Danfoss Electronic system for evaporator liquid injection User guide

Brand: Danfoss

Model: Electronic system for evaporator liquid injection

Type: User guide

Manual

Electronic system for

evaporator liquid injection

EKS 65

RS.1D.A1.02 ➝ RS.1D.A2.02 04-1995

2 Manual RS.1D.A2.02 © Danfoss 04/95 EKS 65

Contents

Introduction ................................................................................................................ 3

Systems components ................................................................................................ 3

Principle ......................................................................................................................4

Application ................................................................................................................. 6

General application .................................................................................................6

Pump down .............................................................................................................6

Several evaporators ................................................................................................7

Water chiller with liquid distribution system .............................................................8

Mode of operation/function ......................................................................................9

Ordering .................................................................................................................... 10

Technical data .......................................................................................................... 10

Mounting...................................................................................................................12

Air cooler ...............................................................................................................12

Water chiller .......................................................................................................... 13

Electrical connection ............................................................................................... 14

Setting ....................................................................................................................... 18

Running in and adjustment .................................................................................... 19

Electrical check .....................................................................................................19

Temperature differential S2 - S1............................................................................ 20

Trouble shooting......................................................................................................21

Installation

considerations

Accidental damage, poor installation, or site conditions, can give rise to malfunctions

of the control system, and ultimately lead to a plant breakdown.

Every possible safeguard is incorporated into our products to prevent this. However, a

wrong installation, for example, could still present problems. Electronic control is no

substitute for normal, good engineering practice.

Danfoss wil not be responsible for any goods, or plant components, damaged as a

result of the above defects. It is the installer's responsibility to check the installation

thoroughly, and to fit the necessary safety devices.

Particular attention is drawn to the need for a “force closing” signal to controllers in the

event of compressor stoppage, and to the requirement for suction line accumulators.

Your local Danfoss agent will be pleased to assist with further advice, etc.

EKS 65 Manual RS.1D.A2.02 © Danfoss 04/95 3

TQ/PHTQ + EKS 65 is an electronically controlled system for the regulation of

refrigerant liquid in evaporators.

The system can be used with advantage for finned evaporators and liquid coolers

designed for dry evaporation.

There are many energy saving benefits to be gained from using the TQ/PHTQ + EKS

65 system:

• The system will not be affected by changes in condensing pressure (∆p min 2 bar

through the TQ valve)

• The system compensates for changes in subcooling ahead of the expansion valve

(min. subcooling 4 K)

• The system adjusts itself quickly and precisely, even to large load changes

• Max. utilization of the evaporator (high degree of filling) throughout the operating

range of the system

• Low superheat gives maximum utilization of the evaporator

• Same setting for the entire operating range

• Electrical connection between system components gives positional flexibility

• MOP (Max. Operating Pressure) setting

In addition to its primary function the TQ/PHTQ + EKS 65 electronic system contains

a series of supplementary functions that can be brought into effect by making extra

connections.

• Forced opening and closing of the TQ/PHTQ

• Standby closing of TQ/PHTQ

• External reference setting of superheat via a potentiometer

• External reference setting of superheat via a computer

• Readout display of superheat temperature

Introduction

TQ/PHTQ + EKS 65 regulating system consists of three main components:Systems components

Electronic controller EKS 65 in

silumin case.

Expansion valve TQ/PHTQ. Pt 1000 ohm sensors for

installation on pipes or in

immersion pockets

Where pressure measurement is

needed for the regulation, two

additional components will be

required:

Pressure transmitter type AKS 32

P/T converter

4 Manual RS.1D.A2.02 © Danfoss 04/95 EKS 65

Principle

The liquid supply is controlled on signals from two Pt 1000 ohm sensors. The

sensors register the difference between the temperature at the evaporator outlet

(S2) and the temperature at the evaporator inlet (S1).

The registered temperature differential is constantly compared in the EKS 65

controller with the required temperature differential (set on the controller).

If the temperature differential between S2 and S1 changes in relation to the set

reference, the controller will immediately send more or fewer electric pulses to the

TQ/PHTQ actuator. The degree of opening of the TQ is changed by the actuator

thereby changing the refrigerant flow to re-establish the required temperature

differential S2 - S1.

