FR3077369A1 - AIR EXTRACTION SYSTEM AND METHOD FOR CONTROLLING AN AIR EXTRACTION SYSTEM - Google Patents

Abstract

This air extraction system comprises a fan, air extraction vents, and a fan control unit adapted to control the speed of rotation of the fan according to an operating law giving the pressure (P) supplied. by the fan according to the flow (Q) of the air extraction system. The control unit is adapted to calculate the operating law according to two affine curves (C1, C2) passing through at least three points including a maximum point (pM) defined by a maximum flow rate (Qmax) necessary for the operation of the system, specified by a user via a control unit control interface, and a maximum pressure (Pmax) to be provided by the fan for the maximum flow rate, a minimum point (pm) defined by a fixed minimum pressure (Pmin) to be provided by the fan and the minimum flow rate (Qmin) to be provided by the extraction system, the minimum flow rate (Qmin) being calculated by the control unit from the maximum flow value (Qmax), an intermediate point (pi) defined by an intermediate pressure (Pint) and a flow (Qint) between the minimum and maximum pressure and flow values, the intermediate pressure (Pint) and the intermediate flow (Qint) being calculated by the control unit from maximum pressure and flow rate values (pM) and minimum (pm).

Description

Air extraction system and method of controlling an air extraction system

The present invention relates to an air extraction system and a method of controlling an air extraction system.

Ventilation systems (VMC), particularly for living quarters, include exhaust air extraction systems. These systems include fans and extractors distributed in different rooms of the premises. When dimensioning a CMV installation, it is necessary to calculate the maximum and minimum operating points (flow, pressure) of the installation. The selection and adjustment of the extraction system is done according to the maximum operating point. Generally, the pressure decreases with the flow (unregulated extraction system) or else the pressure remains constant when the flow increases, for extraction systems called "flat curve".

However, the extraction system operates most of the time near its minimum point. Thus, the extraction system operates at a pressure higher than the pressure required at the extraction ports and this results in a higher electrical consumption than an operation at the real minimum point.

The solutions currently proposed to reduce the consumption of the extraction system are regulated groups with a so-called “rising curve” regulation where the pressure increases as a function of the flow in order to be closer to the real need of the installation and thus reduce power consumption. An ideal solution would be to know at all times the opening and closing of the different outlets and to adapt the flow and pressure of the extraction group. This is difficult to implement because of the large number of sensors required.

Today's existing "rising curve" solutions require the installer to enter a certain number of parameters in a control unit when the extraction system is put into service, namely: the minimum flow rate of the installation (hereinafter referred to as Qmin), the minimum pressure required for the minimum flow rate (hereinafter referred to as Pmin), the maximum flow rate (hereinafter referred to as Qmax) of the installation and the maximum pressure required for the maximum flowrate (hereinafter referred to as P max). EP 1 872 061 describes such a type of regulation system.

However, the installer may not have access to all of these settings.

It is to these drawbacks that the invention intends to remedy by proposing an air extraction system and a method of controlling an air extraction system that are simpler and economical to implement.

To this end, the invention relates to an air extraction system comprising a fan, air extraction vents, and a fan control unit, adapted to control the speed of rotation of the fan according to a law of operation giving the pressure supplied by the fan as a function of the flow rate of the air extraction system. The control unit is adapted to calculate the operating law according to two affine curves passing through at least three points including a maximum point defined by:

- a maximum flow rate required for the operation of the system, specified by a user via a control unit control interface, and a maximum pressure to be supplied by the fan for the maximum flow rate,

- a minimum point is defined by a fixed minimum pressure to be supplied by the fan and the minimum flow to be supplied by the extraction system, this minimum flow being calculated by the control unit from the value of the maximum flow ,

- an intermediate point defined by an intermediate pressure and flow between the minimum and maximum pressure and flow values, the intermediate pressure and the intermediate flow being calculated by the control unit from the pressure and flow values of the points maximum and minimum.

Thanks to the invention, the installer is not obliged to configure all the operating points of the extraction system, since these are automatically calculated by the control unit on the basis of the point of maximum operation which is known to the installer.

