CA1317356C

CA1317356C - Fuel burner control systems

Info

Publication number: CA1317356C
Application number: CA000520274A
Authority: CA
Inventors: Brendan Kemp; Paul James Nichols
Original assignee: Autoflame Engineering Ltd
Current assignee: Autoflame Engineering Ltd
Priority date: 1983-04-21
Filing date: 1986-10-10
Publication date: 1993-05-04
Anticipated expiration: 2010-05-04
Also published as: GB8310834D0; GB2138610B; EP0124330A1; GB2138610A

Abstract

ABSTRACT

"Improvements in or relating to fuel burner control systems"

A fuel burner control system which includes a look-up memory in which are entered values for air valve and fuel valve settings for efficient fuel combustion as confirmed by combustion analysis equipment in a boiler installation, the burner control system being arranged to provide the appropriate valve setting informa-tion in response to a desired temperature setting.
A combustion process control system is capable of operating in a first mode to effect the entry of air and fuel valve setting information in look-up memory and, in a second mode, to supply the stored information in response to a heat demand signal.

Description

1~173~6 "Improvements in or relating to fuel burner control systems"
. _ .

The invention relates to a fuel burner control system capable of controlling the supply of air and fuel to a burner, and to a combustion process contro-system lncluding such a fuel burner control system.
The quantity of air and fuel supplied to a fuel burner should be controlled in such a manner that the fuel is burned completely without having a significant quantity of excess air. The supply of too little air results in incomplete combustion and the waste of fuel whilst the supply of too much air results in the absorption of some heat by the excess air. For efficient combustion the ratio of the quantity of the fuel supplied to the burner to the quantity of air supplied to the burner should be constant at a value which provides just enough oxygen for complete combustion to take place. However, because of the behaviour of the fuel and the air flowing through the respective control valves, the ratio of the extent of opening of the fuel valve to the extent of opening of the air valve to provide a constant fuel : air ratio is not constant over the heat supply range of the burner.
Known burner control systems employ mechanically linked air and fuel supply valves and suffer from the disadvantage that they are capable of achieving .

- 2 - 13 17 3~6 efficient combustion of fuel over a small part only of the burner heat supply range.
It is an object of the present invention to provide a burner control system capable of improved performance compared to existing burner control systems.

13173~6 20648-136~
In accordance with the present invention, there is provided a control system for a fuel burner, the system comprising a fuel supply control valve, an air supply control valve, a memory for holding values of air valve and fuel valve settings~ a processor connected as part of the control system, means for manually setting the system selectively, through the processor, to a commissioning mode or a run mode, manual means for operator control, through the processor, in the commissioning mode~ of at least one of the valves in order to effect operator selection of the settings for that valve, and means for effectlng, through the processor, in the commissioning mode, the entry into the memory of a respective comblnation of the settings of the fuel and air supply valves for each of a plurality of values of an input signal representing a first variable, the processor being operable, in the run mode, to provide, from the memory, respective air and fuel valve settings according to the value of the input signal representing the first variable, which settings are used to control the valves.
The valve settlng values are preferably derived from operator selection of the settlngs of one of the valves and operator derivatlon of the settings of the other of the valves.
The present invention also provides a fuel burner control system including a memory for holding values of air valve and fuel valve settings, a processor connected as part of the control system, means for manually setting the system selectively, through the processor, to a commissioning mode or a run mode, and manual means for operator control, through the processor in the 13173~6 commissioning mode, to effect the generation of output values for setting a fuel valve and an air valve and the entry, into the memory, of selected settings for the fuel valve and corresponding settings for the air valve for each of a plurality of values of an input signal representing a first variable, the processor being operable, in the run mode, to provide, from the memory, respective air and fuel valve settings according to the value of the input signal representing the first variable.
Preferably, the processor is capable of determining a setting value for one valve for each value of the first variable, and is arranged to select increasing setting values for the valve with increasing values of the first variable over a limited range of values of the first variable, and outside the limited range, to select a fixed setting value for the valve.
Preferably, the fixed value setting is the maximum setting avallable for the valve, when the valve is the fuel valve.
Preferably, the lower llmlt of the limited range corresponds to the START condition for the system.
Preferably, the limited range of values of the first variable lies between five and twenty percent of the possible range of the first variable.
Preferably, the processor includes means for ad~usting the limits of the limited range of values of the first variable.
Preferably, the control system includes data as to the number of valve settings the memory is intended to accommodate and is capable of operating in a run mode only when all the air and fuel valve settings are present 13~73~

