WO1993000559A1

WO1993000559A1 - Hot water boiler system

Info

Publication number: WO1993000559A1
Application number: PCT/KR1992/000024
Authority: WO
Inventors: Jin Min Choi
Original assignee: Jin Min Choi
Priority date: 1991-06-29
Filing date: 1992-06-29
Publication date: 1993-01-07
Also published as: CN1070467A; CN1049972C

Abstract

A hot water boiler system of the type of an atmospheric operation, capable of controlling automatically the pressure of room heating water under atmospheric pressure. A supplement water tank of the type open to atmosphere is disposed in a boiler case. A room heating water supplement line equipped with an electromagnetic valve is connected to a hot water supply line and a sensor is provided in the water supplement tank to sense a low water level so that automatic room heating water supplement is achieved by opening and closing operations of the electromagnetic valve according to the sensing operation of the sensor. There is also provided an overheat sensing circuit equipped with an overheat safety switch disposed and exposed outwardly of a boiler case, capable of achieving automatic water supplying upon a shortage of room heating water in a water chamber. The boiler system also comprises a circulation pump anti-fixing circuit for achieving periodical temporary operation of a circulation pump in the summer season that a room heating system is not operated for a long time so that the circulation pump can always be ready for its normal operation.

Description

DESCRIPTION

HOT WATER BOILER SYSTEM

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a hot water boiler system for domestic use using oil or gas as its fuel, and more particularly to a hot water boiler system of the type of an atmospheric operation (hereinafter, referred to as an operation under no pressure), capable of controlling automatically the pressure of hot water under atmospheric pressure.

2. Description of the Prior Art

In general hot water boiler systems which conduct a circulation of hot water to achieve both cf room heating and hot water supplying, water in a heating chamber (namely, a heat exchanging chamber) disposed in a boiler body is heated using fuel such as oil, gas or electric power, as heat source. The water heated to high temperature is circulated to conduct room heating and supplied as water for a bath or other purposes. These boiler systems essentially require a room heating water supplement device for supplementing a portion of room heating water which is naturally lost during its circulation due to certain causes, and an expansion device for reducing the internal pressure of the heating chamber increased due to an increase in the specific gravity of room heating water which is caused by an increase in the temperature of room heating water.

To this end, such conventional boiler systems comprise a supplement water tank (so called, "expansion tank") disposed outwardly of a boiler case and provided with a ball float-controlled valve, as shown in FIGS. 7 and 8. The supplement water tank is connected to a room heating water feedback pipe via the ball float-controlled valve and a supplement water pipe, so as to supplement the naturally lost hot water portion. In order to control the internal pressure of the boiler, an expansion pipe (namely, a relief pipe) is also provided which is connected at one end thereof to an uppermost portion of a room heating water output line and at the other end thereof to the supplement water tank.

However, such a construction is restricted in its installation, because of requiring a separate space in which the supplement water tank occupies and a considerable height for naturally generating a water head. Moreover, foreign matters are likely to enter the supplement water tank and cause clogging of the supplement water pipe due to their deposition. Frequent failures of the ball float-controlled valve which controls the water level in the supplement water tank also may result in a submergence of the boiler chamber, a fatal failure or damage of the boiler operation system equipped with electronic appliances, a precise motor and etc.. The conventional boiler system also has a trouble in use, in that air generated from oxygen dissolved in water for several months after the installation of boiler should be periodically vented out of the boiler.

On the other hand, the conventional boiler system includes an operation system equipped with a control device for automatically controlling the operation of boiler system. However, this control device has simple functions insufficient to provide a perfect automatic control of the overall operations of boiler system. Furthermore, it has no utility and thereby can not meet the demand of users.

That is, the functions of control device are mainly carried out by ON/OFF switchings. In response to pushing of an operation ON button, the control device makes the boiler system carry out its room heating operation, by activating the fuel supply device, operating a burner to burn fuel supplied from the fuel supply device and thus heat water in the water chamber, and activating a circulation pump P to circulate hot water in the water chamber via a room heating water circulating line. In response to pushing of an operation OFF button, the control device shuts off supplying of the fuel, thereby stopping the room heating operation of the boiler system.

With such a control device, room heating temperature can be controlled only by repeating manual ON/OFF switchings of the operation of boiler. As a result, there are disadvantages of inconvenience in use, inefficient room heating, and wastes of fuel and electric power.

In the conventional boiler system, furthermore, the driving of the circulation pump P is performed only when the boiler system operates in its room heating mode, in other words, a room heating system of the boiler system operates. Since such a room heating system is generally not operated for a long time in the summer season, a motor bearing unit which is a driving part of the circulation motor is apt to rust after the rainy season is over. Impeller of the motor also tends to be subjected to a fixing phenomenon caused by an accumulation cf foreign matters (generated due to a thermal deformation of the impeller) thereon. If, as the autumn season sets in, the room heating system is operated without any maintenance, the motor is subjected to a failure. Moreover, such an operation may causes a fire.

SUMMARY OF THE INVENTION

Therefore, an object of the invention is to provide a hot water boiler system wherein a supplement water tank of the type open to atmosphere is disposed in a boiler case, capable of achieving convenience and safety in its installation and automatic supplement and expansion of room heating water.

Another object of the invention is to provide a hot water boiler system wherein a room heating water supplement line equipped with an electromagnetic valve is connected to a hot water supply line and a sensor is provided in a water supplement tank to sense a low water level so that automatic room heating water supplement is achieved by opening and closing operations of the electromagnetic valve according to the sensing operation of the sensor. Another object of the invention is to provide a hot water boiler system wherein an overheat safety switch is disposed and exposed outwardly of a boiler case, capable of facilitating convenience in use, achieving automatic water supplying upon a shortage of room heating water in a water chamber, and achieving periodical temporary operation of a circulation pump in the summer season that a room heating system is not operated for a long time so that the circulation pump can be always ready for its normal operation.

In one aspect, the present invention provides a hot water boiler system having a room heating function and a hot water supply function comprising: a boiler; a boiler case enclosing said boiler; a heat exchanging chamber formed in the boiler and having a water chamber in which hot water to be used as room heating water is contained; a circulation pump for circulating said room heating water along a room heating circulation path; a hot water supply device having a cold water input line and hot water output line; a supplement water tank, of the type open to atmosphere, disposed in said boiler case and communicated with said heat exchanging chamber, said supplement water tank having means for automatically performing an expansion and supplement of room heating water required, due to a variation in density of said room heating water contained in said water chamber, to release an excessive pressure generated in the water chamber; a supplement water line connected at one end thereof to said cold water input line of the hot water supply device and at the other end to the supplement water tank, said supplement water line having a water supply valve adapted to allow water to flow from the cold water input line to the supplement water line, upon opening thereof; and control means for controlling said water supply valve to open it when water level in the supplement water tank reaches a predetermined low water level, said control means having a low water level sensor for sensing the predetermined low water level.

