EP3832224B1

EP3832224B1 - Gas-fired heating appliance with harmful gas detection

Info

Publication number: EP3832224B1
Application number: EP19213429.4A
Authority: EP
Inventors: Mathieu Lionel; David Chauvin; Clementine Cazor; Herve Drillaud; Nicolas Raymond Debias
Original assignee: Vaillant GmbH
Current assignee: Vaillant GmbH
Priority date: 2019-12-04
Filing date: 2019-12-04
Publication date: 2023-08-02
Anticipated expiration: 2039-12-04
Also published as: ES2960744T3; EP3832224A1; EP3832224C0

Description

FIELD OF THE INVENTION

The present invention relates to a gas-fired heating appliance, and more particularly to a gas-fired heating appliance that is able to detect interior air quality thereof.

BACKGROUND OF THE INVENTION

Gas-fired heating appliances generally include gas water heaters and gas boilers. A typical gas boiler is operable to heat a transfer fluid, such as water, which is pumped around a boiler circuit. The boiler circuit is typically connected, via suitable valves to space heating apparatuses such as radiators or under floor heating loop, so that the heat output from the boiler can be used for space heating purposes. The gas boiler usually generates fumes containing harmful gases, like CO (Carbon monoxide), CO2 (Carbon dioxide), NOx (Nitric oxide) etc., which shall be discharged outdoors. For boilers installed on multiple flue configurations, a number of boilers installed in multiple-family houses can be connected to a common chimney via flue pipes to release fumes. The chimney can be a concentric duct composed of coaxial inner and outer tubes, usually the inner tube is provided to discharge the fumes and the outer tube is provided to introduce fresh air. US patent publication US 2015/0096504 A1 discloses one example of such kind of boilers. A circulating-type hot-water supply device 1 having an exhaust pipe 12 for ejecting the combustion exhaust gas of the burner 3 and an air supply pipe 13 covering the exhaust pipe 12 and connecting to a suction duct 15 which communicates with an air inlet of the combustion fan 14 for introducing external air for combustion.
However, there exist some risks. If a neighbor non-return flap installed in the flue pipes is missing or damaged, the fumes in the chimney can return to inside of the boiler. Moreover, if a neighbor or own flue seal is damaged, the fumes can also return inside of the boiler. Such return of the fumes may result in a combustion failure. Since the returning fumes may replace the fresh air or decrease the concentration of the oxygen in the fresh air inside of the boiler, the boiler will not ignite on ignition or lose the flame on combustion, and corresponding fault codes will be displayed accordingly. In addition, the fumes can enter the family house and result in a hazardous pollution if the outer casing of the boiler is not well air sealed. German patent publication DE 30 08 399 A1 discloses a sensor 10 disposed in an exhaust gas backflow duct 9 and connected with a switching device 8 that is electrically connected to a solenoid valve 7. When there exists an exhaust gas backflow, such case can be detected by the sensor 10, and then the switching device 8 is activated to actuate the solenoid valve 7 to interrupt the gas burner 2.
US5,797,358 discloses a water heater equipped with a carbon monoxide sensor positioned proximate to a draft hood to detect the presence of an unacceptable level of carbon monoxide for indicative of a blocked vent pipe and also send a signal to a microprocessor which will prevent or discontinue the operation of the burners. CN 104110869 A discloses a gas water heater having a gas sensor for detection of the gas concentration, and a controller for shutting off a gas valve when the gas concentration detected by the gas sensor exceeds a predetermined threshold.
DE 298 02 545 U1 discloses a heating appliance having an exhaust-gas ducting is provided with a flow safe-guard 24 which has an orifice 32 opening into the installation space of the heating appliance for operating the heating appliance as a function of the room air and also a first connection piece 26 for an exhaust-gas pipe 18 and a second connection piece 30 for the external exhaust-gas ducting. The two connection pieces 26, 30 being arranged so as to be offset horizontally to one another, so that the overall height of the heating device is not significantly increased. An exhaust-gas sensor 34 for the detection of building-up exhaust gas is provided laterally at the first connection piece 26 in the immediate vicinity of the orifice 32. If there exist blockages in the chimney, the exhaust gases pass through the opening 32 into the room. The exhaust gases are detected by the exhaust-gas sensor 34 and the heater is automatically restarted after a pause of about 20 minutes.

