GB2211331A - Water heater diagnostic apparatus - Google Patents

Abstract

An integrated diagnostic module is connected as an integrated part of a hot water heating unit. The module has a circuit board with an electrically isolated power supply and sensing leads connected to sensors in the operating system and coupled to components of the hot water heating unit. The diagnostic module has a visual display and descriptive panel 37 secured to the circuit board as a part of one wall of the housing. The display panel has a vertical row of LEDs 78-87 in a operating display section 42 and a vertical row of LEDs 90-95 in a malfunction display section 43 to the opposite sides of a heater illustration 77. The panel carries indicia to form a descriptive display of the operational status and of the state of the components. Each system state and component is provided with a suitable sensor having a switch connected in the circuit, and connecting the LED of an opto-isolator which includes a transistor turned on by the LED. Each transistor is connected with one of the LEDs units, and selected transistors are connected in an interrelated logic whereby two different conditions control one of more LEDs. The operating section includes a "standby" LED 80 and a "heat" LED 81. A pump display includes a "pump-on" LED 82 and a "cool-down" LED 83. An ignitor LED 84 and a series of three or more burner LEDs 85-87 provide information as to the state of the burner. The malfunction section includes a water flow LED 92, a temperature LED 93, a low gas pressure LED 94 and a restricted gas flow LED 95. Flue LEDs 90, 91 can be provided to monitor a blocked flue or excessive CO in the flue gases. <IMAGE>

Description

WATER HEATER DIAGNOSTIC APPARATUS This invention relates to a water heater diagnostic apparatus and particularly to an integrated module unit which is adapted to be mounted with the water heater and includes an operating section for monitoring and describing the normal operation of the water heater and a malfunction section for detecting malfunction of any one or more components of the water heater with an integrated describing of the several parameters on an exposed descriptive panel.

Industrial water heaters may be operated under various load conditions and generally require periodic monitoring as to proper functioning. The water heater may be a separate storage unit with internal heating unit. Gas fired heaters are desired because of the rapid heating of the water during a heat cycle. The water heater may also provide hot water on demand, or be coupled to one or more separate storage units with a pump means for circulating of the water through a heating coil in the heater unit and the storage unit. Upon termination of a heating cycle in a heater system including separate storage tanks or in a demand system, the pump unit continues to circulate the water to establish a thermal balance in the hot water system, identified as a cool down" period.

Various controls are normally provided in a system. The controls include various power devices, thermostats for monitoring and controlling the temperature level of the water, ignitors for initiating the heater unit, a gas valve control providing either a high or low heat condition as well as a pump control for circulation and cool down cycles. During the system operation, various malfunctions may occur, all of which directly effect the desired or essential operation of the unit. Typically, in order to effectively heat the water in the system including the storage system, sufficient water flow must be established and maintained. Further, the circulating heating coil unit in coil type heaters must be protected against excessive temperature. The burner must be supplied with a proper gas supply.A restricted gas flow to the burner will result in an inefficient and improperly operating heater unit. The burner may include multiple stage firing for different heat input to the water during the heating cycle.

These and similar functions and operating devices are presently manually checked and monitored by an operator. Component mounted sensing devices with an output reading unit have been provided for monitoring some of the factors and components. For example, a thermostat may have an external display, a flow meter may be connected in the circulating line with an output dial providing a flow readout. More recently, the free flow of flue gases from the heater unit have been of some significance. Further, if the flue gas contains excessive carbon monoxide, danger to living things will arise, and monitoring of the flue gas conditions and state may be desirable if not essential. Thus, selected individual elements may provide an output from which other functions and/or malfunctions can be deduced.

Although such systems have been satisfactorily developed and are used in industry, the requirement for an operator monitoring and continuously or periodically checking of the several systems and components is relatively costly. Further, the monitoring is essentially operator dependent and the results are therefore directly related to the care and proper attention by the maintenance and operating personnel. This of course introduces one further source of malfunction or undetected error.

The present invention is particularly directed to an integrated diagnostic module forming an integrated part of a hot water heater unit. In accordance with the present invention, the integrated diagnostic module is an electrical monitoring system having an electrically isolated connection to the operating system and components of the hot water heater, and includes a plurality of means coupled to and monitoring the various functions and components of the heating system to provide a continuous descriptive display indication of the status of the system and malfunction of the particular monitored components.

The status information and malfunction information are displayed on an appropriate display unit directly associated with the heater unit so as to provide operating and maintenance personnel with on site information as to a component malfunction and the operating status of the heater at the time the malfunction occurred. The display unit is provided with separate sections for status information display and for malfunction information display. This provides an immediate and continuous status report on the system which is continuously available to the operating and maintenance personnel.

More particularly in accordance with the present invention and in a preferred embodiment, the various operating and control components are preferably located in a concentrated area or portion of the heater tank in accordance with general known construction.

The operating and control components are generally connected to a 115 volt A.C. power supply such as conventionally distributed throughout the United States for energizing and driving of the system. An outer enclosure is secured over the control components to isolate and protect the components except during periods of necessary attention and maintenance. In accordance with the present invention, a diagnostic module is provided including a visual display and descriptive panel or unit. The display panel is provided with a bank of function display elements in the operating section and a bank of component status display elements in the other or malfunction section.

The display elements are conveniently low voltage lamps such as LED's, crystal displays or other similar indicators. The display elements are mounted on a circuit board as a part of the display unit and exposed through a separate display panel. The panel carries appropriate indicia to form a descriptive display of the functioning and of the status of various individual crucial or significant components. An isolated electrical sensing and display drive unit is provided, preferably as a separate electronic package or unit with circuit inputs coupled to electrical output of the sensing units with appropriate outputs interconnected through a logic circuit to the various visual display elements, and a power input coupled through a step-down isolation unit to the main incoming power supply, such as the 115 volt supply. The isolated circuit includes an electrical isolating and voltage reducing means to step down the 115 volt supply to a low voltage, with a suitable low voltage A.C. supply for operating of the monitoring system and a suitable low voltage D.C.

supply for the display units, with electrical isolation with respect to the high voltage supply. The electronic unit includes a plurality of sensors having a low voltage A.C. input drive side coupled to the control and operating circuit to provide an isolated low voltage signal. The output of each sensor is connected to actuate the individual visual display elements connected, either directly or through a combined logic with certain other components. Each sensor is coupled to the circuit of the display elements through an electrical isolator to further separate the monitor module from the heater control circuit to insure that the control circuit operates without affect by the module circuit. The isolated diagnostic module is therefore readily adapted to providing a remote display, multiheater monitoring, actuating of alarm circuits and the like.

The panel and integrated electronic unit is conveniently mounted within the control housing.or enclosure of the heater unit. Thus, the display unit is preferably with a housing circuit and lamp board and an outer overlay panel closing the housing. A simple plug-in type connector connects an electronic package on the circuit board to various low voltage power and signal leads. The display unit has only low voltage inputs and may also be mounted adjacent the heater and connected to the heater control power units via a low voltage connection cable. The display unit is mounted with the control enclosure which is provided with a front wall opening exposing the panel. The display units can be coupled through an appropriate cable to a remote display panel and/or processing system wherein the status of the system and components is continuously displayed.Various factors such as operation cycles, duration of operation and like inquiring and management factors can also be analyzed as a result of the system monitoring.

