Danfoss EKC 316A User manual

REFRIGERATION AND

AIR CONDITIONING

Controller for operation of

evaporator on water chiller

EKC 316A

Reference manual

2 Reference manual RS8ED102 © Danfoss 03-2006 EKC 316A

Contents

Installation ................................................................................3

AKS33 Pressure transmitter connected to two EKC316A .

controllers ........................................................................................ 3

Stepper motor Output ................................................................ 3

Output relay contacts .................................................................. 3

Settings and checks to be made before start. ........................4

Basic Settings .................................................................................. 4

Finding the optimum settings. ................................................6

Details on the controller algorithm and settings .............. 6

The regulation modes for controlling superheat .............. 6

Problems of start up ..................................................................... 7

Types of regulation. ..................................................................8

Manually operating the valve. .............................................. 11

Operating the valve manually from the EKC316A ..............

controller ........................................................................................11

Operating the valve manually by an extern analogue ......

signal ...............................................................................................11

Operating the valve manually by an extern analogue ......

signal with MOP active ..............................................................11

Battery back-up. .................................................................... 13

Troubleshooting. ................................................................... 13

Alarms .................................................................................... 14

References .............................................................................. 15

Installation

The EKC 316A is normally mounted on a DIN rail, and the neces-

sary connections are shown in the diagram. If the sensor S3 is not

used to measure air temperature in connection with thermostat

function or as part of the controlling loop, then it is not necessary

to connect the S3 sensor. The 18Volt battery input at terminals 5

and 6 is not required if battery back-up is not needed.

Data communication

< --------------- max. 5 m --------------->

Communication to controller is an option and can only be

achieved by inserting the data communication module EKA 174 or

EKA 175 in the EKC 316A controller. EKA 174/175

EKC 316A Reference manual RS8ED102 © Danfoss 03-2006 3

The maximum length of cable between EKC 316A and the ETS

valve is ﬁve meters. If cable lengths are in excess of this value then

it is recommended to use an inductive ﬁlter.

AKS 33 Pressure transmitter connected to two EKC 316A

controllers

An AKS33 pressure transmitter can be connected up to two EKC

316A controllers.

In case of problems the following checks can be made:

1) Ensure that the voltage between terminals 14 and 16 is

approximately 14.5 Volts.

2) Check that the resistance between terminals 15 and 16 is 100

Ohms.

3) If there are problems in connecting the AKS 33 and EKC316A

controllers as shown above, disconnect the controller to the

right and place a 100 Ohms resistor between the wires that

were previously connected at terminals 15 and 16. Check that

the pressure reading in the controller to the right is correct. If

there are still problems and assuming that checks 1) and 2) have

been carried out, check the connections to the AKS 33.

Stepper motor Output

After installation the following checks can be made to the connec-

tion between the EKC316A controller and the stepper motor of

the ETS valve.

1) With the power oﬀ, check that resistance between terminals

21 and 22 and terminals 23 and 24 is approximately 53 Ohms.

Make slight allowances for cable resistance.

2) With the power on and parameter o18 set to 1, measure the

phase current from terminals 21 (or 22) and terminals 23 (or 24)

with a true RMS multimeter when the valve is operating. The

valve can be driven from 0% to 100% and vice versa by chang-

ing valve opening percent in parameter o45. The phase current

should be 70 mA rms when operating.

Remember to set o18 back to 0 after checks.

3) If the checks 1) and 2) are not correct, ensure that motor cable

corrections are correct and the cable length is less than ﬁve

meters (see section 1 )

Output relay contacts

The two output relays in the controller are respectively the relay

for starting refrigeration and alarm relay. Ensure the following

action:

1) The contact for refrigeration will be made when the superheat

regulation in the controller starts operating. The contact will be

broken if the regulation cannot start or is stopped.

2) The contact of the alarm relay will be made when there is an

alarm.

To ETS Valve

Filter

4 Reference manual RS8ED102 © Danfoss 03-2006 EKC 316A

Basic Settings

Before using the EKC 316A controller, there are settings that

have to be made for each individual application. These are the

refrigerant type, the pressure transducer range and the total

number of steps for the ETS valve. It is good practice and some

cases necessary to set the Main Switch r12 to OFF when making

these changes.

Refrigerant Type.

It is possible to choose from a list of 28 diﬀerent refrigerants in the

controller. If refrigerant is not found on the list, it is possible using

AKM and setting o30 to 13 to plug in the Antione constants for the

unlisted refrigerant.

Setting and checks to be made before

start

Refrigerant setting

Before refrigeration can be started, the refrigerant must be deﬁned. You can select the

following refrigerants:

1=R12. 2=R22. 3=R134a. 4=R502. 5=R717. 6=R13. 7=R13b1. 8=R23. 9=R500.

10=R503. 11=R114. 12=R142b. 13=User deﬁned. 14=R32. 15=R227. 16=R401A.

