TEV & EEV

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TEV & EEVTEV & EEV

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All air conditioning units commonly use a traditional thermostatic expansion valve (TEV) as the expansion device: this is the standard component fitted with a sensor bulb and, in more recent models, a pressure fitting for external compensation.

TEV has a number of characteristics that, in many aspects, limit the versatility of the installation and the performance that could be achieved.

TEVTEV

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TEVTEV

LIQUID LINE

TO EVAPORATOR

EXTERNAL EQUALIZATIONREGULATING SCREW

BULB

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TEVTEVA thermostatic expansion valve is built up around a thermostatic element separated from the valve body by a diaphragm.A capillary tube connects the element to a bulb and a valve body with valve seat and a spring.The bulb is usually charged with the same operating refrigerant.

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TEVTEVTEV meters the flow of liquid refrigerant entering the evaporator at a rate that matches the amount of refrigerant being boiled off in the evaporator. This is it's main purpose but like all the other metering devices it also provides a pressure drop in the system, separating the high pressure side of the system from the low pressure side, thus allowing low pressure refrigerant to absorb heat onto it's self.

The valve itself has 3 forces that act upon each other to accomplish this task:

P1 Bulb pressure acting on the upper surface of the diaphragm, in the valve opening direction.

P2 Evaporating pressure acting on the underside of the diaphragm, in the valve closing direction.

P3 Spring pressure acts on the underside of the diaphragm, in the valve closing direction, and is used to set the superheating.

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TEVTEVThe external pressure equalization is used when the evaporator creates a large pressure drop (plate evaporators, coil evaporator with a capillary distributor).In this case, the pressure P2 is not affected by the pressure drop, therefore the balance of the diaphragm is more stable.

BALANCEP3P2P1

NO EQUALIZATION EXTERNAL EQUALIZATION

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TEVTEV

To keep the superheating at 8 °C, the regulating screw has to be adjusted to create the pressure P3

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TEVTEVRe

frig

erat

ion

capa

city

[W

]

Superheating [°C]

residual capacity Nominal

capacity

valve completely open

A = SS = Static Superheat

B = OS = Opening Superheat

C = SH = SS + OS =Total Superheat

Example:Static superheat SS=4°C (factory setting). Opening superheat OS=4°C.The opening superheat is 4°C, i.e. the point from which the valve begins to open up to nominal capacity. Opening superheat is determined by the design and cannot be changed.Total superheat:SH = SS + OS = 4 + 4 = 8 °C Total superheat SH can be changed by changing SS (by using the regulating screw).

For a good selection of the valve, the residual capacity must be 20% of the total capacity

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The main advantages concerning the efficiency of an electronic expansion valve (EEV) compared with the TEV are, basically, in three items:

1)Quicker response time for changes, stable superheat in the whole range of operation conditions, both for full as well as part load operation. 2)The improvement on the COP is highly significant. 3)The more the operation conditions vary, the more the advantages of EEV get measurable.

Why an EEV?Why an EEV?

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The wide range of operation at various differential pressures and the precision terms of control allows significant energy savings.


From 20 to 35% energy saving

The EEV permits the operation of the unit at significantly low condensing pressures: in fact the only limits are the minimum ΔP compatible with the compressor used and outside temperature.

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What are the characteristics of Uniflair EEV?

1) Compatibility with all types of refrigerants and a very wide capacity range:• Logistic: drastically reduce the number of models of EEV that are used in the

various units;• Control range: they work in a very large range of operating conditions;• Energy saving: an increase of around 2% in efficiency can be expected for each

°C decrease in condensing temperature. (the compressors controlled in ON-OFF mode have reduced ON times, while those with capacity control or inverter control operate at a lower rate for the same capacity).

2) Precision in the modulation of the refrigerant flow (thanks to the long stroke of the nozzle):

• Stable and precise superheat set point control;• If a bi-directional EEV is used in a reverse-cycle heat pump, only one EEV;

needs to be installed instead of the two TEVs in the traditional solution.

