RC.1J.51.02 ® RC.1J.53.02 06-2000
Compressor Pack Controller
AKC 25H5
ADAP-KOOL
®
Function description
2 Function description RC.1J.53.02 © Danfoss 06/2000 AKC 25H5
Contents
Introduction ................................................................................................................................ 3
System information ................................................................................................................... 4
Operation .................................................................................................................................... 4
Language .................................................................................................................................... 4
Capacity regulation of compressor ......................................................................................... 5
Regulation ........................................................................................................................ 5
Regulation reference ........................................................................................................ 5
Neutral zone and regulating band .................................................................................... 9
Compressor definition ...................................................................................................... 9
Time delays for cut ins and cut outs .............................................................................. 10
Sequence for cut in and cut out of capacity .................................................................. 10
Signal from the compressor's safety controls ................................................................ 12
Temperature sensor ....................................................................................................... 13
Compressor control, but no condenser control ............................................................. 13
Peak load limitation ........................................................................................................ 13
Liquid injection into the suction line ................................................................................ 14
Capacity regulation of condenser ......................................................................................... 15
Regulation ......................................................................................................................15
Regulation reference ...................................................................................................... 15
Neutral zone and regulating band .................................................................................. 18
Condenser definition ...................................................................................................... 18
Time delays for cutins and cutouts ................................................................................ 18
Signal from the condenser's safety controls .................................................................. 19
Hourmeter ...................................................................................................................... 19
Condenser control, but no compressor control ............................................................. 19
Speed regulation ...................................................................................................................... 20
Valve function .......................................................................................................................... 22
Liquid injection into the suction line ................................................................................ 22
Heat recovery function ................................................................................................... 22
Overriding ................................................................................................................................. 23
Monitoring ................................................................................................................................ 24
Monitoring of maximum discharge gas temperature ..................................................... 24
Monitoring of maximum discharge pressure .................................................................. 24
Monitoring of minimum suction pressure ....................................................................... 25
Monitoring of suction gas superheat .............................................................................. 25
Monitoring of the different parts of the compressor's safety circuit ............................... 26
Monitoring of other automatic controls .......................................................................... 26
Supply voltage ......................................................................................................................... 28
Function switch ....................................................................................................................... 28
Clock function .......................................................................................................................... 28
Refrigerant ................................................................................................................................ 29
Service ...................................................................................................................................... 30
System measurements/data ................................................................................................... 32
Alarms and messages .............................................................................................................34
Access codes ........................................................................................................................... 38
Supporting text ........................................................................................................................ 38
Installation considerations ....................................................................................................38
List of literature ....................................................................................................................... 39
This function description was revised in May 2000 and applies to AKC 25H5 with code
numbers 084B2020 and 084B2021.
Validity
AKC 25H5 Function description RC.1J.53.02 © Danfoss 06/2000 3
Introduction AKC 25H5 is a complete control unit for capacity regulation of compressors and condensers
in commercial refrigeration.
The controller can be used in combination with other controllers in the Danfoss ADAP-KOOL
®
refrigeration control system.
In addition to capacity regulation the controller can transmit signals to other controllers about
operating conditions, e.g. forced closing of expansion valves, alarm signals and alarm
messages.
The controller’s main function is to control the compressors and condensers, so that they will
constantly operate at the optimum pressure conditions from an energy point of view. Both
suction pressure and condensing pressure will be controlled by signals from pressure
transmitters type AKS 32.
Among the various functions can briefly be mentioned:
- It can control a total of nine capacity steps distributed on compressor steps and condenser
steps, as required. One of the nine steps can be used for infinitely variable speed
regulation.
- There are nine digital imputs for monitoring the various automatic controls. The inputs can
be defined to monitor compressors, condensers or other ON/OFF signals, at your option. If
failure of a compressor is registered, the controller will control the capacity with the
remaining compressors.
- When the compressors stop, signals may be transmitted to the electronic expansion valves,
so that they close.
- LED’s on the front plate show the status of outputs and inputs.
- Alarm signals can be generated directly from the controller and via DANBUSS Data
Communication.
- Alarms are displayed with texts, so that it is easy to see the cause of the alarm.