In another aspect, the present invention provides a control device for controlling the operation of a boiler system which comprises a boiler equipped with a burner device having a burner motor, an ignition transformer and an oil pump, a heat exchanging chamber formed in the boiler and having a water chamber in which hot water to be used as room heating water is contained, a circulation pump for circulating said room heating water along a room heating circulation path, an expansion tank for supplementing water in said water chamber, and a water supply valve connecting said expansion tank to an external water supply source, said control device comprising: control means for receiving signals from peripheral equipments, discriminating these signals and outputting drive signals to corresponding boiler system drive units, that is, said burner motor, said ignition transformer, said oil motor, said circulation pump and said water supply valve; a room temperature controller; room signal receiving means for receiving a drive signal from a room temperature controller and outputting a converted signal based on the received drive signal to said control means; output means for receiving output signals from the control means and controlling supplying of electric power to said boiler system drive units, based on the received signals; a temperature sensor for the temperature of room heating water contained in the water chamber; temperature display means for receiving a signal from said temperature sensor and displaying the temperature of room heating water based on the received signal; an overheat sensor for sensing an overheat of the room heating water; overheat sensing means for receiving a signal representative of the sensed temperature from said overheat sensor, comparing the room heating water temperature with a reference temperature and outputting a safety shutoff signal to the control means when an overheat is sensed according to the comparison; a flame sensor for sensing burning flame in the boiler; safety shutoff means for receiving a non-flame signal from said flame sensor and outputting a safety shutoff signal upon receiving the non-flame signal; a low water level sensor for sensing a predetermined low water level in the expansion tank; low water level sensing means for receiving a signal from said low water level sensor and outputting a low water level signal to the control means upon detecting a water shortage, based on the received signal, and simultaneously outputting a water supply signal to said output means; an oil quantity sensor for sensing the quantity of remaining oil; oil quantity sensing means for receiving a signal from said oil quantity sensor and detect the quantity of oil, based on the received signal; alarming means for alarming abnormal operations of the boiler; and anti-fixing means for making a temporary operation of the circulation pump during the operation of the boiler system in a hot water supply mode, to avoid an occurrence of fixing at the circulation pump.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and aspects of the invention will become apparent from the following description of embodiments with reference to the accompanying drawings in which:

FIG. 1 is a schematic view illustrating an overall construction of a ground installation, type oil boiler system in accordance with an embodiment of the present invention;

FIG. 2 is a schematic view illustrating a wall hung gas boiler system in accordance with another embodiment;

FIG. 3 is a schematic view of an automatic internal pressure control device in accordance with the present invention;.

FIG. 4 is a schematic view of an automatic room heating water supplement device in accordance with the present invention;

FIG. 5 is a schematic view illustrating a connection between the devices shown in FIGS. 3 and 4;

FIG. 6 is a schematic view of a connection of a circulation pump according to other embodiment of the present invention; FIG. 7 is a schematic view illustrating an overall construction of a conventional boiler system;

FIG. 8 is a schematic view of a conventional room heating water supplement device;

FIG. 9 is a block diagram of a control device for a boiler system in accordance with the present invention;

FIG. 10 is a circuit diagram of a control unit of the control device according to the present invention;

FIG. 11 is a circuit diagram of an output unit and a safety shutoff unit of the control device according to the present invention;

FIG. 12 is a circuit diagram of a forcible water supply circuit in accordance with the present invention;

FIG. 13 is a circuit diagram cf an overheat sensing circuit in accordance with an embodiment of the present invention;

FIG. 14 is a circuit diagram of an overheat sensing circuit in accordance with another embodiment of the present invention;

FIG. 15 is a circuit diagram of a low water level sensing circuit in accordance with the present invention;

FIG. 16 is a circuit diagram of a circulation pump control circuit in accordance with an embodiment of the present invention; and

FIG. 17 is a circuit diagram of a circulation pump control circuit in accordance with another embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, there is illustrated a hot water boiler system having various functions such as room heating, hot water supplying and operation controlling in sleeping and outing, in accordance with an embodiment of the present invention. The boiler mainly comprises a heat exchanging chamber 2, a burner device 3, a water supplement tank 4, a circulation pump 5, a hot water supply device 6, a fuel supply device, a room heating water supplement device 7, and a control device (namely, an operation controlling device) 10 for automatically controlling the operation of boiler.

The heat exchanging chamber 2 includes a fire chamber, a burning chamber, a water chamber 21 (FIG. 3), and a flue 22.

The hot water supply device 6 includes a hot water supply coil 61 (FIG. 4) disposed in the water chamber 21 of heat exchanging chamber 2, cold water input line 62 and hot water output line 63 (FIG. 1).

The burner device 3 includes a burner motor 31, a combustion gas suction pipe 32, an ignition transformer and a diffuser.

In accordance with the present invention, the water supplement tank (expansion tank) 4 is disposed in a boiler case 1 and shaped into a box. As shown in FIG. 3, the water supplement tank 4 has at its upper portion a port 41 which makes the water supplement tank 4 open to the atmosphere. Accordingly, the water supplement tank 4 is the type open to the atmosphere. The water supplement tank 4 is communicated with the water chamber 21, via an expansion pipe 42, as shown in FIG. 3. The expansion pipe 42 has one end deeply inserted into the interior of water supplement tank 4 and the other end connected to a socket 23 mounted to the upper portion of water chamber 21. In accordance with an embodiment of the present invention, the expansion pipe 42 is a syphon pipe. At the lower portion of water supplement tank 4, a low water level sensor S₄ is disposed to sense a predetermined low water level in the water supplement tank 4. The low water level sensor S₄ is connected to the control device 10 controlling the operation of boiler system according to the present invention.

As shown in FIGS. 1 and 4, the room heating water supplement device 7 includes a supplement water line 71 connected at its one end to the cold water input line 62 of hot water supply device 6, and a water supply valve 72 disposed in the supplement water line 71 and operated under the control of control device 10. The other end of the supplement water line 71 is connected to the water chamber 21, by means of a socket 24 mounted to the water chamber 21. In the socket 24, a temperature sensor S₁ is provided which checks the temperature of room heating water in the water chamber 21, although not shown.

The circulation pump 5 serves to forcibly circulate very hot water, as room heating water, in the water chamber through a load 100 to be heated. As shown in FIG. 1, the circulation pump 5 is installed on the bottom of the boiler and disposed at a room heating water feedback line 101 which is connected to the water chamber 21. With this construction, cooled feedback water in the room heating water feedback line 101 is fed to the lower portion of water chamber 21, by the circulation pump 5. In some cases, the circulation pump 5 may be disposed at a room heating water output line 102, as shown in FIG. 6.

The control device 10 includes a control panel exposed outwardly of the boiler case 1. As shown in FIG. 9, the control device 10 mainly comprises a control unit 12 for receiving signals from peripheral equipments, discriminating these signals and outputting control signals to corresponding units such as the burner device, the circulation pump and etc., a room signal receiving unit 11 for receiving a drive signal from a room temperature controller (not shown) and outputting a converted signal based on the received drive signal to the control unit 12, and an output unit 13 for receiving output signals from the control unit 12 and controlling supplying of electric power to the burner motor 31 and the ignition transformer of the burner device 3, the circulation pump 5, an electromagnetic oil pump and the water supply valve, based on the received signals. The control device 10 also comprises a temperature display unit 14 for displaying the temperature of hot water, namely, room heating water, contained in the water chamber 21, an overheat sensing unit 16 for receiving a signal representative of the room heating water temperature from an overheat sensor S₂, comparing the room heating water temperature with a reference temperature and outputting a safety shutoff signal to the control unit 12 when an overheat is sensed according to the comparison, a safety shutoff unit 17 for receiving a non-flame signal from a flame sensor S₅ sensing burning flames in the boiler and outputting a safety shutoff signal upon receiving the non-flame signal, a low water level sensing unit 18 for receiving a signal from the low water level sensor S₄ and outputting a low water level signal to the control unit 12 upon sensing a water shortage, based on the received signal, and simultaneously outputting a water supply valve opening signal to the output unit 13, an oil quantity sensing unit having an oil quantity sensor S₃ and sensing the quantity of remaining oil, and an alarming unit for alarming abnormal operations of the boiler.

