EP1248044B1 - Method for starting a heater - Google Patents

Abstract

The method involves igniting the burner (14) with a medium gas throughput and holding the throughput to a very low level for a specified heating modulation blocking period after ignition. The heating modulation blocking period can be reduced with increasing modulation throughput required to satisfy the heat demand.

Description

The invention relates to a method for adaptive heater modulation inhibit timing according to the introductory part of the independent claims.

Known wall heaters are often operated in the first few minutes with the smallest possible partial load to ensure long periods of operation and to avoid cycling operation. In this so-called heating modulation blocking time, the actual heat requirement is ignored and instead the device is operated with minimum load. The minimum load corresponds to the minimum permissible load, which results from the basic conditions for a stable and low-emission burner operation (avoidance of lift-off and re-ignition when operating with boundary gases). Disadvantage of this method is that at high actual heat demand this is met only with a corresponding time delay, resulting in loss of comfort. The document JP 04198661 mentioned some features.

The aim of the invention is to avoid this disadvantage and to ensure an early, needs-based performance adjustment at the same time long operating times.

According to the invention this is achieved by a method for starting a heater according to the features of the independent claims. The proposed measures enable a heat-demand-appropriate heating modulation blocking time.

Due to the features of claim 2, there is the advantage that the heating process and the associated change in the temperature of the heating system during the starting phase in the determination of the Heizungsmodulationsperrzeit is taken into account.

Due to the features of claim 3, there is the advantage that only one measurement during the starting phase for determining the Heizungsmodulationsperrzeit is necessary.

According to the features of claim 4 results in a self-inventive way a simplified method in which the Heizungsmodulationsperrzeit is not continuously, but gradually changed.

Due to the features of claim 5, there is the advantage that in the simplified method according to claim 4, the heating process and the associated change in the temperature of the heating system during the starting phase in the determination of Heizungsmodulationsperrzeit is taken into account.

Due to the features of claim 6, there is the advantage that in the simplified method according to claim 4, only a measurement during the startup phase for determining the Heizungsmodulationsperrzeit is necessary.

Hierbei sind C₁, C₂, und C₃ Konstanten, die zumeist im Laborbetrieb für den vorteilhaften Betrieb ermittelt werden müssen. T_Soll ist die Solltemperatur des Heizkreislaufs, T_Ist die momentane Temperatur des Heizkreislaufs, wobei es sich sowohl um eine Vorlauf-, als auch Rücklauftemperaturregelung handeln kann. I_Σ ist die Summe der Regelabweichungen des PI-Reglers. $${\mathrm{I}}_{\mathrm{\Sigma }\mathrm{,}\mathrm{t}}\mathrm{=}\mathrm{\sum }_{\mathrm{i}\mathrm{=}\mathrm{0}}^{\mathrm{l}}\left({\mathrm{T}}_{\mathrm{Soll}}\mathrm{-}{\mathrm{T}}_{\mathrm{lst}\mathrm{,}\mathrm{i}}\right)$$

The modulation setpoint MSW is a measure of the required heating power and specifies a corresponding setpoint. The maximum corresponds to the nominal load, the minimum to the minimum load. The modulation setpoint MSW is calculated as follows: $$\mathrm{MSW}\mathrm{=}{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="imgf0002.png,imgf0003.png"\; state="\{\{state\}\}">C</figure-callout>}}_{\mathrm{1}}\mathrm{\cdot }\left({\mathrm{T}}_{\mathrm{Should}}\mathrm{-}{\mathrm{T}}_{\mathrm{lst}}\right)\mathrm{+}\frac{{\mathrm{<figure-callout\; id="2"\; label="I\; \Sigma \; C"\; filenames="imgf0002.png,imgf0003.png"\; state="\{\{state\}\}">I\; </figure-callout>}}_{\mathrm{\Sigma }}}{{\mathrm{C}}_{}}\mathrm{+}{\mathrm{<figure-callout\; id="3"\; label="C"\; filenames="imgf0002.png"\; state="\{\{state\}\}">C</figure-callout>}}_{\mathrm{3}}$$

Here are C ₁ , C ₂ , and C ₃ constants, which usually have to be determined in laboratory operation for advantageous operation. T _setpoint is the setpoint temperature of the heating circuit, T _is the current temperature of the heating circuit, which can be both a supply and return temperature control. I _Σ is the sum of the control errors of the PI controller. $${\mathrm{I}}_{\mathrm{\Sigma }\mathrm{.}\mathrm{t}}\mathrm{=}\underset{\mathrm{i}\mathrm{=}\mathrm{0}}{\overset{\mathrm{l}}{\mathrm{\Sigma }}}\left({\mathrm{T}}_{\mathrm{Should}}\mathrm{-}{\mathrm{T}}_{\mathrm{lst}\mathrm{.}\mathrm{i}}\right)$$

A change in the clock rate when determining the control deviation causes a corresponding change in the constants.