SUMMARY OF THE INVENTION

It is an object of present invention to provide a gas-fired heating appliance that is able to monitor quality of air inside of the appliance and perform certain operations to improve the air quality and alert installers or users when the air quality is getting worse mainly because of fumes recirculation, thereby increasing the safety of the appliance.
According to present invention there is provided a gas-fired heating appliance adapted for being connected to a common chimney via flue pipes to discharge fumes and introduce outside air. The gas-fired heating appliance includes a housing, a burner, a gas valve, a fan, a harmful gas sensor, and a controller. The housing defines a first port and a second port surrounding the first port, wherein one of the first and the second ports is provided to discharge fumes and the other of the first and the second ports is provided to introduce outside air. The burner is disposed in the housing for combustion of a mixture of introduced outside air and fuel gas to generate fumes. The gas valve is associated with the burner for regulating supply of fuel gas to the burner. The fan is disposed in the housing for driving the introduced outside air supplied to the burner and urging the fumes to be discharge outside through the flue pipes and the common chimney. The harmful gas sensor is disposed in the housing for detecting a concentration of the harmful gases within air inside of the housing. The harmful gas sensor can be used to detect one or several or all of CO, CO2, NOx and other harmful gases normally contained in fumes. The controller is electrically connected with the burner, the gas valve, the fan, and the harmful gas sensor for controlling the fan and/or the burner and/or the gas valve based on the detection of the harmful gas sensor. The controller is configured to start a standby operation when an excess of harmful gases is detected while the appliance is in a standby mode, and the standby operation includes activating the fan to run to evacuate fumes in the air inside of the housing. In this way, when there is fumes recirculation inside of the housing, it will be quickly detected and appreciates actions can be taken against the fumes recirculation.
Wherein, the excess of harmful gases is detected when the harmful gas sensor detects that the concentration of the harmful gases is larger than or equals to a first threshold.
Preferably, the standby operation further includes increasing the fan speed step by step, like every two minutes.
Moreover, the standby operation includes stopping the fan running if the harmful gas sensor detects that the concentration of the harmful gases reduces to a second threshold within a first time duration after the excess of harmful gases being detected.
Furthermore, the standby operation includes displaying a fault code if the harmful gas sensor detects that the concentration of the harmful gases does not reduce to a second threshold within a first time duration after the excess of harmful gases being detected, so that the user or the installer can be notified there is bad air quality inside of the housing.
Preferably, the standby operation further includes keeping the fan running to continue evacuating fumes until the user or the installer stops it, and disabling the combustion of the burner to avoid danger or damages.
Wherein, the second threshold equals to or is lower than the first threshold.
In one embodiment, the controller is configured to stop the combustion of the burner and then enter the standby operation when the appliance operates in a domestic hot water mode for a second time duration after the excess of harmful gases being detected. By this means, a comfort of domestic hot water demand can ensured. For example, a user taking a shower will not be interrupted suddenly.
In one embodiment, the controller is configured to stop the combustion of the burner and then enter the standby operation when the excess of harmful gases is detected while the appliance operates in a space heating mode.
In one embodiment, the appliance further includes a counter that is able to count once when the excess of harmful gases is detected and the burner is in operation, and wherein the controller is configured to display a fault code when the accumulated number of times reaches a predetermined value within a certain time period.
Preferably, the controller is further configured to keep the fan running and disable the combustion of the burner.
In one embodiment, the harmful gas sensor is disposed adjacent to the port for introducing outside air. Since the sensor is positioned at entrance of the fresh air, the fumes recirculation from other boilers can be quickly detected when the appliance is in a standby mode.
In an alternative embodiment, the appliance further includes an air duct disposed in the housing for guiding the outside air to the burner, and wherein the harmful gas sensor is disposed at an inlet of the air duct, which is better to detect fumes recirculation when the appliance is running because the fan is sucking the fresh air and the fumes recirculation from other boilers or this boiler's own thermal module can be detected quickly.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

