Danfoss AK-PC 420 User manual

Capacity controller for dry cooler
AK-PC 420
User Guide
ADAP-KOOL®Refrigeration control systems

2 Manual RS8EL402 © Danfoss 03-2010 AK-PC 420
Introduction
Application
The controller is used for capacity regulation of a dry cooler
including fans, three-way valve and pumps.
Advantages
• Complete dry cooler control
• Several combination options for sensor selection
• Heat recovery acc. to external voltage signal.
Regulation
Capacity regulation can include fans combined with a three-way
valve or just fans. The following sensor signals can be used in
regulation:
• Condensing pressure Pc
• Brine temperature S7, located immediately after the three-way
valve outlet
• Brine temperature S8, located by the outlet from the dry cooler
• Outdoor temperature sensor Sc3, located by the air inlet to the
dry cooler.
• Either S7, Pc or S8 can be used as a regulation sensor.
Functions
• Three-way valve control
• Speed regulation or step-by-step coupling of up to six fans
• Safety monitoring of fans
• Overriding of reference acc. to external voltage signal or outdoor
temperature
• Separate reference for heat recovery
• Control and monitoring of twin pumps
• Monitoring of ow switch
• Contact inputs to alarms
• External start/stop of regulation
• Data communication via extra module
Operation
All operation takes place either via data communication or via
connection of a display type EKA 164 .
Contents
Introduction ....................................................................................................... 2
Function............................................................................................................... 3
Survey of functions.......................................................................................... 8
Operation ..........................................................................................................13
Menu survey.....................................................................................................14
Connections .....................................................................................................16
Data.....................................................................................................................17
Ordering ............................................................................................................17
Montage ............................................................................................................17
Appendix - Reference and regulation.....................................................18

AK-PC 420 Manual RS8EL402 © Danfoss 03-2010 3
Function
Application
Regulation sensor and system type are selected via one single set-
ting. The setting will dene both the regulation sensor, if a three-
way valve is being used, and how the fans are to be controlled.
The fans are controlled either in steps or together with a speed
control. If steps are used, up to six fans can be controlled.
Regulation
(o61)
Regulation
sensor
Optional
sensor
3-way
valve
Fan
control
1 S7 S8 (P + PI) x Step
2 S7 S8 (P + PI) x Speed
3Pc S7 / S7+S8 (PI) x Step
4Pc S7 / S7+S8 (PI) x Speed
5 S8 Step
6 S8 Speed
Application 1-4
The capacity here is controlled via the fans combined with a three-
way valve.
Applications 1 and 2 use brine return temperature S7 at the
three-way valve outlet as regulation sensor and the fan capacity is
controlled either in steps or via speed control.
The S8 sensor, which is tted to the dry cooler’s outlet should be
used in the control if there is a large distance between the dry
cooler and the three-way valve. Use of the S8 sensor will provide
more robust regulation, which takes long pipe lengths into ac-
count. The S8 sensor must be tted close to the dry cooler’s outlet.
Applications 3 and 4 use brine condensation pressure Pc as regula-
tion sensor and the fan capacity is controlled either in steps or via
speed control.
For PI control the use of the S7 and S8 sensors is optional but they
should be tted if there is a large distance between the dry cooler
and the three-way valve. Use of the sensors will provide more
robust regulation, which takes long pipe lengths into account. The
S8 sensor must be tted close to the dry cooler’s outlet.
For P control the S7 and S8 sensors are not used in the regulation,
but they can be tted to ensure that the emergency control func-
tions in the even of the Pc signal failing.
Applications 5-6
Here the capacity is controlled via step-by-step coupling or speed
control on the basis of the dry cooler’s discharge temperature S8.
This application is used in particular when another controller takes
care of the regulation of the three-way valve, e.g. to cool several
parallel-coupled condensers.
NB.
The sensors Pc and S7 must not be located in positions other than
those specied, as they are used for emergency regulation if the
primary regulation sensor develops a fault.
The S8 sensor can be located in a dierent position than the one
indicated if it is not used in the control.
If the S8 sensor is required in the control, the setting "o96, S8
optional" must be selected as ON.