17=R507. 18=R402A. 19=R404A. 20=R407C. 21=R407A. 22=R407B. 23=R410A.

24=R170. 25=R290. 26=R600. 27=R600a. 28=R744. 29=R1270.

(Warning: Wrong selection of refrigerant may cause damage to the compressor).

o30 Refrigerant

ETS Valve type

Each ETS valve has a speciﬁed number of steps as given below:

Total steps ETS 50: 2625 [+160 / -0] steps

ETS 100: 3530 [+160 / -0] steps

ETS 250 and 400: 3810 [+160 / -0] steps

The parameters ”n37” to ”n42” are settings for step motor ETS 100. The settings

in n37 must be changed when another valve is used. The other settings should

not be changed.

Number of steps from 0% to 100% open n37 Max. steps (0 - 5000 step)

The number of steps can be set in the controller at address n37:

”n37” to ”n42” are adapted to valve type ETS 100 and should only be changed through the

use of another valve.

Number of steps from 0-100% opening degree (x10)

(ETS = 262. ETS 100 = 353) n37 000 stp** 5000 stp ** 263

In practise, the EKC316A display can only manage 3 digits.

Therefore the set value at address n37 is always 10 times greater

i.e. if n37 is set to 263 then the true value is 2630. The same applies

to the n37 address in the AKM system.

Working range for pressure transmitter

Depending on the application a pressure transmitter with a given working range

is used. This working range (say, -1 to 12 bar) must be set in the controller. The min.

value is set.

o20 MinTransPres.

The max. value is set o21 MaxTransPres.

The range of the pressure transmitter can be set by entering the

transmitter’s minimum value at address o20 and maximum value

at address o21.

EKC 316A Reference manual RS8ED102 © Danfoss 03-2006 5

Compensation value for spindle play at valve’s closing point (number of steps) n39 Start bcklsh (Menu=Danfoss only)

Compensation value for spindle play during operation (number of steps) n40 Backlash (Menu=Danfoss only)

Valve deﬁnition

1=Valve must open when more capacity is required (NC function)

2=Valve must close when more capacity is required (NO function)

n41 Valve type (Menu=Danfoss only)

Compensation direction

1=Compensation takes place when the valve opens (normal setting)

2=Compensation takes place when the valve closes

n42 Comp.dir. (Menu=Danfoss only)

Backlash Compensation

The controller includes a procedure for compensating for

backlash on the ETS valve spindle. The parameters involved in this

procedure are listed below

These parameters should not be changed and the reason the

parameters are accessible is only historical, and at some point will

be withdrawn from the menu.

6 Reference manual RS8ED102 © Danfoss 03-2006 EKC 316A

Details on the controller algorithm and settings

Kp factor and Kp min

The Proportional Gain is dependant on the value of the measured

superheat SH relative to Reference superheat SH ref. The Propor-

tional Gain has the following values relative superheat SH:

If SH is more than 2.5K greater than SH ref then Gain equals Kp

factor.

If SH is within the range 2.5K and -0.5K from SH ref, then Gain

equals Kp factor times Kp min.

The reason for this variable Gain is to give stabile superheat for

values near the superheat reference.

Note the value of Gain does not change suddenly but gradually

when SH gets close to SH ref.

Initial start-up “Kick start”

In general the valve opening degree is controlled by the measured

value of the superheat SH. This means that during certain situa-

tions during start up, the valve will be slow to open due to the

built of superheat from a small value. To prevent this happening,

the valve is given an initial opening degree dependant on the Kp

factor, the measured superheat SH and SH closes as given in the

following relationship:

Initial OD% = kp factor*(SH – SH close)

The regulation modes for controlling superheat

There two diﬀerent ways of controlling superheat i.e. control-

ling according to the minimum stable superheat (MSS) and Load

Deﬁned superheat.

The parameter SH mode selects the controlling form where it can

be set to MSS when set to 1, or Load Deﬁned superheat when set

to 2.

SH mode = 1

The superheat reference SH ref is adaptive adjusted

The diagram shows how the SH ref is decreased 0.1 K every 30

seconds until instability in SH is detected. The SH ref will continue

increase at 0.1 K every 30 seconds until stability is achieved again.

More less the same behaviour will continue as shown where the

operation is attempting to ﬁnd the minimum stable superheat.

When using this form of control, there are three settings that have

major aﬀect on this mode of control

Finding the optimum settings

SH ref

Kp factor multiplied by Kp min

Kp factor

Proportional Gain

-0.5

2.5

Kp factor * (SH – SH Close)

OD %

Time

START

When Kp factor = 3, SH = 12, SK Close = 2

Initial OD % = 30%

SH_ref

EKC 316A Reference manual RS8ED102 © Danfoss 03-2006 7

Max SH – The maximum limit of SH ref.

