EP1050714B1 - Boiler controlling device - Google Patents

Abstract

Boiler output temperature (6) follows required characteristic (8) within upper and lower limits (8,10). Boiler has first on/ contact (2) and second contact (4). Fan, supplying air to boiler and controlling its power output, accelerates to upper speed (V on closure of second contact (4), and decelerates to minimum speed (X) on opening. Rate of speed change is regulated by microprocessor.

Description

The present invention relates to a regulation device for a boiler, in particular a central heating boiler.

The purpose of such a regulatory system is to maintain a substantially constant temperature in rooms heated from Boiler. A conventional heating system includes a boiler, a three-way valve, two pumps, as well as, of course, the radiators supplied from the boiler. The three-way valve distributes the hot water produced at the level of the boiler by sending a quantity more or less hot water to the radiators. This valve is controlled by a device that receives temperature information (outside temperature, room temperature, water temperature at boiler outlet, etc.). A pump is necessary for the circulation of water to the radiators and another for the return water circulation directly to the boiler.

When the ideal temperature is reached in the rooms, we act on the boiler to avoid exceeding a predetermined temperature. Several devices exist. We can for example have a boiler which is either switched off or operating at 100% of its capacity. We then have a device very simple regulation but there is a relatively significant pollution to each time the boiler is started and stopped. In addition, variations of temperature at the level of the boiler are important which results in high stresses resulting in a lifetime of the boiler limited.

There are also boilers called "two-stage" boilers. Such a boiler can operate either at 100% of its capacity, or with a predetermined intermediate load. We can thus avoid many ignitions and stops and of the boiler. However, we still have constraints relatively high due to sudden variations in engine speed boiler.

American patent US 5,894,988 describes a heating system auxiliary for motor vehicles. This system includes a device control which acts, during the ignition phase of the boiler, on the speed of rotation of the boiler fan, in order to improve the speed and the reliability of the ignition of the heating system. However, there is no regulation of boiler power beyond the ignition period. We have therefore always significant variations in temperature in the boiler during operation in service mode, therefore such a system, adapted to a domestic central heating boiler, does not improve the lifetime of the boiler.

The object of the present invention is therefore to provide the means for modulating the power of a boiler from a regulation of standard heating for two-stage boilers to avoid variations abrupt revs, upon ignition and then in service mode.

To this end, the device it offers is a regulation for a boiler, comprising a fan driven by a variable speed motor, this device comprising a first contact electric and means for varying the rotation speed of the fan, during the ignition phase of the boiler, between positions stop, walk at a first speed which corresponds to the flow of pre-ventilation, or walking at a second pace which corresponds to ignition rate, the device being characterized in that it comprises a second electrical contact provided to vary, after switching on the boiler and during operation in service mode, the rotation speed of the fan between a first minimum speed X and a second speed MAX maximum, these variations taking place gradually thanks to the means to vary the fan speed when the second contact electric is activated.

This regulation device makes it possible to maintain the temperature of the water leaving the boiler at a temperature very close to a temperature setpoint. Thanks to the progressive variation of the fan speed, and therefore consequently of the power of the boiler, the constraints by rapid variations in temperature are avoided. In addition, such a device allows to limit the ignition and shutdown of the boiler. These are repeated only in cases where the hot water requirements are low, which does not represents only a small part of the operation of a boiler in general.

In a preferred embodiment, the means provided for acting gradually on the fan speed include a modulator of microprocessor frequency. It is then possible to store in the microprocessor software that controls the fan speed according to data entered beforehand.

This frequency modulator is advantageously controlled from only from the open or closed state of the electrical contacts. The outside temperatures and water produced by the boiler are used as for them for controlling the electrical contacts.

In the case of an installation comprising, in addition to radiators, heating, for example a domestic hot water tank, the regulation according to the invention may include a third electrical contact, also designed to switch the fan from its first to its second pace or vice versa; means for gradually varying the fan speed when the third electrical contact is activated are then also provided, and the speed variation is different according to that it is controlled by one or other of the electrical contacts.

The present invention also relates to a boiler for central heating which includes a regulating device according to the invention.

The invention also provides a method of regulation for a boiler comprising a fan driven by a variable speed motor, the boiler being provided with a regulation device comprising a first boiler with a fan driven by a speed motor variable, the boiler being provided with a regulating device comprising a first electrical contact which controls the starting and stopping of the fan and a second electrical contact which allows you to choose the speed of the fan between two predetermined speeds.

