DE2715835A1 - Air conditioning plant control system - has air feed ventilator controlled by feed air flow speed to eliminate pressure sensors - Google Patents

Abstract

The control system is for air conditioning plants with variable air feed. It consists of an adjustable air feed ventilator in an air feed channel, and a mixing box in each room, having a circuit-controlled air throttle valve. The circuit contains a servo-motor for the valve, and an air volume control for the motor, having a room temp. sensor and a feeler to scan air flow speed in the box. The air volume control and the servo motor of each box circuit, each have a switch in an electric circuit with a resistance. With a change in the reference value of the flow speed feeler, the switch of the control operates the motor to actuate the valve. The motor switch is closed when the valve is open.

Description

Dipl, -Ing, Donald Herbst Marienplatz 11, 100O Berlin 45

Control arrangement for air conditioning systems with variable supply air volume

The invention relates to a control arrangement for air conditioning systems with a variable supply air volume.

Such known air conditioning systems consist of a supply air duct in which a controllable supply air fan is arranged; the Supply air duct has any number of branch ducts leading into individual separate rooms, which in a End relaxation or mixing box. The relaxation or mixing box has a throttle valve for the supply air, which can be adjusted by a control circuit in which one of the adjustment of the throttle valve Serving servomotor and this controlling air volume regulator are arranged, the one prevailing in the box The flow velocity of the air-sensing probe,

809842/0135

whose setpoint can be adjusted by a room temperature sensor between a lower and an upper limit. The supply air has a temperature which is expediently somewhat below the desired room temperature. if If the room temperature rises due to any influences, the sensor that scans the room temperature changes the setpoint of the flow velocity sensor located in the box, which actuates the servomotor via the volume controller, to lead the throttle valve in a larger open position, so that the cooler supply air to a greater extent in the space is given. When the room air has the desired temperature reached, the setpoint of the flow velocity sensor is lowered, and the throttle valve in its previous one Position returned. If the room temperature falls below the desired value, the room sensor also lowers the setpoint of the flow velocity sensor, and the servomotor is operated in the opposite direction via the flow regulator, to move the throttle valve to the minimum open position and to prevent the room from overcooling. Has the room temperature reaches the desired level again, the setpoint of the flow velocity sensor is also adjusted accordingly increased and brought the throttle valve into its previous open position. Depending on the changing Positions of the throttle valves in the expansion or mixing

8098A2 / 01 35

2 7 1:; ir 3 5

ί "

box, the supply air fan must deliver larger or smaller amounts of air in the unit of time. To always have an even To ensure the distribution of the supply air, different pressures on the fan and in the supply air duct are required necessary. In the known control arrangements a pressure sensor controlling the supply air fan is used to adapt the fan output to the air requirements of the boxes. The fan is always controlled in such a way that a value set on the pressure sensor remains constant. Around The pressure sensor is expediently used to detect as large a part of the pressure change in the supply air duct as possible in the first third of the route of the main channel, if possible installed in front of the first relaxation box. The usage a pressure sensor for controlling the supply air fan is disadvantageous insofar as the pressure sensor is so set it must be that with full power of the fan the supply of all connected boxes with fully open Valves is guaranteed. In the event of a reduction in the amount of air derived from the room sensor, occurs at the pressure sensor a pressure increase, and the pressure sensor lowers the fan output until the one on it set value is reached. If the air volume is reduced by 50%, a pressure reduced by 75% is sufficient Supply of all connected boxes as the ratio

8 ü 9 8 U 2 I 0 1 3 δ ^{0 RIGINAL INSPECTED}

Air volume reduction / pressure reduction changes quadratically. When the air conditioning system is in operation, there will practically always be a pressure in the supply air duct which is higher than necessary, and must therefore be destroyed in the boxes by throttling. The necessary destruction of this Excess pressure energy causes an increase in operating costs, which can be up to 10% and more.

The invention is based on the object of avoiding this disadvantage and of designing the known control arrangement in such a way that that the operating costs with a simple construction at an optimally low, the previously unavoidable additional losses are kept practically excluding the amount.

This object is achieved according to the invention in that the air volume regulator and the servomotor of the control circuit each Box each have a switch in series in a circuit, preferably with a resistor, the switch of the air volume regulator when the target is changed value of the flow velocity sensor uses the servomotor to operate the throttle valve in the opening or closing direction applies voltage, and the switch of the servomotor is closed when the open position of the throttle valve is reached is that the assigned to the individual boxes

8098A2 / 0136 ORIGINAL INSPECTED

/ 1ss

Circuits in parallel on one to a control circuit of the supply air fan leading collecting line are connected, in which the currents flowing in the individual circuits, for example serve the proportional integral open control of the supply air fan by means of a bridge circuit, and that the control circuit of the supply air fan is used to reset the supply air fan after the open control has taken place Owns timer. In the design of the control arrangement according to the invention, the supply air fan is controlled no longer via a pressure, but directly dependent on the flow velocities prevailing in the boxes the supply air, so that the pressure sensor with its Nachtexlen is superfluous. The inventive Control arrangement works as follows.