In a preferred construction, each monitored system and/or component is provided with a suitable sensing element having a switch or other power level control element connected in the control circuit and operable to produce a change in the circuit. The sensor is coupled to an opto isolator switch unit including a light source connected in series with the sensor. The opto isolator includes a solid state switch element optically coupled to the light source to provide a binary or on/off signal in the low voltage diplay circuit. Each switch element of the opto isolator is connected in series with one of the light units, and selected switch elements are connected in an interrelated logic whereby two different conditions control one or more lamp units.In a preferred construction, each opto-isolator switch is a solid state switch element connected directly in series with an appropriate current limiting resistor to the corresponding lamp which is preferably an LED (light emitting diode) connected to a six volt D.C. supply.

The switch is connected in series or in parallel with the lamp depending upon the control logic.

When heat is called for, a thermostat actuates a switch unit to energize the light unit for that opto isolator which then turns on the solid state switch to bypass a "standby" light and turn on a "heat" light. Simultaneously therewith, switches are actuated to turn on a thermal balance or "pump-on" light and turn on various burner status lights. This visually displays the change from "standby" to a "heat.' cycle as a result of the energization of the various related LED units. In addition, individual circuits and LED's are provided for monitoring of the water flow in response to the operation of the pump unit. A high coil limit branch monitors the temperature of the coil and if it rises above a selected level, the corresponding light is illuminated.Certain commercial water heaters may include redundant heating units where a greater hot water supply is essential. Separate branches monitor such redundant units. Similar branch circuits are provided for monitoring of a low gas pressure and a restricted gas flow in each burner. A bank of burner related lamps monitors and indicates the status of the ignitor gas pilot unit, and in a dual stage burner system, a low level burner input and a high level burner input. In addition, further branch circuits may be included for a blocked or restricted exhaust flue and an excess CO flue gas condition in each unit.

A preferred embodiment of the present invention consists of a standard or universal interconnect display circuit and display module with various control switches for selective supply of power to the several display circuits through the individual opto-isolators. The LED display board would include branch circuits for all heaters in a given line as well as a bank of expansion branch circuits. The board is also formed with the appropriate structure for different commercially available components. Thus, opto-isolators are available for response to both half cycles of an A.C. supply. Other opto-isolators however, resopnd to only one half cycle. The latter devices should be provided with a protective diode or the like. Such modification may be incorporated in the basic board.The universal module would thus be designed to provide installation to any of the various water heaters in the line of heaters of the manufacturer. The circuit of the module is then connected to the sensors for the particular heater, with a separate display overlay to the display panel.

The present invention provides an improved system and apparatus for monitoring of a commercial hot water heater system. The display module establishes a complete display of the status of the heater operation as well as the state of the operating components during malfunction of the heater.

The drawings furnished herewith illustrate the best mode presently contemplated by the inventor for carrying out the invention and which is described hereinafter.

In the drawings: Fig. 1 is an elevational view of a commercial hot water heater incorporating a descriptive display panel illustrating an embodiment of the present invention; Fig. 2 is a fragmentary view of the water heater with a part of an outer cover enclosure removed and illustrating certain details of construction; Fig. 2a is an enlarged sectional view illustrating the structure and mounting of a display panel; Fig. 3 is an enlarged plan view of the descriptive display panel shown in Fig. 1; Fig. 4 is a wiring diagram of an operating circuit incorporating certain control elements for energizing of the descriptive display panel shown in Fig. 3; and Fig. 5 is a schematic circuit diagram of the monitor control and drive circuit for the display panel unit illustrated in Figs. 1-4.

Referring particularly to Fig. 1, the present invention is shown with a typical hot water heating system having a water heater 1 connected to a separate storage unit 2. A pump 3 circulates water between the heater 1 and storage unit 2 to establish a common temperature of the water in the system. The heater 1 is a typical device and includes a vertically oriented cylindrical assembly including an inner hot water coil 4 within an outer decorative enclosure shell 5. A burner unit 6 is located beneath the coil 4 and connected through a gas valve control assembly 7 to an incoming gas line 8. An input line 9 supplies cold water from a utility supply or the like. The heater 1 includes a heating coil 4 through which the cold water passes and is heated by hot gases 22 from burner unit 6.A central exhaust gas flue 11 extends upwardly from the water heater 1 and terminates in a chimmey connection 12 in accordance with conventional practice. An elongated rectangular cover housing 13 is secured to a side wall panel mounted to the heater tank and extending throughout a substantial portion of the water heater adjacent to a gas burner control valve assembly 7. Various controls 16 are mounted within the housing 13 and connected to the several operating devices of the heater. The rectangular housing 13 is a generally U-shaped member having an edge flange 14 for mounting to the enclosure. The housing is readily removed to expose the various components. Generally, the controls include various means for monitoring and controlling the system operation.Typically, a thermostat or other temperature control unit 17 is secured to the coil 4 within the housing 13 adjacent the upper end of coil 4. The thermostat unit 17 generally is a dual sensor unit, one of which is set to an upper temperature limit and the other to a lower limt to establish a temperature range and to monitor the temperature of the water. Suitable control switches are actuated by the sensors 17, as well as the other component sensors described in the illustrated embodiment, for controlling the burner valve assembly 7. The sensor 17, as well as other sensors, are known devices and a particular unit is not shown or described.

Temperature control dials 17 and 17a may provide for setting of the desired water temperature limits. Typically, the control provides for setting a temperature range such as 160 to 1800 F. The limits are normally factory set at a certain number of degrees above the maximum water temperature to positively prevent operation of the heater with a dangerous high water temperature condition.

A high temperature limit switch 18 is mounted to the coil to cutoff the burner if the coil temperature is excessive. The switch 18, in accordance with conventional practice, preferably includes a manual reset button for resetting of the switch unitand is only effective if the temperature is dropped below the minimum setting of the system.

A pair of sensors 20 and 21 are shown located in the discharge end of the exhaust flue 11. One sensor 20 constitutes a flow sensor and monitors the flow of exhaust gases 28 when the burner is operating. An exhaust flow drop below a predetermine level indicats that there is a restriction in the exhaust flue. This could create an inefficient if not dangerous condition. The second sensor is a carbon monoxide (CO) sensor also mounted in the upper end of the flue 11 to monitor the exhaust gas content and particularly the level of carbon monoxide in the exhaust gases 22. Excessive carbon monoxide could create a dangerous condition to humans and other living beings. The CO level is therefore monitored.

A gas pressure sensor 23 is attached to a pressure tap on a main gas valve 24 of assembly 7 in gas line 8 and establishes a display output if the pressure drops below an acceptable minimum level.

A gas flow sensor 25 is coupled to the output side of the valve assembly 7 to insure a minimum gas pressure to the burner 6 whenever the heater is in a heat cycle. The malfunction may be defective or plugged valve, a malfunctioning actuator or an erroneous closure of a manually operated main gas valve 24.

A water flow sensor 28 is coupled to the output line 27 from the heater 1 and establishes an output signal if the water flow drops below a selected level.

These are typical functions and components which may be monitored in the illustrated embodiment.

The various control valves and drive circuits for operating of the water heater are controlled from a low voltage operating circuit. In the present invention, the operating circuit includes a plurality of switching and control devices coupled to and operated from the various sensors for monitoring the functional state and operating condition of the water heater and also for monitoring of several critical components. The monitor signals are impressed on a display drive circuit of a descriptive display unit 35 mounted within housing 13 for providing a descriptive output of normal operation as well as the malfunction in a critical component. The descriptive output is presented as two separate series of lamps 36 in a display panel 37.The display unit 35 is housed within the control enclosure 13 with the panel 37 exposed through an outer opening for visual review of the information as to the condition of heater 1.