Temperature and pressure conditions in an evaporator

EKS 65 Manual RS.1D.A2.02 © Danfoss 04/95 5

In contrast to the thermostatic expansion valve, which uses superheat in the suction

line as a signal, regulating system TQ/PHTQ + EKS 65 uses a temperature

differential as a signal.

The electronic controller EKS 65 registers the temperature differential S2-S1 between

the evaporator outlet and the evaporator inlet. Included in this temperature differential

is the pressure drop in the evaporator, so that the suction gas superheat will represent

a higher value than S2-S1.

Where:

∆t

= evaporator superheat

S2 = suction gas temperature

= evaporating temperature at evaporator outlet

∆p

= pressure drop in evaporator

S1 = evaporator temperature at evaporator inlet

∆t

= temperature differential, evaporator outlet - evaporator inlet

It can be seen that the superheat measured by EKS 65 is:

-6 - (-10) = 4 K

The true superheat at the outlet of the evaporator is:

-6 - (-14) = 8 K

It is therefore more correct to use the term temperature differential. This then

differentiates between superheat in connection with mechanical thermostatic valves

and differential in connection with electronically controlled expansion valves.

In a few systems, regulation carried out by two temperature sensors will not be

sufficient. In such systems a pressure measurement and a P/T converter may then be

used instead of the S1 signal. See page 8.

6 Manual RS.1D.A2.02 © Danfoss 04/95 EKS 65

Application Regulating system TQ/PHTQ + EKS 65 is for use with refrigerants R22, R134a and

R404A.

The main function of the system is to control the liquid supply to evaporators with

dry evaporation in for example:

• Air coolers

• Liquid coolers

General application

When thermostat KP 73 is connected, the comperessor will start, solenoid valve

EVR in the liquid line will open* and valve TQ will slowly open from a closed

position.

* During a period of standstill the difference in temperature between S2 and S1 will be equalized. This means

that the controller will lower the actuator temperature by 3 → 5 C° to close valve TQ.

Pump down

Here a refrigeration plant is shown with an evacuation (pump down) of the evaporator

each time the thermostat KP 73 opens.

EKS 65 Manual RS.1D.A2.02 © Danfoss 04/95 7

Several evaporators

Here a refrigeration plant is shown with several evaporators and common compressor,

condensor and recipient.

When several evaporators are placed in the same room and the evaporators have a

common suction line, the individual S1 signals can be replaced by a common pressure

signal. A pressure transmitter is then mounted in the suction line right after the

evaporators. This signal is received by a P/T converter which retransmits a voltage

signal to the EKS 65 controllers' S1 input. One P/T converter can send signals to max.

ten EKS 65 controllers.

The principle in the use of the P/T converter is illustrated on the next page.

8 Manual RS.1D.A2.02 © Danfoss 04/95 EKS 65

Water chiller with liquid distribution system

Water chiller with liquid distribution system*.

On start-up, solenoid valve EVR 3 in the relief line opens and and PHTQ begins to

inject refrigerant liquid into the evaporator.

The superheat is registered by two sensors: temperature sensor S2 and pressure

transmitter type AKS 32.

The P/T converter changes the signal from the pressure transmitter to a voltage

signal adapted to the signal input on EKS 65.

* In water chillers with liquid distributor system the evaporating pressure is best registered with a pressure

signal

In water chillers without liquid distributor system, where the evaporating pressure can be registered

satisfactorily with a temperature sensor instead of a pressure transmitter, the P/T converter is left out.

The temperature sensor (S1) is then mounted in the liquid line right in front of the evaporator.

EKS 65 Manual RS.1D.A2.02 © Danfoss 04/95 9

Mode of operation/

function

The purpose of the TQ/PHTQ + EKS 65 system is to control liquid injection into an

evaporator to give optimum evaporator utilization.

Regulation of liquid injection is based on signals from two Pt 1000 ohm resistance

sensors S1 and S2.

On air coolers sensor S1 is located on a distributor tube, as close to the evaporator as

possible.

If the placing of S1 does not always guarantee a temperature signal corresponding

to the evaporating temperature ("wet sensor"), pressure measurement with P/T

converter is recommended instead.

The S1 signal determines where the TQ valve's P-band should be placed in relation

to the evaporating temperature.

In water chillers with liquid distributor system, temperature measurement S1 is

replaced by a pressure measurement (AKS 32).

The difference in temperature at sensors S2 and S1 is used as a signal to the

controller.