In accordance with the present invention, there is also provided an anti-fixing circuit 15 which serves to avoid an occurrence of fixing at the circulation pump 5. This anti- fixing circuit 15 is incorporated in the control unit 12 and comprises a sensing circuit 15A and a circulation pump controlling circuit 15B connected to the sensing circuit 15Avia a diode D₄₂, as shown in FIG. 16. The sensing circuit 15A is connected to the temperature sensor S₁ and includes a pair of series connected comparators Q₁ and Q₂. The comparator Q₁ is connected at its non-inverting input terminal (+) to the temperature sensor S₁ and connected at its inverting input terminal (-) to a tap on a voltage divider including resistors R₈₁ and R₈₂ coupled between a voltage source Vcc and ground. The output of comparator Q₂ is fed back to the inverting input terminal (-). The circulation pump controlling circuit 15B includes a comparator Q₃ coupled at its input terminals to the voltage source Vcc, a charge circuit constituted by a grounded resistor R₈₆ and a condenser C₂₁, and another comparator Q₄. The comparator Q₃ is connected at its non-inverting input terminal (+) to a voltage bypass resistor R₈₄ and at its inverting input terminal (-) to a tap on a voltage divider including resistors R₉₀ and R₉₂ coupled between the voltage source Vcc and ground. To the output terminal of comparator Q₃ are connected the condenser C₂₁, resistors R₈₅ and R₈₆ , a diode D₄₃ , in this order. The output terminal of comparator Q₃ is coupled to the non- inverting input terminal (+) of comparator Q₄ by a diode D₄₃ and grounded via a resistor R₈₈. The comparator Q, is connected at its inverting input terminal (-) to a tap on a voltage divider including resistors R₉₁ and R₈₇ coupled between the voltage source Vcc and ground. The comparator Q₄ is also connected at its output terminal to a circulation pump drive terminal CP of the output unit 13, via a diode D₂₄ and a resistor R₈₉. The diode D₄₂ is connected between the junction of the output terminal and inverting input terminal (-) of comparator Q₂ and the junction of the resistor R₈₄ coupled to the voltage source Vcc and the non-inverting input terminal (+) of comparator Q₃.

As shown in FIG. 10, the control unit 12 of the control device 10 is connected at its input with a decoder IC₁ constituting the room signal receiving unit 11 and equipped with the anti-fixing circuit 15 which is coupled to a water supply signal output terminal b of the decoder IC₁. This control unit 12 mainly comprises four comparators IC₄, IC₅, IC₆ and IC₇ and two inverters IC₂ and IC₃. The comparator IC₄ is connected at its non-inverting input terminal (+) to a room heating signal output terminal a of the decoder IC₁, via a diode D₁ and resistors R₃ and R₁₀. To the room heating signal output terminal a of the decoder IC_j , the comparator IC₅ is connected at its non-inverting input terminal (+), via the diode D₁ and resistors R₃ , R₇ and R₁₂. The inverting input terminal (-) of comparator IC₄ is connected, via a resistor R₁₁, to a tap .on a voltage divider including resistors R₅ and R₈ coupled between the voltage source Vcc and ground, to the temperature sensor S₁ and to the anti-fixing circuit 15. In similar, the inverting input terminal (-) of comparator IC₅ is connected, via a resistor R_l3, to the tap on a voltage divider including resistors R₅ and R₈ coupled between the voltage source Vcc and ground, the temperature sensor S₁ and the anti- fixing circuit 15. The comparator IC₄ is also connected at its output terminal to both the overheat sensing unit 16 and the output unit 13, via a resistor R₂₀ and a diode D₇. The output terminal of comparator IC₄ is also coupled by the resistor R₂₀ to the collector of a transistor TR₃ which is coupled at its base to the low water level sensing unit 18 by a resistor R₂₁. The transistor TR₃ is also coupled at its emitter to ground and at its base to the water supply signal output terminal b of the decoder IC₁, by diodes D₂ and D₄ and the resistor R₂₁. On the other hand, the comparator IC₅ is also connected at its output terminal to the inverting input terminal of comparator IC₇, via resistors R₂₃ and R₃₀. The comparator IC₅ is connected at its non-inverting input terminal (+), via a resistor R₂₇ , to a tap on a voltage divider including resistors R₂₅ and R₃₁ coupled between the voltage source Vcc and ground. In similar, the comparator IC₇ is connected at its non-inverting input terminal (+), via a resistor R₂₉ to a tap on a voltage divider including resistors R₂₅ and R₃₁ coupled between the voltage source Vcc and ground. The comparator IC₅ is coupled at its inverting input terminal (-) to the output terminal of comparator IC₇ and at its output terminal to the safety shutoff unit 17. The comparator IC₇ is connected at its inverting input terminal (-) to the output terminal of comparator IC₅ , via resistors R₂₃ and R₃₀. The output terminal cf comparator IC₇ is coupled to the output unit 13 by a resistor R₃₂. The inverter IC₂ is coupled at its input terminal to an outing signal output terminal d of the decoder IC₁ and at its output terminal to the base of a transistor TR» by a resistor R₄. The collector of transistor TR, is coupled to an output terminal c of the decoder IC₁. The inverter IC₃ is connected at its input terminal to the output terminal c of the decoder IC₁ and at its output terminal to the base of a transistor TR₄ , via a resistor R₁₈. The transistor TR₄ is coupled at its collector to a temperature control volume VR₁ and at its emitter to ground. The temperature control volume VR₁ is coupled at one side thereof to the voltage source Vcc by resistors R₆, R₇, R₁₄ and R₁₅ and at the other side thereof to ground. A transistor TR₅ is also connected at its base to both the output terminals c and d of decoder IC₁ and at its emitter to ground.

As shown in FIG. 11, the output unit 13 comprises a burner motor drive circuit BMD,, an ignition transformer drive circuit IT_D2, an oil pump drive circuit EPD₃ , a circulation pump drive circuit CPD₄, and a water supply valve drive circuit AWD₅. The burner motor drive circuit BMD, has an input terminal BM coupled to both the inverting input terminal (-) of the comparator IC₅ of control unit 12 and the output terminal of comparator IC₇. The burner motor drive circuit BMD, also has a transistor TR₉ coupled at its base to the input terminal BM and a relay RY₁ coupled to the collector of transistor TR₉. The input terminal IT of ignition transformer drive circuit ITD₂ and the input terminal EP of oil pump drive circuit EFD₃ are coupled to a timer IC₁₀ of a timer circuit 19. The ignition transformer drive circuit ITD, has a transistor TR₁₀ coupled at its base to the input terminal IT and a relay RY₂ coupled to the collector of transistor TR₁₀. In similar, the oil pump drive circuit EPD₃ has a transistor TR., coupled at its base to the input terminal EP and a relay RY₃ coupled to the collector of transistor TR₁₁. The circulation pump drive circuit CPD. has an input terminal CP which is coupled to the output terminal of the comparator IC₄ of control unit 12, the output terminal of the comparator Q₄ of anti-fixing circuit 15 and a forcible water supply button MWB. The circulation pump drive circuit CPD₄ also has a transistor TR₁₂ coupled at its base to the input terminal CP and a relay RY₄ coupled to the collector of transistor TR₁₂. On the other hand, the water supply valve drive circuit AWD₅ has an input terminal AW coupled to the output terminal of a comparator IC₁₈ of the low water level sensing unit 18. The water supply valve drive circuit AWD₅ also has a transistor TR₁₃ coupled at its base to the input terminal AW and a relay RY₅ coupled to the collector of transistor TR₁₃.

The forcible water supply button MWB is one of constituting elements of a forcible water supply circuit which is incorporated in the control device 10 in accordance with the present invention. In addition to the forcible water supply button MWB, the forcible water supply circuit comprises a pair of light emission diodes LED₃ and LED₄, as shown in FIG. 12. The Button MWB is coupled at one side thereof to the source voltage Vcc by a resistor R₅₆ and at the other side thereof to both the input terminal CP of circulation pump drive circuit CPD₄ by a diode D₂₉ and the light emission diodes LED₃ by a resistor R₆₅. The other side of button MBW is also connected to both the input terminal AW of water supply valve drive circuit AWD₅ via a diode D₃₀ and the light emission diodes LED₄ by a resistor R₅₇.