The monitoring of a compressor’s safety
circuit may be extended from being a simple
type of monitoring to a more differentiated
monitoring of several parts of the safety
circuit. To achieve this, the controller must
be linked up with an alarm module type AKC
22H. This alarm module will then receive
signals from the different parts of the safety
circuit and will subsequently give an exact
report on the exact location of the problems
in the circuit.
4 Function description RC.1J.53.02 © Danfoss 06/2000 AKC 25H5
Controller type AKC 25H5 is a unit in the ADAP-KOOL
®
refrigeration control system. The
controller can be linked up with other controllers in the system via a two-core connection - the
DANBUSS Data Communication. Through this connection information can be transmitted
between the units, like settings, measurements, alarms etc.
Remote service
The different messages and alarms can, via the telephone network, be transmitted by modems
to, say, a service company.
Address coding
An address code must be set by means of a number of switches on the controller’s front plate.
There are seven switches for the coding. How coding is performed is explained in the
installation instructions for the data communication cable (literature No. RC.0X.A).
Connection of control panel type AKA 21
A plug for the connection of control panel AKA 21 is mounted right on the front plate of AKC
25H5. (If the control panel is to be used in any other place, a terminal box will have to be
installed (cf. the installation instructions for the data communication cable, literature No.
RC.0X.A).)
Data communication
To obtain correct data communication it is important that the installation instructions for the
data communication cable be adhered to (literature No. RC.0X.A).
The controller can be operated in two different ways. Either by using control panel type AKA
21 or by means of a PC with system software type AKM.
AKA 21 operation
Setting of the different functions is performed via a menu system. The menu system is built up
on several levels where you change around between the different menus by means of arrow
keys.
The complete list of menus is contained in the document “Menu operation via AKA 21”. (Cf. list
of literature).
PC operation
Operation takes place from a PC where Microsoft-Windows and System Software type AKM
have been installed. (The PC is connected to the system via Gateway type AKA 243/244).
Setting of the different functions is performed by means of rolling menus and dialogue boxes.
Settings can either be made via the keyboard or by using a mouse.
For users of AKM system software the complete list of menus is found in the document “Menu
operation via AKM”. (Cf. list of literature).
System information
Operation
There are three languages in the controller. Depending on the code number selected, the
languages are either: English, German and French or English, Danish and Spanish.
When the required language has been selected, the individual functions will be shown in this
language, both when there is operation via AKA 21 and system software type AKM.
NB! When you operate system software type AKM it is important that the language code is
set before an upload of the controller’s data is carried out to the AKM programme (it is the set
language that will be picked up by the AKM programme). Select one of the controller’s three
languages by means of the following settings:
0: English
1: German
2: French
3: Danish
4: Spanish
Activate the selected language by pushing "Enter" and then push "Clear".
Main Function Main Function Settings Language
___
Language
AKC 25H5 Function description RC.1J.53.02 © Danfoss 06/2000 5
The step regulator in the controller can control up to nine capacity steps that can be distributed
on one, two or more compressors. (The controller has a total of nine relay outputs that have to
be distributed between compressor steps and condenser steps).
Regulation
The cut in compressor capacity is controlled by the actual value of the suction pressure and
whether the pressure is rising or falling.
Regulation is performed by an I-controller when the compressors are cut in/out, and by a PI-
controller when they are controlled by means of speed regulation.
The user interface has been designed as for neutral zone setting.
- In the neutral zone there is no cut in/cut out of capacity steps.
- In the “+zone” and “-zone” bands cut in/cut out will depend on whether the pressure is rising
or falling. Cut in/cut out takes place with the selected time delays.
- In the “++zone” and “--zone” bands cut in/cut out takes place with the selected time delays.
- Refrigeration is stopped at pressures that are lower than the set “limit” value. (Cf. section on
“monitoring”).
- Cutin of steps is also adapted to the size of the next step to be cut in. A small step is cut in
earlier than a bigger one.
- Cutout of capacity steps is performed with a hysteresis corresponding to the smallest defined
capacity.
Regulation reference
Regulation is based on a set value which can be displaced with a number of functions to constitute
a general regulation reference. This general regulation reference is subsequently included in the
regulation together with the pressure measured by pressure transmitter P0.