A fixed value of ∆t = S2 - S1 to give regulation without hunting is set on the controller

which then, irrespective of the load, will ensure that this value is maintained constant.

Preconditions for a constant signal are a correct liquid distribution and a stable

signal at the evaporator outlet.

Opening and closing of the valve is performed by an actuator. Instead of the normal

bulb and capillary tube arrangement, an actuator (pressure reservoir) has been fitted

on the top of the TE/PHT element. The actuator reservoir holds a given amount of

liquid, a heating element, and an NTC temperature sensor.

During normal operation the heating element keeps the liquid in the actuator at such

a temperature (pressure) that stable equilibrium between the system pressure under

the diaphragm and pressure in the actuator over the diaphragm is maintained.

EKS 65 controls power supply to the heating element via signals from sensor NTC

and sensors S1 and S2.

The signal from S1 registers the temperature (pressure) at the evaporator inlet, and

the signal from the NTC sensor registers the temperature (pressure) in the actuator.

By comparing these two signals the controller maintains equilibrium between the

pressure on both sides of the diaphragm.

The difference in temperature between sensors S2 and S1 is compared with the ∆t

value set on the controller. If there is a deviation between the set ∆t value and the

difference between S2 and S1, power to the heating element is changed to cool or

heat the acutator.

The PI regulation (proportional integral) of EKS 65 ensures that the signal S2 - S1

does not deviate from the set ∆t on variations in load, evaporating pressure,

subcooling, and pressure drop across valve TQ/PHTQ.

10 Manual RS.1D.A2.02 © Danfoss 04/95 EKS 65

Controller EKS 65 and P/T converterOrdering

Symbol Description Refrigerant Code no.

EKS 65

R22

R134a

R404A

084H3033

P/T converter

R22

R134a

R404A

084H3060

084H3066

084H3067

Silumin case

incl. baseplate and bracket for

front panel mounting

084H3025

Baseplate

for panel mounting

084H3035

Valves type TQ /PHTQ

Please refer to technical brochure: Electronically operated valves for refrigerating plant. Literature

number: RC.0X.B

Temperature sensors (Pt 1000)

Please refer to technical brochure: Temperature sensors type AKS. Literature number: RC.5F.A

Pressure transmitter type AKS 32

Please refer to technical brochure: Pressure transmitter type AKS 32. Literature number: RC.5G.D

(Pressure rang must be -1 to 6 bar)

Setting range SP S2 - S1 2 to 18 K

Neutral zone Nz = +/-1.0 K, fixed setting

Regulation principle PI, proportional integral

Regulation parameters Amplification factor Kp = 1 to 5

Factroy setting Kp = 1

Integration time Tn = 30 to 300 s

Factory setting Tn = 200 s

Refrigerant setting R22, R 134a, R 404A

Ambient temperature Operation -20 °C to +55 °C

Transport/Stock -50 °C to +70 °C

Supply voltage Voltage 24 V a.c. +/-10%, 50/60 Hz

Consumption 3 VA (TQ/PHTQ = 75 VA)

Screwed cable entry Pg 13.5

Enclosure IP 54 according to IEC 529

Controller EKS 65

Technical data

EKS 65 Manual RS.1D.A2.02 © Danfoss 04/95 11

P/T converter

Function Pressure for temperature converter

Input signal 1-5 V from AKS 32 (-1 to 6 bar)

Output signal Voltage signal to S1 input on EKS 65

Refrigerant Refrigerant-dependent. See code number

Ambient temperature Operation -20 °C to +55 °C

Transport/Stock -50 °C to +70 °C

Supply voltage Voltage 24 V a.c. +/-10%, 50/60 Hz

Consumption 3 VA

Technical data for the remaining components appear in the relevant brochures mentioned on the previous page.

Dimensions

With panel mounting, a square hole must be cut in the panel, 138 x 138 mm +/-1 mm. The silumin case can

then be fitted using the bracket supplied.

Weight

Silumin case incl. baseplate 810 g

Baseplate for panel mounting 300 g

EKS 65 controller insert 520 g

P/T converter insert 675 g

12 Manual RS.1D.A2.02 © Danfoss 04/95 EKS 65

Air cooler

Sensor

Sensor S1 must be placed on a distributor tube as close to the evaporator as possible.