• le premier contacteur est prioritaire sur le second, de telle sorte que si le premier contact est en position correspondant à l'arrêt du ventilateur, une action sur le second contact électrique est sans effet sur le ventilateur,
• lorsque le premier contact passe dans la position correspondant à la mise en marche du ventilateur, l'allumage de la chaudière est réalisé,
• lorsque le premier contact est en position de marche et que l'allumage de la chaudière est réalisé, et qu'on agit sur le second contact électrique, le ventilateur passe d'une première allure à une seconde allure progressivement selon une pente croissante ou décroissante prédéterminée.

According to this process:

• the first contactor has priority over the second, so that if the first contact is in the position corresponding to the fan stopping, an action on the second electrical contact has no effect on the fan,
• when the first contact goes into the position corresponding to the start-up of the fan, the boiler is switched on,
• when the first contact is in the on position and the boiler is switched on, and the second electrical contact is acted on, the fan changes from a first stage to a second stage gradually according to an increasing or decreasing slope predetermined.

In this process, it can be expected that during the phase the fan is first blocked by injecting a weak current in the motor, then the fan goes at a speed predetermined pre-ventilation for a predetermined period before switch to ignition speed for a period of time also predetermined, an action on the second contact having no effect on the fan during this entire ignition phase.

Figures 1 et 2 sont des diagrammes expliquant le fonctionnement d'un dispositif selon l'invention avec un dispositif de régulation comportant deux contacts électriques, et

Figure 3 et 4 sont des diagrammes expliquant le fonctionnement d'un dispositif selon l'invention avec un régulateur comportant trois contacts électriques.

In any case, the invention will be clearly understood with the aid of the description which follows, with reference to the appended schematic drawing showing operating curves of a regulating device according to the invention.

FIGS. 1 and 2 are diagrams explaining the operation of a device according to the invention with a regulation device comprising two electrical contacts, and

Figure 3 and 4 are diagrams explaining the operation of a device according to the invention with a regulator comprising three electrical contacts.

In a first embodiment, the regulation device is intended for central heating comprising a boiler supplying several radiators. The boiler is equipped with a regulation of standard heating for "two-stage" boilers. This regulation then has two electrical contacts. A first electrical contact 2, subsequently called on contact 2, controls the start up and shutdown of the boiler. When this on contact 2 is closed, the boiler is switched on while when this on contact 2 is open, the boiler stops.

A second electrical contact 4 is also provided. This second contact 4, subsequently called speed contact 4, allows you to choose between two heating powers. In closed position, the boiler works at full power while in the open position, the boiler operates at an intermediate power.

The power of the boiler modulates by variation of the air flow sent to the burner. A fan sends this air to the burner. It is equipped with a variable speed motor controlled by the regulation of heater. In the device according to the invention, a frequency modulator with microprocessor is placed between the standard heating control "two gears" and the variable speed motor. Specific software stored in the microprocessor allows the boiler to be controlled from the open or closed state of the two electrical contacts 2, 4 of the heater.

In a device of the prior art, when the speed contact 4 is open or closed, the fan speed, at the inertia of the motor and fan close, immediately changes speed.

According to the invention, this variation in speed is done gradually. Figure 1 shows an example of operation of a boiler with a device according to the invention. The upper curve 6 shows the temperature T at the boiler outlet as a function of time t, a curve 8 called setpoint, corresponds to the ideal water temperature in boiler outlet. This setpoint curve 8 is a function of the temperature outside the room heated by the corresponding heating. Of on either side of this setpoint curve 8, is in dotted lines a curve 10.

In the middle of Figure 1, the positioning of the electrical contacts 2 and 4. On line 12, the black area corresponds to the contact closure on 2 while the white zone corresponds to the opening of this contact 2. The same is true on line 14 for the speed contact 4.

The lower curve 16 of FIG. 1 represents the speed V of the motor driving the boiler fan as a function of time t. The time scale is identical for curves 6 and 16. Lines horizontal dotted lines, parallel to the time axis, correspond to four different gears of the engine speed V. A first speed X corresponds to the minimum speed below which we cannot go down. This speed corresponds to the minimum air flow necessary for correct operation of the boiler. A second speed Y corresponds at the boiler ignition speed. The speed Z corresponds to the speed pre-ventilation. Finally, the MAX speed corresponds to the maximum speed motor rotation.

The boiler operates in two operating modes different: ignition mode and service mode.

Each time the boiler is started, the modulator switches imperatively in ignition mode. During the course of this cycle, it ignores any change in state of the speed 4 electrical contact. ignition cycle is complete, the modulator switches to service mode.