The reference can be displaced in several different ways according to the required application.
Altogether the reference is composed of the following functions:
P0 SP Set reference
+ night setback Night setback value that can be started by two functions
1) Short-circuit of input “S6”
2) Internal time schedule
+ k1(EXT.REF./10) Value from external voltage signal
+ k2(t
a ref
-S6) Value from temperature signal
_________________
Total regulation reference
As equation:
Total regulation reference = P0 SP + Night Ref + k1 (EXT.REF./10) + k2(ta Ref - S6)
(The individual functions are described on the following pages).
NB!
When the night setback function is active, the contributions from the other functions will not be
included.
Capacity regulation of
compressor
6 Function description RC.1J.53.02 © Danfoss 06/2000 AKC 25H5
When regulation is performed, all functions are filtered over a period of time so that the
variation of the regulation reference is smoothed away. The change can be max. 0.2K/sec.
Set reference
Basic setting of suction pressure in °C.
Compressor Capacity Ctrl. Settings Compressor Ctrl. P0 SP
°
C___
Night setback
With this function the reference can be displaced by up to 25 K in a positive or negative direction.
(For night setback at a higher suction pressure a positive value must be set).
Compressor Capacity Ctrl. Settings Compressor Ctrl. Night Ref. K___
The function can be activated in three ways:
1) Short-circuit of the S6 input.
When the S6 input is short-circuited, the night setback function is activated.
2) A setting in the controller
Compressor Capacity Ctrl. Settings Compressor Ctrl. Forced Nght OFF/ON ___
(This setting can also be made from a master gateway’s override function).
3) Internal time schedule
The controller contains a clock function that can transmit a signal that will activate the night
setback function.
Start and stop times must be set for each day of the week.
Principle
AKC 25H5 Function description RC.1J.53.02 © Danfoss 06/2000 7
Definitions:
Night: Time when the night setback starts.
Day: Time when the night setback stops.
Night = 0 or Day = 0:
When one of the two times is set at 0, or when both are set at 0, there will be no night setback
the day and night in question.
Night = 1 and Day = 1:
When the two settings are set at the same time, there will be night setback throughout that day
and night.
Settings:
Compressor Capacity Ctrl. Special funct.Compressor Ctrl. Mo day h
___
Mo night h
___
Tu day h
___
Tu night h
___
We day h
___
We night h
___
Th day h
___
Th night h
___
Fr day h
___
Fr night h
___
Sa day h
___
Sa night h
___
Su day h
___
Su night h
___
8 Function description RC.1J.53.02 © Danfoss 06/2000 AKC 25H5
External voltage signal
Simple voltage signal
The voltage signal is sent to terminal “EXT.REF”. The voltage must be 0-10 V. With this signal
the reference can be displaced by up to 50 K in a positive or negative direction. 10 V provides
max. displacement. (K1 indicates the displacement in Kelvin at max. voltage = 10 V).
Reference displacement = k1(EXT.REF./10).
Compressor Capacity Ctrl. Special funct.Compressor Ctrl. P0 Ref. md = 1
Compressor Capacity Ctrl. Settings Compressor Ctrl. K1 Gain K ___
Measurement of relative humidity
Signals can be received from a separate electronic unit that registers the relative humidity. The
signal must be connected, as shown above, but other settings have to be made.
Reference displacement = k1(RH ref %/ 100 - EXT.REF./10).
Compressor Capacity Ctrl. Special funct.Compressor Ctrl. P0 Ref. md = 2
RH ref %
___
Settings Compressor Ctrl. K1 Gain K ___
If the external voltage input is not used, the function can be cancelled with setting K1 = 0. With setting
K1 = 10 there will be an influence of 0.1 K for each % the relative humidity changes (provided that
the moisture sensor’s signal is 0 V at 0% RH and 10V at 100% RH).
Temperature signal
A temperature sensor is connected to input S6.
A reference temperature is set in the controller. The temperature difference between the set
temperature and the measured temperature can now displace the reference by up to 10 K in both
positive and negative direction.
Reference displacement = k2(ta Ref.-S6).