If the temperature rises in one or more rooms equipped with relaxation boxes, so that an increased If the supply of air is necessary, the switch assigned to the air volume regulator is closed and thus the servomotor of the throttle valve is connected to voltage. The throttle valve is moved into the open position by the servomotor, whereby when the throttle valve is in this open position, the switch assigned to the servomotor is closed. Through this two switches in series, a circuit is closed in which a resistor of a certain level is arranged

809842 / 013B

2715635

can be. In this circuit, one flows through size The specific current due to the resistance, which is sent via a collecting line to the central controller for the supply air fan is forwarded. If the switches assigned to the associated servomotors are closed in several relaxation boxes the currents flowing in the individual circuits assigned to the boxes add up in the collecting line, see above that the strength of the current present at the end of the bus line is the sum of the current strengths of the individual circuits is equivalent to. This current strength is measured in the control circuit of the supply air fan and used to open the supply air fan exploited. If in the rooms of the individual relaxation boxes the desired temperature due to the increased Supply of the supply air is reached again, the throttle valve is partially closed, whereby the servomotor of the The switch assigned to the throttle valve is opened. This ends the open regulation of the supply air fan and it kicks in an arbitrary timer in action, arranged in the control circuit of the supply air fan, that controls the supply air fan regulates back from its open position.

In the control arrangement according to the invention, the control circuit of the supply air fan is only influenced when at least the throttle valve of a relaxation box is fully open and the supply of air is still not

809842/0136

2715 * 35

sufficient. This relaxation box sends to the control loop of the supply air fan a weak current defined by the size of the resistance as a signal that the output of the The supply air fan has to be increased.After the supply air fan has reached this increased output, it comes Signal in failure and the supply air fan is regulated back by the timer arranged in its control circuit. In this way it is ensured that the performance of the supply air fan always meets the respective needs of all of the Corresponds to the expansion boxes connected to the supply air duct. If there are several relaxation boxes in the open position If the throttle valve requires more air, the current pulses emitted by the individual boxes add up, so that the supply air fan is controlled with this input signal with proportional-integral control characteristics will. With an increasing number of relaxation boxes located in the aforementioned end position, the The pulse current applied to the control circuit of the supply air fan is increased, thereby reducing the adjustment speed of the supply air fan is accelerated in the direction of larger amounts of air. The reset speed of the supply air fan, which is determined by the The timing element of the control loop assigned to it takes place when no expansion box is in the fully open state set in the control loop to the highest possible value at which oscillation of the entire control system does not occur.

809842/01 35

2 7 1 i '3 5

- J &'-

This reduces the length of time in which the air conditioning system is operated with an unnecessarily high fan output optimal minimum limited.

Another feature of the invention is characterized in that the circuits associated with the individual boxes lying resistors have the same or different values. This inventive dimensioning of the resistors it is possible to use fast control for certain rooms and less fast control for other rooms to reach. The smaller the size of the resistance, the higher the strength of the pulse current and the This means that the supply air fan is regulated up more quickly yes If an optimally fast regulation is to be achieved, the resistance can also have the value zero. To this It is possible to set certain priorities for certain rooms to be ventilated.

Another feature of the invention is characterized in that when using a separate, one supply air fan having, cold and warm air leading channels fed mixing box the cold air channel a higher delivery rate than the hot air duct and the volume controller has the throttle valve and the control circuit of the supply air fan

809842 / 013S ORIGINAL INSPECTED

/ 7

of the cold air duct and the rough air sensor, which changes the setpoint value of the flow rate sensor of the volume regulator, directly controls the throttle valve of the warm air duct. This control arrangement of a mixing box, which must have a supply air fan, a throttle valve and a servomotor operating this for each supply air duct, work in principle in the same way as the relaxation box, only with the difference that only the supply air fan is the cold air conveying line is equipped with the control loop _f since the supply air fan of the hot air conveying line does not have a control loop; Another difference is that the room temperature sensor directly controls the servomotor of the throttle valve of the warm air duct.

The accompanying drawing shows an example embodiment; form of the control arrangement in a schematic representation.