Generally, the unit 35 includes a separate electronic circuit board 38 mounted behind the panel 37. A plugin connector 39 interconnects the board 40 to an incoming power and signal cable 41 for selective energization of the low voltage display lamps 36. Low power and signal cable provides power to the display unit 35 and the connection of the display circuit to the several sensors in the system for establishing related input signals to the display drive circuit.

Generally, the display panel 37 includes a system operating section 42 in which display lamps 36 describe the operating state the heater, including a standby mode, a heating mode and a cool down mode. The panel 37 also includes a malfunction section 43 including a separate series of lamps 36 for describing a malfunction in selected critical components or functions.

Preferring particularly to Fig. 2a, the display unit 35 is illustrated including a shallow rectangular dish-shaped housing 44. A generally Ushaped bracket 45 has its base portion secured to the base or back wall of the housing. The legs of the Ushaped bracket are L-shaped with mounting flanges abutting and releasably secured to the heater to support the housing spaced inwardly from the outer wall of the housing or cover 13. The lamp circuit board 40 fits within a recessed or offset lip of the housing 44, with the lamps 36 projecting forwardly from the outer face. The overlay panel 37 is secured overlying the board 40 with corner screws 46 interconnecting of the panel and circuit board to the housing 44. The outer enclosure has the opening aligned with the panel, with edge seal member 47 secured about the edge of the housing opening and projecting inwardly into abutting engagement with the panel 37 to provide a clear view of the slightly recessed panel. A control assembly such as a main transformer unit, a cool down control unit and the like are mounted to the front of the enclosure 5. Appropriate low voltage cables 49 to cable 41 for interconnection to the plug-in connector 39 and thereby to electronic circuit board 40 of the display unit 35. The circuit connections are described and set forth in the schematic circuit diagrams shown in Figs.

4 and 5. The mounting of the display unit 35 as an integral part of the heater provides a most convenient and effective descriptive display for operating and maintenance personnel. If for any reason the integrated mounting within the heater assembly is considered undesirable because of a temperature conditions or the like, the display unit can be readily mounted in an immediately adjacent area with the appropriate low voltage connecting cable 41 to the display unit.

The heater operating circuit is generally a standard known circuit and is briefly described to establish the background and basis for the interconnection of the several display related functions and status reports as generally provided at the descriptive display unit 35 and the descriptive display of panel 37.

Referring to the drawings and particularly to Fig. 4, the operating circuit is a typical heater control and is illustrated connected to a conventional 115 volt power supply line 50 in series with a douplepole single throw switch 51 for simultaneously making and breaking of the main power supply connection. The main power lines 50 are connected directly to a control transformer relay 52 and to a thermal balance or cool down control unit 53. Unit 53 is mounted to the control board to the front of the heater within enclosure 13, as shown in Fig. 2. A main thermostat demand switch 55 is connected as an input control to the transformer relay -52. The thermostat may be located in the storage unit or some other end use location which operates switch 55.When the thermostat switch 55 closes, the transformer relay 52 is energized and provides output power to the thermal balance or cool down unit 53 and to a control operating transformer 56. The output of the thermal balance unit 53 provides power to the pump 3 to initiate circulation of the water simultaneously with the demand for heat.

The pump 3 is driven just prior to firing of the burner 6 to circulate the water for the heating thereof. The thermal balance unit 53 includes an interlock through the direct power line connection 57 to maintain the pump 3 operating after the thermostat switch 55 opens and further demand for heat is eliminated in order to establish and maintain the cool down cycle. The units 52 and 53 can be of any known or desired construction and since such systems and devices are well known no further specific disclosure is made herein other than as the circuit is interconnected to and forms an input to the monitoring circuit as hereinafter described.

Once the pump 3 starts to circulate, an interlock flow switch 58 is closed. The flow switch 58 is connected between the output of the transformer relay 52 and the AC step-down trnsformer 56. Upon closing of switch 58, power is supplied to the burner operating and control circuit 60 for firing of the heating burner 6.

The step down transformer 56 changes the 115 volt power supply to a 24 volt alternating current power supply suitable for operating of the various controls and solenoid valves of the heater control circuit.

In the illustrated embodiment of the invention, the output of the low voltage transformer 56 is connected to the burner control system through the high/low temperature level thermostat unit 17 consisting of a high level switch 62 and a low level switch 63. The high level switch 62 is connected between the one side of the secondary of the stepdown transformer 56 and the main power connection to an ignition module 64 of the heater control. The high level switch 62 is normally closed to actuate the heater in response to a demand for water and responds to the maximum temperature level of the water to shut down the burner 6. The connection of the high level switch 62 to the control is in series with a plurality of sensor interlock switches 65, anyone of which can open and effectively shut down the heater.The switches 65 are each part of a sensor previously identified and coupled to monitor a critical or desired control or operating component, as hereinafter described. The low temperature level switch 63 is connected between the level switch 62 and a high burner gas solenoid valve 66. Switch 63 is also normally closed and responds to a minimum level temeprature to control a two stage burner. In the illustration of the system, the solenoid valves are diagrammatically illustrated with the solenoid winding connected in circuit with reference thereto as the valve unit.

More particularly, with high level switch closed the 24 volt supply is applied to the ignition module 64 and provides power to turn on the pilot burner assembly 67 as well as providing output power to a pilot solenoid valve 68. The ignition module 64 includes an internal power connection to activate a pilot burner ignitor 70, the pilot gas valve 58 and a main low gas valve 69. The pilot burner ignitor 70 also senses the presence of the flame. The ignition 70 is a high voltage spark ignition unit which is operable to light the pilot assembly 67. The pilot gas valve 68 connects the pilot burner 69 to the gas supply line 8 and the main low gas valve 69 connects the main burner to the gas supply line 8 with a relatively low level of gas supplied. Energization of module 64 therefor provides generation of the ignition spark for establishing the pilot flame 71 and firing of the burner.The ignition 70 detects the pilot flame and permit opening of gas valves via energization of solenoid valves 66 and 69.

The low burn switch unit 63 is connected between the high burn switch 62 and the one side of the main high flow valve solenoid 66. The return side of valves 66, 68 and 69 are connected in common with a return terminal of the ignition module 64.

Thus, the high/low sensing switches 62 and 63 selectively provide for energization of the main burner in a low burn stage or in a high burn stage. Both valves are opened for operating the burner 6 in a maximum heating mode, which is established with the temperature below the minimum heat level. As the water temperature rises above the minimum heat level the switch 63 opens, de-energizing solenoid 66 and closing the related valve. The heater continues to operate with the lower gas input provided by solenoid valve 69. Whenthe water temperature rises to the upper limit, switch 62 opens and the heater shuts down.

Referring to Fig. 3, the visual descriptive display panel 37 in a preferred organization and structure is illustrated.

The front face of the panel 37 includes a diagrammatic and simplified illustration 77 of a water heater. The illustration 77 is located generally centrally of the panel. The system operation monitoring lights 36 are located in section 42 to one side of the heating unit illustration 77. The component function monitoring lights 36 are located in the separate section 43 to the opposite side of the illustrated heating unit illustration 77.