Compressor Capacity Ctrl. Special funct.Compressor Ctrl. P0 Ref. md = 2
K2 Gain ___
ta Ref
°
C ___
AKC 25H5 Function description RC.1J.53.02 © Danfoss 06/2000 9
Limitations
When the reference is displaced by means of signals on the voltage input and the temperature
signal input, respectively, values for the permitted displacement must be set. Both a max. permitted
increase and a max. permitted decrease must be set. The values will not affect the value of the night
setback function.
Compressor Capacity Ctrl. Special funct.Compressor Ctrl. P0 Ref Max K ___
P0 Ref Min K ___
Neutral zone and regulating band
Neutral zone is set.
+zone and -zone bands are set.
Time delay in +zone and -zone band is set.
Time delay in ++zone and --zone band is set.
If all capacities are identical the set values are used. If the capacities however differ, the times
will apply to the average capacity in such a way that a small capacity is cut in faster and a big
capacity slower.
Compressor Capacity Ctrl. Settings Compressor Ctrl. NZ K
___
+zone K
___
+zone s
___
++zone s
___
-zone K
___
-zone s
___
- -zone s
___
Compressor definition
The controller can regulate up to nine compressor steps distributed on one, two or more
compressors. (If all nine steps are used for compressor control, there is no room left for the
control of condenser steps).
The controller can operate with capacity steps of varying sizes. In the definition of each capacity
step, the size of the capacity must be indicated with a percentage of the system’s total capacity.
The compressor steps must be defined in groups, so that the controller will know which steps
belong to compressor 1, which to compressor 2, etc. This definition is made by setting relay
outputs DO1 to DO9. Always use DO1 and up without skipping a relay output. If you skip one
or more, the showing of DI-alarms may cause problems.
For each relay output you select the compressor that is to belong to it. If several are selected
with the same compressor number, it will be the relay with the lowest number that stops and
starts the compressor. The subsequent relays will control the individual unloaders.
Output Configuration DO Relay No. ( ) DO( ) Type
= 1(1=compressor)
DO( ) Dev. No___
DO( ) Cap %___
The total capacity need not necessarily be 100% as long as it is close to 100%. The controller
itself calculates the value based on the defined values.
NB! If there are compressors with identical capacities, they must be set with the same value,
e.g. three identical units must be set with 33%, 33% and 33%.
Regarding infinitely variable speed regulation: See separate paragraph on page 20.
10 Function description RC.1J.53.02 © Danfoss 06/2000 AKC 25H5
Example:
A system consists of three compressors of the same size. One with three steps, and two without
steps.
The definition here is performed, as follows:
Output Configuration DO Relay No. 1 DO1 Type
= 1(1=compressor)*
DO1 Dev. No
= 1
DO1 Cap % = 11
DO Relay No. 2 DO2 Type
= 1(1=compressor)
DO2 Dev. No
= 1
DO2 Cap % = 11
DO Relay No. 3 DO3 Type
= 1(1=compressor)
DO3 Dev. No
= 1
DO3 Cap % = 11
DO Relay No. 4 DO4 Type
= 1(1=compressor)*
DO4 Dev. No
= 2
DO4 Cap % = 33
DO Relay No. 5 DO5 Type
= 1(1=compressor)*
DO5 Dev. No
= 3
DO5 Cap % = 33
The three relay outputs marked with a * will start and stop the compressors, and the others will
cut in and cut out the unloaders.
Time delays for cut ins and cut outs
To protect the compressor motor against frequent restarts, two time delays can be set.
- a minimum period which shall pass from a compressor starts till it can be restarted.
- a minimum period (on-time), during which the compressor must be operating, before it can be
stopped again (to avoid a cutout before the suction pressure has had time to become stable).
The setting ranges are from 0 to 25 minutes.
If the output is used for cutins and cutouts of unloaders, the settings will automatically be
zeroset.
Output Configuration DO Relay No. ( ) DO( ) Recy m ___
DO( ) ON m ___
Sequence for cut in and cut out of capacity
The sequence for cut in and cut out of capacity can be defined in two ways. Either there is a
fixed defined sequence, or the controller itself checks the defined capacity size and then
defines the sequence. The sequence will be established by the following setting:
1. Sequential (step mode = 1).
In general the numbers with which the different compressors are defined will establish the
sequence for the cut ins (the compressor defined with a low number will start before a
compressor with the next number).