If the S8 sensor is not used in the regulation, it can be located
anywhere.

4 Manual RS8EL402 © Danfoss 03-2010 AK-PC 420
Capacity regulation
Three-way valve + step-by-step coupling of fans (applications 1 and 3)
Capacity regulation takes place via a P or PI regulation, which con-
trols the three-way valve and subsequent step-by-step coupling of
the fans.
First of all regulation takes place on the three-way valve via the an-
alogue output. The output can be set at 0-10 V or 10-0 V, depend-
ing on which valve function is desired. Only when the three-way
valve is fully open do the fans start up.
The capacity of the three-way valve is 50% of the total capacity.
The P/PI controller has separate regulation settings (proportional
band and integration time) for the three-way valve and the fans
respectively.
Capacity overlap – start of fans
As mentioned above, the three-way valve comprises a xed 50% of
the total capacity. In some systems it may be necessary to start the
fans slightly before (or slightly after) the three-way valve has been
fully opened. An overlap is created here between the three-way
valve and the start of the fans. This is done by changing the setting
“FanCap OFF%” from 50% to, for example, 40% (the setting denes
the capacity at which the last fan stops). In this case the fans are
started before the three-way valve is fully open.
Three-way valve + speed control of fans (applications 2 and 4)
Capacity regulation takes place via a P or PI regulator, which
controls the three-way valve and subsequent speed control of
the fans. Here the analogue output signal is divided between the
three-way valve and the frequency converter (50% of the ana-
logue output signal is always used for the three-way valve), i.e.
if the analogue output signal is set at 0-10V, 0-5 V is used for the
three-way valve.
The frequency converter/fans are controlled via the relay output
for fan 1 on the basis of the setting“FanCapOFF%”.
In the event of falling capacity, the relay output for fan 1 will be
disabled when the actual capacity has fallen to “FanCap OFF%”.
To achieve hysteresis when starting/stopping the frequency con-
verter, the relay output for fan 1 will, when capacity is increasing,
be enabled when the desired capacity is “FanCap OFF%” + “10%
fan capacity”.
If “FanCapOFF%” is set at above or below 50%, the frequency
converter can be started after or before the three-way valve is fully
opened.
The P/PI controller has separate regulation settings (proportional
band and integration time) for the three-way valve and the fans
respectively.
Fan control only (applications 5 and 6)
Capacity regulation takes place via a P or PI regulator, which con-
trols the fans either with step-by-step coupling or speed control.
The analogue output and a frequency converter are used for
speed control. The relay output for fan 1 is used to start/stop the
frequency converter.
In the event of falling capacity, the relay output for fan 1 will be
disabled when the actual capacity has fallen to “FanCap OFF%”.
To achieve hysteresis when starting/stopping the frequency con-
verter, the relay will become enabled when the desired capacity
is the fan capacity above “FanCap OFF%” (The 10% fan capacity
will correspond to hysteresis of 1 V in the analogue output signal,
when the signal is 0-10 V.)
The P/PI controller only uses regulation settings (proportional
band and integration time) for the fans.

AK-PC 420 Manual RS8EL402 © Danfoss 03-2010 5
Linear/non-linear capacity curve for fans
The rst fan step provides relatively more capacity than the subse-
quent capacity steps. The increase in capacity that an extra step/
speed will generate falls gradually, as more and more steps are
connected/the speed is increased.
The fan regulation therefore has a crooked capacity curve, which
provides optimal reinforcement at both high and low capacities.
However, for some systems a straight curve is required for capacity
regulation, e.g. if the analogue signal is used for more than con-
trolling fans. In this instance the capacity curve can be set at linear.
(The capacity curve for the three-way valve will always be straight.)
Step-by-step coupling of fans
The fans can either be connected in the sequence dened for
them (sequentially) or they can be connected in rotation (sequen-
tially with alternating start).
In sequential operation all fans are enabled at least once every 24
hours, so no fan rusts up due to being inactive for a longer period
of time.
In rotation the various fans take turns in being rst.