Fig. 1 is a schematic diagram showing a gas boiler connected with a common chimney via flue pipes in accordance with a first embodiment of present invention;
Fig. 2 is a schematic diagram showing a gas water heater connected with a common chimney via flue pipes in accordance with a second embodiment of present invention;
Fig. 3 is a flowchart showing operations of the gas boiler shown in Fig. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made to the drawing figures to describe the preferred embodiments of the present invention in detail. However, the embodiments can not be used to restrict the present invention. Changes such as structure, method and function obviously made to those of ordinary skill in the art are also protected by the present invention.
The gas-fired heating appliance of the present invention is suitable for home applications and could be fired with combustible gas, such as natural gas, city gas, liquefied petroleum gas, methane, etc.. Gas-fired heating appliances can be used to heat domestic water for hot water demands of users, such as gas water heaters, or gas boilers that can provide both domestic hot water and needs of space heating. A gas boiler and a gas water heater will be respectively exemplified to explain the present invention in details in the following embodiments.
Referring to Fig. 1, in a first embodiment of present invention, a gas-fired heating appliance and chimney system 100 includes a gas boiler 1, a common chimney 9, and flue pipes 8 connected between the gas boiler 1 and the common chimney 9. The common chimney 9 can be connected by a number of gas-fired heating appliances in multi-family house on multiple flue configurations, for example, the chimney may be out of the building or in the building. Each of the flue pipes 8 and the common chimney 9 may take forms of a concentric duct composed of coaxial inner tube 81, 91 and outer tube 82, 92, wherein, one of the inner and the outer tubes is provided to discharge fumes and the other of the inner and the outer tubes is provided to introduce outside fresh air. In this embodiment, the inner tube 81, 91 is to discharge the fumes and the outer tube 82, 92 is to introduce fresh air.
The gas boiler is preferably a condensing boiler. The boiler 1 includes a housing 11, and a thermal module 121, a gas valve 122, a fan 123 all contained in the housing 11. The housing is usually sealed in appropriate means to prevent gas leakage. The housing 11 defines a first port 181 communicating with the inner tubes 81, 91, and a second port 182 surrounding the first port and communicating with the outer tubes 82, 92. The thermal module 121 typically includes a cylindrical burner combined with ignition and monitoring electrodes for combustion of a mixture of fresh air and fuel gas to generate fumes, and an integral condensation heat exchanger that consists of a number of stacked coils surrounding the cylindrical burner. The gas valve 122 is connected with a fuel gas supplying line 1221 and operable to regulate supply of the fuel gas to the burner. The fan 123 is provided to route the fresh air mainly containing oxygen for combustion preferably through an air duct 13 to the burner, and to urge the fumes to be released into the flue pipes via a flue duct 281.
A plate heat exchanger 14 is disposed in the housing 11. A domestic water path 151 is provided to introduce cold water that can passes through the plate heat exchanger 14 to obtain heat, and output the heated water for sanitary usage, such as showering or bathing. A transfer fluid path 152 is connected with the integral condensation heat exchanger for obtaining heat, and external space heating apparatuses for radiating heat into interior of buildings. The transfer fluid path 152 can also be switched to pass through the plate heat exchanger 14, however, the two paths 151, 152 are physically isolated to avoid mixing the domestic water and the transfer fluid, but allowing heat interchanging therebetween. A flow sensor 153 is disposed in and preferably at the inlet of the domestic water path 151 and able to generate a signal when there is water flow passing through the path 151 for domestic hot water demand.
A harmful gas sensor is provided inside of the housing 11 at a proper position to detect concentration of the harmful gases with the air inside of the housing. The harmful gases can be one or all kinds of harmful gases contained in the fumes, such as CO, CO2, NOx, etc. In other words, if there is a recirculation of fumes from the common chimney 9, or other gas-fired heating appliances in the system, or even the gas boiler 1 itself, such fumes recirculation can be detected by this gas sensor. In this embodiment, the harmful gas sensor can be a CO2 sensor such as TELAIRE^® T6713 series working by NDIR (Non-Dispersive Infrared) technology. The NDIR technology uses a broadband infrared (IR) emitter, which covers all of the wavelengths of interest for a given set of gases to be measured. Optical band pass filter attached to the gas sensor allow that portion of IR wavelengths at which a specific gas, like CO2 absorbs IR energy, then the gas sensor produces a signal that is proportional to the amount of IR energy absorbed by the gas of interest. In this embodiment, the harmful gas sensor 16 is preferably provided at an inlet of the air duct 13, which is better to detect fumes recirculation when the boiler is running because the fan 123 is sucking the fresh air and the fumes recirculation from other boilers or this boiler's own thermal module can be detected quickly.
A controller 17 is also provided in the housing 11 and electrically connected with the burner, the gas valve 122, the fan 123, the flow sensor 153, and the harmful gas sensor 16. The controller 17 is configured to control various operations of the gas boilers, which will be described in details with reference to the flowchart shown in Fig. 3. The controller 17 can be a logic control circuit formed by a number of electronic components connected in accordance with certain wiring patterns; or it may also be a microcontroller (MCU) storing program instructions; or it may be integrated chips with specific use, such as Field-Programmable Gate Arrays (FPGAs).