The overheat sensing unit 16 comprises a pair of series connected comparators IC₁₆ and IC₁₇ and the overheat sensor S₂, as shown in FIG. 13. The comparator IC₁₅ is connected at its inverting input terminal (-) to the overheat sensor S₂ and connected at its non-inverting input terminal (+) to a tap on a voltage divider including resistors R₅₉ and R₇₀ coupled between the voltage source Vcc and ground. The comparator IC₁₇ is connected at its non-inverting input terminal (+) to the output terminal of comparator IC₁₆, via a diode D₃₁ and a resistor R₇₁. The inverting input terminal (-) of comparator IC₁₇ is connected to a tap on a voltage divider including resistors R₇₃ and R₇₅ coupled between the voltage source Vcc and ground. Between the input terminals of comparator IC₁₇, a condenser C₁₀ is connected. The output terminal of comparator IC₁₇ is coupled to the inverting input terminal (-) of the comparator IC₇ of control unit 12 by diodes D₃₅ and D₃₉ and to the collector of transistor TR₅ of control unit 12. At the junction between the resistor R₇₁ and the condenser C₁₀, a manual operation return switch or button RSW is coupled by a diode D₃₂. The manual operation return button RSW is provided at the control panel of control device 10 which is mounted to a front door of boiler case 1 such that it exposes outwardly.

As shown in FIG. 11, the safety shutoff unit 17 comprises a pair of series connected inverters IC₁₃ and IC₁₄, a comparator IC₁₅ and the flame sensor S₅. The input terminal of inverter IC₁₃ is coupled to the voltage source Vcc by a resistor R₃₈. To the junction between the resistor R₃₃ and the input of inverter IC₁₃ is coupled the flame sensor S₅ by a diode D₁₄. The output terminal of inverter IC₁₃ is directly coupled to the inverter IC₁₄. To the output terminal of inverter IC₁₄, a transistor TR₆ is coupled at its base by a. resistor R₄₆. The output terminal of inverter IC₁₄ is also connected to the input terminal of an inverter IC₁₂ which is one of constituting elements of the timer circuit 19. To the output terminal of inverter IC₁₄, a transistor TR₇ is also connected at its base, via a diode D₂₀ and resistors R₅₀ and R₅₁. The emitter of transistor TR₆ is coupled to the timer IC₁₀. To the transistor TR₇, a transistor TR₈ is series connected. The transistor TR₈ is coupled at its base to the output terminal cf timer IC₁₀, by a resistor R₄₂ and a diode D₁₉. The transistor TR₉ is also connected at its collector to the inverting input terminal (-) of comparator IC₁₅ and at its base to ground via a resistor R₅₃. The inverting input terminal (-) of comparator IC₁₅ is connected to a tap on a voltage divider including resistors R₅₄ and R₅₈ coupled between the voltage source Vcc and ground. The comparator IC₁₅ is also connected at its non-inverting input terminal ( +), via a resistor R₅₅, to a tap on a voltage divider including resistors R₅₅ and R₅₉ coupled between the voltage source Vcc and ground. The output terminal of comparator IC₁₅ is coupled to a light emission diode LED₂ by a resistor R₅₅ and to the inverting input terminal (-) of the comparator IC₇ of control unit 12. The output terminal of comparator IC₁₅ is also coupled to the alarming unit. To the junction between the resistor R₅₅ and the non-inverting input terminal (+) of comparator IC₁₅ is coupled the manual operation return switch or button RSW, by a resistor R₆₀ and a diode D₂₂. The button RSW is also coupled to the control unit 12 by a diode D₁₂. The safety shutoff unit 17 also comprises a diode D₂₃ which is coupled at its one side to the output terminal of the comparator IC₅ of control unit 12. The other side of diode D₂₃ is coupled to the timer IC₁₀.

The low water level sensing unit 18 comprises the comparator IC₁₈ and the low water level sensor S₄, as shown in FIG. 15. The low water level sensor S₄ is coupled to the inverting input terminal (-) of comparator IC₁₈, by a bridge rectifier circuit BD and a resistor R₇₁. The non-inverting input terminal (+) of comparator IC₁₈ is connected to the voltage source Vcc. The output terminal of comparator IC₁₈ is coupled to the resistor ₂₁ of control unit 12 by a diode D₃₇, to the input terminal AW of water supply valve drive circuit AWD₅ by a diode D₃₆ and to both the inverting input terminal (-) of the comparator IC₇ of control unit 12 and the alarming unit by a diode D₃₈.

The operation of the control device mentioned above will now be described.

As user pushes a room heating switch of the room temperature controller positioned in a room or hall, a room heating signal is generated and applied to the control device 10. That is, the room heating signal is applied to the room signal receiving unit 11 equipped in the control device 10. In the room signal receiving unit 11, the decoder IC₁ converts the room heating signal into a voltage pulse signal waveform-shaped to be recognizable by the control unit 12 and then sends it to the control unit 12.

The voltage pulse signal is outputted at the room heating signal output terminal a of the decoder IC₁ and thus applied to the non-rinverting input terminal (+) of comparator IC₄ via the diode D₁ and resistors R₃ and R₁₀. Accordingly, the comparator IC₄ generates a high level output signal which is, in turn, sent to the input terminal CP of the circulation pump drive circuit CPU₄ of output unit 13, via the resistor R₂₀ and the diode D₇. In the circulation pump drive circuit CPD₄, the transistor TR,₂ is activated by the signal received at its base, thereby causing the relay RY₄ to be activated. By the activation of relay RY₄, AC power is supplied to the circulation pump 5 disposed in the boiler case 1, thereby enabling the circulation pump 5 to drive. On the other hand, the signal from the room heating signal output terminal a of the decoder IC₁ is also applied to the non-inverting input terminal (+) of comparator IC₅, via resistors R₇ and R₁₂. The comparator IC₅ also receives the source voltage Vcc at its inverting input terminal (-) via resistors R₅ and R₁₃, in that the temperature sensor S₁ is at its OFF state. Since the voltage level at the inverting input terminal (-) of comparator IC₅ is higher than that at the non-inverting input terminal (+), the comparator IC₅ outputs a low level signal, so that the comparator IC₇ which receives at its inverting input terminal (-) the low level output from the comparator IC₅ via resistors R₂₈ and R₃₀ outputs a high level signal. At this time, the temperature sensor S₁ is at its OFF state. This high level signal from the comparator IC₇ is sent to the input terminal BM of the burner motor drive circuit BMD. of output unit 13. In the burner motor drive circuit BMD,, the transistor TR₉ is activated by the signal received at its base, thereby causing the relay RY₁ to be activated. According to the activation of relay RY₁, the burner motor 31 of burner device 3 drives. By the driving of burner motor 31, combustion air enters the diffuser via the combustion air suction pipe 32. At the same time, the comparator IC₆ outputs a high level signal which is, in turn, sent to the timer IC₁₀ of timer circuit 19 via the diode D₂₈ of safety shutoff unit 17. In response to the signal from the comparator IC₆, the timer IC₁₀ applies an output signal to the input terminal EP of the oil pump drive circuit EPD₃ of output unit 13. In the oil pump drive circuit EPD₃, the transistor TR₁₁ is activated by the signal received at its base, thereby causing the relay RY₃ to be activated. Accordingto the activation of relay RY₃, the electromagnetic pump which is a fuel supply device drives and supplies oil to the burner device 3. After the lapse of a predetermined time, the timer IC₁₀ applies an output signal to the input terminal IT of the ignition transformer drive circuit ITD₂. In the ignition transformer drive circuit ITD₂, the transistor TR₁₀ is activated by the signal received at its base, thereby causing the relay RY₂ to be activated. By the activation of relay RY₂, power is supplied to the ignition transformer, thereby achieving an ignition and thus combustion of oil. By continued combustion of oil, water in the water chamber 21 is heated, thereby carrying out room heating. That is, by the forcible pumping operation of circulation pump 5, hot water in the water chamber 21 as room heating water is repeatedly circulated along a room heating water circulation path constituted by the room heating water output line 102, the load 100 arranged around the room and room heating water feedback line 101, so as to achieve room heating.