Ignition is controlled when the on contact 2 changes from the open position to the closed position. During a time T _O the modulator injects a weak current into the motor to block the fan wheel and eliminate any possible free rotation, due for example to the natural draft in the boiler. Then the modulator sends a control voltage to switch the motor to speed Z which corresponds to the pre-ventilation rate of the boiler and remains at this speed for a time T _P. The modulator then commands the engine to switch to speed Y which corresponds to the ignition rate of the main burner of the boiler and remains in this state for the time T _A. The boiler ignites during this time T _A and the temperature of the water leaving the boiler begins to increase.

At the end of time T _A , the ignition cycle is finished. The total duration of this cycle and the different times taken into account are synchronized with a cycle carried out by a boiler control and safety box.

When the speed contact 4 is closed, it tends to run the engine at its maximum speed while when in the open position, it tends to run the engine at minimum speed X. At the end of the ignition time T _A , the speed switch 4 is closed. This is explained by the fact that the temperature T is still, at the end of ignition, lower than the set temperature given by curve 8. The speed contact 4 remains closed until the temperature T reaches the upper X curve. While the speed contact 4 is closed, the fan speed gradually increases according to a slope curve a. The motor speed increases until the MAX speed is reached or, as is the case in FIG. 1, until the temperature curve 6 reaches the upper dotted curve 10. At this time , the speed contact opens, commanding a reduction in the motor speed. This decrease in speed is also progressive and is also done with a ramp slope a. The decrease in fan speed results in a decrease in boiler power and the temperature at the boiler outlet decreases. The speed contact 4 remains in the open position until the temperature curve 6 reaches the lower dotted curve 10. The speed contact 4 then returns to the closed position. Figure 1 shows that thus by alternative openings and closings of the speed contact 4, the temperature curve 6 T follows, without deviating much, the setpoint curve 8. The speed of the motor driving the fan of the boiler then oscillates between minimum speed X and maximum speed MAX.

Figure 2 is equivalent to Figure 1 but for a curve of different setpoint 8. We can assume here that at the start, the temperature outside temperature is relatively high and therefore the temperature at the outlet of boiler is relatively small. As we can see, during the cycle the temperature of the water leaving the boiler is such that the temperature curve 6 already reaches the upper dotted line 10 even before the end of the ignition cycle. At this time, the contact works 2 opens and the fan stops. To then maintain the temperature of setpoint at the boiler outlet, several successive ignition cycles and boiler shutdowns are performed. When the outside temperature decreases, and therefore the temperature at the outlet of the boiler must be higher high, the speed 4 contact closes and we find an operation similar to that described with reference to Figure 1.

In Figures 3 and 4 we find in addition to the on contact 2 and from speed 4 contact a contact called DHW contact 18. Such a regulator with three electrical contacts is used for central heating also including a domestic hot water tank. Speed contact 4 and DHW contact 18 each order an increase or decrease the fan speed to move the fan to the maximum speed MAX or minimum X. The open or closed state of the contact speed 4 is controlled by a temperature sensor located on the circuit heating supplying the radiators while the open or closed state of the DHW 18 electrical contact is controlled by a probe placed in the circuit supplying the domestic hot water tank.

In Figure 3, the temperature at the boiler outlet has not been represented. We find lines 12 and 14 showing the open state and closed electrical contacts 2 and 4 as well as a line 20 to show the open or closed state of the DHW contact 18. In FIG. 3, the DHW contact is always in the open position. In Figure 4, line 20 shows the periods during which the DHW contact 18 is opened by a strong black line.

The operating mode in FIG. 3 is identical to the operating mode in FIGS. 1 and 2. There is a period 22 of ignition of the boiler, then a period of 24 service followed by a stop of the boiler. We then again have a succession of modes 22, 24 service and boiler shutdown.

In Figure 4, we can see the influence of the DHW electrical contact 18. When this DHW contact 18 is closed, the speed of the motor, and therefore of the fan, increases. This speed increase is done gradually but the ramp of the speed increase slope is of a value b. This value b is greater than the value a of the ramp speed increase when speed contact 4 closes. This allows a faster rise in temperature for hot water health. On the other hand, when the DHW electrical contact 18 opens, the speed variation at the fan and its motor is done according to a slope ramp a.

In summary, we find in Figures 3 and 4 also a ignition mode and a service mode. During the cycle ignition, change of state of speed 4 and DHW electrical contacts 18 is ignored. On the other hand, if the on 2 contactor opens, the modulator stops the boiler and remains waiting for a new start order.

In service mode, when the electrical contacts speed 4 and DHW 18 is open, there is no need for domestic hot water or water hot for heating. The modulator then decreases the speed of the fan with a ramp a. If the speed arrives at the minimum speed allowed X, this speed remains set at this value until a new order from the regulator.

