GB1560188A - Fluid heater - Google Patents

Description

(54) FLUID HEATER (71) We, HONEYWELL B.V. a Dutch Company of Rijswitjkstraat 175, Amsterdam, Netherlands, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement: This invention relates to a fluid heater such as a gas heated, continuous flow water heater.

According to the invention, there is provided a fluid heater comprising a heat exchanger; a main gas burner for providing heat to the heat exchanger; a pilot burner for enabling the lighting of the main burner and disposed so that in use the pilot burner will heat a portion of the inlet pipe to the heat exchanger; a first temperature sensor for sensing the temperature of the fluid in the heat exchanger; a second temperature sensor for sensing the temperature of the fluid at said pipe portion; and a gas control apparatus for varying the gas supply to the main burner; said sensors controlling said apparatus such that the main burner is rendered inoperative either when the temperature of the fluid in the heat exchanger exceeds a predetermined upper limit, or when the temperature of the fluid at said pipe portion exceeds a predetermined lower limit.

An embodiment of the invention will now be described by way of example only with reference to the accompanying drawing which is a schematic view of a water heater according to the invention.

Referring to the drawing the water heater 1 is provided with a main burner 2, a pilot burner 3, a heat exchanger 4 exposed to the heat of the main burner, and a gas control apparatus 5. At a suitable place in the heat exchanger 4, a first temperature sensor 7 is inserted into a hot water tube 6; this sensor being in the shown embodiment a capillary tube sensor and is preferably located a short distance from the hot water outlet. The heated water, for instance, is tapped by a cock 8. In the domestic water inlet, a second temperature sensor 9 is provided which mainly serves as a flow sensor and in the shown embodiment is also a capillary tube sensor. It controls an electrical switch 11 via a capillary tube 10.The inlet tube 12 of the heat exchanger is subjected to heating by the pilot flame of the pilot burner 3 so that the water contained in inlet tube 12 is continuously heated and if no domestic water is tapped assumes a temperature which lies above a lower temperature limit of, for instance, 30"C. If, however, hot water is tapped at cock 8, the cold water entering through inlet 13 cools the sensor 9 and the sensor signals a decrease of the inlet water temperature below the lower limit whereby the electrical switch 11 closes to switch on the gas control apparatus which controls the gas supply from gas inlet 14 to main burner 2. Gas control apparatus 5 may be provided in well-known manner with an ignition safety device which monitors the proper burning of the pilot flame.The gas control apparatus 5 preferably has the structure as described in applicants prior patent application no. 42587/77 in which a pressure regulator 17 controlled by temperature sensor 7 regulates in a modulating manner by means of a servo system the gas supply to main burner 2 as long as the temperature measured by sensor 7 lies below a predetermined upper limit. If, however, this temperature exceeds the limit, for instance, when terminating the hot water tapping, an electrical switch 18 within gas control apparatus 5, also controlled by sensor 7 switches the servo system off so that the main burner valve under the force of its closure spring is quickly brought into its closed position and any further heat supply to the water volume within water heater 1 remains inhibited.The contact of switch 11 is connected in series with the contact 18 of the pressure regulator into the circuit of the solenoid valve operator for the servo system, with contact 18 of the pressure regulator being controlled by temperature sensor 7 and opening when the upper temperature limit is exceeded. In the shown embodiment this servo system is supplied with current by a mains AC voltage connected to wires 15. Instead of this the energizing current for the solenoid valve operator can be generated by a chain of thermocouples exposed to the pilot flame; or the pressure in the capillary tubes of temperature sensors 9 and 7 may directly control a valve operator of the servo system via a pressure capsule or the like.