The sequence for the cut outs will furthermore be established by the compressor type:
Compressors with one step
The sequence is not changed (last cut in step will be cut out first, when the required
capacity drops again).
Compressors with several steps
When there are cut outs, the steps on the borderline between the two compressors will
be changed around. The function will produce the effect that the last started compressor
will not stop until the control has cut out the “last” step of the previous compressor.
AKC 25H5 Function description RC.1J.53.02 © Danfoss 06/2000 11
Example:
Cut in Cut out
2. Automatic equalisation of operating time or capacity-based regulation (Step mode = 2).
With this setting the controller itself examines whether the set capacity steps are of the same
size, or whether they differ in size.
When the capacity steps have been defined to be
identical
:
The compressor performs an automatic equalisation of operating time between the compres-
sors.
- At the different starts, the compressor with the lowest amount of run time will be started
first.
- At the different stops, the compressor with the highest amount of run time will be
stopped first.
- For compressors with several steps there will be no changes of the steps, as is the case
with sequential cut ins and cut outs.
- For compressors with more steps, there can only be one compressor at a time with cut-
out unloaders.
When all capacity steps have
not
been defined to be identical:
The controller now registers the actual capacity steps according to size. The controller will
subsequently cut in and cut out the individual capacity steps, so that the calculated capacity
requirement is covered in the best possible way.
If a part of the compressors of the same size without unloaders have been defined, these
compressors will take part in a rota arrangement, so that the operating times are equalised.
Compressor Capacity Ctrl. Settings Compressor ctrl. Step Mode
1 / 2
12 Function description RC.1J.53.02 © Danfoss 06/2000 AKC 25H5
Signal from the compressor's safety controls
The controller requires a signal on the status of each compressor’s safety circuit. The signal
taken directly from the safety circuit is connected to a “DI” input. This input is a 230 V a.c. input.
(The safety circuit must stop the compressor without the help of AKC 25H5).
If the safety circuit is broken, the controller will cut out all output relays for the compressor in
question and give an alarm. The other compressors will continue the regulation. (A broken
circuit at the DI input will interrupt the output).
An input from a compressor and the compressor’s number are defined.
Input Configuration Alarm input No. 1..9 DI( ) Type
= 1(1=compressor)
DI( ) Dev. No. ___
(compressor No.)
A time delay has to be defined in connection with all alarms. It covers the period of time from
the cut out moment until the alarm is registered.
Input Configuration Alarm input No. 1..9 DI( ) Del. m ___
The alarm message concerning a failure in the safety circuit can be extended into a more
concrete message by using alarm module type AKC 22H. Read the later section on
monitoring.
Hourmeter
The run time of a compressor motor is constantly registered. It can be shown on the display
how many hours the compressor has been operating since the hourmeter was last reset, and
how many starts there have been during the past 24 hours. (About resetting, see later).
Compressor status Compressor No.( ) ( ) Run time
Compressor status Compressor No.( ) ( ) Cut / 24 h
All relay outputs are registered by a counter. The run time is registered here for whatever has
been connected to the output. This registration can be shown on the display, and reset, if
required.
Output Configuration DO Relay No.( ) DO( ) Time h
The hourmeter range is from 0 to 30,000 hours.
AKC 25H5 Function description RC.1J.53.02 © Danfoss 06/2000 13
Temperature sensor
The controller has three inputs for temperature measurements. Their application is primarily, as
follows:
S6: Reference displacement of suction pressure and/or night setback signal when the input is short-
circuited.
S7: Reference control of the condensing pressure with a temperature signal from the condenser’s
inlet air.
S8: Reference temperature for a heat recovery function utilising the condenser heat.
Depending on whether the inputs are used for their primary purpose or not, the registered
measurements may be logged.
Only if the S6 input is used for a night setback signal is simultaneous logging of data not possible.
If the sensors are used for random temperature registration, which is not their primary function, no
alarm message will be sent in case of a sensor error.
