Danfoss AK-PC 520 User guide

User Guide

Capacity controller

AK-PC 520

ADAP-KOOL® Refrigeration control systems

Introduction

Application

The controller is used for capacity regulation of compressors or
condensers in small refrigerating systems.
There are eight outputs and up to 4 compressors and 4 fans can
be coupled.

Advantages

• Energy conservation during:

- Suction pressure optimisation (P0)

- Variable condensing pressure (Pc)

• Patented neutral zone regulation

• Many possible combinations for compressor constellations

• Sequential or cyclic operation

• Possibility of suction pressure optimisation via the data commu­nication

Regulation

Regulation is based on signals from one pressure transmitter for
the compressor regulation and one pressure transmitter for the
condenser regulation plus one temperature sensor for the air
temperature before the condenser.
The two pressure transmitters can be replaced by two
temperature sensors when regulation has to be carried out on
brine systems.

• Pressure regulation P0 (pack)

• Temperature regulation Sx (chiller)

• Pressure regulation Pc (pack / chiller)

• Pressure regulation with variable reference Pc (Sc3)

Functions

• Relays for compressor and condenser regulation

• Voltage output for capacity regulation of condenser

• Status inputs. An interrupted signal indicates that the safety
circuit has been activated and the respective circuit stopped

• Contact inputs for indication of alarms

• Contact inputs for displacement of references or for indication of
alarms

• Alarm relay

• External start/stop of regulation

• Possibility of data communication

Operation

All operation takes place either via data communication or via
connection of a display type EKA 164 or EKA 165.

Combinations

The controller has ten relay outputs two of which have been
reserved for the alarm function and for the ”VLT start/stop”
function.
For a start relays are reserved for compressor capacities starting
from DO1, DO2, etc.
The next relay and the following will be for fans (max. 4 fans).
Another solution could be that the fan speed is controlled via the
analog output and a frequency converter.

Compressors and unloaders can
be combined in various ways. Cf.
survey on page 11.

Contents

Introduction ....................................................................................................... 2

Function ............................................................................................................... 3

Survey of functions .......................................................................................... 4

Operation .......................................................................................................... 13

Menu survey .....................................................................................................14

Connections ..................................................................................................... 18

2 Manual RS8FK202 © Danfoss 12-2009 AK-PC 520

Data ..................................................................................................................... 19

Ordering ............................................................................................................19

Montage ............................................................................................................ 19

Safety function ................................................................................................ 20

Override ............................................................................................................. 21

Appendix ........................................................................................................... 22

Function

Capacity regulation

The cut-in capacity is controlled by signals from the connected
pressure transmitter/temperature sensor and the set reference.
Outside the reference a neutral zone is set where the capacity will
neither be cut in nor out.
Outside the neutral zone (in the hatched areas named +zone and

-zone) the capacity will be cut in or out if the regulation registers a
change of pressure “away” from the neutral zone. Cutin and cutout
will take place with the set time delays.
If the pressure however “approaches” the neutral zone, the con­troller will make no changes of the cut-in capacity.
If regulation takes place outside the hatched area (named ++zone
and --zone), changes of the cut-in capacity will occur somewhat
faster than if it were in the hatched area.
Cutin of steps can be dened for either sequential or cyclic opera­tion.

Sequential (rst in - last out)
The relays are here cut in in sequence – rst relay number 1, then
2, etc.
Cutout takes place in the opposite sequence, i.e. the last cut-in
relay will be cut out rst.

Cyclic (rst in - rst out)
The relays are coupled here so that the operating time of the
individual relays will become equalised.
At each cutin the regulation scans the individual relays’ timer,
cutting in the relay with least time on it.
At each cutout a similar thing happens. Here the relay is cut out
that has most hours on the timer.

Rx = random relay
h = number of hours

If capacity regulation is carried out on two compressors with one
unloader each, the following function can be used:
Relays 1 and 3 are connected to the compressor motor.
Relays 2 and 4 are connected to the unloaders.
Relays 1 and 3 will operate in such a way that the operating time
for the two relays will become equalised.

