Microcool / AKC 114B
User Guide
(Functional Specification)
LL01-301 (Issue C) 12.08.98
RC.8A.V1.02 09-10-2001
RC.8A.V1.02 10-2001
RC8AV102
Danfoss endeavours to ensure that this publication is correct and up to date. However, development of
systems and services is continuous and published information may not be up to date.
Danfoss accepts no liability for any error or omission.
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Reference number: LL01-301 (Issue C) 12.08.98 = RC.8A.V1.02 10-2001
Date of Issue: 08/98
At the end of 2001 the controller obtained the type designation: AKC 114B.
After this date this User Guide comprises both Microcool and AKC 114B.
After this date Danfoss undertakes all service on the controller.
Copyright © Danfoss / Woodley Electronics, The Quadrangle, Grove Technology Park,
Wantage, Oxon. OX12 9FA.
This document must not be reproduced or copied in whole or part without the prior written consent of
Danfoss.
Comments on this publication are welcome and should be sent to:
Danfoss A/S
RC-ET
Nordborgvej 81
DK-6430 Nordborg
Contents
LL01-301 (Issue C) 12.08.98 / RC8AV102 10-2001 Page iii
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Page
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1.1 General 1
1.2 Versions 2
1.3 Language 2
1.4 Function Switch (Main Switch) 2
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2.1 Introduction 4
2.2 Definition of Thermostat Function 4
2.2.1 Standard Thermostat 4
2.2.2 Modulating Thermostat 4
2.3 Definition of Thermostat Sensor Locations 6
2.3.1 Sensor is Placed in the Return Air to the Evaporator (Air On) 6
2.3.2 The Sensor is Placed in the Outlet Air From the Evaporator
(Air Off) 7
2.3.3 Two Sensors are Mounted 7
2.3.4 S6 Temperature Sensor/Input 8
2.4 Night Operation 9
2.4.1 Night Operation (S6 Input) 9
2.4.2 Night Operation (Internal Timeclock) 9
2.4.3 Night Operation via Display Keyswitch 10
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3.1 Introduction 12
3.2 Alarm Sensor 12
3.3 Alarm Limits 12
3.4 Time Delay 12
([SDQVLRQ9DOYH)XQFWLRQ 14
4.1 Introduction 14
4.2 Superheat 14
4.3 MOP Control 15
4.4 Forced Closing 15
4.5 TEV Function 15
4.6 Glide Function 16
'HIURVW)XQFWLRQ 17
5.1 Introduction 17
5.2 Start of Defrost 17
5.2.1 Manual Defrost 17
5.2.2 External Signal 17
Contents
Page iv LL01-301 (Issue C) 12.08.98 / RC8AV102 10-2001
5.2.3 Internal Clock 18
5.2.4 Auxiliary Function 18
5.3 Defrost Stop 19
5.3.1 Stop Based on Temperature 19
5.3.2 Stop Based on Time 20
5.4 Start after Defrost 20
5.4.1 Delayed Liquid Injection 20
5.4.2 Delayed Fan Start (primarily used in freezing rooms) 21
5.5 Defrost Based on Demand 21
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6.1 Fan Control 23
6.2 Rail Heat Control 23
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7.1 Display Signal 24
7.1.1 Codes 25
7.1.2 Displacement of the Displayed Value 25
7.2 Output to TEV 25
6HUYLFHDQG)DXOWILQGLQJ26
8.1 Service 26
8.1.1 Measurements 26
8.1.2 Forced Control of Outputs 26
8.2 Alarms and Messages 28
8.2.1 List of Alarm Activities 29
8.2.2 Information from the Controller 29
8.2.3 This is How the Various Messages are Transmitted 30
8.2.4 Alarm Receivers 31
8.3 Failsafe Functions 32
8.3.1 Injection Function 32
8.3.2 Thermostat Function 33
8.3.3 Defrost Function 33
8.3.4 Delayed Fan Start 33
8.3.5 Fan Stop 33
8.4 Clock Function 34
3ODQW0HDVXUHPHQW'DWD 35
9.1 Operation of AKA 21 35
9.2 PC Operation 36
9.3 Access Codes 37
9.4 Supporting Text 38
,QVWDOODWLRQ&RQVLGHUDWLRQV 39
Introduction
LL01-301 (Issue C) 12.08.98 / RC8AV102 10-2001 Page 1
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Microcool / AKC 114B, when combined with valves and sensors, is a complete
evaporator control system for refrigeration appliances and small cold rooms. It more
or less replaces all other automatic controls, containing day and night thermostats,
defrost, fan control, rail heat control, alarm functions, etc. The controller is equipped
with DANBUSS® data communication and is operated by means of control panel
type AKA 21 and/or a Woodley Mk 5.