In the two sections, 42 and 43, the lights 36 are located in a vertical orientation and alignment with the lights mounted to the backside of the openings in panel 37 on the display board 40 and exposed through appropriately aligned openings 78. The openings and lamps are spaced and grouped in a logical manner with an appropriate identifying indicia as shown located immediately adjacent to the lamp.

In the illustrated embodiment, the operating section 42 includes a power light 79, shown as an uppermost display which is lit whenever power is supplied to the heater control.

The status of the heat demand thermostat unit 55 is displayed immediately below the power light. The demand display includes a pair of vertically oriented lamps, and including a first lamp 80 indicating a standby condition and a second lamp 81 indicating a call for heat.

The operating system lamps 36 are selected with a common unique color when lit, such as green, with the exception of the standby lamp 80 which is different, such as yellow.

Spaced downwardly from the heat demand display is a pair of lamps related to the operating pump mode, and includes a first lamp 82 which is lit when the pump 3 is on and a second lamp 83 which is lit when the pump is operating in the cool down mode. This of course provides direct indication of the status of the flow system.

The burner ignitor 70 is provided with a separate indicator lamp 84 which is lit whenever the ignitor is operating.

Finally, in the operating display section 42, a gas valve monitor array is illustrating including three lamps. The first lamp 85 monitors the pilot valve 68, the second lamp 86 monitors the low input valve 69 and the third lamp 87 monitors the high input valve 66. The combination of the gas valve lamps 86 and 87 and the pilot lamp 85 provide a continuous indication of the status of the burner 6 with respect to the supplying of heat to the water heater.

The malfunction display section 43 is located to the right side of the diagrammatically illustrated water heater 77 and includes the series of lamps 36 located in vertical orientation to indicate malfunction of selected control and operating components. Again, appropriate indicia is provided to identify the particular malfunction. Lamps 36 in the malfunctioning display section are provided with a unique color, such as red. The lamps are normally off and energized to indicate a malfunction of the related component or function.

In the malfunction display section, a coupling indicia line 88 is provided between the associated lamp 36 and the particular element or component of the water heater which is monitored for malfunctioning.

In the illustrated embodiment of the invention, the malfunction display section 43 includes a first lamp 90 which provides an indication of the condition of the flue. If there is any adverse blockage of the flue, the lamp 90 is lit. A second lamp 91 indicates the state of excess carbon monoxide (CO) existing in the flue gases and if present, the corresponding lamp is turned on.

A flow lamp 92 is coupled in the circulating line to indicate whether adequate flow of water is circulating through the system for the proper operation of the system. If not, the lamp is turned on.

A high temperature coil lamp 93 is provided for indicating the over heating of the coil proper.

A pair of lamps 94 and 95 provide display for a low gas pressure and for a restricted gas flow respectively.

The operator by merely viewing the display panel readily determines the status and normal functioning of the system as well as the source of any malfunction which might be present.

The electronics for the diagnostic module includes low voltage connection to the appropriate sensors and drive circuits for operation of the LED lamps or other display and/or signalling devices.

Referring particularly to Fig. 5, the display panel drive board is schematically illustrated in an across the line type of circuit. The driver display circuit is a low voltage D.C. circuit. A step down transformer 100 is connected to the main incoming supply lines 50. A full wave rectifier 101 connects the secondary of the transformer 100 to a pair of D.C.

output lines 102-103 for driving of the display lamp circuits. The transformer rectifier circuit establishes a 6 volt D.C. supply between lines 102 and 103. The output is unfiltered as the LED lamps 36 provide a clear display with the unfiltered D.C.

voltage and current. The transformer 100 is mounted to the heater within enclosure 13 and the low voltage leads from the transformer are a part of the cable to the display module connector 39. A single pole doublethrow switch 104 is shown having a first set of contacts 105 connecting certain components as hereinafter described to the return line 103. The second set of contacts 106 of the switch 104 provide a common circuit connection for manual testing of the several lamps 36 to insure functioning. With the lamps in an off state the switch units 104 can be momentarily actuated to monitor the condition all lamps for necessary replacement and the like.

In the illustrated embodiment of the invention, a plurality of parallel circuits are connected between lines 102 and 103 for monitoring each of the several conditions as set forth on the display panel. In Figs. 4 and 5, the corresponding monitoring lines are correspondingly identified.

The power lamp 79 is connected directly across lines 102 and 103 in series with a current limiting resistor 107. Whenever power is supplied to the operating circuit as shown in Fig. 4, power should also appear at the D.C. drive lines 102 and 103 with corresponding turn-on of lamp 79. If lamp 79 is not lit, it is an indication that power is not being supplied to the diagnostic module or to the heater controls and immediate attention should be given to the system to insure proper operation. With the lamp 79 connected directly across the lines, an unlit lamp should be checked to insure that the lamp 79 has not burned out. The other lamps 36 are connected in circuit through a special control switch means as hereinafter described. Actuation of switch 104, will indicate whether or not the other lamps 36 are operational or some other part of the circuit has failed. Thus as illustrated, switch 106 of the switch 104 has one contact directly to line 102. The opposite side of the contacts 106 is connected in series with a blocking diodes 109 to the corresponding lamps 36.

Closing of the switch interconnects power directly from the power line 102 to the lamp to provide a direct test drive.

The first three across-the-line circuit branches after power LED 79 include a thermostat heat branch 110 and a thermostat stand-by branch 111.

Branch 110 controls "heat" lamp 81 while branch 111 controls "standby" lamp 80. Lamp 80, which is the stand-by lamp, should be normally lit. Branch 111 is therefore connected directly across the power lines 102 and 103 with lamp 80 in series with a dropping resistor 112. Upon application of power to the system, lamp 80 should be lit to provide the desired yellow illumination. The lamp is de-energized through an opto-isolator 113 which is connected to the output of the transformer relay 52 of the operating and control circuit. The opto-isolator 113 is illustrated as a standard known device such as a Model PS2506-4 manufactured and sold by NEC Corporation of Japan.

NEC's high gain amplifier unit identified above is sold as a integrated packaged unit including four opto-isolator devices having their own individual input/outputs. The units are correspondingly illustrated in Fig. 5 by the dashed outline about the groups of opto-isolators for purposes of illustration only.

Each opto-isolator package has a high gain switching unit including a pair of LEDs 114 connected in inverse parallel. The diodes 114 are rated to operate from a suitable voltage such as provided with dropping resistors as shown in Fig. 5 connected to a 24 or 110 volt supply. The LEDs provide optical coupling to a rapidly acting optically responsive solid state switch device shown as a high gain NPN transistor. The high gain construction is desirable to provide a high conductivity switch having minimum voltage drop. The switch is operable to shunt and cutoff a low voltage display LED, which may have a voltage drop of about 0.8 volts, and the like as hereinafter described. In addition to the dual LED gain devices, single LED optoisolators are widely used and available. In such devices, a single LED is provided for illumination of a switching transistor.The LED being a diode conducts during only one half cycle of the A.C. input.

Generally, a reverse-connected protective diode is connected across the input of such an isolator. In accordance with the concepts involved in the present invention, the display circuit board 40 is preferably specially constructed with appropriate openings in the circuit board for mounting and connecting of such a protective diode across the input lines to a low gain opto-isolator. As described above, the dual LED optoisolator units are preferred to provide a more effective energization of the effective and reliable energizing or control of the several LEDs of the display unit.