C = compressor, L = Unloader

AK-PC 520 Manual RS8FK202 © Danfoss 12-2009 3

Survey of functions

The total function content is shown below – not all functions are present at the same
time. The setting of o61 determines which functions are present.
The menu overview on page 14 shows the various functions and settings.

Para-

Function
Normal display

If the two displays are mounted:
P0 will be shown on EKA 165 (the one with buttons)
Pc will be shown on EKA 163. Both readouts will be in temperature or in bar.

Compressor regulation reference Compressor control
P0 setpoint

Regulation is based on the set value plus an oset, if applicable. An oset can be cre­ated from night setback r13 and/or from a system units override function.

Oset

The set reference may be displaced with a xed value when a signal is received at the
DI4 input or from the function "Night setback" (r27).
(Cf. also Denition of DI4 input).

Night setback (Displacement of P0)
OFF: No change of the reference
ON: Oset value forms part of the reference

Reference

The regulation reference is shown here

Set point limitation

With these settings the setpoint can only be set between the two values.
(This also apply if regulation with displacements of the reference).

Max. permissible setpoint value. r25 P0RefMax °C / P0RefMax b
Min. permissible setpoint value. r26 P0RefMin °C / P0RefMin b

Neutral zone

There is a neutral zone around the reference. See also page 3.

Correction of pressure measurement

An oset adjustment of the registered pressure can be made.

Unit

Here you can select whether the display is to indicate in SI units or US units.

0: SI (°C / bar)
1: US (°F / psig)

Start/stop of refrigeration

With this setting the refrigeration can be started and stopped. 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).

Condenser regulation reference Condenser control
Pc setpoint

Regulation is based on the set value plus an oset, if applicable. An oset can be cre­ated via the “r34” function and/or from a system units override function.

Oset

The set reference may be displaced with a xed value when a signal is received at the
DI5 input. (Cf. also Denition of DI5 input).

Pc reference variation. See also page 22
Regulation with setting 1 (or 2 if the reference is to vary with the outdoor tempera­ture) will give the best regulation if the system is in balance. But if a lot of condenser
steps are cut in and out and the compressor capacity often becomes low, it will 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 Pc-oset at max. compres­sor capacity can be accepted).
1: No change of the reference. Regulation based on set setpoint. And oset with the
DI5 function is allowed.
2: Outdoor temperature forms part of the reference. The outdoor temperature is
measured with Sc3. When the outdoor temperature drops one degree, the reference
is lowered one degree.
Here is oset with the DI5 function not allowed. At DI5 signal the reference will
change to the set setpoint.
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)

meter

Parameter by operation via
data communication

P0 °C or P0 b
Pc °C or Pc b

r23 P0Set Point °C / P0Set Point b

r13 Night oset

r27 NightSetBack

r24 P0 ref. °C / P0 ref. b

r01 Neutral zone

r04 AdjustSensor

r05

(In AKM onlySI (bar and °C) is used,
whatever the setting)

r12 Main Switch

r28 PcSet Point °C / PcSet Point b

r34 PcRefOset

r33 Pc mode

4 Manual RS8FK202 © Danfoss 12-2009 AK-PC 520

Condenser reference

The regulation reference is shown here.

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. r30 PcRefMax °C / PcRefMax b

Min. permissible setpoint value. r31 PcRefMin °C / PcRefMin b

Correction of pressure measurement

An oset adjustment of the registered pressure can be made.

Dimensioning temperature Dim tm

The mean temperature dierence across the condenser at maximum load (tm dier­ence at max. load). This is the temperature dierence between the air and condensing
temperature.

Dimensioning temperature Min tm

The mean temperature dierence across the condenser at the lowest relevant
compressor capacity (tm dierence at min. load). This is the temperature dierence
between the air and condensing temperature.