The controller's main function is to control the liquid injection into the evaporator.
The liquid supply is controlled by signals from four temperature sensors (S1, S2, S3
and S4).
The temperature in the evaporator section is controlled by an ON/OFF thermostat.
Setting of the various functions takes place via a menu system. The menu system is
based on several levels according to the following principle.
Introduction
Page 2 LL01-301 (Issue C) 12.08.98 / RC8AV102 10-2001
Shown in the following section is the menu selection to be made to set the functions.
The settings are indicated the way they appear in the control panel type AKA 21, e.g.
(Number of defrosts is set)
(Hour value is set)
The total menu is contained in the following document: - "0LFURFRRO0HQX
'HVFULSWLRQ".
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There are two controller versions:-
• Pt No P84-053 uses S1 temperature sensor for Sh. reference
• Pt No P84-054 uses an AKS 32R pressure sensor for Sh. reference
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There are three languages in the controller, English, German and French. When the
required language has been selected, the individual functions will be shown in this
language, when there is operation via AKA 21.Select one of the controller’s three
languages by means of the following settings:
0: English
1: German
2: French
Activate the selected language by pushing "Enter" and then push "Clear".
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The function switch is used for stopping and starting the regulating function. The
switch has three positions:
• Regulation (Setting = +1)
• Controller stop (Setting = 0)
• Service (Setting = -1)
+1/0/-1
If the switch is set in pos. 0 or -1, all the controller’s functions are inactive. In
the menu the "Standby mode" message is shown, when setting is selected to
"0" or "-1". If the switch is in pos. +1, regulation is started for the functions
selected as "ON".
Introduction
LL01-301 (Issue C) 12.08.98 / RC8AV102 10-2001 Page 3
Thermostat Function
Page 4 LL01-301 (Issue C) 12.08.98 / RC8AV102 10-2001
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The thermostat function can be defined in various ways according to the controller
type and application used, e.g., regulating principle / sensors to be used / will night
setback be required, etc.
It is a requirement that each evaporator section must always be fitted with one air
sensor. This applies no matter which thermostat function is selected - even if no
thermostat function is required. It is likewise a requirement that the thermostat’s cut-
out temperature ("CutOut°C") is set at the correct air temperature, as the value is
used by the injection function.
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You may choose between two thermostat functions:
• Standard thermostat
• Modulating thermostat
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The thermostat function is attached to one evaporator section.
The controller compares the measured air temperature with the set point and when
the air temperature drops to the cut-out value, refrigeration is stopped. (The
expansion valve is closed, and the compressor output is cutout).
The air temperature is measured with the relevant sensor (see later). As the
injection function uses this measurement, the alarm function and the display function
can also use the measurement, if the functions are selected "ON"
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A Modulating thermostat function is attached to the evaporator section.
Thermostat Function
LL01-301 (Issue C) 12.08.98 / RC8AV102 10-2001 Page 5
When the air temperature in the section has dropped to the cut-out value, the
expansion valve for this section will be closed.
• The function can RQO\be used in central systems.
• Each individual evaporator section will be controlled by means of a
modulating thermostat function,
• Cut-out value and differential are set as for an ON/OFF thermostat.
• The air temperature is measured with the attached sensor (see later).
Principle
When products are initially cooled down, and in conjunction with major load
variations where the temperature has been outside of the differential zone, regulation
is carried out according to the MSS principle.
At stable loads the thermostat will reduce the AKV valve’s opening time, so that the
flow of refrigerant will be limited to exactly the quantity that is needed to keep the
temperature at the required reference value.