Generally, the opto-isolator 113 is a solid state relay and includes a pair of LEDs 114 which are connected to the operating control circuit and particularly the transformer relay 52 via a signal line for selective energization whenever power is applied to the transformer relay as presently hereinafter described. The LEDs 114 are optically coupled to a solid state optical transistor 116. The transistor is shown as a NPN transistor having its base exposed to the light rays 117 from LEDs whenever the LEDs 114 are energized. The collector 118 of the transistor is connected directly to the junction of the dropping resistor 112 and the lamp 80. The emitter 119 of the transistor 116 is connected to the interconnecting return line 120 and to return line 103 via normally closed contacts 105 of switch 104.Thus, when LEDs 114 are energized, the transistor 116 is rapidly driven into conduction and effectively interconnects line 120 to the anode side of the lamp 80. The cathode side of the lamp 80 is connected directly to the return line 103. Consequently, the opposite sides of the lamp 80 are connected to the common return potential and the lamp is de-energized.

Each opto-isolator shown is identically constructed with the LEDs and a switching transistor.

Consequently, each of the corresponding elements of each opto-isolator may be referred to by corresponding numbers applied to the opto-isolator 113 for simplicity and clarity of explanation.

The thermostat "heat" branch 110 is connected in circuit through an opto-isolator 121. The collector of the opto-isolator switch 121 is connected directly to line 102 while the emitter 119a is connected in series with a dropping resistor 122 in the branch circuit with lamp 81 having its cathode connected directly to the return line 103. Thus when the optoisolator 121 is energized it turns on its associated transistor and thus completes the circuit from line 102 through the lamp 81 to line 103. Lamp 81 is then lit indicating a demand for heat on the display panel as the result of the illumination of the lamp 81.

The input side of the opto-isolator 121 is connected to the operating circuit through a coupling resistor 123 in a connecting signal line 124 which is correspondingly numbered in Figs. 4 and 5. Line 124 is shown connected to the main output of the transformer relay 52 and cool down module 53 and flow switch 58 to the control transformer 56. Line 124 is connected to a 115 volt line in the control. The dropping resistor 123 limits the current through the opto-isolator LED's. Whenever the thermostat 55 closes, power is supplied to those components as previously discussed and simultaneously a low voltage signal is transmitted to the display circuit. It thus provides power to the opto-isolators 121 and 113.

In the illustrated embodiment, the pump "cool down lamp 83 is operated by the cool down unit 53 and is also interlocked with the thermostat status display. In particular, the cool down lamp 83 is connected in circuit via a branch 125. The lamp 83 is normally off. An opto-isolator 126 has its transistor 126a connected between return line 120 and the anode side of the LED lamp 83. Thus when the opto-isolator is energized, it turns on its transistor to energize lamp 83 indicating that the pump is operating in the cool down mode. The opto-isolator 126 is connected in series between the opto-isolator 113 and the resistive network to the return side of the 110 volt supply.

Thus, the three opto-isolators 113, 121 and 126 are energized from the 115 volt supply through the one dropping resistor 123 and the resistive network upon appropriate actuation of the thermostat switch 55.

With all three of the opto-isolators 113, 121 and 126 energized, the corresponding lamp 80 is de-energized while lamps 81 and 83 are energized. This provides an indication of the demand for heat and the interlocking and creation of the pump cool down cycle.

Pump3 has a pump-on lamp 82 connected in a branch 127 and is in series circuit with an optoisolator 128 between lines 102 and 103. Lamp 82 is therefore normally off and only energized when the opto-isolator 128 is energized. Opto-isolator 128 is separately connected to the operating circuit and particularly to the input signal power line from the cool down unit 53 for pump 3 as shown by the interconnecting line 129, which also includes a voltage dropping resistor similar to resistor 123. Thus, whenever power is supplied to the pump, a 110 volt signal is transmitted through resistive network 129a to the lamp side of the opto-isolator 128. It in turn provides illumination of the corresponding transistor 128a for turn on of the lamp 82.

With the circuit as described to this point, the normal operating section 42 of the diagnostic module has the lamp 79 on, the stand-by lamp 80 off, the heat demand lamp 81 on and the pump "on" lamp 82 on indicating the demand for the power for heat and the operation of the pump. As previously noted, the pump must be operated through the cool down unit to establish flow and operation of the flow switch 58 to provide power to the A.C. step down transformer 56.

Thus, with the above lamps on as indicated, the ignitor and pilot lamp should be appropriately energized simultaneously or very shortly thereafter.

An ignition branch 130 has the ignition lamp 84 connected in circuit through an electro opto-isolator 131 for monitoring the power to the pilot burner valve. Thus the pilot lamp 85 and branch circuit 132 has the lamp 85 connected generally to the anode side of the lamp 84. The opto-isolator 131 is connected via a signal line 13.3 for energization whenever power has been applied to the pilot valve 68. The transistor of the opto-isolator 131 has its collector connected to line 102 and its emitter connected to the interconnecting node 134, which is common to the branch circuits 130 and 132, and the cathode side of the LED lamp 85 is connected directly to the return line 103.

Lamp 85 is therefore energized whenever the optoisolator 131 is energized. This also connects the anode side of the ignition LED 84 to power. The cathode side of the ignition LED 84 is connected to the return line 120. Thus upon energization of the optoisolator i31, Led 84 is also energized as a result of the return path 120. Thus, upon initial actuation of the ignition module 64, both lamps 84 and 85 are turned on through the opto-isolator 131 with slightly different return circuits indicating the ignition condition. Upon establishment of energization of the burner, the ignition lamp 84 is turned off as follows.

An opto-isolator 136 has its transistor 136a connected directly in parallel with the ignition LED 84. Thus, when the opto-isolator 136 is energized by a signal from the operating circuit, the transistor 136a conducts and shorts the lamp 84 thereby terminating the illumination of the ignition unit.

The opto-isolator 136 is connected via a signal line 137 to the main valve output terminal of the operator and ignition module 64. The main valve output terminal is connected to the low main burner valve 69. The opto-isolator 136 is interconnected in series with an opto-isolator 138 which is connected in the low main burner valve branch 139 of the display drive circuit. The opposite side of the opto-isolator 138 is coupled to the A.C. return line 133a to complete energization of units 136 and 138 upon completion of ignition. The transistor 138a of opto-isolator 138 has its collector connected to line 102 and its emitter connected in series to the branch 139 for series connection with the LED 86 to the return side 103 of the power supply. Thus, energization of the optoisolator 138 turns on LED 86.Upon receiving of an appropriate signal via the line 137, both of the optoisolators 136 and 138 are energized. The opto-isolator 136 turns off ignition lamp 84 and simultaneously turns-on the low main burner valve lamp 86.

After the firing of the burner 6, the ignitor lamp 84 is turned off, the pilot lamp 85 remains on and the low main burn valve lamp 86 is on.