in the memory.
Preferably, the memory holds data as to the open and shut positions of the valves.
Preferably, the first variable is the difference between second and third variables, and, preferably, the second and third variables are the actual and desired operating temperatures, respectively, of a medium arranged to be heated by a burner controllable by the control system.
Preferably, the control system includes display means and is capable of displaying the second and third variables alternately on common display elements.
Arrangements of the control system for a fuel burner, referred to above, may, of course, be included in boiler installations.
According to another aspect, the present invention provldes a method of commisslonlng and running a control system for a fuel burner, the system comprising a fuel supply control valve, an air supply control valve, a memory for holding values of valve settlngs, and a processor, the method comprising the steps of manually setting the system, through the processor, to a commissioning mode, operating the burner, selecting a respective combination of air valve settlng and fuel valve setting for each of a plurallty of values of an input signal representing a first variable, where the setting of at least one valve ls effected manually through the processor, and entering the selected combinations into the memory, manually setting the ~ystem, through the processor, to a run mode, operating the burner and providing 13173a6 2064~-1364 an input signal to the processor representing a first variable, which results in the processor obtaining from the memory a respective value of fuel value setting and a respective value of air valve setting according to the value of the input signal representing the first variable, and setting the fuel valve and the air valve according to the settings obtained from the memory.

5a ~317356 A control system for a fuel burner in accordance with the present invention and a combustion process control system including the burner control system will now be described by way of example only and with reference to the accompanying drawings, in which :-Fig. 1 is a schematic representation of a com-bustion process control system arranged as the central unit of an electrical system capable of controlling a boiler, Fig. 2 is a block schematic representation of the combustion process control system of Fig.
1 , Fig. 3 is an illustration of a control panel of the combustion process control system of Fig. 1, Fig. 4 is a flow chart representation of the opera-tion of the combustion process control system of Figs. 1 and 2, Fig. S is a graphical representation of the rela-tionship between the fuel valve setting and, (i) the deviation of the actual temperature from the thermostat setting (the upper abscissa scale), and, (ii) the temperature relative to the thermo-stat setting T C (the lower abscissa scale), for the burner control system and, Fig. 6 is a diagrammatic representation of the arrangement of fuel and air valve setting 13173~6 - data in an addressable data store, for the burner control system.
Referring to Fig. 1, an electrical system capable of controlling a boiler includes a combustion process control system 1, an air supply control valve 2, a fuel supply control valve 3, an air control valve motor 4, a fuel control valve motor 5, position indicating potentio~
meters 6 and 7, a thermostat 8, and a fuel selector switch 9. The combustion process control system 1 includes a plurality of input ports by means of which it receives information from its sensors and output ports by means of which it provides information to actuators and the .
like. The combustion process control system 1 includes input ports Fl, F2 one of which is energised by means of the fuel selector switch 9 to signal the type of fuel in use, a temperature sensor input port Tl/T2 for receiving information as to an actual temperature, a remote load control input port 10, a boiler thermostat input port S10, an open /
start switch position-sensing input port S13, switch position-sensing ports S14 and S15, a load control switch sensing port S7, an air valve position sensing input port A, and a fuel valve position sensing port F. Also in-cluded are output ports A+ and A- for controlling the air control valve motor 4 and output ports F+ and F-for controlling the fuel valve control - 8 - 13173~6 motor 5.
Referring to Fig. 2, the combustion process control system 1, of Fig. 1, includes a microprocessor 100, a serial timer interrupt controller 101, an electrically 5 erasable memory 102, a plurality of display5103, input/
output controllers 104 and 105, a fixed programme memory 106, a random access memory 107, and an analogue-to-digital converter 108. The microprocessor is a Type Z80 integrated circuit which, under the direction of the fixed programme memory 106, reads the signals at the various input ports and executes the actions for providing control signals at the appropriate output ports in addition to providing information for the displays 103. The serial timer interrupt controller 15 101, which is a Type MK 3801 integrated circuit, is a multifunction device providing a USART (Universal Synchronous/Asynchronous Receiver/Transmitter), four timers (two binary and two full function), and eight bidirectional input/output lines with individually pro-grammable interrupts. The random access memory 107 acts as a short term store for the signals received from in-put ports and the signals to be presented to output ports.
The random access memory 107 acts also as a scratchpad memory for the microprocessor 100. The input/output 25 controllers 104 and 105 control the activation and de-activation of the ports as instructed by the micropro-cessor 100 and the serial timer interrupt controller 101.
The signals from - 9 - 13173~6 the temperature sensor port (T1 - T2) and the valve motor position indicator ports (F, A) are subjected to analogue-to-digital conversion by the analogue-to-digital converter 108. The signals from the remote load sensing port 10 and other port3 in its group (S7, S10, S13, F1, F2) are each subject to modification by means of a level-translating circuit 109 which also provides electrical isolation by means of optical coupling. There are provided manual controls capable of effecting the operations listed below. The manual controls are identified on the ront panel represented in Fig. 3.. The manual controls are switches connected to a plurality of control input ports shown in Fig. 2.
The operations referred to above are :-1. Placing the combustion process control system in either the commiqsioning mode or the run mode, and, in the commissioning mode :-2. Increasing or decreasing the fuel ~upply.