The invention also relates to a method for controlling an air extraction system comprising a fan, air extraction vents, and a fan control unit, the control method comprising a step consisting in controlling the speed of rotation of the fan according to an operating law giving the pressure supplied by the fan as a function of the flow rate of the air extraction system, defined by two affine curves passing through at least three points comprising:

- a maximum point defined by the maximum flow rate necessary for the operation of the system, specified by a user via a control interface of the control unit at the start of the extraction system, and the maximum pressure supplied by the fan for the maximum flow rate ,

- a minimum point defined by the minimum pressure to be supplied by the fan and the minimum flow to be supplied by the extraction system,

- an intermediate point defined by an intermediate pressure and an intermediate flow between the minimum and maximum pressure and flow values.

The control method is characterized in that it also comprises a step consisting in calculating, by means of the control unit and from the value of the maximum flow, the value of the minimum flow, and from the values of flow and minimum and maximum point pressure, the pressure and flow values of the intermediate point.

According to advantageous but not compulsory aspects of the invention, such a control method can incorporate one or more of the following characteristics, taken in any technically admissible combination:

- The minimum flow is calculated by the control unit by dividing the maximum flow by a coefficient greater than 1 determined according to stages consisting:

a) calculate the ratio between the maximum flow and the minimum flow fixed by law for each of the configurations of premises from which the air is extracted;

b) select the largest of these ratios.

- The control method includes an additional step consisting in recalculating, by means of the control unit, the operating law as a function of a value of minimum flow rate and minimum pressure determined from an aeraulic analysis of the system d 'extraction.

- The maximum flow taken into account for the calculation of the minimum flow and the intermediate flow is the maximum flow expanded.

- The maximum expanded pressure is used for the calculation of the intermediate pressure.

The invention will be better understood and other advantages thereof will appear more clearly in the light of the following description of an air extraction system and of a control method in accordance with its principle, made by way of nonlimiting example and with reference to the appended drawings in which:

- Figure 1 is a schematic view of an air extraction system according to the invention installed in a building;

- Figure 2 is a graph showing flow-pressure curves illustrating a control method according to the invention.

FIG. 1 represents an air extraction system S integrated in a collective building I comprising several independent premises L. These premises may be residential accommodation or be for professional use. Each of the premises L is equipped with an air exhaust outlet B adapted to extract the stale air therefrom according to known techniques, for example with a hygro-regulated extraction rate. Each of the outlets B is connected to an air extraction network comprising, inter alia, an air duct 2 which directs the stale air, according to the arrow FA, to a treatment center 4 advantageously located in a technical area located under the roof, as an attic, or on the roof, on the terrace, of the building. The central processing unit 4 includes an extraction fan 8. The pipe 2 thus connects each of the outlets B to the central processing unit 4.

The air extraction system S contributes to the fire safety of the premises L of the building I. In the event of a fire, the air extraction system S allows the smoke to be evacuated outside the building I. In this case, the air flow extracted from the premises L is directly evacuated outside the building I via line 6.

The air flow rates extracted from each accommodation can be different and vary over time depending on the occupation and activity in the accommodation.

The central processing unit 4 is connected to an evacuation pipe 6 which gives directly to the exterior of the building.

The outlets B, the lines 2, 6 and 7 and the processing unit 4 together constitute the air extraction system S.

The central processing unit 4 also includes a control unit 10 for the fan 8, adapted to control the speed of rotation of the fan 8 according to an operating law giving the pressure supplied by the fan as a function of the flow rate of the air extraction system. . In other words, the control unit 10 communicates with the fan 8 by electrical signals to regulate the supply voltage of the fan 8 and to vary the speed of rotation so as to obtain the necessary air extraction pressure. .

The operating law is defined by two affine curves C1 and C2 passing through at least three points comprising a maximum point pM, a minimum point pm and an intermediate point pi.

The maximum point pM is defined by the maximum flow Qmax necessary for the operation of the extraction system S, and the maximum pressure Pmax supplied by the fan 8 for the maximum flow Qmax. The maximum flow Qmax is determined from the number and types of dwellings in building I. The maximum flow Qmax can be taken as the sum of all the maximum flows of outlets B, i.e. the maximum flow absolute, which is the addition of the flow rates of the outlets B in the case where all of these are open at their maximum opening. The maximum pressure Pmax is determined by an upper limit, generally set by regulatory technical documents, such as a technical opinion. This upper limit is set by usual practice. By way of nonlimiting example, this upper limit corresponding to Pmax can be fixed, in certain cases, at 200 Pa.