Reading your P0

This is where you can see the actual pressure that is being measured by the pressure
transmitter.
The value is part of the regulation, since the regulation signal for capacity regulation
originates from the pressure transmitter.
The value is part of the frost protection regulation, since the regulation signal for
capacity regulation originates from the temperature sensor.

Reading your T0

This is where you can see the actual pressure being measured by the sensor chosen
for capacity regulation (the sensor is dened in o81). The value is displayed in °C.

Compressor capacity Compressor pack cong.
Running time

To prevent frequent start/stop, values have to be set for how the relays are to cut in
and out.
Min. ON time for relays.
(The time is not used if the relay cuts an unloader in or out).
Min. time period between cutin of same relay.
(The time is not used if the relay cuts an unloader in or out).

Setting for neutral zone regulation

Regulation band over the neutral zone c10 + Zone k / + Zone b
Time delay between step cut-ins in the regulation band over the neutral zone c11 + Zone m
Time delay between step cut-ins in the regulation band over the "+Zone band". c12 + + Zone m
Regulation band under the neutral zone c13 - Zone k / - Zone b
Time delay between step cut-outs in the regulation band under the neutral zone c14 - Zone m
Time delay between step cut-outs in the regulation band under the "-Zone band" c15 - - Zone m

Pump down limit

The factory setting for this function is OFF.
Activate by setting a value corresponding to pressure under the zone and over the P0
min. limit.
The function keeps the last capacity step going until the pressure comes down to the
pump down limit. When this value is reached the last compressor will cut out.
Do not reconnect capacity until the pressure is once more above the neutral zone.

Compressor conguration

Here you set the predened combination of number of compressors and any unload­ers.

1 = One compressor, 2 = two compressors, 3 = three, 4 = four.
5 = One compressor + one unloader. 6 = One compressor + two unloaders.
For 7 to 8: See survey on page 11
Selection of coupling mode

1. Sequential: First relay 1 cuts in, then relay 2, etc. Cutout takes place in the opposite
sequence. (”First in, last out”).

2. Cyclic: An automatic operating time equalisation is arranged here, so that all steps
with motor connection will have the same operating time

Unloaders’ cutin and cutout mode

The relays for unloaders can be set to switch on when more capacity is required (set­ting = 0), or they can switch o when more capacity is called for (setting = 1).

Manual control of compressor capacity

This sets the capacity that is to be cut in when switching to manual control.
(c01 and c07 will still apply)

Manual control

Manual control of the compressor capacity is enabled here.
When set to ON, the capacity that is set in “c31” is cut in.

r29 Pc ref. °C / Pc ref. b

r32 AdjustSensor

r35 Dim tm K

r56 Min tm K

r57 P0°C / P0 b

r58 Cmp.CtrlSens

c01 Min.ON time

c07 MinRecyTime

c33 PumpDownLim.

c16 Compr mode

c08 Step mode

c09 Unloader

(switch on = 0)
(switch o = 1)

c31 CmpManCap%

c32 CmpManCap

AK-PC 520 Manual RS8FK202 © Danfoss 12-2009 5

- - - - Comp. Cap %
Read cut-in compressor capacity

Actuel zone state:
0=o. 1= --zone. 2=-zone. 3=Neutral­zone. 4=+zone. 5=++zone

Condenser capacity
Denition of condenser and number of fans

Here you set the number of fan steps with which regulation has to be carried out (but
max. four).
1-4: All fans are cut in and out with relays. The rst vacant relay number is assigned to
fan 1, the next to number 2, etc.

5-8: Not used
9: All fans controlled via the analog output and a frequency converter.
10: Not used
11-14: Total number of fan relays (as 1-4), but here the starting sequence is altered

after each time all fans are stopped.