Upon initial energization and with the water temperature below the minimum level set by switch 63, the low switch 63 of the high/low control thermostat 61 is closed and valve 66 is energized. Lamp 87 is then energized through a branch circuit 140 of the display circuit shown in Fig. 5, as follows. An opto-isolator 141 has its LEDs connected by a signal line 142 to the operating circuit and particularly to the line from the switch 63 to valve 66. With the switch 63 closed, the opto-isolator 141 is energized. The switching transistor 141a of the opto-isolator 141 has its collector connected to a common node 143 between the emitter in the branch circuit 139. With the optoisolator 138 energized and the opto-isolator 141 energized, the collector of the transistor 141a is connected to the main power line 102 in series with the switching transistor 138a.The transistor 141a has its collector to emitter circuit connected in series in branch line 140 to the return line 103 thereby providing energization of the LED 87. Thus in this state, all three of the lamps 85, 86 and 87 will be energized indicating the corresponding status of the gas valve, with the pilot light burning and the ignitor off.

This provides a complete display of the normal operation on a continuous basis. Thus as previously noted, the water heater first operates to heat the water from a temperature below a minimum level. The water heats up gradually, with both the low and high valves 66 and 69 open to establish maximum input heat to the heating system. As the temperature approaches the low or minimum level temperature and reaches and exceeds such temperature, the switch 63 opens of the high/low control unit 61. Valve 66 is deenergized. Simultaneously, the power is removed from the signal line 142 and the opto-isolator 141 is deenergized. Transistor switch 141a turns off and the lamp 87 turns off. The operator then knows that the device is operating with the low heat input as the result of the fact that only the pilot light 85 and the low input light 86 are illuminated.As the temperature continues to rise, it reaches the maximum temperature level at which time switch 62 opens de-energizing both the pilot light 85 and the low input valve light 86.

The thermostat 55 may remain closed as the result of a demand from the separate thermostat valve. The pump mode lamps automatically indicate the continuation of the cool down cycle.

Thus thermostat 55 will open de-energizing the opto-isolator 121, 113 and 126. The bypass of the thermostat heat branch opens as the result of the deenergization of opto-isolator 121. De-energization of opto-isolators 113 and 126 also terminates conduction through the switching transistors of such optoisolators. These switches as previously described are connected in parallel with the lamps 80 and 83 respectively. Consequently, the bypass or short circuit across such lamps are released and the lamps turned on. The standby lamp 80 will turn on and the cool down lamp 83 will turn on. The "pump-on" LED will still be energized as the result of the continued energization of the opto-isolator 128. The cool down period is indicated to the operating and maintenance personnel.

The branch circuits for monitoring the malfunction section lamps 90 through 95, inclusive, are similarly connected into the circuit of the low voltage D.C. supply lines 102 and 103, with the individual inputs to the corresponding opto-isolators coupled to the bank of switches 65 of the operating control circuit. With the devices functioning properly, each of the LEDs is de-energized. In the event of malfunction, a related opto-isolator in a corresponding branch circuit of the control drive unit is activated to turn-on the corresponding LED.

Referring te Fig. 5, the LED 92 is connected in the branch circuit 145 to detect insufficient water flow through the system. The lamp or branch 145 is connected in circuit through the pump on branch line 127. Thus the anode side of lamp 92 is connected through the current limit resistor to the emitter of the pump-on opto-isolator 128. When the pump is operating the corresponding switching transistor 128a is conducting and provides power not only to pump LED 82 but to the anode side of the LED 92. The cathode side of the LED 92 is connected to the common return line 120. The LED 92 is thereby energized. An optoisolator 147 including a switching transistor 147a is connected in series with the LED 92 and when energized bypasses the lamp circuit to ground thereby effectively turning off the lamp 92.The opto-isolator 147 has its input connected by a signal line 148 to the secondary of transformer 56. Flow switch 58 closes with sufficient flow and power is now supplied to the optoisolator 147. The transistor is enegized and turns off the LED 92.

The other systems are similarly interconnected in branch circuits.

The high coil limit LED 93 is connected in a branch circuit 151. The switching transistor 152a has the collector connected to the power line 102 and its emitter connected to the branch circuit 151 with the cathode side of the LED 93 connected to the return line 103. Thus with the opto-isolator 152 energized the transistor 152a conducts and energizes LED 93. The high temperature coil sensor 18 is coupled to the coil and controls a high coil limit switch 154 connected in series with the bank of switches 65 for completing of the one side of the A.C. voltage circuit to the ignition module. The opto-isolator 152 is connected in parallel with the switch 154. Thus, a signal line 155 connects one side of the opto-isolator to the one side of switch 154. A second signal line 156 connects the opposite side of the opto-isolator to the opposite side of switch 154.With switch 154 closed, the lamp circuit of the opto-isolator 152 is bypassed. If the switch 154 opens as a result of an excessive coil temperature, current flows through via line 155 and the lamp side of the opto-isolator returning via the line 156. Energization of the opto-isolator energizes its switching transistor 152a and thereby providing power to the coil high temperature limit LED 93.

The low gas pressure unit 94 is connected in a branch circuit 157. The branch circuit 157 is connected across the power into D.C. power supply lines 102-103 by the switching transistor 158a of an optoisolator 158. The opto-isolator 158 is connected to the operating circuit in parallel with a low gas pressure switch 159, one side of which is connected to the signal line 156 and the opposite side of which is connected to a signal line 160. Switch 159 is coupled to the sensor 23 in the gas line to the valve assembly 7. If the gas pressure drops below a selected minimum level, switch 159 opens. The switch normally bypasses the opto-isolator 158. Opening of the switch 159 removes the bypass and A.C. power now flows through the LEDs of the opto-isolator 158, energizing the associated switching transistor 158a and providing power to branch 157 for turning on LED 94.Turn on of LED 94 immediately signals the operator that gas pressure is low. Blocked flue lamp 90 is similarly connected in a branch 161 having an opto-isolator 162 similarly providing power to the lamp 90. The optoisolator 162 is connected in parallel with a blockedflue switch 163 in the bank of switches 65. The opposite sides of the switch 163 are connected to the signal line 160 and to a signal line 166. Lines 160 and 166 are connected to the opposite sides of the input of the opto-isolator 162 and the circuit operates in the same manner as the previous circuits to signal a blocked flue condition.

The excess CO LED 91 is similarly connected in a branch circuit 167 and an opto-isolator 168. A CO sensor switch 170 is connected in the bank of switches 65 and connected via the signal lines 166 and a signal line 169 to the opto-isolator 168.

The restricted gas flow LED 95 is similarly connected in a branch circuit 171 through the low main burner branch circuit 139, with a by-pass opto-isolator unit 172. A restricted gas-flow switch 173 is connected to the connection between the operating transformer 56 and switch unit 61 and is connected by a signal line 174 to unit 172. The switch 173 is held closed by normal gas pressure. A restricted gas flow, opens switch 173. The open switch 173 holds optoisolator 172 off and LED 95 is turned on through the low main burner branch 139. When flow is created, switch 173 closes, energizes opto-isolator 172 and the transistor 172a clamps LED 95 off. The system as described provides a continuous monitoring of the various selected components with the several LED's 90 through 95 selectively energized in accordance with a condition of the several components.Malfunction of any one of the components provides a corresponding illumination of the descriptive display LED.

Simultaneously, the main operating circuit to the ignition module is opened resulting in an immediate shut down of the operating unit and in particular shut down of the heater 1. The display section 42 describes the turn off of the heater unit with the heat LED 81 turned on, and a stand-by LED 80 turned off indicating there is a demand for heat, and with the other lamps enegized to indicate the state of the heater at shutdown. One or more of the malfunction lamps 90 through 95 is energized indicating the location of the malfunction and the reason for the shutdown of the heater unit.