When putting the water heater into operation, the water temperature measured by the second sensor 9 is below the lower limit, so that switch 11 closes. The temperature at the hot water outlet measured by sensor 7 is below the upper limit so that also switch 18 within pressure regulator 17 is closed. The circuit for the solenoid valve operator 16 is thereby closed and the system can be initiated by igniting the pilot burner and subsequently igniting the main burner. In this connection the inlet tube 12 which is exposed only to the flame of the pilot burner is heated up slowly so that at first the first temperature sensor 7 senses a temperature increase and with increasing temperature throttles the gas supply to the main burner to provide a modulating operation.If the temperature at sensor 7 exceeds the predetermined upper limit, switch 18 controlled by this sensor interrupts the circuit for the solenoid valve operator 16 and the gas supply to the main burner is completely interrupted. In the meantime, sensor 9 at the domestic water inlet senses a temperature which is above the lower temperature limit so that switch 11 additionally interrupts the current circuit. If now the temperature of the water within the water heater decreases due to cooling, temperature sensor 7 firstly responds and closes its contact without initiating the burner. It is not until cold water entering via inlet 13 into the inlet tube 12 when cock 8 is opened thereby cooling sensor 9 to below the lower temperature limit that the contact of switch 11 also closes to connect the servo system to the voltage source to initiate the main burner as described above.In this condition the water flowing through water heater 1 is heated in heat exchanger 4.

As soon as cock 8 is closed. the temperature in the water heater rises rapidly so that sensor 7 indicates that the upper temperature limit is exceeded. It interrupts again the energizing circuit of the solenoid valve operator 16 so that the main burner is switched off. If later the temperature at sensor 7 falls below the upper limit and if contact 18 within pressure regulator 17 and controlled by sensor 7 closes, the circuit for the solenoid valve operator nevertheless remains interrupted because sensor 9 provided in the inlet tube 12 is heated via the water surrounding the sensor from the pilot flame and is thereby exposed to a temperature which is above the lower temperature limit. Temperature sensor 9 therefore ensures that the gas supply to the main burner remains interrupted provided no hot water is tapped.Sensor 7 provides the quick switching-off of the main burner and sensor 9 takes care of maintaining this switched-off state.

WHAT WE CLAIM IS: 1. A fluid heater comprising a heat exchanger; a main gas burner for providing heat to the heat exchanger; a pilot burner for enabling the lighting of the main burner and disposed so that in use the pilot burner will heat a portion of the inlet pipe to the heat exchanger; a first temperature sensor for sensing the temperature of the fluid in the heat exchanger; a second temperature sensor for sensing the temperature of the fluid at said pipe portion; and a gas control apparatus for varying the gas supply to the main burner; said sensors controlling said apparatus such that the main burner is rendered inoperative either when the temperature of the fluid in the heat exchanger exceeds a predetermined upper limit, or when the temperature of the fluid at said pipe portion exceeds a predetermined lower limit.

2. The fluid heater of claim 1, wherein the gas control apparatus includes a solenoid valve operator, the energising circuit of which includes first and second series connected switches controlled by said first and second sensors.

3. The fluid heater of claim 1 or 2 wherein the gas control apparatus includes a servo pressure regulator controlled in a modulating manner by the first sensor provided said first sensor senses a temperature below said upper limit and said second sensor senses a temperature below said lower limit.

4. The fluid heater of claim 2 or claim 3 as appendant to claim 2, wherein the solenoid valve operator is energised in use by mains voltage.

5. The fluid heater of claim 2 or claim 3 as appendant to claim 2, wherein the solenoid valve operator is energised by a series of thermocouple heated in use by the pilot flame.

6. The fluid heater of claim 3, wherein the servo system of the gas control apparatus includes a mechanically controllable operator valve exposed to a mechanical control movement generated by said sen

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (7)