3) Microprocessor control:• MOP (maximum operating pressure);• LOP (lowest operating pressure);• HiTcond and Lownoise.


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EEV is a servo-controlled and electro-mechanic device which expands the flow of refrigerant in a variable manner, using commonly a pressure sensor and a temperature sensor (corresponding to the pressure fitting for compensation and the sensor bulb in the TEV).

Both these sensors are fitted to the evaporator outlet, and the measurements are read and processed by a controller that decides the best degree of opening of the valve in real-time.

EEV SystemEEV System

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Carel EEV RangeCarel EEV Range

E2V

The E2V, E3V and E4V series electronic expansion valves cover a range of cooling capacities from 1 kW to 250 kW.

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EEV Technical FeaturesEEV Technical Features

The best features of the E2V are:

• Large rangeability (15 mm stroke);• High-level materials;• Mechanical precision;• One code for all the refrigerants;• Bi-directional mounting;• Up to 50 kW;• Equipercentage flowrate;

The E3V and E4V valves completes the range of electronic expansion valves for medium–large capacity air-conditioning units:

• Same reliable design and materials of E2V;• Up to 250 kW;• Inspection porthole (E4V);• Separated body for easy maintenance;• Bi-directional mounting;

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Operating specifications of E2VCompatibility R22, R134a, R404A, R407C,R410A, R744, R507A,

R417AMaximum Operating Pressure (MOP) up to 42 barsMaximum Operating DP (MOPD) 35 bar except E2V35 (30bar)Refrigerant temperature -40T65°C (-40T122°F)Room temperature -30T50°C (-22T122°F)E2V statorTwo pole low voltage stator (2 phases - 24 polar shoes)Phase current 450 mADrive frequency 50 HzPhase resistance (25°C / 77°F) 36 W ± 10%Index of protection IP65 with E2VCON*, IP67 with E2VCAB*Step angle 15 °Linear advance/step 0,03 mmConnections 4 wires (AWG 18/22)Complete closing steps 500Control steps 480

Technical Features of the ETechnical Features of the E22VV

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Technical Features of the ETechnical Features of the E22VVLOW SUPERHEATING

The superheating value can be lowered by decreasing the set point to the desired value: this feature of EEV control does not involve the risk of swings that are typical of a TEV.

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Technical Features of the ETechnical Features of the E22VVBI-DIRECTIONAL MOUNTING

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Technical Features of the ETechnical Features of the E22VV

EEVEEV

TEVTEV

PIN LENGTH

TEV usually has a pin about 1 mm long;E2V has 480 steps on a 15 mm pin.

This gives a good compromise between This gives a good compromise between theoretical and mechanical resolution:theoretical and mechanical resolution: - Precise refrigerant modulation- Precise refrigerant modulation - Wide capacity modulation range- Wide capacity modulation range

With thousands of steps on few millimetersWith thousands of steps on few millimetersthe single step has no effect on refrigerant flow

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Technical Features of the ETechnical Features of the E22VVPROPORTIONAL MODULATION

Axial movement of the pin gives perfect linearity in refrigerant flow.

Refr

iger

ant

flow

(kg

/h)

Valve opening (%)

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The control of the electronic valve can be divided into two categories:

Superheat control with reference to the corresponding set point.

Control of unit safety with protections:they are activated only if the pressure or temperature reach

dangerous values that can be set by the user.

Control FeaturesControl Features

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Superheating Control ParametersSuperheating Control ParametersThe superheat control function involves calculating the position of the valve based on the measure of the superheating and the corresponding set point.

1.Valve opening at start-up2.Superheat set-point3.PID - proportional gain4.PID - integral time5.PID - derivative time

1. Valve opening at start-up: Defines the percentage of opening steps that the valve will reach immediately and before to start the superheating control. It should be set as near as possible the normal working position.

As an initial approximation, it can be determined by calculating the ratio between the cooling capacity of the evaporator and the cooling capacity of the valve. A 10 kW valve installed on a 5 kW evaporator will presumably operate at 50 % opening.

