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%
0
2
4
6
8
10
12
14
16
18
SH
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.
S2
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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