Monitoring fans
The controller must receive a signal of the status of each dened
condenser step’s safety circuit. The signal is taken directly from the
safety circuit and connected to a“DI” input.
If the safety circuit is broken, the controller will lose the signal and
emit an alarm.
The associated relay output will not be disconnected. The reason
is that fans are often connected in pairs, but with one single safety
circuit. If there is a fault in one fan, the other will continue to oper-
ate.
If no monitoring is desired, the input must be permanently wired
at 24 V.
Reference
Regulation reference
The regulation reference can be dened in one of the following
two ways:
• Fixed setting
The set point for the regulation sensor is set in °C.
If displacement is required, the reference can be displaced
with a 0-10 V signal. During setup you dene how great the
displacement is to be at the signal’s max. and min. value.
• Floating reference according to outdoor temperature
This function allows the reference to vary according to the
outdoor temperature within a dened range.
The outdoor temperature is measured with the Sc3 sensor,
and the reference will always fall within a xed value (min. tm)
above the measured outdoor temperature.
Heat recovery
When heat recovery is enabled via the digital input, the reference
will switch to another set point“Heat SP”, although this too can
be overridden via the external 0-10 V signal. At the same time the
relay for heat recovery is enabled, which then transmits a signal to
either a pump or a valve. The reference's max. value (r30) is over-
riden from the set value to 99.9° C.
If heat recovery is in progress and the temperature by the regula-
tion sensor is lower than the reference’s set minimum value, the
following happens (see also the following section on limiting the
reference):

6 Manual RS8EL402 © Danfoss 03-2010 AK-PC 420
The heat recovery relay is disconnected and can only be re-ena-
bled once the temperature by the regulation sensor has reached 2
K above the reference’s minimum setting.
Ramp function
To avoid overswing and underswing of the reference, a ramp
function has been included to guarantee that the reference cannot
change more quickly than the preset ramp in Kelvin/minute.
Limitation of reference
To protect against regulation reference that is too high or too low,
a limit must be set for the reference. The limit is valid under normal
regulation, but is increased during heat recovery to 99.9° C.
The upper limit is always an absolute value. The lower limit can
either be an absolute value or it can vary in accordance with the
outside temperature Sc3 whereby the limit has a xed value ("r56,
Min tm") above the outside temperature. This means that a refer-
ence below the minimum value, making all fans run continuously,
can be avoided.
P or PI regulation with oating or xed reference
See appendix.
Safety functions
Monitoring of condensation pressure
The controller has a safety function that provides protection
against the condensation pressure being too high.
The function can be enabled in two ways.
• Digital input - HP safety
When the digital input is connected, full capacity is cut in to
both fans and three-way valve. An alarm is emitted at the same
time.
The capacity remains cut in until the digital input is inter-
rupted, at which point the alarm is also cancelled. The digital
input can possibly be connected to an external safety pressure
control.
• Measuring the Pc/S7 temperature
This function always uses condensation pressure Pc if the
pressure signal is connected. If Pc is not tted, brine return
temperature S7 is used instead.
The function cuts in all condenser steps and emits an alarm
if the measured temperature is higher than 3 K below the set
limit “S7/Pc max”.
Normal capacity regulation is restored when the temperature
(pressure) has once more fallen to 3 K below the limit, and a
delay time of 60 seconds has passed.
Pump controL
The controller can control and monitor one or two pumps that
circulates the brine.
If two pumps are used and operating time equalisation is selected,
the controller can also execute a switch between the two pumps if
operating alarms occur.
Pump selection is performed using the following settings:
0: Both pumps are stopped
1: Pump 1 is started
2: Pump 2 is started
3: Both pumps are started
4: Automatic switch between the pumps is permitted. Start before
stop
5: Automatic switch between the pumps is permitted. Stop before
start
Ref. Max.
Ref. Max.
Ref. Min.
Ref. Min.

AK-PC 420 Manual RS8EL402 © Danfoss 03-2010 7
Automatic switch between the pumps. Start before stop
(only for setting = 4)
This setting allows a rotation between the two pumps, enabling a
kind of operating time equalisation. The period time between the
pump switches can be set as “p37 PumpCycle”.