Settings
If the modulating thermostat function is required, the thermostat function must be set
in pos. 3. Cut-out temperature and differential are set as for a normal ON/OFF
thermostat. In other words, the differential should not be smaller than 5 K, when the
thermostat sensor is mounted behind the evaporator (S4), or 2 K, when the
thermostat sensor is mounted in front of the evaporator (S3). (If the differential is
smaller, load changes may disturb the modulating thermostat function).
The reference temperature will be set as the cut-out temperature plus half the
differential.
Thermostat Function
Page 6 LL01-301 (Issue C) 12.08.98 / RC8AV102 10-2001
Select one of the two thermostat functions by keying a figure between 0 and 2:
0: Thermostat function disabled
1: Thermostat function attached to evaporator section
2: Modulating thermostat function enabled
0/1/2
1RWH:- With setting = 0 the following will apply:-
• No thermostat function
• No pulse operation of fans
• No day and night operation function
• All measured values will be updated
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All thermostat sensors must be mounted. If a sensor has not been mounted or is
cut-out or short-circuited, this will result in the error message "Sensor error" and an
alarm.
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You may choose between three locations as to where the sensors are placed:-
• in the air in the evaporator inlet (air on)
• in the evaporator outlet (air off)
• both before and after the evaporator:
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This location can both be used for thermostat functions 1 and 2.
Thermostat Function
LL01-301 (Issue C) 12.08.98 / RC8AV102 10-2001 Page 7
Required cut-out temperature = CutOut°C.
Required differential = Diff. K.
If night setback is required, define this by putting day/night in position ON
If position ON is selected, the setback value must be set.
OFF / ON
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This location can both be used for thermostat functions 1 and 2.
Required cut-out temperature = CutOut°C.
Required differential = Diff. K.
If night setback is required, define this by putting day/night in position ON.
If position ON is selected, the setback value must be set.
OFF / ON
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Sensors are mounted, one on either side of the evaporator (weighted control). 7KLV
ORFDWLRQFDQRQO\EHXVHGIRUWKHUPRVWDWIXQFWLRQ. (Standard thermostat
control)
The measured values are weighted with a percentage of S3 (air inlet) and a
percentage of S4 (air outlet).
Example: S4 measures -25°C and S3 measures -20°C.
Required as regulation parameter is a weighted average consisting of 60% S4 and
the rest from S3 (only the S4 share is programmed). This gives a regulating value of
p
n 0.6 x -25°C + 0.4 x -20°C = -23°C
Thermostat Function
Page 8 LL01-301 (Issue C) 12.08.98 / RC8AV102 10-2001
Required cut-out temperature = CutOut°C.
Required differential = Diff. K.
Required S4 sensor influence = S4 Day %. (S3 is weighted automatically).
If night setback is required, define this by putting day/night in position ON.
If position ON is selected, the setback value must be set.
Furthermore sensor S4's influence during night operation must be set.
3
OFF / ON
As a result of the weighting, a minimum value may be entered for the S4
temperature.
If the S4 temperature becomes lower than the minimum value, the refrigeration will
be stopped and the alarm activated. When the temperature rises to 2 K above the
minimum value, refrigeration will start again and the alarm will be cancelled.
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S6 can be a temperature sensor input or a volt free switch input depending upon the
function required.
The selection is made in the Day/Night Settings menu.
option 0 = No night setback. (S6 can be used as temperature sensor)
1 = Day/Night select via S6 (S6 used as switch input)
2 = Day/Night set via internal timeclock. (S6 can be used as temperature
sensor).
Thermostat Function
LL01-301 (Issue C) 12.08.98 / RC8AV102 10-2001 Page 9
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Change-over between day and night operation is performed with an external signal
connected to the controller's "S6" input or by the controller’s internal clock.
The input S6 registers the resistance value of the connected sensor / contact
function. (A resistance value greater than 1400 ohm will give night operation, a
resistance value smaller than 1100 ohm will give day operation).
A light-sensitive sensor placed in the refrigeration appliance may be used as signal
transmitter. When the appliance is covered for the night (with a night blind), this is
registered by the sensor, and there will be a change-over to night operation after a
fixed time delay of 5 minutes.