3. Increasing or decreasing the air supply.

4. Increasing or decreasing the desired tempera-ture.

5. Signalling to the system the positions of the air and fuel valves relative to their respective open and closed positions.
Referring to Fig. 4, the operations carried out by the combustion process control system commence with switch-on and the selection of fuel (1). The system then checks whether or not it has a look-up memory with information for the fuel selected (2) and, if not, . ~

-- ],o, places itself in the commissioning mode permitting control by means of the manual controls shown in Fig. 3 and illuminating the CLOSE POSITION and ENTER ~EMORY
displays at the control panel (3). The manual control~
for the air and fuel valve motors are then used by the operator to close both valves (indications of the positions of the valves are given at the control panel) and the operator presses ENTER MEMORY on the front panel when he is satisfied that the valves are closed (4). The system then illuminates a SET STAT display, indicating that the operator should enter a temperature setting at which the burner is to be extinguished in order to prevent a further rise in the temperature of the medium being heated e.g. water in a boiler. The OPEN POSITION and ENTER MEMORY displays on the control panel are next illuminated ~7) and the operator uses the manual controls to open both valves fully and presses ENTER MEMORY on the first panel when he is satisfied that both valves are.open (8). The system next purges waste gases from the combustion chamber (9) after which it illuminates the START POSITION display on the control panel (10, 11, 12). The manual controls are then used by the operator to open partially both valves to allow ignition and combustion of fuel and he then presses START POSITION ( 13) to initiate boiler operation. The system then illuminates the HIGH POSITION and ENTER
MEMORY displays on the front panel (14 ? . The manual ll 13173~

controls are used by the operator to obtain, from the burner, a maximum heat output suitable for the inAtalla-tion in which it is being used while ensuring efficient combustion at the maximum heat demand (15). This part of the operation is executed with the aid of combustion analysis equipment and requires an.operator skilled in the use of such e~uipment. When the operator is satis-fied that efficient combustion is taking place at the high heat demand setting he presses ENTER MEMORY (15).
10 The system then decides whether subsequent operation is to be ~or the entry of intermediate or start data (17), and,for the entry of intermediate data, illuminates the lNTER POSITION and START displays on the front panels (16). For the entry of intermediate data, the operator 15 presses INTER ( 18), selects ~ome fuel valve setting below the maximum value set previously, adjusts the air valve to provide efficient combustion at this new intexmediate heat demand setting, and when he is satis-fied that the combustion is efficient he presses ENTER
20 MEMORY (19). The system continues to illuminate the INTER and START displays (return to 16) until the required number of locations in the look-up memory are filled with values for intermediate fuel valve and air valve settings. On completion of the entrie~ for intermediate settings the START and ENTER MEMORY
displays are illuminated (20), the operator uses the manual controls to set a selected START position for the fuel valve, adjuststheair valve forefficient combustion .