The minimum point pm is defined by the minimum pressure Pmin which is a fixed value, at least that imposed by regulatory technical documents and which must be supplied by the fan 8, and the minimum flow rate Qmin which must be supplied by the extraction system S The value of Pmin can be, for example, 95 Pa.

The intermediate point pi is defined by an intermediate pressure Pi and an intermediate flow Qi which are between the minimum pressure and flow values Pmin and Qmin and maximum Pmax and Qmax. The pressure and flow values of the intermediate point pi are defined by regulatory technical documents with calculation relationships using the maximum and minimum values. For example, the intermediate flow Qi can be equal to half the sum of the maximum flow Qmax and the minimum flow Qmin. The intermediate pressure Pi is generally greater than half the difference between Pmax and Pmin.

Curve C defines the operating range of the fan 8. Curve C defines the maximum pressure that the fan 8 can provide as a function of the flow rate. The area to the left of curve C represents the pressure and flow values for which the fan 8 is capable of operating.

The value of the maximum flow rate Qmax is generally known by the installer of the extraction system S. This may have been calculated by an aeraulic analysis of the extraction network. However, the installer does not necessarily know the value of the minimum flow rate Qmin, because it does not need this value to choose the fan used. In order to allow the extraction system to start up, the value of the minimum flow rate Qmin is calculated by the control unit 10 from the value of the maximum flow rate Qmax. From the value of Qmin, the control unit 10 also calculates the values of Pi and Qi and calculates the other points defining the curves C1 and C2. The control unit 10 includes for this purpose a microprocessor and a memory.

More precisely, the minimum flow rate Qmin is calculated by dividing the maximum flow rate Qmax by a coefficient K greater than 1. The coefficient K is determined according to steps consisting in calculating the ratio between the maximum flow rate and the minimum flow rate fixed by regulation for each of the configurations L rooms from which air is extracted, then select the largest of these ratios. For example, living quarters are classified by type according to the number of rooms, in particular F2, F3, F4, etc. The regulatory technical prescriptions specify maximum and minimum flow rates for each of these premises configurations.

For example, if building I includes two types of premises L, we obtain two ratios R1 and R2 defined by:

Omaxl

----- = ffl

Qminl

OtîmiïZ --- 7 = ^{s 2} φτιίηζ

Where Qmaxl and Qmin 1 are respectively the maximum and minimum flow for the first type of housing L, and Qmax2 and Qmin 2 are respectively the maximum and minimum flows for the second type of housing L. The coefficient K is therefore the largest of the ratios R1 and R2.

The installer therefore only has to specify, via a control interface (not shown) of the control unit 10, the maximum flow rate Qmax at the start of the extraction system S. The pressures Pmax and Pmin can be considered to be equal respectively to the upper and lower limit of regulatory technical documents.

The algorithm used guarantees that the calculated minimum flow Qmin is lower than the actual minimum flow, since the ratio maximum flow / minimum flow is generally lower than the coefficient K.

The control unit 10 then calculates the coordinates of the intermediate point pi and then the points of the curves C1 and C2.

In practice, a value of the coefficient K can be preprogrammed in the control unit 10 based on the value assumed to be the highest of the coefficient K for all of the possible types of housing.

Several ventilation systems exist for a building. For example ventilation systems with hygroregulated extraction but hygroregulated or non-hygroregulated air inlets. In such a case, the coefficient K may be different for these two systems. In this event, the coefficient K chosen is the greater of the two.

If the installer subsequently wishes to modify the operation of the extraction system S from a new value of Qmin and Pmin determined by aeraulic simulations, the control unit 10 can recalculate the operating law as a function of 'a new value of minimum flow Qmin-corr and minimum pressure Pmincorr. The installer therefore specifies the value Qmin-corr and Pmin-corr in an interface of the control unit 10 and a correction algorithm is initiated. This new value of Qmin-corr and Pmin-corr replaces the value Qmin previously calculated and Pmin as the minimum reference value, and the control unit 10 calculates a new minimum point p'm and a new intermediate point p'i with a corrected intermediate flow Qi-corr and corrected intermediate pressure Pi-corr. New curves C’1 and C’2 are determined to form a new operating law.

Likewise, the maximum pressure Pmax can be adjusted following an aeraulic analysis.

For flow rates lower than Qmin and higher than Qmax, the operating law is at constant pressure: the pressure remains respectively equal to Pmin or Pmax.