Do not forget to apply heat conducting paste and to insulate the sensor.

Sensor S2 must be placed on the first vertical riser of the suction line, if the riser is

no more than 2 m away from the evaporator. If only a horizonal suction line is

available, sensor S2 must be placed on the suction line at least 0.5 m away from the

evaporator.

Solenoid valve

A solenoid valve EVR ahead of valve TQ is recommended to obtain improved shut-off

during standstill.

Since supply voltage is constantly applied to controller EKS, the TQ/PHTQ + EKS

system is in stand-by mode during standstill.

The normal function of the system starts when the solenoid valve opens.

For steel tubes with thick walls sensor AKS 21W (immersion sensor) is recommeded.

For steel tubes with thin walls and copper tubes sensor AKS 21A (surface sensor) is

recommended.

Do not forget to apply heat conducting paste and to insulate the sensor.

The pressure equalising line must be connected just after valve TQ/PHTQ, between

valve and distributor.

Mounting

EKS 65 Manual RS.1D.A2.02 © Danfoss 04/95 13

Water chiller

Water chiller with liquid distribution system

Sensor S2 must be located on the first vertical suction line after the evaporator,

provided this point is not more than 2 m from the evaporator. If only a horizontal

suction line is available, sensor S2 must be placed at least 0.5 m away from the

evaporator.

The pressure equalisation line is connected to the liquid line right after the expansion

valve.

The relief line (for PHTQ only) must be connected immediately after valve PHTQ.

Note!

On water chillers without liquid distribution system, sensor S1 can be installed

immediately ahead of the evaporator. The pressure transmitter and P/T converter can

thus be omitted.

14 Manual RS.1D.A2.02 © Danfoss 04/95 EKS 65

Supply voltage

Stabilized 24 V a.c. ±10%, 50/60 Hz to be connected to terminal 1 and 2.

Max. consumption, incl. TQ/PHTQ = 80 VA.

A class II transformer (CEE 15) must be used.

If the secondary side of the transformer is to be earthed, make the connection to

terminal 1 (N).

Pt 1000 ohm sensors S1 and S2

Sensor S2 must be connected to terminal 24 and 25.

Sensor S1 must be connected to terminal 25 and 26

Note! S1 and S2 must not be swapped over (neither must the terminals). Therefore

test the sensor after installation: Heat the sensors and using an ohmmeter measure

the change in resistance.

The total resistance in the connection cable, incl. connector, must not exceed 2 ohm.

Typical resistance values for copper wire:

0.75 mm

: 2.4 ohm/100 m

1.5 mm

: 1.2 ohm/100 m

2.5 mm

: 0.7 ohm/100 m

(Note! 100 m wire corresponds to a distance of 50 m between EKS 65 controller and

Pt 1000 ohm sensor.)

Forced opening and forced closing

Forced opening

of theTQ/PHTQ can be obtained by making a relay contact across

terminal 1 and 63.

By closing the contact the actuator receives full power and the TQ/PHTQ becomes

fully open.

Forced closing

of the TQ/PHTQ can be obtained by making a relay contact across

terminal 1 and 61.

By closing the contact, power to the actuator is cut off and the TQ/PHTQ closes.

This forced closing cannot replace a solenoid valve in the liquid line. A solenoid

valve should be fitted ahead of TQ to ensure complete shut-off of liquid supply.

Standby closing

of TQ/PHTQ is obtained by cutting in a relay switch via terminal 1

and 64.

When the relay switch has cut in, the actuator temperature will be maintained at a

value 20 K below the valve's opening point. In this way the heating time for the valve

will be shorter when it has to reopen.

This function should be used whenever the compressor is stopped.

In large systems with only one compressor the function may help preventing the

compressor from cutting out at low pressure.

Electrical connection

EKS 65 Manual RS.1D.A2.02 © Danfoss 04/95 15

TQ/PHTQ

Cables between the power supply, controller EKS 65 and actuator TQ/PHTQ must be

sized to give min. 21 V a.c. and max. 26 V a.c. on TQ/PHTQ terminal 77 and 78 at full

power.

Full power is indicated by the red lamp in EKS 65 lighting up constantly.

The voltage drop from the transformer to the actuator TQ/PHTQ must not exceed 3 V.

6-core cable can be used with advantage when the TQ/PHTQ and EKS 65 are

installed a long distance apart.