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3. PID - proportional gain: It’s defined by the parameter K. The proportional action opens or closes the valve whenever the superheat increases or decreases of 1°C. Consequently, the higher the value of K, the faster the reaction of the valve to variate the superheating. The proportional action is fundamental, as it affects the speed of the valve response, however it only considers the variation in the superheat, and not the corresponding set point. Therefore if the superheat does not vary significantly, the valve will essentially remain steady and the superheat set point may not be reached.

Superheating Control ParametersSuperheating Control Parameters2. Superheat set-point:

A low SH set point ensures better efficiency of the evaporator, a lower air or water temperature and the temperature control set point is reached more easily. Nonetheless, instability may be created in the system, with wider swings in the superheat and the return of liquid to the compressor.

A high SH set point ensures greater system stability and less or negligible swings in the superheat. Nonetheless, this may penalise the efficiency of the evaporator and prevent the temperature control set point from being reached.

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The advised range is given by the formula :

Superheating Control ParametersSuperheating Control Parameters

%20QQ

100StepsMax K

EEV

CIRC

Max Steps: the maximum regulation steps;QCIRC : the capacity in kW of the cooling circuit in normal operating conditions;QEEV: the capacity in kW of the EEV in the same conditions.

In the event that multiple operating conditions exist which are noticeably different (cooling capacity, Te, Tc), it is necessary to use an average Kp from those which are calculated by the formula or from the tests carried out in different conditions generally favouring low values and reducing the integral protection terms (LOW, SH. MOP…)

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If valves made by other manufacturers are used, the same recommended parameters can be used initially, modifying the “Proportional gain” based on the maximum number of control steps for the valve installed.

Example of adapting the proportional gain for the different valves:

Reference CAREL E2V (480 maximum control steps):

SPORLAN SEI - 1, (1596 steps):

ALCO EX-5 (750 steps):

5K CAREL

16480

15965K SPORLAN

84807505K ALCO

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4. PID - integral time: It’s defined by the parameter Ti. The integral action is related to time and makes the valve move in proportion to how far the superheat temperature is away from the set point. The higher the difference, the more intense the integral action; the lower the integration time (Ti), the more intense the integral action.

The integral action is required to ensure that the superheat reaches the set point. Without this, in fact, the proportional action alone may stabilise the superheat at a value different respect to the set-point.

5. PID - derivative time: It’s defined by the parameter Td. The derivative action is related to the speed with which the superheat varies, that is, the instant-by-instant gradient of superheat variation.

This action tends to contrast sudden variations in the superheat, bringing forward the corrective action; the effect is more intense the higher the time Td.


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The software that manages the valve includes 4 protection functions:

1. LowSH (low superheat) protection:It acts quickly to close the valve in the event where the superheat is too

low, to prevent the return of liquid to the compressor.

2. MOP (high evaporation temperature) protection:It acts moderately to close the valve and limit the evaporation

temperature if this reaches excessive values, so as to prevent the compressor from stopping due to thermal overload.

Protection Control ParametersProtection Control Parameters

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3. LOP (low evaporation temperature) protection:It acts quickly to open the valve when the evaporation temperature is too low, to prevent the compressor from stopping due to low pressure.

4. HITCond (high condensing temperature, optional) protection:It can only be enabled if the controller measures the condensing pressure/temperature. It acts moderately to close the valve if the condensing temperature reaches excessive values to prevent the compressor from stopping due to high pressure.

Protection Control ParametersProtection Control Parameters

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As concerns the control parameters, the following general indications can be used as a guide:

Proportional gain (from 3 to 30):Increasing the proportional gain K increases the reaction speed of the valve and is recommended if the system is particularly perturbed or to make superheat control faster. If high (>20), may cause swings and instability.

Integral time (from 40 to 400 sec):Increasing the integration time Ti improves stability but makes the valve slower in reaching the superheat set point.If lowered (<40 sec) generates swings and instability. If the system is already perturbed, high values (>150 sec) are suggested so as to avoid creating further disturbance.