Read temperature at sensor Sc3 u44 Sc3 temp

Read temperature at sensor Sc4 (sensor is only used for monitoring) u45 Sc4 temp

Regulation parameters for the condenser regulation
Proportional band xp (P = 100/Xp)

If the Xp value is increased, the regulation becomes steadier

I: Integration time Tn

If the Tn value is increased, the regulation becomes steadier

Manual control of condenser capacity

This sets the capacity that is to be cut in when switching to manual control.

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.

Speed control start value

Speed control will only be activated when the capacity requirement reaches this
value.

Speed control stop value

Speed control will be stopped when the capacity requirement falls below this value.

Alarm Alarm settings

The controller can give alarm in dierent situations. When there is an alarm the light­emitting diodes (LED) will ash on the display and the alarm relay will cut in.

P0 min. (Alarm and safety function, see also page 20.)
Here you set when the alarm at too low suction pressure is to enter into eect. The
value is set as an absolute value.

Alarm delay P0 alarm

The time delay is set in minutes. At min. setting the alarm is cancelled.

Pc max. (Alarm and safety function, see also page 20.)
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.

Alarm delay Pc alarm

The time delay is set in minutes. At min. setting the alarm is cancelled.

Alarm delay DI1 (an interrupted input will give alarm).

The time delay is set in minutes. At max. setting the alarm is cancelled.
Alarm delay DI2 (an interrupted input will give alarm).

The time delay is set in minutes. At max. setting the alarm is cancelled.
Alarm delay DI3 (an interrupted input will give alarm).

The time delay is set in minutes. At max. setting the alarm is cancelled.

Alarm limit for high temperature of the “Saux1” sensor

With setting = O the alarm has been opted out.

Alarm delay from "Saux1" (A32)

If the limit value is exceeded, a timer function will commence. The alarm will not be­come active until the set time delay has been passed. The time delay is set in minutes.

Give the top button a brief push to zeroset the alarm and to have the message shown
on the display.

c29 Fan mode

- - - - Fan Cap %
Read cut-in condenser capacity

n04 Xp K

n05 Tn s

n52 FanManCap%

n53 FanManCap

n54 StartSpeed

n55 MinSpeed

A11 Min. P0. b

A44 P0AlrmDelay

A30 Max. Pc. b

A45 PcAlrmDelay

A27 DI1AlrmDelay

A28 DI2AlrmDelay

A29 DI3AlrmDelay

A32 Saux1 high

A03 Alarm delay

Reset alarm
The function zerosets all alarms when
set in pos. ON.

With data communication the impor­tance of the individual alarms can be
dened. Setting is carried out in the
“Alarm destinations” menu.

6 Manual RS8FK202 © Danfoss 12-2009 AK-PC 520

Miscellaneous Miscellaneous

Choice of application

The regulator can be congured in various ways. The use that is required out of the
two uses available is set here. The functions for the two uses can be viewed on page

14. This menu must be set as the rst of all menus, as it enables the associated settings to

be set.

1. Show temperature
2: Show pressure

Sensor type (Sc3, Sc4 and "Saux1") (see also overview page 21)
Normally a Pt1000 sensor with great signal accuracy is used for temperature measure­ment and AKS 32R for pressure measurement. But a PTC sensor may also be used (r25
= 1000) in special situations.
All temperature sensors must be of the same kind.
In brine cooling the pressure measurements are replaced by temperature measure­ments.
The following settings are possible:
0=PT1000. 1=PTC1000. 2=PT1000 on sensors and on Po. 3=PTC1000 on sensors and
on Po. 4=PT1000 on sensors and on Pc. 5=PTC1000 on sensors and on Pc. 6=PT1000
on sensors, on Po and on Pc. 7=PTC1000 on sensors, on Po and on Pc.
(If a temperature sensor is mounted on P0 or Pc, the respective settings in o20, 21, 47
and 48 will not be required).