The service function is used for displaying the temperature values.
Service mode Measurements of input terminals S6
°
C
S7
°
C
S8
°
C
Forced control of compressor capacity
There can be forced control of the capacity where the normal regulation and the safety
function are disregarded. The capacity is set in per cent of the regulated capacity.
Compressor Capacity ctrl. Settings Compressor ctrl Man. Cap OFF/ON
Man. Cap. % ___
Compressor control, but no condenser control
The controller is normally used for controlling both the compressor and the condenser. If the
controller is only used for controlling the compressor, a missing signal at the pressure
transmitter input Pc will trigger an alarm signal. To avoid this alarm, a signal can be picked up
from pressure transmitter PO. Connect terminal 72 to 76 (“s” to “s”). The monitoring function for
PCmax must be set at the highest possible value.
Peak load limitation
The controller has an input that can receive signals from other automatic controls when they register
a max. limit value for the momentary power consumption.
When the controller input “LOAD SHED” is short-circuited, it will start a function in the regulation
ensuring that the cut-in compressor capacity will not be higher than a set value. This value is set
as a percentage of the whole compressor capacity.
Compressor Capacity Ctrl. Special funct.Compressor Ctrl. Load Shed %___
If further adaptation of the capacity is required, the input can be fitted with, say, a
potentiometer.
- when R < 50 ohm the capacity will be as mentioned above.
- when 50 < R < 1000 ohm the capacity will be linear between the set value and 100%
capacity.
- when R > 1000 ohm the function will be inactive
Liquid injection into the suction line
14 Function description RC.1J.53.02 © Danfoss 06/2000 AKC 25H5
The pressure gas temperature can be kept down by means of liquid injection into the suction line.
The function is controlled on the basis of the superheat measured by Ss and Po. Two values are
set in the controller: Max. superheat and a value for when liquid injection has to be started. The
value is set as the difference from the set max. superheat.
Re valve connection: Read the section “Valve function” on page 22.
Compressor Capacity Ctrl. Special funct.Compressor Ctrl. Inj. Diff. K ____
AKC 25H5 Function description RC.1J.53.02 © Danfoss 06/2000 15
The step regulator in the controller can control up to nine capacity steps that may be
distributed on one or more condensers. (The controller has nine relay outputs that may be
distributed between compressor steps and condenser steps).
Regulation
The cut in condenser capacity is controlled by the actual value of the condensing pressure,
and on whether the pressure is rising or falling.
Regulation is performed by a I controller when the condenser fans are cut IN/OUT, and by a PI-
controller when they are controlled by means of speed regulation.
The user interface has been designed as for neutral zone setting.
- In the neutral zone there is no cut in/cut out of capacity steps.
- In the “+zone” and “-zone” bands cut in/cut out depends on whether the pressure is rising or
falling.
Cut in/cut out takes place with the selected time delays.
- In the “++zone” and “--zone” bands cut in/cut out takes place with the selected time delays.
- Cutin of steps is also adapted to the size of the next step to be cut in. A small step is cut in
earlier than a bigger one.
- Cutout of capacity steps is carried out with with a hysteresis corresponding to the smallest
defined capacity.
Regulation reference
The reference for regulation can be defined in two ways. Either as a fixed set reference or as a
reference that varies according to the outdoor temperature.
Fixed set reference
The reference function is defined and the condensing pressure set in °C.
Condenser Capacity Ctrl. Special function Condenser Ctrl. PcRef.md. =
1
Condenser Capacity Ctrl. Settings Condenser Ctrl. Pc SP
°
C
___
Capacity regulation of
condenser
16 Function description RC.1J.53.02 © Danfoss 06/2000 AKC 25H5
Variable reference
This function permits a change of condensing pressure reference within a defined range. A basic
value for the condensing pressure is set, and a max. and a min. limit based on this value are set.
The reference function is defined with setting Pc Ref. md. = 2.
Condenser Capacity Ctrl. Settings Condenser Ctrl. Pc SP
°
C
___
Condenser Capacity Ctrl. Special function Condenser Ctrl. PcRef.md. =
2
Condenser Capacity Ctrl. Pc Ref Max K ___
Pc Ref Min K ___
NB! When the heat recovery function is used, this function may raise the reference, so that it will
be higher than the set max. value.