When the temperature of room heating water in the water chamber 21 increases above the temperature set by the temperature control volume VR₁ (FIG. 10) during the room heating operation, the temperature sensor S₁ which is a thermistor is activated, thereby causing the voltage source Vcc to be coupled to ground via the resistor Re and the temperature sensor S₁. As a result, a low level signal is applied to the inverting input terminal (-) of comparator IC₅, so that the comparator. IC₅ outputs a high level signal. As the high level signal from the comparator IC₅ is applied to the inverting input terminal (-) of comparator IC₇ via resistors R₂₃ and R₃₀, the comparator IC₇ applies a low level output signal to the burner motor drive circuit BMD₁, so that the transistor TR₂ is deactivated, thereby causing the relay RY₁ for driving the burner motor to be switched to its OFF state. At the same time, in response to a high level signal from the comparator IC₆, the t.imer IC₁₀ applies a low level output signal to the oil pump drive circuit EPD₃. Accordingly, the transistor TR₁₁ is deactivated, thereby causing the relay RY₃ for driving the electromagnetic oil pump to be switched to its OFF state. As a result, the temperature of room heating water increases no longer. When the temperature of room heating water decreases below a predetermined temperature, the burner and the oil pump are operated again, to increase the temperature of room heating water. Thus, the temperature of room heating water can be maintained at a desired level, by repeating the above-mentioned operations.

During the room heating operation of boiler, the water in the water chamber 21 should be maintained at the level needed for its room heating circulation. Also, the internal pressure of water chamber 21 which may be increased due to overheating of the heat exchanging chamber 2 should be maintained at a proper level. To this end, the present invention provides the supplement water tank 4 disposed in the boiler case 1 and communicated with the water chamber 21 via the expansion pipe 42, and the supplement water line 71 constituting the room heating water supplement device 7 connected to the water chamber 21 (conventionally, a supplement water tank disposed outwardly of boiler is provided for the same purposes).

That is, as the pressure of room heating water (namely, the density of water) in the water chamber 21 increases due to continued heating, the increment of the water pressure, that is, the excessive water pressure is released to the supplement water tank 4 of the type of open to atmosphere disposed in the boiler case 1, via the internal pressure controlling socket 23 provided at the upper portion of water chamber 21 and the expansion pipe 42 connected between the socket 23 and the supplement water tank 4. Accordingly, the internal pressure of water chamber 21 is automatically controlled and maintained at a proper level. If the density of water is decreased due to an decrease in the water pressure caused by lowering of the water temperature in boiler, the quantity of water which was discharged into the supplement water tank 4 during the expansion of water in the water chamber 21 is fed back from the supplement water tank 4 to the water chamber 21, via the expansion pipe 42. Therefore, supplement of water from external is unnecessary. Air bubbles which are generated during the above-mentioned operations also vent automatically to atmosphere, through the port 41 of supplement tank 41. Inconvenience of periodically venting air as in prior art is naturally eliminated. That is, water expansion and supplement operations are automatically achieved under no pressure.

On the other hand, when the room heating water in the water chamber 21 decreases in quantity, due to its evaporation or leakage, its decreased quantity is supplemented from the supplement water tank 4. If water in the supplement water tank 4 is decreased below a predetermined low water level by its supplement to the water chamber 21, this is sensed by the low water level sensor S₄ which, in turn, makes the water supply valve 72 disposed in the supplement water line 71 open under the control of control device 10. Accordingly, the water passing through the cold water input line 62 enters the water chamber 21 through the water supply valve 72, so that the water chamber 21 is filled again with the water to a proper level. The supplement of water is continued until the water level in the water chamber 21 reaches a predetermined water level higher than the predetermined low water level. That is, when the water level in the water chamber 21 reaches the predetermined water level, the water supply valve 72 is closed, thereby completing the supplement of room heating water. Simultaneously with the low water level sensing of low water level sensor S₁, the heating operation of boiler is automatically stopped. Therefore, the above-mentioned supplement of water is carried out under non-operation of boiler.

Now, this room heating water supplement operation will be described, in conjunction with the control circuits of the present invention.

When the low water level sensor S₄ senses a shortage of room heating water, it disables supplying of voltage through the bridge rectifier circuit BD to the comparator IC₁₈ of low water level sensing unit 18 shown in FIG. 15. As a result, the comparator IC₁₈ maintains LOW level at its inverting input terminal (-) and thus outputs a high level signal. This high level signal from the comparator IC₁₈ is applied to the resistor R₂₁ of control unit 12 via the diode D₃₇, thereby causing the transistor TR₃ to be activated. By the activation of transistor TR₃, the output terminal of comparator IC₄ is coupled to ground. Thereby, supplying of voltage to the circulation pump drive circuit CPD₄ of output unit 13 is shut off, and thus the operation of circulation pump 5 is stopped. At the same time, the high level signal from the comparator IC₁₈ is applied to the alarming unit via the diode D₃₈, so that the room temperature controller displays alarm. The output signal from the comparator IC₁₈ is also applied to the inverting input terminal (-) of comparator IC₇ via the diode D₃₈ and the diode D₃₃ of overheat sensing unit 16, thereby causing the comparator IC₇ to output a low level signal. As a result, the operations of burner device 3 and oil pump constituting the fuel supply device are stopped. The output signal from the comparator IC₁₈ is also applied to the input terminal AW of the water supply valve drive circuit AWD₆ of output unit 13, via the diode D₃₆. In the water supply drive circuit AWD₅, the transistor TR₁₃ is activated by the signal received at its base, thereby causing the relay RY₅ to be activated. By the activation of relay RY₅, the water supply valve 72 is opened to supply water to the water chamber 21.

When the water level in the water chamber 21 reaches a predetermined water level higher than the predetermined low water level, the low water level sensor S₄ enables supplying of voltage through the bridge rectifier circuit BD to the comparator IC₁₈ so that the comparator IC₁₈ outputs a low level signal. Accordingly, the alarm displaying is stopped and the boiler is ready for its normal operation.

As apparent from the above description, the low water level sensing system of the present invention makes it possible to automatically supplement water to the water chamber without any troublesome manipulation, upon sensing a shortage of water. Therefore, there is provided a convenience in manipulation.

On the other hand, when the temperature of room heating water increases excessively and reaches a dangerous level, due to the operation of boiler at a high temperature for a long time or hot water supplying for a long time, the overheat sensing unit 16 sends a safety shutoff signal to the control unit 12, so as to stop the operation of boiler.

This operation will now be described, in conjunction with the circuit of overheat sensing unit 16 shown in FIG. 13.

When overheat occurs during the operation of boiler, it is sensed by the overheat sensor S₂ which is disposed in the heat exchanging chamber 2 and integrated with the temperature sensor S₁. Accordingly, the comparator IC₁₆ which is coupled at its inverting input terminal (-) to the overheat sensor S₂ outputs a low level signal which is, in turn, sent to the non- inverting input terminal (+) of comparator IC₁₇, via the diode D₃₁, resistor R₇₁ and condenser C₁₀. Thus, the comparator IC₁₇ outputs a high level signal which is a safety shutoff signal. This signal from the comparator IC₁₇ is applied to the inverting input terminal (-) of the comparator IC₇ of control unit 12 via the diodes D₃₅ and D₃₉, so that the comparator IC₇ outputs a low level signal. Since the comparator IC₇ can not send a high level signal, the operation of boiler is stopped, thereby achieving a safety shutoff against the overheat. The output signal from the comparator IC₁₇ is also sent to the alarming unit via the diode D₃₅, so that the alarming unit displays an alarm for informing the user of the overheat.