Fig. 2 shows a gas-fired heating appliance and chimney system 200 in a second embodiment of present invention, wherein, a gas water heater 2 is connected to a common chimney 9 via flue pipes 8. The gas water heater 2 includes an air tight housing 21 having a first port 281 and a second port 29, a burner 221 combined with ignition and monitoring electrodes 2211, 2222, a finned tube heat exchanger 222 connected with a cold water incoming line 251 and a hot water output line 252, a gas valve 23 connected in a fuel gas supplying line 231, a fan 24 for driving introduced outside air and urging fumes discharged into the flue pipes 8 via a gas hood 28. A harmful gas sensor that can also be a CO2 sensor provided adjacent to the second port 29 where outside fresh air is introduced. Since the sensor is positioned at entrance of the fresh air, the fumes recirculation from other boilers can be quickly detected when the gas water is in a standby mode. A controller 27 is also provided in the housing 21 and electrically connected with the burner 221, the gas valve 23, the fan 24, the flow sensor 253, and the harmful gas sensor 26. As the components in present embodiment are the same as or similar to those in the first embodiment, a detailed explanation of functional operation is omitted for sake of brevity and simplicity.
Referring to Fig. 3, in conjunction with Fig. 1, a flowchart of controlling operations of the gas boiler in accordance with the first embodiment of present invention is shown. The controller 17 monitors CO2 concentration of the air inside of the housing 11 via the CO2 sensor 16 in real time or periodically (step 411). If the concentration of CO2 is larger than or equals to a first threshold, such as 9000ppm (step 411), which means there is an excess of CO2, the controller 17 will further check if the burner is in operation through the monitoring electrode (step 413). If the burner is not in operation, which means the gas boiler is in a standby mode, the controller 17 then starts a standby operation. The controller 17 first activates the fan 123 to run to evacuate fumes in the fresh air so that the quality of the fresh air becomes good for ignition (Step 421). In a preferred embodiment, the fan 123 runs at a lowest speed at first, then increases the speed step by step. It is well known to the skilled person that the fan speed can be regulated by adjusting the PWM signal to the current of the fan. During the fan running, the controller 17 continues to check if the CO2 concentration reduces to a second threshold within a first time duration after the excess of CO2 being detected (Step 422). The second threshold equals to or is lower than the first threshold. If the CO2 concentration can reduce to the second threshold within the first time duration, which means the quality of the air inside of the housing is good enough for a successful ignition, the controller 17 stops the fan running (Step 423) and then continues to monitor the CO2 concentration. Preferably, the controller can stop the fan after a delay. If the CO2 concentration does not reduce to the second threshold within the first time duration, which means the air quality is still not good enough for ignition, the controller 17 then displays a fault code on a display panel (not shown) of the gas boiler to remind the user so that the user can inspect the boiler and take appropriate actions against fumes, preferably, the controller 17 also disables the combustion of the burner, such as cutting off the gas valve 122 to avoid danger and damages, meanwhile keeps the fan running to evacuate fumes (Step 424).
Return to the step 413, if the burner is in operation, a counter for fumes recirculation will count once (Step 414), then the controller 17 further checks if the accumulated number of times reaches a predetermined value within a certain time period (Step 415). In this embodiment, the predetermined value is five, and the certain time period is 24-hour. Therefore, if the accumulated number of times of the counter reaches five within past 24 hours, which means there is a high frequency of detection of excess of CO2, then the controller 17 displays a fault code, and preferably, disables the combustion of the burner and keeps the fan running to evacuate fumes (Step 424); otherwise, the controller 17 further checks if there is a demand of domestic hot water (Step 416). The controller 17 can detect domestic hot water demand via the flow sensor 153, that is, if there is a water flow in the domestic water path 151, the flow sensor will send a corresponding signal to the controller 17, then the controller 17 will wait for a second time duration after the excess of CO2 being detected, like three hours to ensure the comfort of users using the hot water (Step 417). If there is no domestic hot water demand, namely the boiler is in operation in a space heating mode, or the second time duration lapses after the excess of CO2 being detected in the domestic hot water mode, the controller 17 stops the combustion of the burner, such as by cutting off the gas valve 122 (Step 418) and then enters the standby operation. It is obvious to the skilled person that, for a gas water heater, the step 416 can omitted because if the burner is in operation, the flow sensor shall detect a water flow at the same time, so there is no need to detect "domestic hot water demand".
The harmful gas detection can also be used by an installer. On installation, the controller is operable to conduct the detection of harmful gases on site, and if there is an excess of harmful gases being detected, he or she can inspect and take actions against fumes recirculation right now. Moreover, since the fumes usually contain CO, CO2, NOx and other harmful gases, an excess of CO2 also reflects an excess of CO or NOx, therefore, the excess of CO and NOx can also be limited by only detection of CO2 and thus the excess limitation. Furthermore, for a condensation boiler, the risk of condensation in air side caused by potential fumes recirculation can be reduced because the fumes recirculation can be detected quickly and the fan will be started to evacuate the fumes.
It is to be understood, however, that even though numerous, characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosed is illustrative only, and changes may be made in detail, especially in matters of number, shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broadest general meaning of the terms in which the appended claims are expressed.