Within the set limits the condensing temperature can now vary, based on contributions from 3
functions. These functions will all be included in the regulation reference and subsequently in the
regulation, and be compared to the pressure measured by pressure transmitter Pc.
PC ref = min
tm
+ variable contribution + S7 temperature + contribution from the TC function.
All changes of the reference are filtered over a period of time, so that the change is distributed on
this period (this, however, does not apply to changes of set values). The period of time is set in
minutes.
Condenser Capacity Ctrl. Special function Condenser Ctrl. Pc Ref Del m ___
1. The condensing pressure is reduced as a function of the cut-in compressor capacity.
It is based on:
- dimensioned condenser capacity (temperature difference between air temperature and
condensing temperature)
- how large a part of the compressor capacity has been cut in
Set the required temperature differential (min. tm) at minimum load (fx 7 K). Set the dimensioned
differential (dim tm) at maximum load (fx 15 K). The controller will now contribute with a value
to the reference that depends on how large a share of the compressor capacity has been cut
in.
Condenser Capacity Ctrl. Special function Condenser Ctrl. min. tm K
___
dim. tm K
___
Cut-in
compressor capacity
AKC 25H5 Function description RC.1J.53.02 © Danfoss 06/2000 17
2. The condensing pressure is reduced as a function of the outdoor temperature
A sensor is connected to the S7 input.
The temperature value is used directly in the reference. When the measured temperature rises
by one degree, the condensing temperature is increased by one degree.
3. The condensing pressure is reduced as a function of the expansion valve's opening degree (Tc
signal)
The function can be used in systems where controllers with a Tc output type AKC 114D-116D
have been installed.
All the relevant Tc outputs are connected in series and then connected to AKC 25H5, so that
it will receive a 230 V signal.
When the expansion valve on one of the connected controllers opens so much that it reaches
a set opening degree, it will break the signal.
The reference for the condensing temperature will then start rising, and hence increase the
system’s capacity. When a signal is again received at the Tc input, this will result in a drop of
the reference value.
If regulation is carried out with a variable reference and the Tc function is
not
used,
230 V a.c.
must
be connected to the Tc function’s terminals.
18 Function description RC.1J.53.02 © Danfoss 06/2000 AKC 25H5
Neutral zone and regulating band
The neutral zone is set.
The +zone and -zone bands are set.
The time delay for the +zone and -zone bands is set.
The time delay for the ++zone and --zone bands is set.
If all capacities are identical the set values are used. If the capacities however differ, the times
will apply to the average capacity in such a way that a small capacity is cut in faster and a big
capacity slower.
Condenser Capacity Ctrl. Settings Condenser Ctrl. NZ K
___
+zone K
___
+zone s
___
++zone s
___
-zone K
___
-zone s
___
- -zone s
___
Condenser definition
The controller can control several condenser steps that are cut in and out sequentially.
The condenser steps must be defined in a sequence so that the controller will know which
output belongs to condenser step 1, which output to condenser step 2, etc. The individual
compressor steps will control the capacity defined for the output, and they will be cut in and out
in sequence. The steps defined with the lowest number will be cut in first, then the step defined
with a higher number, etc. Cut out takes place in the opposite sequence. Thus, the last cut in
step will be cut out first.
Output Configuration DO relay No. ( ) DO( ) Type 2
(2=condenser)
DO( ) Dev. No
DO( ) Cap % ___
Re speed regulation: Read the separate paragraph on page 20.
Example:
A system consists of three condenser steps. Here the definition can be made, as follows:
Output Configuration DO relay No. ( ) DO5 Type
= 2 (2=
condenser
)
DO5 Dev. No
= 2
DO5 Cap % = 33
DO6 Type
= 2 (2=
condenser
)
DO6 Dev. No
= 1
DO6 Cap % = 33
DO9 Type
= 2 (2=
condenser
)
DO9 Dev. No
= 3
DO9 Cap % = 33
Here the cut in and cut out sequence will be, as follows: 1, 2, 3 - 3, 2, 1.