Alternatively, the overheat sensing unit 16 may be constructed by using a single comparator IC₁₇, as shown in FIG. 14. In this case, it is possible to obtain a simple and inexpensive construction, although the sensitivity is degraded.

Return of the normal operation of control device 10 after stopping .of the boiler caused by the overheat can be accomplished by simply pushing the manual operation return button RSW (FIG. 13), in that the button RSW is arranged on the control panel of control device 10 mounted to the front door of boiler case 1 such that it exposes outwardly. Such an arrangement of the button RSW on the control device 10 can be made by constituting the overheat sensor S₂ by a thermistor and incorporating the overheat sensing unit 6 in the control device 10.

The return operation will now be described in conjunction with FIG. 13.

When the manual operation return button RSW is pushed, the high level voltage outputted from the comparator IC₁₆ is bypassed into ground via the diode D₃₁, resistor R₇₁, and diode D₃₂. Accordingly, the comparator IC₁₇ maintains HIGH level at its non-inverting input terminal (+) and thus outputs a low level signal. As a result, alarm displaying of the alarming unit is stopped. At the same time, sending of high level signal to the inverting input terminal (-) of the comparator IC₇ of control unit 12 is shut off. At this state, the room heating operation can be restarted by a high level signal from the comparator IC₇, and thus the boiler operates in a normal condition.

Since the manual operation return button RSW connected to the safety shutoff unit 17 is connected to the overheat sensing unit 16 in accordance with the present invention, as mentioned above, its manipulation for restating the boiler can be carried out without a requirement of opening the front door of boiler case, thereby providing a convenience. Such a requirement is encountered in the prior art. It is noted that the pushing manipulation of button RSW makes only the boiler return to its restating condition.

In a normal operation of boiler, oil should be injected into the burner device 3 by the oil pump and its burning should be normally achieved. However, if such a burning is not performed, then oil is undesirably accumulated in the fire chamber due to its continued supplying. In order to avoid an occurrence of this phenomenon, a safety shutoff device is needed. In this regards, the present invention provides the safety shutoff unit 17 including the flame sensor S₅ disposed adjacent to the burner device 3.

Now, the operation of safety shutoff unit 17 will now be described, in conjunction with FIG. 11. When no flame (namely, burning light) is sensed by the flame sensor S₅ during the operation of oil pump, the inverter IC₁₃ maintains HIGH level at its input so that the inverter IC₁₄ series connected to the inverter IC₁₃ outputs a high level signal. This high level signal from the inverter IC₁₄ is applied to the base of transistor TR₇ via the resistor R₅₀, diode D₂₀ and resistor R₅₁, thereby causing the transistor TR₇ to be activated. Simultaneously with the activation of transistor TR₇, the voltage which has flowed into the inverting input terminal (-) of comparator IC₁₅ flows into the collector of the transistor TR₆ which is coupled at its emitter to the collector of transistor TR₇. As a result, the comparator IC₁₅ maintains LOW level at its inverting input terminal (-) and thus outputs a high level signal, sc that the light emission diode LED, emits light to display the abnormal condition of boiler. The output signal frcm the comparator IC₁₅ is also sent to the alarming unit, so as to give an alarm indicative of the abnormal condition of boiler. At the same time, the output signal from the comparator IC₁₅ is sent to the inverting input terminal (-) of the comparator IC₇ of control unit 12, thereby causing the comparator IC₇ to output a low level signal. Accordingly, the operation of burner device 3 is stopped. Also, the timer IC₁₀ applies a low level output signal to the oil pump drive circuit EPD₃. Accordingly, the transistor TR₁₁ is deactivated, thereby causing the relay RY₃ for driving the electromagnetic oil pump to be switched to its OFF state. Thus, supplying of oil is shut off.

At this state, pushing of the manual operation return button RSW makes the voltage which has applied to the non-inverting input terminal (+) of comparator IC₁₅ flow into ground through the button RSW. As a result, the comparator IC₁₅ outputs a low level signal, thereby causing the light emission diode LED₂ and the alarming unit to be deactivated.

Since the button RSW is coupled to the control unit 12 by a diode D_|2, its pushing also makes the voltage from the control device 12 flow into ground, thereby causing the burner device to be deactivated. Thus, a safety is provided even during the return operation of control device.

As mentioned above, the control device of the present invention also has the forcible water supply function. Now, the forcible water supply operation of control device 10 will be described, in conjunction with FIG. 12.

When the forcible water supply button MWB is pushed for supplying water to the water chamber 21, the source voltage Vcc is applied to the input terminal CF of circulation pump drive circuit CPD₄ via the diode D₂₃ and to the input terminal AW of water supp l y drive circuit AWD: via the diode D₃₀ In the circulation pump drive circuit CPD₄, the transistor TR₁₂ is activated by the signal received at its base, thereby causing the relay RY₄ to be activated. By the activation of relay RY₄ , the circulation pump 5 drives. In the water supply drive circuit AWD₅, the transistor TR₁₃ is activated by the signal received at its base, thereby causing the relay RY; to be activated. By the activation of relay RY₅ , the water supply valve 72 is opened, thereby enabling supplying of water to the water chamber 21 through the water supply valve 72. The source voltage Vcc is also sent to both the light emission diodes LED₃ and LED₄, via the resistors R₆₅ and R₆₇ , respectively, so that the light emission diodes LED₃ and LED₄ emit light to inform of both the operation of circulation pump 5 and the water supplement through the water supply valve 72. As mentioned above, the anti-fixing circuit 15 is also provided to avoid an occurrence of fixing at the circulation pump 5, in accordance with the present invention. In case of, for example, selecting the water supply mode using the room temperature controller, a corresponding signal, namely, a water supply signal is applied to the control unit 12 via the room signal receiving unit 11, so that the control unit 12 outputs an active signal for operating the water supply system to the output unit 13. Accordingly, the burner motor drive circuit BMD₁, the ignition transformer drive circuit ITD₂ and the oil pump drive circuit EPD₃ are activated. Thus, water in the water chamber 21 is heated to a temperature ranging from about 85ºC to about 90ºC to obtain hot supply water at a temperature ranging from about 40ºC to about 60ºC. In conventional boiler systems wherein both the burner device and the circulation pump are continuously operated in the room heating mode, however, the circulation pump is designed not to be operated in the water supply mode (although the circulation pump is generally disposed at the room heating water feedback line, it may be disposed at the room heating water output line, as in the embodiment of the present invention illustrated in FIG. 6). As a result, the operation of circulation pump is shut off for several months in the summer season. However, the operation of water supply system is achieved even in the summer season, so as to avoid an occurrence of fixing at the circulation pump 5.

Now, this anti-fixing operation will now be described in conjunction with FIG. 16.

When a water supply signal from the room temperature controller is sent to the room signal receiving unit 11 and thus the control unit 12 (FIG. 9), that is, when the generation of water supply signal is recognized by the anti-fixing circuit 15, the source voltage Vcc flows through the diode D₄₂ via the resistor R₃₄ and is also applied to the non-inverting input terminal (+) of comparator Q₃, thereby causing the comparator Q₃ to output a high level signal. This high level signal from the comparator Q₃ is sent to the non-inverting input terminal (+) of comparator Q₄ via the charge circuit including the condenser C₂₁ and diode D₄₃ , so that the comparator Q₄ outputs a high level signal. This high level signal from the comparator Q₄ is sent to the circulation pump drive circuit CPD₄ via the diode D₂₄ and resistor R₈₉, thereby causing the circulation pump drive circuit CPD₄ to be activated. In this case, the operation time of circulation pump 5 is determined by RC time constant of the charge circuit and is preferably about 30 seconds to about 40 seconds.