Settings at water cooler application

Denition of the signal inlet when compressor regulation is controlled with signal
from a temperature sensor:

0. Temperature signal on terminal 57-58 (P0 inlet)

1. Temperature signal on Saux inlet

2. Temperature signal on Sc4 inlet
(P0 min. function (A11) will not be aected by the denition)
If frost protection is required, you must connect a pressure transmitter on P0 and the
temperature sensor must be connected to the Saux or Sc4 input.

Display connection

This is where you dene the type of display that is connected to the controller
O: EKA 164
On: EKA 165. The extended display with LEDs.

Read temperature at sensor "Saux1" o49 Saux1 temp
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 12 bar
The values must be set in bar if display in °C has been selected. And in psig, if °F has
been selected.

P0-Min. value o20 P0MinTrsPres
P0-Max. value o21 P0MaxTrsPres
Pc-Min. value o47 PcMinTrsPres
Pc-Max. value o48 PcMaxTrsPres

Use of DI1 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: Fan alarm when contact cuts out. Alarm "A34" is given.
2: Alarm function when the contact cuts out. Alarm “A28” is given.

There is time delay for the alarm. Setting in "A27".

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: Regulation reference P0 displaced when contact is cut in
2: Alarm function when the contact cuts out. Alarm “A31” is given. There is no time

delay.

Use of DI5 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: Regulation reference Pc displaced when contact is cut in
2: Alarm function when the contact cuts out. Alarm “A32” is given. There is no time

delay

o61 This setting cannot be made via data

communication. It must be set directly
on the controller.

o06 Sensor type

o81 Ctrl.Sensor

o82

If the values are to be set from the
AKM programme, they must be set in
bar.

o78 Di1 control

o22 Di4 control

o37 Di5 control

AK-PC 520 Manual RS8FK202 © Danfoss 12-2009 7

Operating hours

The operating hours for the compressor relays can be read and set in the follow­ing menus. The read value is multiplied by 1000 to obtain the number of hours (f.ex.
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.

Value for relay number 1 to 4 o23-

o26

Refrigerant setting

o30 Refrigerant
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.
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.

Manual control (stopped regulation only)

o18 - - ­From this menu the relays can be cut in and out manually. 0 gives no override, but a
number between 1 and 10 will cut in a belonging relay. 1 will cut in relay number 1, 2
relay 2, etc.
11-18 will produce voltage on the analog output. Setting 11 will give a voltage of

1.25 V, setting 12 will give 2.5 V, etc.

(In the AKM display the hour number
has not been multiplied)

DO1 run hour.....

DO4 run hour

Frequency

o12 50 / 60 Hz
Set the net frequency.

Address

If the controller is built into a network with data communication, it must have an
address, and the master gateway of the data communication must then know this
address.
These settings can only be made when a data communication module has been
mounted in the controller and the installation of the data communication cable has
been completed.
This installation is mentioned in a separate document “RC8AC”.

The address is set between 1 and 240 (gateway determined) o03
The address is sent to the gateway when the menu is set in pos. ON o04

Access code

o05
If the settings in the controller are to be protected by a numerical code, you can set a
numerical value between 0 and 100. If not, you can cancel the function with setting
OFF.

Special settings

Outputs DO9 and DO10 are normally used for the ”AKD start/stop” function and for the alarm
function, but they may be redened in special cases.

DO9 function:

o75 DO9 function
0: AKD Start/stop
1: Inject-on function (see drawing below)
2: Boost ready function (see drawing below)
3: Not used

DO10 function:

o76 DO10 function
0: Alarm relay
1: Not used

Status on the digital inputs

The signal on the DI inputs can be read in the following menus:
Status on DI 1 u10
Status on DI 2 u37
Status on DI 3 u87
Status on DI 4 u88
Status on DI 5 u89

(50=0, 60=1)

Following installation of a data com­munication module, the controller can
be operated on a par with the other
controllers in ADAP-KOOL® refrigera­tion controls.

DI 1 Status

DI 2 Status

DI 3 Status

DI 4 Status

DI 5 Status

8 Manual RS8FK202 © Danfoss 12-2009 AK-PC 520