from the storage tank and having a compact heat exchanger for the flow of water therethrough from the storage tank, a water pump for pumping of water from lower regions of the storage tank into and through the heat exchanger and back into the storage tank, and a thermostat having water temperature sensing means positioned in the storage tank and serving for actuating the water pump and the gas water heater in response to the temperature of the water in the storage tank falling below a predetermined temperature value.

Abstract: A device is divulged for controlling and regulating the gas supply to the burner of a boiler or similar, which device comprises a piloted regulator (R) with a leak valve (8) for the gas flow. The burner is also fed with pressurized air and opening of the leak valve is slaved to the flow of this pressurized air so that the ratio between the two air and gas flows permanently has a value providing excellent combustion of the air-gas mixture in the burner.

Abstract: The delivery side of a refrigerant compressor is connected through an inside heat exchanger to a refrigerant heater, the outlet side of the refrigerant heater being connected with the suction side of the compressor. First and second temperature sensors are provided at inlet and outlet sides of the refrigerant heater, respectively for sensing inlet and outlet refrigerant temperatures. A fuel gas supply unit for the refrigerant heater is fitted with a fuel gas control value which is controlled by the temperature differences existing between sensed temperatures by the first and second sensors.

Abstract: A solar heat collector system including a heat collector circuit containing a compressor that compresses and outputs thermal media and is capable of varying its own capacity by conversion of operative frequencies; a condensor being part of the heat collector circuit, which is connected to the output of the compressor; a plurality of heat collectors integrally built with housing materials, one end of which being connected to the condensor via a squeezer and the other end of the heat collector system being connected to the compressor, where each unit heat collector contains a plurality of thermal media tubes allowing thermal media to pass through the inside thereof and heat collect fins connected to the thermal media tubes for transferring heat; a hot-water pool storing hot water for use inside the house; and a fluid heating circuit inclusive of a fluid heater held in heat-exchange relationship with the condensor outside of the hot-water pool.

Abstract: A system is described for use with a hot water supply for hotels, apartment buildings and similar multi-unit structures, which controls the temperature T.sub.1 of water at the outlet of a water tank to make it close to a desired temperature DTEMP that is low during times of low demand to save energy and which is high at times of high demand to assure adequate hot water at all times. The desired temperature at the tank outlet, DTEMP, is adjusted according to the sensed demand for hot water during an immediately preceding period of given duration, such as 45 minutes. The circuitry is used in parallel with an existing Aquastat on a commercial tank type water heater.

Abstract: A system is described for use with a hot water supply for hotels, apartment buildings and similar multi-unit structures, which controls the temperature T.sub.1 of water at the outlet of the water tank that circulates past the units and back to the tank, to make the actual temperature T.sub.1 close to a desired temperature DTEMP. The desired temperature at the tank outlet, DTEMP, is adjusted according to the measured temperature T.sub.3 of recirculating water prior to its reentry into the tank. In cold weather, when T.sub.3 decreases below a preset limit such as 105.degree. F., indicating there is a considerable temperature drop along the pipeline before water reaches the last unit, the desired tank outlet temperature DTEMP is raised to more than it would otherwise be. As T.sub.3 increases back toward the limit such as 105.degree. F., the temperature DTEMP is lowered.

Abstract: A system is provided for heating and storing a liquid within a tank. Disposed within the tank is a heating unit which effects stratification of the tank into upper and lower liquid storage sections whereby the liquid in the upper storage section is at a first predetermined temperature which is higher than the temperature of the liquid within the lower storage section. A first control element is operatively connected to the heating unit and controls the operation thereof so as to maintain the liquid in the upper storage section at the first predetermined temperature. The upper and lower storage sections are interconnected by a passage assembly. The passage assembly includes a pump for effecting controlled circulation of the liquid from the upper storage section to the lower storage section.