Derivative time (from 0 to 10 sec):Increasing the derivative time Td improves the reactivity of the valve, in particular in perturbed systems, reducing the amplitude of swings in the superheat. If high, may in turn generate excess reactivity and consequently swings.

Settings GuideSettings Guide

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Protector thresholds:The thresholds used for the 4 protectors should be set based on the features of the system being controlled.All are expressed as temperatures (°C):

Settings GuideSettings Guide

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Exploded ViewExploded View

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If the valve is undersized, the performance of the system will be affected, as it will not be possible to reach the desired temperature and the superheat will generally be high or greater than the set point.

If, on the other hand, the valve is oversized, the problems may involve system “swings” (there may be wide variations in temperature, pressure and superheat), and consequently poor efficiency, or alternatively there may be the return of liquid to the compressor.

DimensionsDimensions

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Positioning the valvePositioning the valve

Always install a filter dryer before the refrigerant inlet; if the installation is bi-directional (flow of refrigerant in both directions, reverse-cycle heat pumps), a bi-directional liquid/gas filter should be fitted on both expansion valve connections, or other solutions can be used, depending on the layout of the installation.

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Positioning the valvePositioning the valveIn no circumstances is upside-down installation allowed,

that is, with the stator facing downwards.

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Welding the valveWelding the valveUnscrew the locking nut and remove the stator (winding). If necessary, remove the connector if inserted. Before starting welding, wrap the body of the valve (without the stator) in a wet rag, to avoid overheating the inside parts.When finished welding, replace the stator and tighten the valve-stator locking nut.

NO!

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Positioning the probesPositioning the probesThe ideal position for both probes is immediately at the evaporator outlet, so as to be able to measure the effective refrigerant superheat.

Superheating measurement

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Suction temperature probeSuction temperature probe

The position of this probe is extremely important, as it determines the accuracy of the superheat value and the speed of response to variations in this.

The probe should be installed after the evaporator outlet, in a straight and horizontal section. Comparing the section of pipe to the face of a clock, the probe must be positioned at 12 o’clock for pipes with a diameter less than 22 mm, and at 4.30 or 7.30 for pipes with a diameter greater than or equal to 22 mm.

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Suction temperature probeSuction temperature probeAll precautions must be taken to maximize the thermal coupling between the pipe and probe, conductive paste on the point of contact between the probe and the pipe, fastening the probe with a clamp. The probe cable must be looped in the immediate vicinity of the probe and then secured by elastic band.

Finally, the pipe-probe assembly should first be covered with aluminium tape, and then with thermal insulating material.

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Evaporator pressure transducerEvaporator pressure transducer

The pressure transducer must be installed near the temperature probe on the top of the pipe. It can be positioned away from the point of temperature measurement only if the section of pipe that separates the two probes does not contain devices that alter the pressure (heat exchangers, flow indicators, valves, etc.).

Ratiometric transducer needs 3 wires. Operating voltage is supplied to the drive circuit from a power supply, and the gain of the drive circuit is adjusted in accordance with variations in the operating voltage to make the drive signal and the output signal proportional to the operating voltage.

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1. Completely insert the stator into the valve body and tighten the locking nut. Never leave the stator in place without the locking nut or with the nut partially unscrewed because water may infiltrate inside.

2. Fit the cable with the co-moulded IP67 connector, connecting it to the stator and fastening it carefully with the screw provided. IP67 protection is not guaranteed if the screw is not properly secured.

3. Connect the wires on the other end of the cable to the terminals on the driver, carefully following the instructions shown on the driver instruction sheet, and observing the correct sequence of the colours. If connected incorrectly, the valve may not move or may move in reverse compared to the direction controlled by the driver.

Electrical valve connectionsElectrical valve connections

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Pay attention to the polarity: contact number 4 is wider than the others so don’t force, otherwise the valve will not open correctly.

Electrical valve connectionsElectrical valve connections

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The EVD family drivers mainly differ as regards:

Type of pressure transducer (ratiometric or 4-20 mA);User interface for programming the parameters;Local network connection (tLAN, pLAN, RS485 supervisor).