~3~7~

and then presses the ENTER MEMORY display/switch to effect entry of the settings into the memory ~
The system then illuminateq the RUN display on the front panel to indicate that it is ready for operation (22) which is effected by pressing RUN (23).
When the RUN control is operated at the end of the commisqioning phase the combustion process control system deactivat~s all of the front panel controls with the exception of the COM (commission) and RUN
controls and thereafter functions as a burner control system capable of providing it~ stored valve setting data in response to a remote load control input.
Following the operation of the RUN control as described above, the system waits for 20 second (24) and then responds to the remote control, checking periodi-cally for a change in demand ~25).
Further shown in Fig. 4, the combustion process control system may be reprogrammed by switching it off and on (return to 1), and then operating the COM control on the front panel which returns it to the commissioning cycle via check point (27) and decision (2a).
Referring still to Fig. 4, should the flame be extinguished by external influences, the system switches off (29) and will restart when the pilot flame is reestablished (30 to 37).
The programmer/operator is required to set, by means of a presettable control forming part of the apparatus, an "offset" temperature difference to be - 13 - 13173~6 ~, used by the apparatus in normal operation. The function of the "offset" temperature difference and the relation-ship between the START, INTERMEDIATE, and ~IGH settings will now be explained with reference to Fig. 5.
In Fig. 5, the relation~hip between the fuel valve ~etting and the deviation of th~- actual temperature from the thermostatically set temperature is represented by a graph having two straight portions, one (the first) portion rising at a constant rate to meet the other portion which has zero slope. The first portion of the graph represents an increasing fuel valve setting, that is, the extent of opening of the fuel valve, from the START
value to the HIGH value. The increase in the fuel valve setting from the START value to the HIGH value occurs over a change from 0 C to 10 C in the deviation of the actual temperature from the thermostatically set temperature. The fuel valve setting then remains con-stant at the HIGH value for temperature deviations in excess of 10C. It will be appreciated that the thermo-statically set temperature T C is represented by a O Ctemperature deviation and T - 10 C is represented by a 10 C deviation, as shown in the alternative temperature scale of Fig. 5. The"offset" temperature difference referred to above is, in Fig. 5, the 10 C difference at which the change occurs in the slope of the graph. Values of fuel valve setting which lie on the rising part of the graph are the intermediate fuel valve etting values.

13~7356 ~he equipment is capable of "constructing" the graph of Fig. 5 by calculation, since it is given the START
value, the HIGH value, and the "offset"temperature difference. As stated above the HIGH value represent~
the setting for the maximum heat output which may be used with the particular installation, e.g. a boiler, which incorporates the burner control system.
The fuel burner control system, according to the invention, in operation, monitors the actual temperature of a medium e.g. water in a boiler, which is being heated by the fuel burner and compares the said actual temperature with a thermostatically set temperature for the medium. The fuel burner control system is capable of calculating the deviation of the actual temperature from the thermostatically set temperature and also of performing the operations necessary to obtain a value for fuel valve setting for any temperature deviation value in accordance with the relationship represented by Fig. 5.
Therefore the fuel burner control system selects the START value of fuel valve setting if the temperature deviation is zero and selects the HIGH value of fuel valve setting if the temperature deviation is 10 C or more. For a temperature deviation between 0 C and 10 C, the fuel burner control system calculates the fuel valve setting (angular position in degrees) in accord-ance with the relation3hip :-Fuel valve rHIGH fuel START fuel 1X temp.deviation po~ition ~alve ~etting valve settingJ 10 ~ 13~7356 Also shown in Fig. 5 are alternative forms of therelationship between fuel valve settings and temperature deviation having break points at X C (less than 10 C) and Y C (more than 10 C), respectively, the break points representing a range of values of temperature deviation which may lie between five and twenty per cent of the possible range of temperature deviation. The fuel burner control system shuts off the fuel supply if the temperature deviation becomes negative.
Referring now to Fig. 6, data required by the fuel burner control system in its operation is stored as fuel valve settings in a first addressable data store, repre-sented diagrammatically on the left in Fig. 6, and as air valve settings in a second addressable data store, repre-sented diagrammatically on the right in Fig. 6. Once the fuel burner control system has determined a fuel valve setting, as described above with reference to Fig. 5, it locates the said fuel valve setting, in the fuel valve setting data store (or the fuel valve setting closest to the said valve setting), notes the address at which the relevant fuel valve setting was located, and selects the air valve setting data at a corresponding address in the air valve setting data store. Once the fuel burner control system has acquired both fuel valve and air valve setting data it proceeds to apply the fuel valve setting data to its fuel valve control output port and to apply the air valve setting data to its air valve control output port.
Referring to Fig. 6, the fuel valve setting data available in the first data store includes control , . . .... , . . . . ~ . _ . ... _ , , .. _ _ _ _ _ _ _ _ _ _ _ ` - 16 _ 13173~6 data glving the following positions of the fuel valve :
CLOSED, at which the fuel valve is shut.
OPEN, at which the fuel valve is open fully.
HIGH, at which the fuel valve is open to a position which provides the maximum heat output which the installation, e.g. a boiler, can use.
INTERMEDIATE 1 to INTERMEDIATE N, a set of positions along the sloping part of Fig. 5 representing pro-gressive opening of the fuel valve for a minimum heat output START position to the maximum heat output HIGH position. There may be 25 such INTER-MEDIATE positions chosen along the sloping part of Fig. 5 ~N = 25).
START, at which the fuel valve is slightly open to provide enough heat to compensate for heat losses of the system in order to maintain the medium being heated at the thermostatically set temperature ~T in Fig. 1).
The data store also includes an indication of the value of N ~the number of INTERMEDIATE positions of the fuel valve available in the data store), so that the system can check on whether or not it holds a full set of INTERMEDIATE data.
Referring again to Fig. 1, the accuracy of control of the air and fuel valves 2 and 3 is of the order of a quarter degree and the valve positions are read as those of the motors 4 and 5 by the feedback provided by the potentiometers 6 and 70 The positions of the motors .. . : . . . _ _ _ . ._. _ _ . .