When switching, the pump will be kept running for the time “p36
PumpDel” until it stops.
Automatic switch between the pumps. Stop before start
(only for setting = 5)
This setting allows a rotation between the two pumps, enabling a
kind of operating time equalisation. The period time between the
pump switches can be set as “p37 PumpCycle”.
When switching, the pumps will be stopped in the time "p36
PumpDel".
Monitoring pumps
The controller monitors the pumps’operation via the safety input
“Flowswitch”. The signal may, for example, originate from a pres-
sure dierence pressure switch or a ow switch.
Also set a delay time to dene how the alarm is to be activated.
The delay time is the time from when the input loses the signal
until the controller emits an alarm and executes a pump switch if
necessary.
Special information about operating time equalisation
If the pumps are operating with operating time equalisation, the
controller can perform a switching of the pumps in the event of
a lack of ow (however, the pump switch will only be performed
when the delay time on the alarm has expired).
Depending on whether the pump switch recties the alarm situa-
tion or not, the following happens:
1) The pump switch recties the alarm situation
If the pump switch recties the alarm situation, the non-faulty
pump, which is now in operation, will run until the normal cycle
time has expired. It then switches back to the“faulty pump”, as
it is assumed that this has been repaired. At the same time the
alarm situation is reset (the alarm is acknowledged).
If the “faulty pump” has not been repaired, another alarm will be
triggered and cause one more switch to the non-faulty pump.
This is repeated until the situation has been rectied.
2) The pump switch does not rectify the alarm situation
If, however, the alarm is still active after the pump switch, the
controller will also emit an alarm for the other pump. At the
same time both pump outputs are enabled in an attempt to
create sucient ow for the alarm situation to be rectied. The
controller will then have both pump outputs enabled until the
normal cycle time has expired. A normal pump switch is then
conducted and the active alarms are reset.
Separate alarm priorities can be set for the failure of one pump
and the failure of both pumps. See section entitled “Alarms and
messages”.

8 Manual RS8EL402 © Danfoss 03-2010 AK-PC 420
Survey of functions
Function Para-
meter
Parameter by operation via
data communication
Normal display
If the two displays are mounted:
The regulation temperature is displayed on EKA 164 (the one with buttons) (Pc or S7
or S8)
Pc will be shown on EKA 163. Both readouts will be in temperature
S7 °C
Pc °C
S8 °C
Reference Condenser control
Unit
Here you can select whether the display is to indicate temperatures in °C or °F
0: Will give °C / bar
1: Will give °F / psig
r05 Unit
(In AKM only °C is used, whatever the
setting)
Start/stop of refrigeration
Start/stop of refrigeration may also be performed with an external contact function
connected to the input named “ON input”. (The input must be wired).
r12 Main Switch
Set point
When “r33 ctrl.mode”is set at 1 or 3, it is regulated according to the set value + a pos-
sible displacement from a 0-10 V signal.
See also page 18.
r28 Set Point °C
Reference variation. See also page 18.
Regulation with setting 1 (or 2 if the reference is to vary with the outdoor tempera-
ture) will give the best regulation if the system is in balance. But if a lot of fans are
connected, it may be necessary to select setting 3 instead (or 4, if there is regulation
with the outdoor temperature). (Settings 3 and 4 will generally be preferable if a o-
set can be accepted between the reference and the actual regulation temperature)
1: No change of the reference. Regulation based on set setpoint + displacement with
a 0-10 V signal.
If there is a heat recovery signal, the reference will switch to the preset set point in
"r64".
2: Outdoor temperature forms part of the reference. The outdoor temperature is
measured with Sc3 sensor and the reference will always have a xed value “r56 Min
tm K” over the measured outdoor temperature.
If there is a heat recovery signal, the reference will switch to the preset set point in
"r64".
Setting 1 and 2 operate with a PI regulation, but if the system is unstable and the PI
regulation not satisfactory the I element may be left out, so that the controller will be
with P regulation only.