The illustrated embodiment of the invention provides a continuous monitoring of the heater status without interference or in any way affecting the heater operating system. The opto-isolators or any other similar functioning device permits the monitoring of the heater control operation with complete electrical isolation of the monitor devices from the heater control circuit. The opto-isolator with the series coupling resistors define high input impedance devices to insure the normal operation of a heater control circuit, with the monitoring circuit as shown and described. As a result the monitoring is completed without in any way affecting the normal operation of the heater control circuit.

The display circuit with its isolated power supply to the light emitting diodes or other lamp units function both as solid state relays and as logic devices to provide proper interrelated control in sequencing of the indicators particularly in the normal sequencing and turn on operation and turn on and turn off of the heater unit. The system maintains and continuously produces a descriptive visual display of the several functions of the heater control and the status of the heater components which may now function. The monitor in particular not only will indicate the shut down point in the sequence but the malfunctioning component or components, thereby permitting efficient and rapid servicing of the heater control and the heater operating system.

The isolation of the monitoring circuit from the operating control and from the A.C. incoming power lines establishes a diagnostic module which is particularly useful not only as the integrated descriptive display of the water heater but permits interconnection to other systems. Thus, for example, the integrated diagnostic module can readily be interconnected to a remote display, multiple heater monitoring, alarm circuits, and the like for providing optimum system control in a large industrial complex.

A separate overlay display panel 37 is secured to the circuit board 40 with a construction to provide a universal application to a line of heaters.

For example, in a commercial production line of the assignee of this application, three different basic commercial gas fired water heaters are produced. Each heater includes the gas burner with an appropriate gas valve assembly and means for controlling of the temperature of the water and the like. Various heaters however have various different types of optional constructions. For example, certain heaters will have redundant valves which are operated to insure shutdown. These different types of systems require different types of operation monitoring. Multiple burners may have individual pilot valves, with a single stage or dual stage burner operation. Other more simplified models may use a standing pilot in contrast to an ignition system. In such a system, it is merely necessary to monitor whether or not the gas valve is energized or de-energized.For energy conservation, certain gas fired units may have a flue damper for opening and closing of the exhaust flue in accordance with the turn-on and off of the burner. Generally, the water heaters of the latter type do not provide for a pump circulation. The flue damper state may then be indicated in place of the pump mode unit. Generally, the panel display circuit board and the display panel are constructed to provide and control the maximum number of vertically oriented lamps. The overlay panel 37 is constructed with appropriate openings and indicia for alignment with the lamps provided for the particular module or the particular heater. The circuit board 40 can be of a basic construction providing for the appropriate mounting and connection of the maximum number of lamps. The number of lamps provided of course will again be directly related to the particular heater unit.The board is preferably formed with at least one additional four unit optoisolator unit to provide an additional four branch circuits.

The module can be readily constructed and mounted as an integrated part of the water heater as illustrated. The electronic circuitry and its fabrication is based on readily available and wellknown circuit technology. The components can generally operate in the environment of most commercial hot water heaters. Certain commercial water heaters operate at temperatures which may adversely affect the life of the lamp units of the descriptive display module. The electrically isolated and low voltage D.C. display system permits the convenient mounting of the display unit 35 adjacent the heater proper with a reliable low voltage connecting cable.

The present invention thus provides a significant improvement in a monitor for on-site analysis of a hot water heater and the associated system.

Claims (20)

1. In a hot water heater system having an A.C. driven operating system and a plurality of different controls and operating elements related to the operation of a heating unit for heating the water, a diagnostic module for establishing a descriptive display of the status of the hot water heater heating system, comprising means for monitoring the operating state of said heating unit, separate means for individually monitoring the individual status of said plurality of control and operating components, a descriptive display panel including an operating display section including a plurality of individual display elements, said display elements being related to the various operating modes of said water heating unit and providing a plurality of different displays for each mode of operation, said descriptive display panel including a malfunction display section including a plurality of display means one for each of said monitored or selected critical components, and circuit means interconnecting of said component display means to each of said components for monitoring the state of said components and driving said display means, whereby the combination of said descriptive operating display sections and said descriptive malfunction display section identify the status of the heating unit and the components including identification of the status of the heater at shut down and the malfunctioning component.

2. In the system of claim 1 wherein said diagnostic module is mounted on said heating unit.

3. In the system of claim 1 wherein said heating unit includes a control assembly mounted to a common support, said module being mounted to said support.

4. In the system of claim 1 wherein said module includes a support housing having an open face, a circuit board mounted to said housing with said display means oriented in accordance with said display means, and a descriptive panel secured to said board.

5. In the system of claim 1 wherein said hot water heating unit includes a gas burner with a gas pilot operater, a valve assembly including a pilot valve means and a main burner valve means, said operating display section including a gas valve assembly subsection including a plurality of adjacent display means including a pilot burner display means and a burner valve gas display means for individually and separately establishing the status of said valve means.

6. In the system of claim 2 wherein said pilot burner includes an electrical ignition means, said operating display section including an ignitor display means for displaying the status of said ignition means.

7. In the system of claim 1 wherein said main burner is a multi-stage burner and said valve assembly includes a plurality of different valve means for varying the gas supply to said burner, said operating display section including a plurality of a separate display means for each of said plurality of valves for monitoring and displaying the status of said valves and thereby the gas supply to said burner.

8. In the system of claim 1 wherein a circulating pump is operated to circulate water through a heat exchange coupled to said burner, a pump control for operating said pump in response to a demand for heat and to a predetermined time after shutdown of said heating unit, said operating display section having first display means operable in response to pump operation and second display means operable in response to operating the pump during said predetermined time.

9. In the system of claim 1 wherein said malfunction display section includes individual branch circuits including individual branch circuits for each of said components, each of said branch circuits including a display means, and means to actuate said display means in response to the state of said monitored component to identify a malfunction.

10. In the system of claim 7 wherein said last named means simultaneously with the actuation of said malfunction display means operates to disable said heating unit with said operating section establishing and maintaining the identification or description of the state of said heating means at the time of said malfunction.

11. A water heater apparatus, comprising a heating unit having a burner and water container coupled to the burner for heating the water passing through the container pump means establIshing flow through said container, thermostat means for establishing a demand for heat, means for operating said burner and said pump means, sensing means connected to burner for sensing the operation of said burner, sensing means connected to said pump means for sensing operation of said pump means, sensing means for sensing the status of said thermostat means, an operating and control circuit connected to said thermostat means, a display module having a support housing and an outer display panel defining one wall of said housing, a display circuit means located in said housing having a low voltage D.C. supply cable and a low voltage sensing cable having sensing leads connected to said sensing means, said panel having a plurality of lamp means indicating the operating status of said heating unit including a first display means indicating the status of said thermostat means, a second display means indicating the input to said burner means, a third display means identifying the start up cycle of said heater unit, and said panel having a plurality of display means including a first display means monitoring the operation of the gas pressure means and second display means monitoring the presence of water in said container, and third display means establishing the level of operation of said heating means.

12. The hot water heater of claim 11 wherein said display module includes individual display branch means for each display means, each of said display lines including an opto-isolator connecting the display line to said low voltage D.C. supply, each optoisolator including input lamp means having input connectors and a switch transistor means, sensing leads including a coupling resistor means connecting said input connectors to said sensing means for operating said transistor means, said transistor means being connected to control the energizing of the lamp means in said branch lines.