**WARNING** start of CLMS field may overlap end of DESC **. is connected in series with the contact 18 of the pressure regulator into the circuit of the solenoid valve operator for the servo system, with contact 18 of the pressure regulator being controlled by temperature sensor 7 and opening when the upper temperature limit is exceeded. In the shown embodiment this servo system is supplied with current by a mains AC voltage connected to wires 15. Instead of this the energizing current for the solenoid valve operator can be generated by a chain of thermocouples exposed to the pilot flame; or the pressure in the capillary tubes of temperature sensors 9 and 7 may directly control a valve operator of the servo system via a pressure capsule or the like. When putting the water heater into operation, the water temperature measured by the second sensor 9 is below the lower limit, so that switch 11 closes. The temperature at the hot water outlet measured by sensor 7 is below the upper limit so that also switch 18 within pressure regulator 17 is closed. The circuit for the solenoid valve operator 16 is thereby closed and the system can be initiated by igniting the pilot burner and subsequently igniting the main burner. In this connection the inlet tube 12 which is exposed only to the flame of the pilot burner is heated up slowly so that at first the first temperature sensor 7 senses a temperature increase and with increasing temperature throttles the gas supply to the main burner to provide a modulating operation.If the temperature at sensor 7 exceeds the predetermined upper limit, switch 18 controlled by this sensor interrupts the circuit for the solenoid valve operator 16 and the gas supply to the main burner is completely interrupted. In the meantime, sensor 9 at the domestic water inlet senses a temperature which is above the lower temperature limit so that switch 11 additionally interrupts the current circuit. If now the temperature of the water within the water heater decreases due to cooling, temperature sensor 7 firstly responds and closes its contact without initiating the burner. It is not until cold water entering via inlet 13 into the inlet tube 12 when cock 8 is opened thereby cooling sensor 9 to below the lower temperature limit that the contact of switch 11 also closes to connect the servo system to the voltage source to initiate the main burner as described above.In this condition the water flowing through water heater 1 is heated in heat exchanger 4. As soon as cock 8 is closed. the temperature in the water heater rises rapidly so that sensor 7 indicates that the upper temperature limit is exceeded. It interrupts again the energizing circuit of the solenoid valve operator 16 so that the main burner is switched off. If later the temperature at sensor 7 falls below the upper limit and if contact 18 within pressure regulator 17 and controlled by sensor 7 closes, the circuit for the solenoid valve operator nevertheless remains interrupted because sensor 9 provided in the inlet tube 12 is heated via the water surrounding the sensor from the pilot flame and is thereby exposed to a temperature which is above the lower temperature limit. Temperature sensor 9 therefore ensures that the gas supply to the main burner remains interrupted provided no hot water is tapped.Sensor 7 provides the quick switching-off of the main burner and sensor 9 takes care of maintaining this switched-off state. WHAT WE CLAIM IS:

1. A fluid heater comprising a heat exchanger; a main gas burner for providing heat to the heat exchanger; a pilot burner for enabling the lighting of the main burner and disposed so that in use the pilot burner will heat a portion of the inlet pipe to the heat exchanger; a first temperature sensor for sensing the temperature of the fluid in the heat exchanger; a second temperature sensor for sensing the temperature of the fluid at said pipe portion; and a gas control apparatus for varying the gas supply to the main burner; said sensors controlling said apparatus such that the main burner is rendered inoperative either when the temperature of the fluid in the heat exchanger exceeds a predetermined upper limit, or when the temperature of the fluid at said pipe portion exceeds a predetermined lower limit.

2. The fluid heater of claim 1, wherein the gas control apparatus includes a solenoid valve operator, the energising circuit of which includes first and second series connected switches controlled by said first and second sensors.

3. The fluid heater of claim 1 or 2 wherein the gas control apparatus includes a servo pressure regulator controlled in a modulating manner by the first sensor provided said first sensor senses a temperature below said upper limit and said second sensor senses a temperature below said lower limit.

4. The fluid heater of claim 2 or claim 3 as appendant to claim 2, wherein the solenoid valve operator is energised in use by mains voltage.

5. The fluid heater of claim 2 or claim 3 as appendant to claim 2, wherein the solenoid valve operator is energised by a series of thermocouple heated in use by the pilot flame.

6. The fluid heater of claim 3, wherein the servo system of the gas control apparatus includes a mechanically controllable operator valve exposed to a mechanical control movement generated by said sen

sors.

7. A fluid heater substantially as herein described with reference to the accompanying drawings.