On the other hand, the anti-fixing circuit 15 is constructed so that when the temperature of water in the water chamber 21 is high, 'it disables the temporary operation of circulation pump 5 even though recognizing the water supply signal from the room signal receiving unit 11.

That is, when the temperature sensor S₁ (FIG. 10) senses the high water temperature of above 40º C, the comparator Q₁ of sensing circuit 15A maintains LOW level at its non-inverting input terminal (+) and thus outputs a low level signal. Accordingly, the comparator Q₂ series connected to the comparator Q₁ also outputs a low level signal. As a result, the source voltage Vcc flows through the diode D₄₂ so that the comparator Q₃ of circulation pump control circuit 15B maintains LOW level at its non-inverting input terminal (+) and HIGH level at its inverting input terminal (-) and thus outputs a low level signal. Therefore, the circulation pump 5 is not operated, in the same manner as mentioned above.

Alternatively, the anti-fixing circuit 15 may be constructed in accordance with another embodiment of the present invention illustrated in FIG. 17.

In this case, the anti-fixing circuit comprises a sensing circuit A coupled at its input terminal to the room signal receiving unit 11 and at its output terminal to the timer circuit D including a timer MC and a circulation pump control circuit B including an inverter Q₁₃, a transistor TR₂₁ and a diode SD₁, and an oscillation circuit C coupled to the timer MC of timer circuit D and including a pair of inverters Q₁₄ and Q₁₅, three resistors R₁₀₁, R₁₀₂ and R₁₀₃. The sensing circuit A includes a comparator Q₁₁ and an inverter Q₁₂. The comparator Q₁₁ is connected at its inverting input terminal (-) to the temperature sensor S₁ via a resistor R₁₀₀ and at its non-inverting input terminal (+ ) to a tap on a voltage divider including resistors R₁₀₈ and R₁₀₉ coupled between a 12V voltage source and ground. The output terminal of comparator Q₁₁ is coupled to the 6th input terminal of timer MC, by a diode SD₂. The inverter Q₁₂ is coupled at its input terminal to the room signal receiving unit 11, to sense a water supply signal. The output terminal of inverter Q₁₂ is coupled to the 6th input terminal of timer MC, by a diode SD₃. The inverter Q₁₃ of circulation pump control circuit B is coupled at its input terminal to the 3th output terminal of timer MC and at its output terminal to the collector TR₂₁ by the diode SD₁. The output terminal of inverter Q₁₃ is also coupled to the control unit 12 by the diode SD, and a resistor R₁₁₁.The transistor TR₂₁ is coupled at its emitter to ground and at its base to the diode SD₂ of sensing circuit A, by a resistor R₁₀₆. The inverter Q₁₄ of oscillation circuit C is connected at its output terminal to an input terminal of the timer MC via the resistor R₁₀₁. The inverter Q₁₅ series connected to the inverter

Q₁₄ is coupled at its input terminal to the 10th output terminal of timer MC by a diode SD₄. The resistor R₁₀₂ is coupled between the output terminal of inverter Q₁₀₃ and the junction of the diode SD₄ and the resistor R₁₀₃. With th i s construction, the circulation pump 5 can be temporarily operated during the operation of water supply system so that it is always maintained at its normal operation condition. The anti-fixing circuit of this embodiment may be activated upon not only sensing the water supply signal, but also sensing an outing signal.

The operation of anti-fixing circuit with the above- mentioned construction will now be described.

Upon pushing of the water supply button equipped in room temperature controller, a water supply signal from the room signal receiving unit 11 is applied to the inverter Q₁₂ of sensing circuit A, thereby causing the inverter Q₁₂ to output a low level signal. At this time, if the temperature sensor S₁ senses the water

temperature of not more than 40ºC in the water chamber 21, the comparator Q₁₁ maintains HIGH level at its inverting .i nput terminal

and thus outputs a low level signal. This low level signal from the comparator Q₁₁ is sent to the 6th input terminal of the timer MC, so that the timer MC is activated and outputs a low level signal at the 3th output terminal thereof for a predetermined period". In response to the low level signal from the timer MC, the inverter Q₃ of circulation pump control circuit B outputs a high level signal which is, in turn, applied to the control unit 12. Thus, the circulation pump 5 is operated for several ten seconds.

At the same time, the timer MC outputs a high level signal at the 10th output terminal thereof. In response to this signal from the timer MC, the oscillation circuit C oscillates to make the timer MC initiate its timing operation.

When the timing operation of timer MC is switched to OFF state after the lapse of the setting time during which outputting of the low level signal is maintained at the 3th output terminal thereof, the voltage level at the 3th terminal is switched to High level. As a result, the inverter G, of circulation pump control circuit B outputs a low level signal, thereby the circulation pump 5 to be deactivated. In a manner similar to that of the above-mentioned embodiment illustrated FIG. 16, when the water temperature in the water chamber 21 is above 40ºC, the comparator Q₁₁ maintains LOW level at its inverting input terminal and thus outputs a high level signal. In response to this high level signal, the timer MC and thus the circulation pump 5 are deactivated.

The transistor TR,. of circulation pump control circuit B is activated by a high level signal from the comparator Q₁₁ and serves to bypass the circulation pump driving signal from the timer MC.

As apparent from the above description, the present invention provides a hot water boiler of the type of an operation. under no pressure comprising a water supplement tank disposed in a boiler case and having a water expansion function, thereby capable of achieving a smooth room heating water circulation under atmospheric pressure. In accordance with the present invention, water expansion and supplement operations are automatically accomplished without any water supplying from external, so that the content of oxygen dissolved in the room heating water is minimized (upon being subjected to heat, oxygen in water is vaporized and forms air bubbles which will be vent to atmosphere through the supplement water tank). Accordingly, it is possible to reduce the loss of heat, eliminate an inconvenience caused by a periodical air venting work, and avoid an occurrence of corrosion phenomenon. When a shortage of room heating water occurs during the operation of boiler, a supplement of room heating water is accomplished by an opening operation of a water supply valve based on a low water level sensing operation of a low water sensor, in accordance with the present invention. Since the supplement water tank having a water pressure control function is arranged in the interior of boiler, the overall size of boiler can be also compact. Furthermore, it is possible to easily carry out boiler installation and piping works, avoid a contamination of room heating water and provide an improvement in safety . In accordance with the present invention, there is also provided a manual operation return button equipped in a control device. By the provision of manual operation return button, there is obtained advantageous functions of releasing an operation shutoff caused by an occurrence of overheat and of forcibly supplying water. Accordingly, it is possible to provide a reliable boiler having improvements in safety and utility. In accordance with the present invention, temperature sensors for sensing the overheat and the temperature of room heating water are comprised of thermistors which can be integrated into a single sensor. Therefore, there is an effect of providing both the overheat sensing function and the room heating water temperature sensing function, with a single sensor. In accordance with the present invention, the return operation for releasing an operation shutoff caused by an occurrence of overheat is achieved by the control device, thereby obtaining a convenience in use. When a shortage of water occurs during the operation of boiler, the present invention also makes it possible to sense the shortage of water, safely shut off the operation of boiler upon the sensing and simultaneously supply water to replenish the shortage, thereby improving an efficiency in operation. The control device also includes a circulation pump anti-fixing circuit which enables an intermittent operation of the circulation pump in every hot water supply operation. Such an intermittent operation of the circulation pump makes it possible to prevent fixing of impellers, thereby preventing an accident possibly caused by the fixing of impellers and lengthening the life of circulation pump. In particular, there is provided a safety circuit which prevents the boiler from operating during the return operation for releasing an boiler operation shutoff for a safety. Thus, the present invention provides a boiler exhibiting an improvement in safety and a convenience in use.