13. The hot water heater of claim 12 having 115 volt input means and wherein said means for operating said burner means and said pump means includes a "cool down" timer connected to operate the pump in response to a demand for heat and to maintain operation for a predetermined period of time after shut down of the burner and including an ignition module for firing of said burner, said timer being connected to a 110 volt input means, said ignition module having a step-down transformer coupled to said 110 volt input means and establishes a 24 volt A.C. operating voltage for said ignitor module, said leads including said resistors to drop the voltage to said lamp means.

14. The apparatus of claim 14 wherein said connection of said input means to said A.C. operation means is selected and arranged to actuate said lamp means in response to the state of said monitored means whereby the lamp means is illuminated in the event of a malfunction, said switch means simultaneously with the actuation of said malfunction branch line operating to disable said heating unit with said operation section establishing and maintaining the identification or description of the state of said heater means at the time of said malfunction.

15. The apparatus of claim 11 wherein said burner is a gas fired burner with a pilot operated gas burner having a valve assembly including a pilot valve means and a main burner valve means, said operating section including a gas valve assembly subsection including a plurality of adjacent lamp means including a pilot burner lamp means and a burner valve gas lamp means for individually and separately establishing the status of said valve means.

16. The apparatus of claim 15 wherein said pilot burner includes a high voltage ignition means and a flame sensing means, said operating display section including an ignitor display lamp means for displaying the status of said ignition means.

17. The apparatus of claim 16 wherein said main burner is a multi-stage burner and said valve assembly includes a plurality of different valve means for adjusting or varying the gas supply to said burner, said operating display section including a plurality of a separate display lamp means for each of said plurality of valves for monitoring and displaying the status of said valves and thereby the gas supply to said burner.

18. A water heater apparatus, comprising a heater tank having a central vertically extended flue, a gas burner mounted to the lower end of said tank and establishing a gas flame coupled to said tank for heating of said water passing through said tank, a gas valve assembly coupled to said gas burner and including a pilot burner for establishing a turn on flame adjacent said burner, said gas assembly having a first gas valve means connecting said burner to said burner input line to a gas supply line and establishing a gas flow at a relatively high rate of flow, said gas valve assembly including a second main gas valve connecting of said supply line to said gas input line in parallel with said first gas valve means and establishing a further supply of gas to said gas burner, each of said pilot valve and said first and second named gas valve means including an individual electrical operator, means having first and second switch means, said first switch means including a low temperature switch means operable to demand heat at a minimum selected temperature and said second switch means operated at a second higher temperature level, an operating circuit for actuating of said gas valve assembly in accordance with the setting of said switches and said pilot burner, a high voltage demand circuit including a demand thermostat for initiating operation of said heater and including a tranformer relay and a pump control relay, said pump control relay having a first input means connected to an output of said transformer relay and a second input connected directly to said power line, said pump control relay providing power to said pump unit in response to power from said transformer relay and operable and having timing means to maintain said pump operation after removal of said power from said transformer relay for a predetermine time through said direct power connection to establish a cool down cycle, said step down transformer of said operating circuit having its primary connected to the output of said transformer relay for energizing of said operating circuit in response to the output of the transformer relay, a flow switch means connected in series in a connecting line between said transformer relay and said step down transformer to turn off said heater unit in response to abnormal flow conditions, a descriptive display unit having an operating display section and a component malfunction display section, said operating display section having a plurality of lamp means indicating the operating status of said heater unit including a first display means indicating the heating or standby status, a second display means indicating the heating status including the heat input status of said burner means, said operating section including a intermediate display means identifying the start up cycle of said heater unit, said malfunction display including a first display means monitoring the status of the heating means and including the status of the input to said heating means and a second display means establishing the temperature of said heating means and a third display means indicating a minimum flow of water.

19. In a water heater system including a water heater unit having a circulating coil for ondemand of heating of water and at least one separate hot water storage unit connected to said water heater in a closed recirculation loop, said water heater having a gas fired burner with a valve assembly including a pilot valve means for supplying gas to a solenoid pilot burner, a main high solenoid valve means for applying gas to said burner and a low solenoid valve means for supplying gas to said burner, said water heater having an exhaust flue extending upwardly from the heater for exhausting of flue gases from said water heater, comprising a thermostatic control means including a first low temperature switch and a high temperature switch defining a heating range for maintaining of said water substantially in said range, a flow sensitive switch means connected in said recirculation system or loop for monitoring the flow rate therethrough, a low pressure gas sensor connected between said valve assembly and said burner and operable to continuously monitor the pressure and being actuated in response to a pressure below a selected pressure level, means coupled to said gas line and monitoring the flow through said gas line and actuating a switch means in response to a flow below a predetermined level, means coupled to said coil means for monitoring the temperature of the coil and operating of a switch means in response to in the temperature of the coil above a selected temperature level, flow means coupled to said flue for monitoring the rate of flow of said flue gases and having a switch means actuated in response to a flow rate below a selected level, gas monitoring means coupled to said flue means and monitoring the C02 content of the flue gases and having switch means actuated in response to a C02 gas content above a selected level, a display unit including a display panel having vertically oriented side-by-side display sections including a first display section identifying the operating status and sequence of said water heater, said second section having indicia identifying the selected monitored components of said water heater, said operating display section having a first power lamp means, a pair of thermostat lamp means including a standby lamp means and a heat demand lamp means, said operating section having a pair of pump mode lamp means including a pump on lamp means and a cool down lamp means, said operating section having an ignitor lamp means, said operating section having three valve assembly related lamp means including a pilot lamp means, a high burn lamp means and a low burn lamp means, a low voltage D.C. drive circuit for said lamp means including an isolating transformer rectifier unit coupled to said A.C. supply and establishing a low voltage D.C. supply lines to said lamp means of said operating section, each of said lamp means being connected to said D.C. power supply lines by a branch circuit including an electro optoisolator including a signal input lamp means and a optically coupled solid state switching means, said input means of said opto-isolator being selectively coupled to said operating circuit to monitor the status of said thermostat means, said pump on lamp means being coupled to monitor the supply of power to said pump directly from the thermostat means, said cool down lamp means being coupled to said cool down unit for monitoring the pump during the cool down cycle, said opto-isolator means of said ignitor lamp means being coupled to the input power to said ignition module to monitor operation of said ignition means, said pilot valve means and said low burn solenoid lamp means having a common opto-isolator circuit having its input means connected to the output of the ignition module, said high burn lamp means having the input means of its opto-isolator means connected to the connection of said thermostat to said high burn solenoid valve means, said malfunction monitoring section for said drive circuit including individual branch circuits for controlling of said malfunction lamp means and including individual branch circuits for each of said lamp means, each of said last named branch means including an opto-isolator coupled to said A.C.

operating circuit and having an input means coupled to said A.C. operating circuit and having a solid state switching transistor means connected to control energization of said lamp means, said connection of said input means to said A.C. operating means being selected and arranged to actuate said lamp means in response to the state of said monitored means whereby the lamp means is illuminated in the event of a malfunction, said switch means simultaneously with the actuation of said malfunction line means operating to disable said heater means with said operating section establishing maintaining the identification or description of the state of said heater means at the time of said malfunction.

20. A hot water system substantially as described with reference to the accompanying drawings.