For example, for a distance of 100 to 200 m a 6-core 1.5 mm

cable can be used.

The connection must be made as follows:

Two cores connected to terminal 78

Two cores connected to terminal 77

One core connected to terminal 35

One core connected to terminal 36

TQ/PHTQ feedback terminals 35 and 36

Controller EKS 65 receives a feedback signal from the actuator TQ/PHTQ. This signal

must be connected to terminal 35 and 36.

It is important to connect 35 and 36 on controller EKS 65 to terminal 35 and 36 on the

actuator TQ/PHTQ. Incorrect connection can cause damage to controller and actuator

because terminal 35 and 36 are the input to the controller measuring circuit.

If the secondary side of the transformer is to be earthed, make the connection to

terminal 1 (N).

The dimensions of the cable between the actuator TQ/PHTQ and controller EKS 65

terminal 35 and 36, must be as follows:

0 to 100 m: 0.75 mm

100 to 200 m: 1.5 mm

16 Manual RS.1D.A2.02 © Danfoss 04/95 EKS 65

External reference setting S2 - S1 via potentiometer

External setting of the reference S2 - S1 can be obtained by connecting a

potentiometer to terminal 26, 27 and 30.

A resistor of 1.7 kohm, 0.25 W must be fitted between terminal 26 and the

potentiometer.

The potentiometer must be linear and 10 kohm.

When external reference setting is used, the reference knob S2 - S1 on EKS 65 is

non-operative. Remove jumper between terminal 30 and 31.

External reference setting S2 - S1 via computer

External setting of reference S2 - S1 can be controlled by a computer, using a

standard signal of 4 to 20 mA.

The connection with EKS 65 must be made on terminal 26, 28 and 30.

4 mA corresponds to 0°C

12 mA corresponds to 9°C

20 mA corresponds to 18°C

When this connection has been made, the reference knob on EKS 65 becomes non-

operative. Remove jumper between terminal 30 and 31.

Temperature differential S2 - S1 readout

The temperature differential S2 - S1 can be read from a voltmeter or display

connected to terminal 26 and 29.

The resistance in the measuring instrument must be greater than 100 kohm.

The output signal from the terminals is 100 mV/°C.

0 V corresponds to 0°C

1.8 V corresponds to 18°C

Note! When connecting other electrical equipment there must be no galvanic

connection between several controllers, and between a controller and the other

equipment.

AB C

Controller, P/T converter

The signal can be used by several controllers (max. 10).

Separate transformers will then be required for each EKS 65.

Setting

Indicator lamps

Red: TQ power

Green: Superheat is equal to reference ±1 K

Yellow: Superheat beyond reference ±1 K

Setting knop S2 - S1

Scale graduation 2 to 18°C.

Factory setting = 18°C.

Kp setting

Setting screw for proportional amplification factor Kp.

Scale graduation 1 to 5.

Factory setting Kp = 1

Tn setting

Setting screw for integration time Tn.

Scake graduation 30 to 300 s.

Factory setting Tn = 200 s.

Refrigerant setting

Switch positions: 1=B, 2=R134a, 3=R404A and 4=R22

(“B” = particularly fluorinated refrigerants having a saturation pressure lower than

R404A. Please contact Danfoss.)

Factory setting = R22.

Setting of MOP (Maximum Operating Pressure)

Potentiometer for setting MOP is printed on the circuit board in the controller.

Scale 0 to 6 bar p

Factory setting: Point marking, i.e. without MOP function.

K max

The potentiometer is used for adapting the proportional bands of EKS 65 and TQ/

PHTQ to one another. An adjustment corresponds to a change of the valve’s inside

max. operating temperature (the pressure in the controller).

Adjustment to a higher value may be required, if there is large pressure drop through

the liquid distributor.

Lower value = colder valve = shorter P-band.

Higher value = warmer valve = longer P-band.

Warning! At a too high value the valve is heated more than necessary. When it has to

close later, the valve will react slowly (liquid flow/damage to compressor). The valve

will for example try to open more (heat), if there is inadequate subcooling of the liquid.

K max

MOP

Refrigerant

Running in and

adjustment

Electrical check

All electrical connections must be checked before the EKS 65 controller insert is

installed on the baseplate. A multimeter can be used for the purpose.