3: As 1, but with P regulation (xp-band)
4: As 2, but with P regulation (xp-band)
5: As for 1, but with a minimum reference limit in accordance with outdoor tempera-
ture Sc3
6: As for 3, but with a minimum reference limit in accordance with outdoor tempera-
ture Sc3
r33 Ctrl. mode
Reference
The regulation reference is shown here.
r29 Ref. °C
Set point limitation
With these settings the setpoint can only be set between the two values.
(This also applies to regulations where the Xp band lies above the reference).
Max. permissible setpoint value. (Is set as an absolute value) r30 RefMax °C
Min. permissible setpoint value. (Is set as an absolute value when "r33" = 1-4) r31 RefMin °C
Correction of pressure measurement Pc
An oset adjustment of the registered pressure can be made.
r32 AdjustPc
Dimensioning temperature Min tm
The mean temperature dierence across the condenser at low capacity (tm dier-
ence at max. load). This is the temperature dierence between the air and condensing
temperature.
When “r33 Ctrl. Mode” is set at 2 or 4, regulation takes place according to a reference
that is “Min tm” over the measured outdoor temperature.
r56 Min tm K
Reading of regulation temperature
This is where you can see the actual temperature being measured by the sensor cho-
sen for capacity regulation. The value is displayed in °C.
r58 Ctrl temp
Set point value for heat recovery
When a heat recovery signal is received, regulation takes place according to the value
set here + any displacement via 0-10 V signal.
r64 Heat SP°C
Average value for reference changes
A switch in the reference will be ramped up or down over this period of time. Set in
Kelvin/minute.
r65 RefRamp

AK-PC 420 Manual RS8EL402 © Danfoss 03-2010 9
Reference displacement at max. signal (Ext. ref.)
Here the value is set by which the reference is to be displaced when the input signal
Ext. ref. is max. (10 V).
r68 ExtRefMax
Reference displacement at min. signal (Ext. ref.)
Here the value is set by which the reference is to be displaced when the input signal
Ext. ref. is min. (0 V).
r69 ExtRefMin
Correction of signal from S7
Compensation possibility due to long sensor cable
r72 Adjust S7
Correction of signal from S8
Compensation possibility due to long sensor cable
r73 Adjust S8
Condenser capacity Condenser cong.
Denition of condenser and number of fans (may only be set if step-by-step
coupling is being run, i.e.“o61 Applic mode” is set at 1, 3 or 5).
Here you set how many fan steps are to be used for regulation (to max. 6).
1-6: All fans are connected with relays. Relay 1 is assigned fan 1, the next one number
2, etc.
7-10: Not used
11-16: Total number of fan relays (as 1-6), but here the starting sequence is altered
after each time all fans have been stopped.
NB
The controller must receive a signal of the status of each condenser step’s safety
circuit. The signal must be connected to the associated DI input.
c29 Fan mode
Denition of output voltage to valve/speed control
Output signal is 0-10 V or 10-0 V. The signal can be either linear or un-linear, so that it
can be adapted to the desired characteristics.
1: 0-10 V, linear
2: 10-0 V linear (not at shunt and fan speed)
3: 0-10 V, unlinear
4: 10-0 V unlinear (not at shunt and fan speed)
c34 AO type
- - - - Cond Cap %
Read cut-in condenser capacity
Regulation parameters
Proportional band xp for valve regulation (P = 100/Xp)
If the Xp value is increased, the regulation becomes steadier
n04 Valve Xp K
I: Integration time Tn for valve regulation
If the Tn value is increased, the regulation becomes steadier
n05 Valve Tn s
Manual control of condenser capacity
This sets the capacity that is to be cut in when switching to manual control.
n52 ConManCap%
Manual control
Manual control of the condenser capacity is enabled here.
When set to ON, the capacity that is specied in “n52”is cut in.
The setting will fall back to“O” if the Main switch is set to O or if there is a power
outage.
n53 ConManCap
P: Proportional band xp for fan regulation (P = 100/Xp)
If the Xp value is increased, the regulation becomes steadier
n60 Fan XP K
I: Integration time Tn for fan regulation
If the Tn value is increased, the regulation becomes steadier
n61 Fan Tn s
Capacity overlap between valve and fans
In valve regulation the rst 50% of the capacity is controlled by the valve. When the
valve is fully open continues with fan cut-in.