• Dabei zeigt Fig. 1 ein Blockschaltbild eines Heizgerätes, mit dem das erfindungsgemäße Verfahren durchgeführt werden kann,
• Fig. 2 den Verlauf des Modulationswertes,
• Fig. 3 ein Flußdiagramm für ein erfindungsgemäßes Verfahren,
• Fig. 4 einen möglichen Zusammenhang zwischen dem durchschnittlichen Modualtionssollwert und der Heizungsmodualtionssperrzeit,
• Fig. 5 beispielhaft den zeitlichen Verlauf des Modulationssollwertes und des Modulationsvorgabewertes sowie die Messpunkte zur Bestimmung der Heizungsmodualtionssperrzeit und
• Fig. 6 ein weiteres Flußdiagramm für ein erfindungsgemäßes Verfahren.

The invention will now be explained in more detail with reference to the drawings.

• It shows Fig. 1 a block diagram of a heater with which the inventive method can be performed
• Fig. 2 the course of the modulation value,
• Fig. 3 a flow chart for a method according to the invention,
• Fig. 4 a possible relationship between the average module setpoint and the heater module lockout time,
• Fig. 5 for example, the time profile of the modulation setpoint and the modulation default value and the measuring points for determining the Heizungsmodualtionssperrzeit and
• Fig. 6 another flow diagram for a method according to the invention.

In Fig. 1 is a block diagram of a heater, in which the inventive method is applied, shown. The heater 27 has a burner 14 which is connected to a blower 16. On the suction side 29 of the blower 16 are an air inlet 18 and a gas fitting 17, which in turn is connected to a gas port 19. The burner 14 is located in a combustion chamber 28, which is separated by a heat exchanger 15 from an exhaust gas outlet 30. The heat exchanger is connected on one side with a return line 23 and on the other side with a feed line 22. In the flow line 22 is a temperature sensor 24, which in turn is connected to a control device 21. This controller 21 has a memory module 25 and a computing module 26. The controller 21 is connected to a motor 20 which drives the blower 16, an ignition electrode 31 and a monitoring electrode 32 directly to the burner 14.

When the heater is started, first the control unit 21 controls the motor 20 of the fan in such a way that the fan delivers a defined volume flow. The gas fitting 17 adapts a particular fuel gas flow via its integrated gas-air composite to the volume flow that the fan 16 promotes. This fuel gas flow is smaller than the fuel gas flow at rated load and greater than the fuel gas flow at minimum load. The controller 21 causes a spark between the electrodes of the ignition electrode 31 to ignite the fuel gas-air mixture exiting the burner 31. As soon as the monitoring electrode 31 detects the flame, the controller 21 reduces the Blower speed until the gas valve 17 promotes the minimum allowable gas flow. Now the heating modulation blocking time is determined. For this purpose, the temperature sensor 24 detects the flow temperature and transmits its signal to the control. By means of the memory module 25 and the computing module 26, the controller 21 determines the Heizungsmodulationsperrzeit. There are several possibilities for doing this: On the one hand, the modulation setpoint at a certain time or the average modulation setpoint from a series of measurements is determined at specific times. The value thus determined is assigned, by means of a continuous function, a certain heater modulation inhibit time or, according to another assignment method, by comparison with a threshold, allocated a certain short or a certain longer heater modulation disable time. After the determined Heizungsmodulationsperrzeit the controller 21 controls the motor 20 of the blower 16 as needed, whereby the gas valve automatically adapts the necessary fuel gas flow rate. As a result, the device performance of the heat request is adjusted.

Fig. 2 shows the modulation setpoint for two different power requirements according to the prior art and the inventive method. In the case of a power requirement, according to the prior art, the burner is first started with a specific modulation load M _Start . If the burner is safely started, which is usually determined by measuring an ionisation current in the flame, then the burner load is then reduced (time t ₀ ) to a minimum load M _min and during the modulation blocking time 1 (until time t ₁ ) Burner operated with this minimum load M _min . After that, the load corresponds to the modulation request. If the modulation setpoint is very high (solid line 1), the unit is operated at maximum power; this corresponds to the maximum modulation setpoint M _max .