Claims

A gas-fired heating appliance (1, 2) adapted for being connected to a common chimney (9) via flue pipes (8) to discharge fumes and introduce outside air, comprising:
a housing (11, 21) defining a first port (181, 281) and a second port (19, 29) surrounding the first port, wherein one of said first and said second ports is provided to discharge fumes and the other of said first and said second ports is provided to introduce outside air;

a burner disposed in the housing for combustion of a mixture of introduced outside air and fuel gas to generate fumes;

a gas valve associated with the burner for regulating supply of fuel gas to the burner;

a fan disposed in the housing for driving the introduced outside air supplied to the burner and urging the fumes to be discharge outside through the flue pipes and the common chimney;

a controller electrically connected with the burner, the gas valve and the fan; characterized in further comprising:
a harmful gas sensor disposed in the housing for detecting a concentration of the harmful gases including at least one of CO, NOx within air inside of the housing; and in that the controller being electrically connected with the burner, the gas valve, the fan, and the harmful gas sensor for controlling the fan and/or the burner and/or the gas valve based on the detection of the harmful gas sensor; wherein said controller is configured to start a standby operation when an excess of harmful gases is detected while the appliance is in a standby mode, and said standby operation includes activating the fan to run.
A gas-fired heating appliance according to claims 1, wherein the excess of harmful gases is detected when the harmful gas sensor detects that the concentration of the harmful gases is larger than or equals to a first threshold.
A gas-fired heating appliance according to claim 1, wherein said standby operation further includes increasing the fan speed step by step.
A gas-fired heating appliance according to claims 1 or 3, wherein said standby operation further includes stopping the fan running if the harmful gas sensor detects that the concentration of the harmful gases reduces to a second threshold within a first time duration after the excess of harmful gases being detected.
A gas-fired heating appliance according to claims 1 or 3, wherein said standby operation further includes displaying a fault code if the harmful gas sensor detects that the concentration of the harmful gases does not reduce to a second threshold within a first time duration after the excess of harmful gases being detected.
A gas-fired heating appliance according to claim 5, wherein said standby operation further includes keeping the fan running and disabling the combustion of the burner.
A gas-fired heating appliance according to claims 6 or 5, wherein the second threshold equals to or is lower than the first threshold.
A gas-fired heating appliance according to any of claims 2-7, wherein said controller is configured to stop the combustion of the burner and then enter said standby operation when the appliance operates in a domestic hot water mode for a second time duration after the excess of harmful gases being detected.
A gas-fired heating appliance according to any of claims 2-7, wherein said controller is configured to stop the combustion of the burner and then enter said standby operation when the excess of harmful gases is detected while the appliance operates in a space heating mode.
A gas-fired heating appliance according to claim 1, further comprising a counter that is able to count once when the excess of harmful gases is detected and the burner is in operation, and wherein said controller is configured to display a fault code when the accumulated number of times reaches a predetermined value within a certain time period.
A gas-fired heating appliance according to claim 10, wherein said controller is further configured to keep the fan running and disable the combustion of the burner.
A gas-fired heating appliance (2) according to claim 1, wherein said harmful gas sensor (26) is disposed adjacent to the port for introducing outside air.
A gas-fired heating appliance (1) according to claim 1, further comprising an air duct (13) disposed in the housing for guiding the outside air to the burner, and wherein said harmful gas sensor (16) is disposed at an inlet of the air duct.