I.e., the relay outputs will be activated in this sequence: DO6, DO5, DO9 - DO9, DO5, DO6.
Time delays for cutins and cutouts
Output Configuration DO Relay No. ( ) DO( ) Strt m ___
DO( ) ON m ___
Once a day (at 13:00 hrs) all steps will be activated for one minute.
AKC 25H5 Function description RC.1J.53.02 © Danfoss 06/2000 19
Signal from the condenser's safety controls
The controller can receive signals on the status of each condenser step’s safety circuit. The
signal is taken directly from the safety circuit and is connected to a “DI” input.
This input is a 230 V a.c. input.
If the safety circuit is broken, the controller will cut out the output relay for the relevant step and
give an alarm. The remaining steps will continue the regulation. (A broken connection on the
DI input will cut out the output).
An input from a condenser step and the number of the condenser step are defined.
Input configuration Alarm input No. 1..9 DI( ) Type
= 2 (2= condenser)
DI( ) Dev. No. ___
A time delay must be defined for the period from the alarm is registered until it is transmitted.
Input Configuration Alarm input No. 1..9 DI( ) Del. m ___
Hourmeter
The run time of the different outputs is registered by a counter. This registration can be
displayed and reset, if required.
Output Configuration DO Relay No.( ) DO( ) Time h
The hourmeter’s range is from 0 to 30,000 hours.
Forced control of condenser capacity
Forced control of the capacity can be arranged, where the normal regulation is disregarded.
The capacity is set in per cent of the regulated capacity.
Condensor Capacity ctrl. Settings Condenser ctrl. Man. Cap OFF/ON
Man. Cap. % ___
Condenser control, but no compressor control
The controller is normally used for controlling both compressors and condensers. If the
controller is only used for controlling condensers, a missing signal from pressure transmitter
input PO will trigger an alarm signal. To avoid this alarm, a signal may be picked up from
pressure transmitter Pc. Connect terminal 72 to 76 (“s” to “s”). The monitoring function for
POmin is now set at the lowest possible value.
20 Function description RC.1J.53.02 © Danfoss 06/2000 AKC 25H5
One of the defined capacity steps for either the compressor regulation or the condenser regulation
can be linked up with a speed regulation that for example can be a frequency converter type VLT
®
.
(Compressors with step unloading
cannot
be speed-regulated).
The DO9 output is defined the normal way, with indication of the connected capacity and the setting
determining whether it is a compressor or a condenser that is to be regulated. The output is
connected to the frequency converter’s ON/OFF input, and the analog “AO” output for the frequency
converter’s analog input is connected at the same time.
The ON/OFF signal will start and stop the frequency converter, and the analog signal will indicate
the speed.
Two values must be set in the motor control - one for the max. speed and another for the min.
speed. They are both based on the nominal value, the max. value being, say, 1.3 times the
nominal value and the min. value, say, 0.8 times the nominal value.
When the step is in operation it will consist of a fixed capacity and a variable capacity. The
fixed capacity will be the one that is cut in when the frequency converter starts up, and the
variable capacity will lie in between the min. and max. speed. To obtain the best possible
regulation the variable capacity must be bigger than the “biggest gap” to be covered during
regulation. (The “gaps” will typically be bigger during sequential operation than during binary
operation, as the binary operation will itself find the optimum cutin/cutout pattern. If there are
many short variations in the system’s capacity requirement it will increase the need for
variable capacity.
The definition is based on the capacity produced by the compressor at max. speed. This value
is now used in conjunction with the system’s other capacity for determining the setting of the
step’s capacity.
Example: Three compressors of 5, 5, and 10 kW, respectively, where the 10 kW unit is speed-
regulated at between 0.8 and 1.3 times the nominal speed. The capacity here will be 1.3 x 10
= 13 kW. This will give a setting of 56% (13 x 100/(5+5+13) = 56).
Min. capacity at 0 V must be defined, as follows:
The setting is a value based on the step’s min. capacity seen in relation to the step’s max.
capacity. It can be calculated in the following manner:
Value = min. speed/max. speed (e.g. 0.8/1.3 = 0.62).
This is how steps are cut in and out
Speed regulation
Max.
Nominel
Min.
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