In a method according to the invention for adapting the heating modulation blocking time, the modulation blocking time is terminated after a shorter modulation blocking time 3 (time t ₃ ) for the same heat demand and corresponding modulation setpoint and the device is subsequently operated with maximum power and corresponding modulation setpoint M _max (dot-dash line 3). , At a slightly lower modulation setpoint, the corresponding modulation blocking time _{2 is} terminated at a time t ₂ (t ₁ > t ₂ > t ₃ ) and the device is operated at partial load (modulation setpoint M ₂ ) (dashed line 2).

Fig. 3 shows the flow chart for a method according to the invention for shortening the heating modulation blocking time. Here, at certain predetermined times n times the modulation setpoint is determined and detected. From these n values, the average is formed. If the average value is greater than a certain threshold (ie, high heat demand), then a short, predetermined heater modulation inhibit time (in this case 1 minute), otherwise a longer predetermined heater modulation inhibit time, heater modulation inhibit time (in this case, 2 minutes) is used.

A further variant according to the invention for determining the heating modulation blocking time is shown in FIG Fig. 4 shown. Again, n values of the modulation setpoint are first recorded at specific times and then the mean value is formed. Based on this mean value, the heating modulation blocking time is determined from a linear relationship (according to function 4).

Fig. 5 shows for a variant of the method according to the invention the relationship between the measurements and the modulation. Line 5 corresponds to the respectively calculated modulation setpoint as a function of time. Line 6 corresponds to the modulation default value. At the times t ₇ to t _{12 in} each case the modulation setpoint (7, 8, 9, 10, 11 and 12) determined: From these values, the average value is formed and determines the Heizungsmodulationssperrzeit, so that after the heating modulation blocking time at time t _M, the load from the minimum load to the setpoint is increased.

It exists according to Fig. 5 however, it is also possible to determine a specific modulation target value ₁₃ only at a specific time t ₁₃ and to determine the heating modulation blocking time from this. The flowchart for this is in Fig. 6 shown.

Claims (6)

1. A process for starting up a heater (27) comprising a heat exchanger (15) which is heated by a burner (14) whose fuel throughput is variable, characterised in that the burner (14), when the heater (27) is started, is ignited with a medium volume of gas supply and that subsequently, after the ignition has been effected, this volume of gas supply is kept at a minimum for a determinable heater modulation blocking time, which latter is variable in such a way that it is the more reduced the higher the modulated volume of gas flow necessary for meeting the required heat demand is in relation to the minimum volume of gas flow.
2. A process for starting up a heater (27) as claimed in Claim 1, characterised in that, after the ignition of the burner (14) has been effected, the modulated volume of gas flow necessary for meeting the required heat demand is determined at several defined points of time and therefrom, in turn, a mean value is determined and, on the basis of such mean value and a continuous function, the heater modulation blocking time is determined.
3. A process for starting up a heater (27) as claimed in Claim 1, characterised in that, after the ignition of the burner (14) has been effected, the modulated volume of gas flow necessary for meeting the required heat demand is determined at a certain defined point of time and therefrom, with the aid of a continuous function, the heater modulation blocking time is determined.
4. A process for starting up a heater (27) comprising a heat exchanger (15) which is heated by a burner (14) whose fuel throughput is variable characterised in that the burner (14), when the heater (27) is started, is ignited with a medium volume of gas supply and that subsequently, after the ignition has been effected, this volume of gas supply is kept at a minimum for a determinable heater modulation blocking time, which latter is variable in such a way that, when a certain modulation volume of gas flow is exceeded, it corresponds to a certain, defined heater modulation blocking time, and when it falls short of such predetermined modulation volume of gas flow, it corresponds to a certain longer defined heater modulation blocking time.
5. A process for starting up a heater (27) as claimed in Claim 4, characterised in that, after the ignition of the burner (14) has been effected, the modulated volume of gas flow necessary for meeting the required heat demand is determined at several defined points of time and therefrom, in turn, a mean value is determined and, on the basis of such mean value, the heater modulation blocking time is determined.
6. A process for starting up a heater (27) as claimed in Claim 4, characterised in that, after the ignition of the burner (14) has been effected, the modulated volume of gas flow necessary for meeting the required heat demand is determined at a certain defined point of time and therefrom the heater modulation blocking time is determined.

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