When the speed 4 electrical contact is closed and the contact electric DHW 18 is open, there is a need for hot water for the heating but no need for domestic hot water. The modulator does then gradually increase the fan speed with a ramp at. If you reach the MAX speed, this speed is kept until further order from the regulator.

When the two electrical contacts speed 4 and DHW 18 are closed there is both a need for hot water for heating and a need for domestic hot water. As domestic hot water production priority, it is this contact which defines the behavior of the modulator. This will gradually increase the fan speed with a ramp b until the MAX speed is reached. The fan remains on this MAX speed until the DHW electrical contact 18 opens.

Finally, in the last case, in which the contact electric speed 4 is open and DHW contact 18 is closed, there is no need for hot water for heating but there is a need for water domestic hot water. The modulator then gradually increases the fan speed with ramp b to maximum speed MAX which remains set at this value until the DHW electrical contact 18 opens.

Throughout the service operating mode, the state of contact on step 2 is preponderant. So regardless of the open state or closed of speed 4 and DHW 18 contacts, when the on contact 2 is open, the boiler stops.

All operating parameters, speeds X, Y, Z, time T _O , T _P , T _A and ramps a and b, are adjustable. They are programmed in the software stored in the microprocessor of the frequency modulator. These variables can also be adjusted by adjustment devices accessible on the modulator. These variables are of course dependent on the type of boiler and the needs.

As shown above we can therefore have with a regulation standard heating for "two-stage" boiler one modulating boiler which modulates the operation of the boiler by staying close of a given setpoint curve.

The use of such a regulating device in a central heating allows only one pump to be used instead of two pumps usually used in combination with a three-way valve tract. The additional cost generated by the installation of the frequency modulator integrated microprocessor is significantly lower than the cost of the pump and three-way pilot valve that can be saved. So we get a little costs a modulating central heating system.

Claims (7)

1. Regulating device for a boiler having a fan driven by a variable-speed motor, the said device having a first electrical contact (2) and means which make it possible to vary the rotational speed of the fan, in the firing phase of the boiler, between positions for stopping, running at a first speed which corresponds to the flow of preventilation air, or running at a second speed which corresponds to the flow of firing air, the device being characterised in that it has a second electrical contact (4) which is designed to vary, after firing of the boiler and during operation in the service mode, the rotational speed of the fan between a first, minimum speed (X) and a second, maximum speed (MAX), the said variations taking place progressively owing to the means which make it possible to vary the speed of the fan when the second electrical contact (4) is activated.
2. Regulating device according to claim 1, characterised in that the means which are designed to act progressively on the speed of the fan comprise a microprocessor-type frequency-modulator.
3. Regulating device according to claim 2, characterised in that the frequency-modulator is guided solely from the open or closed state of the electrical contacts (2, 4, 18).
4. Regulating device according to one of claims 1 to 3, characterised in that it has a third electrical contact (18) which is also designed to cause the fan to pass from its first speed (X) to its second speed (MAX) or vice versa, in that means are provided which make it possible to progressively vary the speed of the fan when the third electrical contact (18) is activated, and in that the variation in speed is different according to whether it is controlled by one or other of the electrical contacts.
5. Boiler for central heating, characterised in that it has a regulating device according to one of claims 1 to 4.
6. Method of regulation for a boiler having a fan driven by a variable-speed motor, the said boiler being equipped with a regulating device having a first electrical contact (2) and means which make it possible to vary the rotational speed of the fan, in the firing phase of the boiler, between positions for stopping, running at a first speed which corresponds to the preventilation flow, or running at a second speed which corresponds to the firing flow, in which method the firing of the boiler is carried out when the first contact (2) passes into the position corresponding to the starting-up of the fan, characterised in that the regulating device has a second electrical contact (4, 18) which make it possible, after the firing phase and when the boiler is in service mode, to choose the speed of the fan between two predetermined speeds (X, MAX), and in that :

   the first contact (2) has priority over the second (4, 18) in such a way that, if the first contact (2) is in a position corresponding to the stopping of the fan, action on the second contact (4, 18) has no effect on the said fan,

   when the first contact (2) is in the running position and the firing of the boiler has been carried out, and when the second electrical contact is acted upon with the boiler in the service mode, the fan passes from a first speed (X) to a second speed (MAX) progressively along a predetermined rising or falling gradient (a, b).
7. Method according to claim 6, characterised in that, during the firing phase, the fan is first of all brought to a standstill by the injection of a low current into the motor, then the said fan passes to a predetermined preventilation speed (Z) for a predetermined duration (T_P) before passing to a firing speed (Y) for a duration (T_A) which is likewise predetermined, action on the second contact (4, 18) having no effect on the fan during the whole of the said firing phase.

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