~3173~6 - 17 ~

are checked eight times per second.
Referring again to Fig. 3, the front panel displays include "fuel ~elected" indicators, "commission" and "run" indicators, and a temperature indicator which displays the desired and actual temperatures alternately.
The front panel al~o includes an 2 display and ~etting control for establishing an optimum level of oxygen in the exhaust gases during commissioning. The system may be arranged to maintain a boiler to provide the optimum oxygen level in the exhaust gases by fine control of the valves (over and above the fixed control set on commis~ioning). The 2 display is arranged to display the actual and desired values alternately.
In the equipment described above the temperature (or more precisely the difference between the actual and desired temperatures) of the boiler water is used as a variable con.rol quantity. It is also possible to use other variables; for example the steam pressure of the boiler, the temperature of the products of combustion 20 of the boiler, the process or output temperature of the boiler, or a variable re~ated to the heat load re~uire-ments of, for example, a building heated by the boiler.

~ .

13173~6 As is explained above, the control system will provide, from the memory, in response to each of a plurality of input signal values representing values of output heat demand, respective values for air valve and fuel valve settings. Examples of the operation of the system are as follows:-(i) The control system will select fuel valveand air valve setting values from the memory and apply them to the output ports without alteration if the memory holds valve setting values corresponding exactly to the current input signal value.
(ii) In addition to carrying out (i) above, the control system will select fuel valve and air valve setting values from the memory and alter them before applying them to the output ports if the memory does not hold valve setting values corresponding exactly to the current input signal value. The values taken from the memory are those corresponding to input signal values closest to the current input signal value and the control system provides intermediate values from the values taken from the memory.

Claims

1. A control system for a fuel burner, the system comprising a fuel supply control valve, an air supply control valve, a memory for holding values of air valve and fuel valve settings, a processor connected as part of the control system, means for manually setting the system selectively, through the processor, to a commissioning mode or a run mode, manual means for operator control, through the processor, in the commissioning mode, of at least one of the valves in order to effect operator selection of the settings for that valve, and means for effecting, through the processor, in the commissioning mode, the entry into the memory of a respective combination of the settings of the fuel and air supply valves for each of a plurality of values of an input signal representing a first variable, the processor being operable, in the run mode, to provide, from the memory, respective air and fuel valve settings according to the value of the input signal representing the first variable, which settings are used to control the valves.

2. A fuel burner control system, as claimed in claim 1, in which the valve setting values are derived from operator selection of the settings of one of the valves and operator derivation of the settings of the other of the valves.

3. A fuel burner control system including a memory for holding values of air valve and fuel valve settings, a processor connected as part of the control system, means for manually setting the system selectively, through the processor, to a commissioning mode or a run mode, and manual means for operator control, through the processor in the commissioning mode, to effect the generation of output values for setting a fuel valve and an air valve and the entry, into the memory, of selected settings for the fuel valve and corresponding settings for the air valve for each of a plurality of values of an input signal representing a first variable, the processor being operable, in the run mode, to provide, from the memory, respective air and fuel valve settings according to the value of the input signal representing the first variable.

4. A control system as claimed in claim 1, wherein the processor is capable of determining a setting value for one valve for each value of the first variable, and is arranged to select increasing setting values for the valve with increasing values of the first variable over a limited range of values of the first variable, and outside the limited range, to select a fixed setting value for the valve.