Abstract: An instantaneous hot water heater having a coiled heat exchanger (4) through which water to be heated passes. A fuel supply assembly (22) is provided for supplying air and gas to the interior of the exchanger for combustion in such a way that combustion occurs as a series of rapidly occuring pulses at a rate of typically 50 to 100 ignitions per second. There is considerable turbulence in the combustion products whereby good heat exchange takes place enabling very efficient operation.

Abstract: Domestic tankless water heating is incorporated into a space heating system. The space heating system includes a fluid flow loop with a fluid pump for circulating the fluid in the loop and a remote fan coil for transferring heat to the air in the space to be heated. The heat source is an infrared burner and the heating of the domestic water may be either directly by the burner through radiative and convective heat exchange in an open loop system or by heat exchange in a tube-in-tube heat exchanger which is in series with the fan coil in a closed loop system.

Abstract: A hot water heater having upper and lower electric heating elements and associated thermostatic switch controls in their electric circuits is provided with an energy saving control circuit for maintaining the lower heating element deenergized at all times except when it is needed to assist the upper heating element to heat the entire contents of the hot water heater tank. The energy saving control circuit includes an energy saving switch in the electric circuit of the lower heating element. A full tank relay switch is connected in parallel with the energy saving switch and the relay coil is connected to a transformer secondary winding through a holding circuit provided by a holding relay switch the coil of which is connected to the transformer secondary through a momentary make switch. The holding relay switch serves to maintain the holding relay coil connected to the transformer secondary after the momentary make switch is opened.

Abstract: System for regulating temperature of hot water in a wall-hung instantaneous mixed gas heating unit, in which the value of the temperature detected by a sensor inserted on the output of the secondary circuit of the hot water exchanger is compared with a set value, and their difference or error value is sent to the input of an amplifier of proportional-integrational-derivative type (P.I.D.), whose output is connected to one input of a selector of minimum value or power, to the other input of which is sent the difference or error value between the temperature of the heating system water and the corresponding maximum tolerable set temperature. The output of the selector then commands the gas modulating valves through a power amplifier, as well as the gas on/off operating valve through comparison with a signal proportional to the minimum thermal power that can be supplied by the heating unit.

Abstract: A water heater secondary control device which terminates the flow of gas to the heater thermostat when water has not been withdrawn from the tank for a period of time. The secondary control device includes a temperature sensor attached directly to the outside of the cold water inlet pipe and a tube to be attached to the heater tank pilot line to provide a continuous pilot light. The secondary control device is inserted between the natural gas pipe inlet and the heater thermostat and prevents flow of gas to the burner through the thermostat when the temperature of the water in the cold water inlet is above a predetermined threshold.

Abstract: Regulating device for a central heating plant containing a hot water supply, comprising a boiler for heating a heating medium, a pipe for feeding the heating medium to space heating elements, a distribution device which is accommodated in the feed pipe and has a connection to a flow-through heat exchanger which is also connected to a return pipe from the space heating elements to the boiler. A pipe for tap water being provided in the flow-through heat exchanger and said flow-through heat exchanger being provided with a thermostat which operates the distribution device in order to change from circulation through the space heating elements to circulation through the flow-through heat exchanger and vice versa. The thermostat being adjustable to permit setting of the minimum temperature in the flow-through heat exchanger at which the distribution device switches over from space heating to circulation through the flow-through heat exchanger.

Abstract: An electronic water heater thermostat system for controlling the heating of water in residential and commercial water heaters, the system incorporating improved circuitry for controlling the water temperature set point and hysteresis and enabling the use of low cost, low tolerance potentiometers providing a precision voltage ratio for use in the system circuitry.

Abstract: A point of use, instantaneous, high-volume water heating system includes a compact accumulator tank fed by one or more instantaneous gas-fired auxiliary water heaters operating asynchronously to provide a supply of hot water on demand heated to a predetermined temperature. The accumulator tank includes a baffle which separates water in the tank into two temperature zones. A thermostat within the accumulator controls a pump which feeds water from a conventional water heater to the auxiliary water heaters, or alternatively recycles tank water to the auxiliary heaters, when the temperature in the accumulator tank drops below a predetermined minimum.