If the driver is not compatible with the pLAN or tLAN, the driver must operate in stand-alone mode, activating and deactivating the control of the valve based on the status of the digital input:

digital input open: the driver closes the valve and deactivates control;digital input closed: the driver opens the valve and starts control.

EVD Family DriversEVD Family Drivers

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EVD Family DriversEVD Family Drivers

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EVD4 DriverEVD4 DriverEVD4 driver can operate independently (stand alone), connected to a supervisor to control the fundamental parameters by RS485, or connected to the pCO or μC2 controllers by tLAN.

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EVD4 DriverEVD4 Driver

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NOT USED

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EVD4 DriverEVD4 DriverBecause the EVD4 driver communicates with pCO boards by tLAN, the addressing of the driver is required in order to allow the main board to recognize the correct driver.

For example, if a unit has 2 refrigerant circuits, 2 E2V valves and 2 EVD drivers will be required. The addressing of the driver is as it follows:Circuit 1 Driver address: 1Circuit 2 Driver address: 2

By default, the factory driver address is set to 2; in this case, if a replacement of the driver of the first refrigerant circuit is necessary, the address must be changed to 1.

EVD4 User Interface allows the changing of addresses and other parameters.

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EVD4 User InterfaceEVD4 User Interface

The software used to install EVD4 UI is available in the following configurations: “EVD4_UI Address”, to set the address of the EVD4; “EVD4_UI Key”, to program the key; “EVD4_UI Stand Alone” to program the stand-alone EVD4; “EVD4_UI MCH2” to program the EVD4 with μC2; “EVD4_U positioner” to use the EVD4 as a positioner with 4 to 20 mA or 0 to 10 V.

This box is used to set the Driver+Valve system configuration values.These parameters should be set and checked before activating the unit.

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Service serial port allows access to the functions of the EVD4 via PC. To access this connector:

1) Remove the cover by levering it with a screwdriver on the central notch;2) Locate the white 4-pin connector and insert the special converter cable.3) Connect the USB cable to the PC; if the EVD4 is not powered by the 24 Vac line, it will take its power supply from the serial converter.4)Start EVD4 User Interface.

This serial port can be connected and disconnected without needing to remove the USB cable from the PC.

4-pin connector

tLAN

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EVD4 User InterfaceEVD4 User InterfacePreparing the user interface:

The program does not require installation; simply copy the entire contents of the distribution directory to the required location on the hard disk. The program cannot run from the CD as it requires write access to the configuration files.Open the IN\EVD400UI.INI file from the path where EVD4_UI.exe is located and make sure that the Paddr parameter is set to 1.

Start the EVD4_UI program using the shortcut icon to the application and not the EVD4_UI.exe fi le, then press COM SETUP and set:• Port = COM address of the serial port used to connect the USB converter;• Baud Rate = 4800• Parity = NO PARITY• Byte Size = 8• Stop Bits = 1Press SAVE.

Now, if the converter is connected to an EVD4, image of the driver will be displayed in the top left and the EVD version window will show the following data:• Firmware rev. = firmware version of the EVD4 connected;• Param key rev. = parameter key version (for future use);• Hardware rev. = hardware version;• Network address = network address of the main serial port;

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EVD4 User InterfaceEVD4 User InterfaceModifying the parameters:

To modify a numerical parameter:• check the box containing the value of the parameter;• click the right mouse button;• set the new value;• Press ENTER.

To reverse the value of a digital parameter (red or green rectangle):• check the box containing the value of the parameter;• click the right mouse button.

Meaning of the red or green rectangle:- GREEN = FALSE or OFF or 0 or DISABLED, in relation to the meaning of the reference parameter;-RED = TRUE or ON or 1 or ENABLED, in relation to the meaning of the reference parameter.

If the AUTO WRITE checkbox is selected, the data is sent to EVD4 immediately after having been modified, otherwise, after having modified all the required data, press WRITE.