Supply voltage

The supply voltage must be 24 V a.c.

±10% and can be measured across

terminal 1 and 2.

If the secondary side of the transformer

is to be earthed, make the connection to

terminal 1 (N).

Actuator power circuit (PTC circuit)

The actuator power circuit can be

checked sing an ohmmeter across

terminal 77 and 78.

The resistance across the terminals must

be 8 to 30 ohm.

Actuator measuring circuit (NTC circuit)

The resistance across terminal 35 and 36

must be 100 ohm to 100 kohm.

Sensor circuit

The connection for temperature sensors

S1 and S2 must be checked as follows:

S1 to be checked across terminal 25 and

26.

S2 to be checked across terminal 24 and

25.

The resistance must correspond to the

resistance value of the Pt 1000 sensor at

the actual temperature and must not

exceed this value by more than 2 ohm.

Resistance values of Pt 1000

°C ohm °C ohm

0 1000.0 0 1000.0

1 1003.9 -1 996.1

2 1007.8 -2 992.2

3 1011.7 -3 988.3

4 1015.6 -4 984.4

5 1019.5 -5 980.4

6 1023.4 -6 976.5

7 1027.3 -7 972.6

8 1031.2 -8 968.7

9 1035.1 -9 964.8

10 1039.0 -10 960.9

11 1042.9 -11 956.9

12 1046.8 -12 953.0

13 1050.7 -13 949.1

14 1054.6 -14 945.2

15 1058.5 -15 941.2

16 1062.4 -16 937.3

17 1066.3 -17 933.4

18 1070.2 -18 929.5

19 1074.0 -19 925.5

20 1077.9 -20 921.6

21 1081.8 -21 917.7

22 1085.7 -22 913.7

23 1089.6 -23 909.8

24 1093.5 -24 905.9

25 1097.3 -25 901.9

26 1101.2 -26 898.0

27 1105.1 -27 894.0

28 1109.0 -28 890.1

29 1112.8 -29 886.2

30 1116.7 -30 882.2

35 1136.1 -35 862.5

40 1155.4 -40 842.8

45 1174.7 -45 822.9

50 1193.9 -50 803.1

Temperature differential S2 - S1

Setting

On starting the refrigeration plant, the reference knob S2 - S1 must be at 18°C.

When the plant is in balance S2-S1 must be reduced in steps of 2°C, until hunting

occurs in the system. S2-S1 must then be increased by 2°C and TQ/PHTQ is set.

Hunting can be observed in three ways:

a) Visually with a pressure gauge.

Hunting in the system will show itself on a pressure gauge.

Evaporating pressure and suction pressure will oscillate.

b) Observing the indicator lamps on the EKS 65.

Hunting in the system will be revealed by the indicator lamps flashing alternately

between SP (green) and SP (yellow).

c) With a voltmeter or line recorder connected to terminal 26 and 29.

When the system hunts, oscillations in the temperature differential S2 - S1 will

appear on the voltmeter or line recorder.

The output signal from the terminals is 100 mV/°C (0 V corresponds to 0°C).

Kp amplification factor (P-stage) and Tn integration time (I-stage)

Normally, the factory setting K

= 1 and T

= 200 s will be adequate. However, if

stable regulation cannot be obtained using the S2 - S1 setting, it might be necessary

to readjust K

and T

. Running-in and adjustment can be performed as follows:

Reduce S2 - S1 in steps of 2°C until the system hunts. Then increase S2 - S1 by 2°C

until the hunting stops.

This setting will be the best starting point for re-adjustment of K

and T

Fast and stable regulation can be obtained by increasing proportional amplification

factor K

and decreasing integration time T

. The changes must be made

systematically: change K

first and then T

. Between each change, observe the

reaction of the system. A step function must be performed every time K

and T

are

changed.

Step function is obtained by reducing S2 - S1 with 2°C and then immediately

increasing it back to its initial point.

The adjustment procedure is shown schematically above.

MOP, Maximum Operating Pressure

The upper limit for evaporating pressure can be set using the MOP knob. The

limitation on pressure set will be the pressure effective under the diaphragm of the

valve, i.e. where the equalising line is connected.

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Danfoss Electronic system for evaporator liquid injection User guide

Danfoss Electronic system for evaporator liquid injection User guide

Danfoss Electronic system for evaporator liquid injection User guide

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