In the drawing, three relaxation boxes 4 are shown, which are connected to a common supply air duct 1 via branch ducts 2 are, in which a common supply air fan 3 supplying all the relaxation boxes 4 is arranged. In each branch duct 2 there is a throttle valve 5 which can be actuated by a servomotor 6,

- 10 -

809842/0136

27 ι 5ο35

A room temperature sensor 7 is arranged in each room assigned to a relaxation box 4, and a room temperature sensor 7 is arranged in the relaxation box 4, which measures the flow rate of the supply air Sensor 8 arranged. The room temperature sensor 7 and the flow rate sensor 8 control together a volume controller such that, depending on the room temperature, the setpoint value of the air volume controller 9 via the Flow rate sensor 8 is changed within certain limits that the throttle valve 5 either in the direction the open or closed position is actuated by the servomotor 6.

The air volume regulator 9 has a switch 10, which is closed when the setpoint changes and via a Supply line 14 applies voltage to servomotor 6. If the throttle valve 5 is in the fully open position, the servomotor 6 closes a switch 11 which is in a circuit 13. The circuits 13 of all relaxation boxes 4 are parallel to a collecting line, which consists of a core of the required supply line and a wire serving as a return line 15 exists. This collecting line 14, 15 is connected to the control circuit 16 of the Supply air fan 3 connected,

- 11 -

609842/01 35

2 7 Ί 5 8 35

If the one relaxation box has to be supplied with a larger amount of air in the unit of time, the first is the Volume controller 9 actuated, which energizes the servomotor 6 via the closed switch 10, which the throttle valve 5 in the Open position leads. When this open position is reached, the switch 11 is closed, and through the line 14, the Circuit 13 and line 15, a current that is dependent on the magnitude of the resistor 12 flows to the control circuit 16, where the current intensity is measured and in any manner to control the supply air fan 3 in the direction higher speed takes place. When this open regulation is ended, the switches 10 and 11 are open and thus the circuit 13 interrupted. Now the supply air fan 3 is regulated down again by a timer, and if so by closing the switch 10, 11 in the circuit 13 of the same or a different relaxation box 4 a new current surge occurs, the supply air fan 13 is regulated up again via the control circuit 16. In this way, the power fluctuates of the supply air fan 3 by the respective value of the amount of air required for the entire relaxation boxes 4. The lower the resistance is 12 or, 17 or 18, the faster the up regulation takes place; the same applies if in two circuits 13 are generated at the same time by the resistors 12 and 17 or dependent current pulses that are in the bus Add 14, 15.

- 12 -

809842/0135

Claims (3)

EXPECTATIONS Control arrangement for air conditioning systems with variable supply air volume, consisting of one in one to one A plurality of separate rooms leading supply air ducts arranged controllable, common supply air fan and from an expansion or mixing box arranged in each room, which has a throttle valve for the supply air that can be adjusted by a control circuit, wherein in the control circuit is a servomotor which is used to adjust the throttle valve and a servomotor which controls it adjustable by a room temperature sensor in its setpoint, the flow rate of the air scanning sensors having air flow regulators are arranged in the box, thereby characterized in that the air volume regulator (9) and the servomotor (6) of the control circuit each box one in series in a circuit, preferably one having a resistor (12, 17, 18) (13) have horizontal switches (10, 11), the switch (10) of the air volume regulator (9) when changing the setpoint of the flow velocity sensor (8) the servomotor (6) to operate the Droesel valve applies voltage in the opening or closing direction, - 13 - 8 0 9 8 A 2/0 1 3 S ORIGINAL INSPECTED 7 7 ii: ΐ j, 5 and the switch (11) of the servomotor (6) is closed when the open position of the throttle valve (5) is reached that the circuits (13) assigned to the individual boxes (4) are connected in parallel to a control circuit (16) of the supply air fan (3) leading collecting line (14, 15) are connected, in which the currents flowing in the individual circuits (13), for example by means of a bridge circuit, the proportional-integral «η open control of the supply air fan (3) is used, and that the control circuit (16) of the supply air fan (3) resets the supply air fan after the open control has taken place (3) has serving timing element. 2. Control arrangement according to claim 1, characterized in that that the resistors located in the circuits (13) assigned to the individual boxes (4) (12, 17, 18) have the same or different values, 3. Control arrangement according to claim 1 and 2, characterized in that when using a separate, One supply air fan each having, cold and warm air leading channels fed mixing box of the cold air channel a higher flow rate than the hot air duct - 14 - ORIGINAL INSPECTED 809842/0135 / 7 15.-35 -pr- and the flow regulator controls the throttle valve and the control circuit of the supply air fan of the cold air duct and the room air sensor that changes the setpoint value of the flow rate sensor of the volume controller directly controls the throttle valve of the hot air duct. ORIGINAL INSPECTED H0984? / 013S