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PIDSH Set-Point System

Sensors

Error Input

LN

Output

SN

+

+

+

++ -

Load Noise

Sensors Noise (p + T)

Superheat PID controllerSuperheat PID controller

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EFFECT OF K

Increasing the value of the proportional gain, increases the reactivity of the valve, to the limit where this may cause instability and not reach the set point with precision. This depends on the ratio between the circuit capacity and the valve capacity, and on the maximum number of valve control steps.

Proportional actionProportional action

The proportional action guarantees control over the process variable that is proportional to the system error at the instant t. The controller performs a corrective action on the control variable, at the instant t. The proportional action makes its contribution in the initial transient periods; then, when the error decreases, it loses effectiveness.

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The proportional action follows the logic whereby the greater the error, instant by instant, the more intense the action on the process so as to bring the controlled variable to the desired value.


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Example with three different values of K applied to the controller. Higher values of K grant a quicker reaction, but create swings, lower values grant slower reactions and more difficulties reaching the SH set-point.


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EFFECT OF Ti

Increasing the value of the integral time Ti, the valve reaches the set point more slowly but avoids excessive swings. This depends on the type of evaporator and the inertia of the circuit.

Integral actionIntegral action

The integral action is used to guarantee that the error is null in steady state. Indeed, the integral action is not zero if there is no error; quite the opposite, if for example the error remains stable, it continues to increase linearly, following the principle whereby “until the controlled variable decides to move in thedirection I want, I will continue to apply an increasingly intense action”. Consequently, the integral action not only considers the current value, at the instant of the error, but also the past values.

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The integral action, by definition, does not make “jumps” and therefore is the slowest to react. Indeed, it has almost no effect during the initial transient periods: these periods are dominated by the other two actions. To define the integral time, the P+I actions are considered.

Integral Action

Proportional Action

Ti integral time: increasing “C”, the action made from “A” will be slow and precise.

Integral actionIntegral action

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EFFECT OF TD

Increasing the value of the derivative time TD decreases swings, however there may be fluctuations around the set point.

Derivative actionDerivative action

• The derivative action makes the control depending on the “future” of the error, that is, on the direction it is moving in and the speed it varies.

• In fact, the derivative action calculates an estimate for the error after t seconds based on the trend of the curve at the instant t.

• It therefore ensures that control will depend on a prediction of TD instants after.

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The derivative action “tries to understand where the error is going and how fast it is moving” and reacts as a consequence; the parameter TD determines how far into the future the prediction is made.

The derivative action is the fastest to react (including to measurement noise, unfortunately) and it is only helpful if the prediction is good, that is, if TD is not too high compared to the temporal changes in the error: the difference can be seen by examining cases A and B in the figure.

Derivative actionDerivative action

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EEV TesterEEV TesterEEV tester can perform three types of tests on stepper motor electronic expansion valve:

1) Measurement of motor windings resistance:

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2) Measurement of motor current when driven by an external driver:

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2) Forced opening or closing of the valve:

Opening

Closing

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Software Parameters ListSoftware Parameters List

EEV PositionWith this parameter, the regulation function of the EVDriver (AUTO setting) is activated, it can also be opened manually (MANUAL setting). This results in two further indicators being displayed: the desired opening of the valve and the absolute position of the valve itself in the regulation steps.

EEV TypeThis selects the expansion valve which is to be used. The selection of the CUSTUM field enables the use of the following manual configuration parameters.

RefrigerantWith this parameter the type of refrigerant to be used in the unit can be set: this setting is necessary for calculating the saturated temperatures by using the dew point.

SHeat StpThis indicates the set point for superheat regulation.Values which are lower than 3°C are not advised.The advised value is 6°C.

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Dead ZoneThe dead zone is the temperature semi-interval (±) which straddles the superheat setpoint at which regulation is ignored.Values which are above 2°C are not advised.The advised value is 0.0°C, which can be increased to 1°C in the event of instability of the system but only after attempts have been made to solve the problem with other constants which are described below.

Prop. Int. Dif. (PID) factorThe proportional, integral and derivative constants are the main regulation parameters of the EVDriver. They define the PID regulation section of the superheat: please refer to the classic PID regulation theory for a more detailed description of their meaning.