Abstract: An instantaneous demand gas fired hot water heater apparatus having the water temperature sensing thermostat disposed in the upper hot water outlet header with the inlet flow of unheated water directed to flow in a preferred flow path across the temperature sensing element. The temperature sensing element location in the upper header of the heater provides an extremely sensitive and efficient burner control. Upon initial output demand of hot water the lower temperature of the unheated water is immediately sensed by the temperature sensing element to immediately commence burner operation. Upon termination of heater water demand, the heated water temperature is rapidly sensed by the temperature sensing element to promptly terminate the supply of the gas to the burner and minimize unnecessary heating of the water.

Abstract: A conventional hot water heating system generally of the type for heating water in multiple units of hotels, motels, schools and the like and using any heating medium has a processor and control assembly which is operationally connected to at least a water temperature sensing means and a heating control means thereof. The processor and control assembly divides the time into exact time periods, say one-half hour, and the time periods are grouped into a group of consecutive time periods, say a week. Taking any individual time period, the time periods are checked around the time period which the present time period is a repeat and time periods directly preceding the present time period, and the operational water temperature for the present time period is chosen, as well as the amount of heat required to maintain the water at that temperature on a percentage basis of heating taken from one hundred percent.

Abstract: A hot water heating system for a building has a hot water storage tank, a combustor, a burner for firing the combustor, a plurality of radiators, a pump for circulating hot water to and from the plurality of radiators, a first thermostat for measuring the temperature of the hot water in the storage tank and for controlling the burner in response to such temperature, a heat exchanger in the storage tank, a cold water inlet line, and a hot water outlet line. The improvement comprises a cold water heating element arranged around a portion of the inlet line, a temperature sensing element arranged in close proximity to the heating element, and a second thermostat for anticipatorily controlling firing of the combustor by the burner via the first thermostat. Also, the second thermostat, via an electrical line, shuts off the pump when the second thermostat is causing firing of the combustor by the burner.

Abstract: A domestic hot water heating system which disables the normal aquastat during set-back periods where the temperature of the water source is sensed at the output manifold and the temperature of the water also is sensed a predetermined distance along the manifold to determine a demand or lack of demand for hot water. The system will enable the aquastat during a set-back period when demand is made and disable the aquastat when there is no longer a demand.

Abstract: A domestic hot water zone controlled external coil which takes heated water from the hot water outlet of a hydronic boiler and passes the hot water through a tankless coil before returning it to the hydronic boiler. Return water from the tankless coil is returned to the hydronic boiler by using the existing circulator on an existing operating heating zone, which saves electrical energy. An aquastat and a unique analysis and switching circuit is also provided.

Abstract: The invention relates to a method and a plant for the central heating of a building provided with at least one thermodynamic machine such as a heat pump or a refrigerating machine. The method is characterized in that, without affecting the normal operation of the thermodynamic machine, during the heating period:when the temperature of the heat transfer fluid in the exchanger-accumulator tank reaches a certain threshold, the conduits via which the auxiliary boiler is connected to the circuit supplying the exchanger network are isolated and the return of this circuit to the tank is released while, on the other hand, when the temperature of the heat transfer fluid in the exchanger-accumulator tank drops below a certain threshold, the return to the exchanger-accumulator tank of the circuit supplying the exchangers is cut off and the auxiliary boiler whose discharge and return conduits are connected to the circuit is actuated.

Abstract: Water temperature sensors in the form of thermisters are in physical thermal contact with the inlet and outlet pipes of a water heater and may be surrounded by insulating material to make them more insensitive to the ambient air temperature and more sensitive to the temperature of the respective water pipes and the water contained therein. These two thermisters are connected in a bridge circuit connected to an operational amplifier whose output will be of a given polarity only if the measured temperature difference exceeds a predetermined value. The operational amplifier's output is then used to adjust the effective thermostatic setting of the hot water heater in a two-valued control arrangement.