5. A control system as claimed in claim 2, wherein the processor is capable of determining a setting value for one valve for each value of the first variable, and is arranged to select increasing setting values for the valve with increasing values of the first variable over a limited range of the first variable, and, outside the limited range, to select a fixed setting value for the valve.

6. A control system as claimed in claim 3, wherein the processor is capable of determining a setting value for one valve for each value of the first variable, and is arranged to select increasing setting values for the valve with increasing values of the first variable over a limited range of values of the first variable, and, outside the limited range, to select 20a a fixed setting value for the valve.

7. A control system, as claimed in claim 4, 5, or 6, wherein the fixed value setting is the maximum setting available for the valve, when the valve is the fuel valve.

8. A control system, as claimed in claim 4, or 5, or 6, wherein the lower limit of the limited range corresponds to a START condition for the system.

9. A control system as claimed in claim 4, or 5, or 6, wherein the limited range of values of the first variable lies between five and twenty percent of the possible range of the first variable.

10. A control system as claimed in claim 4, or 5, or 6, wherein the processor includes means for adjusting the limits of the limited range of values of the first variable.

11. A control system as claimed in claim 4, or 5, or 6, wherein the fixed value setting is the maximum setting available for the valve, when the valve is the fuel valve, and the lower limit of the limited range corresponds to a START condition for the system.

12. A control system as claimed in claim 4, or 5, or 6, wherein the fixed valve setting is the maximum setting available for the valve, when the valve is the fuel valve, the lower limit of the limited range corresponds to a START condition for the system, and the limited range of values of the first variable lies between five and twenty percent of the possible range of the first variable.

13. A control system as claimed in claim 4, or 5, or 6, wherein the fixed value setting is the maximum setting available for the valve when the valve is the fuel valve, and the limited range of values of the first vairable lies between five and twenty percent of the possible range of the first variable.

14. A control system as claimed in claim 4, or 5, or 6, wherein the fixed value setting is the maximum sett-ing available for the valve, when the valve is the fuel valve, and the processor includes means for adjusting the limits of the limited range of values of the first variable.

15. A control system as claimed in claim 4, or 5, or 6, wherein the fixed value setting is the maximum setting available for the valve, when the valve is the fuel valve, the lower limit of the limited range corresponds to a START condition for the system, and the processor includes means for adjusting the limits of the limited range of values of the first variable.

16. A control system as claimed in claim 1, wherein the memory is so organised that the address of each fuel valve setting value points to the address of the corresponding air valve setting value, or vice-versa.

17. A control system as claimed in claim 2, wherein the memory is so organised that the address of each fuel valve setting value points to the address of the - 22a -corresponding air valve setting, or vice-versa.

18. A control system as claimed in claim 3, wherein the memory is so organised that the address of each fuel valve setting value points to the address of the corresponding air valve setting value, or vice-versa.

19. A control system as claimed in claim 16, or 17, or 18, which includes data as to the number of valve settings the memory is intended to accommodate and is capable of operating in a run mode only when all the air and fuel valve settings are present in the memory.

20. A control system as claimed in claim 16, or 17 or 18, wherein the memory holds data as to the open and shut positions of the valves.

21. A control system as claimed in claim 1, wherein the first variable is the difference between second and third variables.

22. A control system as claimed in claim 21, wherein the second and third variables are the actual and desired operating temperatures, respectively, of a medium arranged to be heated by a burner controllable by the control system.

23. A control system as claimed in claim 21 or claim 22, including display means and capable of displaying the second and third variables alternately on common display elements.

24. A method of commissioning and running a control system for a fuel burner, the system comprising a fuel supply control valve, an air supply control valve, a memory for holding values of valve settings, and a processor,the method comprising the steps of manually setting the system, through the processor, to a commissioning mode, operating the burner, selecting a respective combination of air valve setting and fuel valve setting for each of a plurality of values of an input signal representing a first variable, where the setting of at least one valve is effected manually through the processor, and entering the selected combina-tions into the memory, manually setting the system, through the processor, to a run mode, operating the burner and providing an input signal to the processor representing a first variable,which results in the processor obtaining from the memory a respective value of fuel value setting and a respective value of air valve setting according to the value of the input signal representing the first variable, and setting the fuel valve and the air valve according to the settings obtained from the memory.