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Software Parameters ListSoftware Parameters ListProportional gain/factorThe advised range is given by the formula:

Max Steps: the maximum regulation steps of the EEV;QCIRC: the capacity in kW of the cooling circuit in normal operating conditions;QEEV: the capacity in kW of the EEV in the same conditions.

In the event that multiple operating conditions exist which are noticeably different (cooling capacity, Te, Tc), it is necessary to use an average Kp from those which are calculated by the formula or from the tests carried out in different conditions generally favouring low values and reducing the integral protection terms (LOP, MOP,…):

Carel E2V 3Alco EX5-EX6 7Alco EX7 15Alco EX8 20Sporlan SEI 0.1-11 15Sporlan SEH 25 20Sporlan SEH 50 30Sporlan SEH 100-250 30Danfoss ETS 50-100 3

Compressors with continuous regulation (inverter or screw stepless): In the event that the regulation dynamic is particularly fast, it is useful to increase the proportional constant values to allow the valve to reach the cooling capacity quickly. It can therefore be necessary to increase the input values to even 300% according to the situation.

%20QQ

100StepsMax K

EEV

CIRC

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Software Parameters ListSoftware Parameters ListIntegral timeThe range of the various applications is between 10 to 100 depending on the dynamic of the evaporator which is used.The advised values are:Plate heat exchanger 15Finned coil 25Tube bundle heat exchanger 30

Values which are higher than 80 seconds are only advised for evaporators with a high average contact time, which is the case for the majority of centralized units.

Differential timeThe advised value is 2.5 seconds and it is not generally necessary to modify this value.

Low Sheat protection - Low limitThe low superheat threshold: an integral regulation which is additional to the integral PID starts under this value which has a constant which can be set.The advised value is 2°C with a set point for a superheat higher than 4°C. In the event of a lower setpoint, the low superheat threshold must also be lowered to ensure a difference between the two values of at least 2°C.

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Low Sheat protection - Integral timeThis parameter is the integration constant which protects the low superheat.N.B. A value of 0 (zero) completely disables the protection.The advised value is 1 second with a threshold of 2°C. In the event that the threshold is lower than the time is must also be reduced by 0.5°C.

LOP Protection - LOP limitThe low operating pressure threshold is indicated in saturated °C. This parameter defines the intervention threshold of the low operating pressure: an integral regulation starts under this value with a constant which can be set to return to and maintain a temperature above that which has been set.The low superheat pressure protection always has, in any case, priority over that of the low operating pressure protection (LOP).The advised value is about 3°C under the minimal saturated evaporation temperature allowed in the system.For example: for chillers with nominal evaporation at 3°C and a minimal permitted evaporation of -1°C, the LOP limit must be set at -4°C.

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LOP protection - Integral timeThis parameter if the integral constant for the protection of the low operating pressure (LOP).N.B. A value of 0 (zero) completely disables the protection.The advised value is 4 seconds, which can be increased to about 10 seconds if there is too much energetic action (excessive opening of the valve as a result of low pressure) and can be reduced to 2°C if there is not a high level of action (when the evaporation temperature is too low).

MOP protection - Start up delayThis refers to the waiting time of the start up of the unit for the intervention of the protection routine of the MOP.Starting from the start up of the unit until the end of the time programmed, the protection routine of the MOP remains inactivated in order to allow the regular start up of the unit with a starting evaporation pressure higher than the threshold value assigned to the MOP.The advised value is 60 seconds but the variability of the start up dynamic of the different units needs an optimisation of the time: it is necessary that in the time which has been set, the evaporation pressure falls to below the value which has been set as a MOP limits in the event that it is not effectively recovered in MOP.

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MOP protection - MOP limitThe maximum operating pressure is indicated in saturated °C.This parameter defines the MOP intervention protection threshold: above which integral regulation starts with a constant which can be set to return to and maintain a temperature above that which has been set.The value to be set depends on the unit and its design and it therefore depends on the unit itself so possible values cannot be suggested here.