According to a variant not shown of the invention, the maximum bit rate taken into account can be the maximum bit rate Qmax-times, that is to say a fraction of the maximum bit rate 5 Qmax of the sum of all the maximum bit rates outlets B. As the configuration in which all the outlets B are at their maximum opening occurs only exceptionally and the actual maximum flow rate is generally less than Qmax, the maximum flow rate Qmax is used to determine the operating law. -times, and the corresponding overrun maximum pressure Pmax-times. Pmax-times is defined as the pressure necessary to obtain the maximum expanded flow Qmax-times.

In this case, the control unit 10 uses the maximum expanded flow Qmax-times and the maximum expanded pressure Pmax-times for the calculation of the minimum point pm and the intermediate point pi.

Claims (6)

1. Air extraction system (S) comprising a fan (8), air extraction vents (B), and a fan control unit (10) (8), adapted to control the speed of rotation of the fan (8) according to an operating law giving the pressure (P) supplied by the fan (8) as a function of the flow rate (Q) of the air extraction system (S), characterized in that the control unit (10) is adapted to calculate the operating law according to two affine curves (C1, C2) passing through at least three points including: - a maximum point (pM) defined by a maximum flow (Qmax, Qmax-times) necessary for the operation of the system, specified by a user via a control interface of the control unit (10), and a maximum pressure (Pmax , Pmax-times) to be supplied by the fan for maximum flow, - a minimum point (pm) defined by a fixed minimum pressure (Pmin) to be supplied by the fan and the minimum flow (Qmin) to be supplied by the extraction system, this minimum flow (Qmin) being calculated by the control unit (10) from the value of the maximum flow rate (Qmax), - an intermediate point (pi) defined by an intermediate pressure (Pint) and an intermediate flow (Oint) between the minimum and maximum pressure and flow values, the intermediate pressure (Pint) and the intermediate flow (Oint) being calculated by l control unit (10) from the pressure and flow values of the maximum (pM) and minimum (pm) points. 2. Method of controlling an air extraction system (S) comprising a fan (8), air extraction vents (B), and a fan control unit (10) (8) , comprising a step consisting in controlling the speed of rotation of the fan (8) according to an operating law giving the pressure (P) supplied by the fan (8) as a function of the flow rate (Q) of the air extraction system ( S), defined by two affine curves (C1, C2) passing through at least three points comprising: - a maximum point (pM) defined by the maximum flow (Qmax, Qmax-times) necessary for the operation of the system, specified by a user via a control interface of the control unit (10) at the start of the extraction system (S), and the maximum pressure (Pmax, Pmax-times) supplied by the fan (8) for the maximum flow, - a minimum point (pm) defined by the minimum pressure (Pmin) to be supplied by the fan (8) and the minimum flow (Qmin) to be supplied by the extraction system (S), - an intermediate point (pi) defined by an intermediate pressure (Pint) and an intermediate flow (Qint) between the minimum and maximum pressure and flow values, characterized in that it comprises a step consisting in calculating, by means of the control unit (10) and from the value of the maximum flow (Qmax, Qmax-times), the value of the minimum flow (Qmin), and from the value of flow and pressure of the minimum points (pm) and maximum (pM), the pressure (Pint) and flow (Qint) values of the intermediate point (pi). 3. Control method according to claim 2, characterized in that the minimum flow rate (Qmin) is calculated by the control unit (10) by dividing the maximum flow rate (Qmax, Qmax-times) by a higher coefficient (K) to 1 determined according to stages consisting of: a) calculate the ratio between the maximum flow and the minimum flow fixed by law for each of the configurations of premises from which the air is extracted; b) select the largest of these ratios. 4. Control method according to one of claims 2 and 3, characterized in that it comprises an additional step consisting in recalculating, by means of the control unit (10), the operating law according to a value of minimum flow (Qmincorr) and minimum pressure (Pmin-corr) determined from an aeraulic analysis of the extraction system (S). 5. Control method according to one of claims 2 to 4, characterized in that the maximum flow rate taken into account for the calculation of the minimum flow rate (Qmin) and the intermediate flow rate (Qint) is the maximum expanded flow (Qmax-times ). 6. Control method according to one of claims 2 to 5, characterized in that the maximum expanded pressure (Pmax-times) is used for the calculation of the intermediate pressure (Pint).