Min SH – The minimum limit of SH ref. Care should be taken not to

set value too low in order to avoid ﬂooding back in the

compressor.

Stability – This factor determines how much instability can be

accepted. Small values will cause the SH ref to increase

if the slightest instability in SH is detected. Conversely,

higher values will accept a higher degree of instability.

SH mode = 2

SH ref follows a deﬁned curve as shown below. This curve is deﬁ-

ned by three values: SH close SH max and SH min.

This form of regulation is similar to the thermostatic valve where

the spring force can be adjusted to keep the SH (superheat) in the

stable region to the right of the curve.

The advantage over the thermostatic valve is that there are three

settings to deﬁne the operating curve.

Problems of start up

Sometimes in one to one applications, the valve does not open

suﬃciently on start-up, and troublesome low pressure trips hap-

pen. This problem is typical when using the single loop control

where the only the SH controls the opening of valve.

The force opening of valve function has been implemented in the

EKC 316A controller. This is not stated in the controller manual,

but please be aware that this function will give after start up, a

constant set minimum opening degree during a set time period,

without any regard to the superheat value. The setting parameters

are called Start OD% (n17) and StartUp time (n15), and are found

in the For Danfoss only menu in AKM and also in the EKC 316A

controller.

Please observe that the Start OD% is a minimum value after start

up and if the measured superheat (u21) produces a value greater

than Start OD% then this value will be valve opening degree (u24)

- see diagram.

8 Reference manual RS8ED102 © Danfoss 03-2006 EKC 316A

Types of regulation

Single Loop (address o56 Reg.type = 1)

The EKC 316A has the traditional PI controlling function with the

Kp factor for Proportional Gain and Tn for Integration Time in se-

conds. This also is known as the Single loop control with only one

PI block as shown in the diagram below.

Evaporator Temp. S1

PI Control

Refrigerant Temp.

Superheat Ref.

SHref

Superheat

(S2 – S1)

ETS Valve

Evaporator

Kp factor and Tn settings

Instability cause by too much Proportional Gain can be corrected

by reducing to value of the Kp factor. This should be done redu-

cing with small steps at a time and observing the results before

making further reductions.

If the superheat response is slow to changes, it can be increased

by reducing the value of the Integration Time Tn.

When tuning the superheat stability, it is good practise to have a

ﬁxed superheat reference by making SH max the same as SH min.

EKC 316A Reference manual RS8ED102 © Danfoss 03-2006 9

Double Loop (address o56 Reg.type = 3)

The controller can regulate the superheat using a double loop

system. The so called outer loop is really the same as in the single

loop system except output of PI block is the reference for the inner

loop.

The inner loop also has also PI block with Proportional Gain factor

is KpT0 and the Integration Time is TnT0.

The double loop control system is shown in the diagram below.

Evaporator Temp. S1

PI Control

Refrigerant Temp. S2

Superheat Ref. SHref

Superheat

(S2 – S1)

Evaporator

ETS Valve

PI Control

(S3 – S1)

Kp factor and Tn settings KpT0 and Tn T0 settings

The feedback of the inner loop is temperature diﬀerence between

media temperature S3 and S1. This value represents the load on

the evaporator and large values will tend to increase the opening

degree OD% of the valve.

The tuning of the double loop is more complicated than the

single loop and it is advisable not change to many parameters at

the same time. The starting point should be to use the following

settings.

Parameter Value Address

Kp factor 0.7 n04

Tn sec 120 n05

KpT0 3 n20

TnT0 sec 30 n44

If the superheat is unstable, the KpT0 parameter should be slightly

reduced. The value parameter Kp factor is not large so little is gain

by reducing this parameter.

10 Reference manual RS8ED102 © Danfoss 03-2006 EKC 316A

When to use Single or Double loop

In most applications and especially air coolers, the single loop is

the best option because of simplicity and easier to tune.

In water chillers where the S3 sensor is located at the leaving wa-

ter outlet, the double loop gives some advantages in terms of be-

ing less susceptible to compressor or fan step changes. Further, it

gives a quicker opening of the valve during start up. However the

double loop is less advantages on air coolers of slower response of

the media temperature.

NOTE

The settings Atten.factor (address n43) and Min.Lim.Ref (address

n45) should not be changed without the help of trained staﬀ.

The S3 sensor has to be connected when Reg.type = 3, or else an

alarm is given.

Recommended control loop type and settings for some ap-

plications

From the experience of using single loop and double regulation,

the following recommendations are given for the applications

that EKC 316A has been used in. These are only recommendations

and the ﬁnal choice is made by the end user.

Application Reg. type Kp factor Tn sec Kp T0 TnT0 sec

address n56 address n04 address n05 address n20 address n44

Air cooler 1 (Single loop) 3.0 120 0.4 -

Water chiller 3 (Double loop) 0.7 120 2.0 30

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