MOP protection - Integral timeThis parameter is an integral constant for the protection of the maximum operating pressure (MOP).N.B. A value of 0 (zero) completely disables the protection.The advised value is 4 seconds, which can be increased to about 10 seconds if there is too much energetic action (excessive closing of the valve as a result of high pressure) and can be reduced to 2°C if there is not a high level of action (when the evaporation temperature is too high).

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Software Parameters ListSoftware Parameters ListHiTcond protection - HiTcond limitThe high condensation pressure threshold is indicated in saturated °C. This parameter defines the intervention threshold of the high condensation pressure: above which integral regulation starts with a constant which can be set to return to and maintain a saturated condensation temperature above that which has been set.If the compressor is blocked because of thermal protection intervention, it is necessary to resolve the high condensation pressure situation by using another method: this is because there is a HiTcond threshold which is excessively low and /or incompatible with the operating conditions.

HiTcond protection - Integral timeThis parameter is the integration constant for high condensation pressure protection (HiTcond).N.B. A value of 0 (zero) completely disables the protection.The advised value is 4 seconds, which can be increased to about 10 seconds if there is too much energetic action (excessive closing of the valve as a result of high pressure) and can be reduced to 2°C if there is not a high level of action (when the condensation temperature is too high).

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Software Parameters ListSoftware Parameters ListSuction temperature high limitThis parameter sets the maximum temperature (thermometric) allowed for the outlet gas of the evaporator.In the event that the MOP situation is reached with values which are particularly high or normal for superheat (for example in the event of a start up of the unit with a particularly high refrigeration fluid level) there is the risk that a MOP action which is not limited and is prolonged involves excessively high suction temperatures in order for correct operation of the compressor: for this reason a limit has been introduced for the maximum suction pressure. This parameter limits the action of the MOP protection in such a way as, when it is reached, it stops the corrective protection action completely until the refrigeration temperature returns to below the set value.

Circuit/EVV ratioThe percentage value of the cooling capacity of the compressor compared to that if the valve is noted in the relationship between the maximum cooling capacity of the EVD driver slave unit and that of the electronic expansion valve (100% opening) in the same operating conditions.The advised value for the first approach is 60% unless there is a particular disproportion between the valve and the unit.

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Software Parameters ListSoftware Parameters ListRegulation stepsRegulation steps of the electronic expansion valve connected to the EVDriver. The regulation steps are always intended from an opening of 0 (zero) to the opening which is indicated in the parameter.

Closing stepsThe steps set for the valve in closure (for switching off the machine or in error).N.B. It is possible that some expansion valves have a number of regulation steps which is slightly less than the maximum number which are actually physically feasible: it is especially important in this case that the regulation steps and the maximum steps are not confused.

Minimum stepsMinimum regulation steps of the expansion valve: this parameter sets the minimal opening allowed for the expansion valve. In the regulation phase the valve can however reach zero.

Back stepsBack steps follow a complete closing of the valve. The value is useful for decompressing any eventual closing springs within the valve (in the case of the Carel valve) or to avoid the sealing of the circuit and therefore allows an equalization of the cooling circuit (evc monophase compressor).

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TroubleshootingTroubleshootingProblem: Liquid returns to the compressor during the operation of the controller

Problem: The unit switches off due to low pressure during control (units with on-board compressor only)

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TroubleshootingTroubleshooting

Problem: During start-up with high evaporator temperature, the evaporation pressure is high

Problem: During start-up the unit switches off due to low pressure (units with on-board compressor only)

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Problem: The system swings

Problem: Liquid returns to the compressor only when starting the controller (after being OFF)

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TroubleshootingTroubleshootingProblem: During start-up with high evaporator temperature, the evaporation pressure is high

Problem: The showcase does not reach the set temperature, despite the value opening to the maximum (for showcases only)

Problem: The showcase does not reach the set temperature, and the position of the valve is always to 0 (for showcases only)

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Please remember, before changing the EEV parameters, since they are critical for the proper functioning of the unit,

always refer to the After Sales Team.


TEV & EEV

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Transcript of TEV & EEV