Abstract: A heat generating system using solid fuel in a water jacketed combustion chamber for supplying hot water to units for space heaters and hot water storage units, and in which control means is provided for operating the fuel combustion mode to obtain recovery of the products of combustion during low rates of combustion, and to greatly reduce emissions during increased rates of combustion, the control means including thermostatic units having selected points of active and inactive responses.

Abstract: An apparatus for actuating the temperature setting means of a water heater is provided with a drive motor (2) adapted to move the temperature setting means from a low to a high temperature setting and vice versa. The drive motor (2) is connected to a power supply through a switching means (14). The switching means (14) is operable by a programmable timer (15) in such a manner that the temperature setting means is set on a high temperature only during at least one desired period.

Abstract: A conventional hot water heating system generally of the type for heating water in multiple units of hotels, motels and the like and using any heating medium has a processor and control assembly operationally connected to at least a heating control means, a water temperature sensing means and a water flow sensing means thereof. The processor and control assembly divides the time into exact time periods, say one-half hour, and the time periods are grouped into a group of consecutive time periods, say a week. Taking any individual time period, a directly preceding time period is checked with the same time period in the preceding group of time periods and if the two match within a given degree, the assembly adopts all of its settings from its particular time period a week ago. In addition, the assembly exactly records the various settings throughout that particular time period and when that time period comes up again one week from now, those are the new settings by the processor and control assembly to be used.

Abstract: A hot water control system for providing necessary hot water to a structure at optimum energy saving conditions includes a programmable control system for selectively programming preselected quantities of hot water at preselected time periods over a given interval of time and includes a mode selector for selectively overriding the control system to permit adjustment of the system to meet unscheduled changes in demand. The system includes mode selectors for selecting the programmed mode wherein predetermined supplies of hot water are available at predetermined time periods over a seven day period or the like and other modes may be selected such as pilot only operation, normal service wherein the water heater operates in its normal manner, pilot off or complete shutdown of the system for periods of time such as for vacation and the like.

Abstract: In a water heating system, vapor in the products of combustion gases is condensed in a secondary heat exchanger positioned in a housing with the primary heat exchanger and combustion chamber. The two heat exchangers are coaxial coils with the secondary coil surrounding the primary. Gases flow radially through the primary coil, axially along a baffle and then axially through the secondary coil at an increased velocity. The gas/air mixture is burned in a burner within the primary heat exchanger and the gas product are drawn through the exchangers by a blower. A water storage tank is designed to enhance stratification of hot water over cooler water. The cooler water is used to condense vapor in the secondary heat exchanger.

Abstract: Hot water supply temperature is set by a temperature setting device in response to an instantaneous flow rate signal from a water flow rate sensor arranged in a water supply pipe and a feeding water temperature signal from a feeding water temperature sensor which are compared with a predetermined hot water supply temperature and calculated in a control unit. A proportional valve and other devices in a gas supply pipe are controlled in response to the result of the comparison and calculation to define a required volume of gas for ignition and heating. At the same time, a fan damper is controlled by a damper control device so as to adjust the volume of combustion air. A signal representing discharging hot water temperature from a discharging hot water temperature sensor arranged in a hot water feeding pipe is fed back to the control unit and calculated therein, and a valve in the hot water supply pipe is adjusted in response to the result of calculation to attain the desired hot water supply temperature.

Abstract: A method and apparatus for controlling the operation of an add-on heat pump water heater unit is disclosed. A combination of a thermally conductive tube having a flattened portion and a thermostat mounted thereto is utilized to sense the temperature level of water in a tank to which the heater unit is connected. The tube and thermostat are additionally insulated from the ambient. A circulating pump is provided and connected to the water thermostat such that the pump is energized only when it is necessary to operate the heat energy adding unit.

Abstract: A temperature comparison apparatus contains current-producing temperature sensors to measure outdoor temperature and heater temperature, a summing circuit to add the output currents from the sensors and a comparator circuit to compare the sum of the sensor currents to a presettable reference value.