Although the preferred embodiments of the invention have been disclosed for illustrative purpose, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims

WHAT IS CLAIMED IS:

1. A hot water boiler system having a room heating function and a hot water supply function comprising:

a boiler;

a boiler case enclosing said boiler;

a heat exchanging chamber formed in the boiler and having a water chamber in which hot water to be used as room heating water is contained;

a circulation pump for circulating said room heating water along a room heating circulation path including a room heating water output line and a room heating water feedback line; a hot water supply device having a cold water input line and hot water output line;

a supplement water tank, of the type open to atmosphere, disposed in said boiler case and communicated with said heat exchanging chamber, said supplement water tank having means for automatically performing an expansion and supplement of room heating water required, due to a variation in density of said room heating water contained in said water chamber, to release an excessive pressure generated in the water chamber;

a supplement water line connected at one end thereof to said cold water input line of the hot water supply device and at the other end to the supplement water tank, said supplement water line having a water supply valve adapted to allow water to flow from the cold water input line to the supplement water line, upon opening thereof; and

control means for controlling said water supply valve to open it when water level in the supplement water tank reaches a predetermined low water level, said control means having a low water level sensor for sensing the predetermined low water level.

2. A hot water boiler system in accordance with Claim 1, wherein saiad means for automatically performing an expansion and supplement of room heating water comprises an expansion pipe connected between said supplement water tank and said heat exchanging chamber and a socket provided at said expansion p i pe and adapted to control the internal pressure of said water chamber, so that the pressure of room heating water which varies depending upon a variation in density of the room heating water in the water chamber is automatically controlled, said variation in density being caused by a variation in temperature of the room heating water in the water chamber.

3. A hot water boiler system in accordance with Claim 1, wherein said supplement water tank further comprises an air port open to atmosphere and adapted to make the supplement water tank open to atmosphere.

4. A hot water boiler system in accordance with Claim 2, wherein said expansion pipe communicating said supplement water tank and said heat exchanging chamber with each other is a syphon pipe.

5. A hot water boiler system in accordance with Claim 1, wherein said circulation pump is disposed in the interior of said boiler case.

6. A hot water boiler system in accordance with Claim 1 or Claim 5, wherein said circulation pump is connected to said room heating water feedback line.

7. A hot water boiler system in accordance with Claim 1 or Claim 5, wherein said circulation pump is connected to said room heating water output line.

8. A hot water boiler system in accordance with Claim 1, wherein said supplement water tank is disposed in the interior of said boiler case,

9. A control device for controlling the operation of a boiler system which comprises a boiler equipped with a burner device having a burner motor, an ignition transformer and an oil pump, a heat exchanging chamber formed in the boiler and having a water chamber in which hot water to be used as room heating water is contained, a circulation pump for circulating said room heating water along a room heating circulation path, an expansion tank for supplementing water in said water chamber, and a water supply valve connecting said expansion tank to an external water supply source, said control device comprising:

control means for receiving signals from peripheral equipments, discriminating these signals and outputting drive signals to corresponding boiler system drive units, that is, said burner motor, said ignition transformer, said oil motor, said circulation pump and said water supply valve;

a room temperature controller;

room signal receiving means for receiving a drive signal from a room temperature controller and outputting a converted signal based on the received drive signal to said control means;

output means for receiving output signals from the control means and controlling supplying of electric power to sai d boiler system drive units, based on the received signals;

a temperature sensor for the temperature of room heating water contained in the water chamber;

temperature display means for receiving a signal from said temperature sensor and displaying the temperature of room heating water based on the received signal;

an overheat sensor for sensing an overheat of the room heating water;

overheat sensing means for receiving a signal representative of the sensed temperature from said overheat sensor, comparing the room heating water temperature with a reference temperature and outputting a safety shutoff signal to the control means when an overheat is sensed according to the comparison; a flame sensor for sensing burning flame in the boiler; safety shutoff means for receiving a non-flame signal from said flame sensor and outputting a safety shutoff signal upon receiving the non-flame signal;

a low water level sensor for sensing a predetermined low water level in the expansion tank;

low water level sensing means for receiving a signal from said low water level sensor and outputting a low water level signal to the control means upon detecting a water shortage, based on the received signal, and simultaneously outputting a water supply signal to said output means;

an oil quantity sensor for sensing the quantity of remaining oil;

oil quantity sensing means for receiving a signal from said oil quantity sensor and detect the quantity of oil, based on the received signal;

alarming means for alarming abnormal operations of the boiler; and

anti-fixing means for making a temporary operation of the circulation pump during the operation of the boiler system in a hot water supply mode, to avoid an occurrence of fixing at the circulation pump.

10. A control device for controlling the operation of a boiler system in accordance with Claim 9, wherein said overheat sensor and said temperature sensor are integrated with each other to construct a single sensor disposed at the heat exchanging chamber.

11. A control device for controlling the operation of a boiler system in accordance with Claim 9, wherein said overheat sensing means comprises, a first comparator coupled to said overheat sensor and adapted to compare the temperature sensed by the overheat sensor with the reference temperature to generate an overheat sensing signal, and a second comparator coupled to said first comparator and output the safety shutoff signal to the control means upon receiving said overheat sensing signal from the first comparator.

12. A control device for controlling the operation of a boiler system in accordance with Claim 9, wherein said overheat sensing means comprises a single comparator coupled to said overheat sensor and adapted to compare the temperature sensed by the overheat sensor with the reference temperature and output the safety shutoff signal to the control means upon detecting the overheat.

13. A control device for controlling the operation of a boiler system in accordance with Claim 9, further comprising operation return means for releasing an operation shutoff caused by the safety shutoff signal from said overheat sensing means.

14. A control device for controlling the operation of a boiler system in accordance with Claim 13, wherein said operation return means comprises a manual operation return button disposed exposed to external and adapted to bypass the safety shutoff signal which is sent from the overheating sensing means to the control means.

15. A control device for controlling the operation of a boiler system in accordance with Claim 9, further comprising means for bypassing a burner motor drive signal which is sent from the control means to the output means during when sai d operation return means performs its operation shutoff releasing, so as to prevent an operation of the boiler system.

16. A control device for controlling the operation of a boiler system in accordance with Claim 9, further comprising means for generating a forcible drive signal and sending it to the output means, so _.as to for driving forcibly the circulation pump and the water supply valve.

17. A control device for controlling the operation of a boiler system in accordance with Claim 9, wherein said anti-fixing means comprises a water supply sensing circuit for receiving the water supply signal from the low water level sensing means and outputting a water supply sensing signal, a circulation pump control circuit for receiving said water supply sensing signal from said water supply sensing circuit and outputting a circulation pump drive signal to the output means, a charge circuit for allowing outputting of the circulation pump drive signal from said circulation pump control circuit for a predetermined time period.

18. A control device for controlling the operation of a boiler system in accordance with Claim 9, wherein said anti-fixing means comprises a water supply sensing circuit for receiving the water supply signal from the low water level sensing means and outputting a water supply sensing signal, a circulation pump control circuit for receiving said water supply sensing signal from said water supply sensing circuit and outputting a circulation pump drive signal to the output means, a timer circuit for allowing outputting of the circulation pump drive signal from said circulation pump control circuit for a predetermined time period, and an oscillation circuit for initiating the timing operation of said timer.

19. A control device for controlling the operation of a boiler system in accordance with Claim 17 or Claim 18, wherein said anti-fixing means further comprises a shutoff circuit for sensing a predetermined room heating water temperature and preventing the outputting of the circulation pump drive signal from said circulation pump control circuit, upon sensing the predetermined room heating water.

20. A control device for controlling the operation of a boiler system in accordance with Claim 17 or Claim 18, wherein said predetermined time period is 30 seconds to 40 seconds.

21. A control device for controlling the operation of a boiler system in accordance with Claim 17, wherein said charge circuit comprises a condenser and a resistor for cooperating to determine a predetermined RC time constant corresponding to the predetermined time period.