The fans then take over.
If the fans are to start before the three-way valve is fully open, a value must be set
that is lower than 50%.
If the fans are only to start after the three-way valve is fully open, a value must be set
that is higher than 50%.
n62 FanCap OFF %
Alarm Alarm settings
The controller can give alarm in dierent situations. When there is an alarm the light-
emitting diodes (LED) will ash on the display and the alarm relay will cut in.
Pc max. (Alarm and safety function, see also page 18.)
Here you set when the alarm at too high condensing pressure is to enter into eect.
The value is set as an absolute value.
A30 Max. Pc. / S7
Alarm delay DI1 (an interrupted input will give alarm).
The time delay is set in minutes. At min. setting the alarm is cancelled.
A27 DI1AlrmDelay

10 Manual RS8EL402 © Danfoss 03-2010 AK-PC 420
Alarm delay DI2 (an interrupted input will give alarm).
The time delay is set in minutes. At min. setting the alarm is cancelled.
A28 DI2AlrmDelay
Alarm delay DI3 (an interrupted input will give alarm).
The time delay is set in minutes. At min. setting the alarm is cancelled.
A29 DI3AlrmDelay
Pump alarm delay
The time delay is set in seconds. At min. setting the alarm is cancelled.
A63 Pump Al. Del
Give the top button a brief push to zeroset the alarm and to have the message shown
on the display.
Reset alarm
The function zerosets all alarms when
set in pos. ON.
With data communication the impor-
tance of the individual alarms can be
dened. Setting is carried out in the
“Alarm destinations” menu.
Miscellaneous Miscellaneous
Choice of application
The regulator can be congured in various ways. The application that is required out
of the six applications available is set here.
1: S7 + 3-way valve + Step of fans
2: S7 + 3-way valve + VSD (speed) of fans
3: Pc + 3-way valve + Step of fans
4: Pc + 3-way valve + VSD (speed) of fans
5: S8 + Step of fans
6: S8 + VSD (speed) of fans
o61 Applic.Mode
Sensor type (Sc3, S7 and S8)
Normally a Pt1000 sensor with great signal accuracy is used for temperature measure-
ment. But a PTC sensor may also be used (r25 = 1000) in special situations.
0=Pt1000
1=PTC1000
o06 Sensor type
Pressure transmitter’s working range
Depending on the pressure, a pressure transmitter with a given working range is
used. This working range must be set in the controller (e.g.: -1 to 34 bar
The values must be set in bar if display in °C has been selected. And in psig, if °F has
been selected.
If the values are to be set from the
AKM programme, they must be set in
bar.
Pc-Min. value o47 PcMinTrsPres
Pc-Max. value o48 PcMaxTrsPres
Use of DI4 input
The digital input can be connected to a contact function, and the contact can now be
used for one of the following functions:
Setting / function:
0: DI input not used
1: Safety signal from high-pressure pressure control. If the signal is cut o, all capacity
is cut in. There is no time delay.
o22 DI4 control
Operating hours
The operating hours for the pomp relays can be read and set in the following menus.
The read value is multiplied by 1000 to obtain the number of hours (fx. shows 2.1 for
2100 hours). On reaching 99.9 hours the counter stops and must now be reset to, say,
0. There will be no alarm or error message for counter overow.
(In the AKM display the hour number
has not been multiplied)
Value for relay number 7 (pump 1) o52 DO7 run hour
Value for relay number 8 (pump 2) o53 DO8 run hour
Refrigerant setting (only if a Pc pressure transmitter is tted)
Before refrigeration is started, the refrigeration must be dened. You may choose
between 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 dened. 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. 30=R417A.
31=R422A. 32=R413A. 33=R422D. 34=R427A. 35=R438A.
Warning: Wrong selection of refrigerant may cause damage to the compressor.
Other refrigerants: Select setting 13 here, and subsequently three factors have to be
set – fac1, fac2 and fac3 – via AKM.
o30 Refrigerant