The function can also be obtained by connecting an external relay. A short-circuited
S6 input will give day operation. The relay contact must be goldplated.
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In the Microcool it is also possible to use an internal time schedule, to change
between day and night operation.
The start and stop times are set for each day of the week.
Principle
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Night: The moment when night operation starts
Day: The moment when night operation stops
Night = O or Day = 0:
When one of the two times is set at 0, or when both are set at 0, there will be QR
night operation for that particular 24-hour period.
Night = 1 and Day = 1:
When the two settings are set to the same time, there will be night operation during
the HQWLUH 24-hour period.
Thermostat Function
Page 10 LL01-301 (Issue C) 12.08.98 / RC8AV102 10-2001
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Definition of function:
Day / Night =
0: No night setback
1: Night operation according to signal at S6 input
2: Night operation according to internal time clock
Thermostat Function
LL01-301 (Issue C) 12.08.98 / RC8AV102 10-2001 Page 11
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The change-over between Day and Night operation can be actioned by the display
mounted Keyswitch. This mode is set by choosing option 5 in the Display Control
and Option 3 in the Day / Night Menu.
The unit will then cycle through the 3 case options with every action on the
keyswitch:
0 Ambient (No Cooling) Display shows Ab for 2 secs.
1 Day (Yellow) Display shows yel for 2 secs.
2 Night (Red) Display shows red for 2 secs.
Alarm Thermostat
Page 12 LL01-301 (Issue C) 12.08.98 / RC8AV102 10-2001
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The alarm thermostat function is used for sounding the alarm before the product
temperature at the refrigeration site becomes critical.
You can set alarm limits and time delays for high and low temperatures for both Day
and Night operations. Alarm will be given if the set limit is exceeded, but not until the
time delay has expired. The alarm sensor may be chosen independently of the
sensor used for the thermostat function.
1RWH On large sites the alarms will be set and handled in the Woodley Mk5 and so
do not require setting in the Microcool.
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You may select either alarm sensor S3 or S4.
The alarm thermostat is activated, and the alarm sensor is defined by keying a figure
between 0 and 3:
0: Alarm thermostat not operating
1: S3A is used
2: S4A is used
3: Both S3A and S4A are used
0/1/2/3
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The required temperature is indicated in °C.
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Three time delays can be set for alarms:
For too high temperature:
High1 Del m: Time delay after activation of the ON input,.
Time delay following defrost.
Time delay after a power failure .
The time delay will apply until the actual air temperature has
dropped below the "upper alarm limit".
High2Del m: Time delay during normal regulation.
Alarm Thermostat
LL01-301 (Issue C) 12.08.98 / RC8AV102 10-2001 Page 13
For too low temperature:
Low Del m: After the time delay the alarm will sound
The time delay is indicated in minutes:
Example
IN: Thermostat cut-in value
OUT: Thermostat cut-out value
Lim: Alarm limit for high temperature and low temperature
S: Alarm ceases
Curve 1: Cooling stage
(1): Time delay “High1Del m” has been exceeded. Alarm becomes
active
Curve 2: Normal regulation where the temperature becomes too high.
(2): Time delay "High2Del m" has been exceeded. Alarm becomes
active.
Curve 3: Temperature becomes too low
(3): Time delay "Low Del m" has been exceeded. Alarm becomes
active.
Expansion Valve Function
Page 14 LL01-301 (Issue C) 12.08.98 / RC8AV102 10-2001
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A type AKV 10-n expansion valve is connected to each Microcool..
Select ON or OFF for the injection function.
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The function contains an adaptive algorithm that independently adjusts the valve’s
degree of opening, so that the evaporator constantly has the smallest permissible
superheat (MSS). The value of the optimum superheat will be remembered after
stops and after power failures.
The established superheat reference is stored in the memory twice a day (at 12.00
noon and at 11.59 pm). The value is then used for restarts after power failures.
The superheat reference will be limited by the settings for min. and max. superheat.
Expansion Valve Function
LL01-301 (Issue C) 12.08.98 / RC8AV102 10-2001 Page 15
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(MOP = Max. Operating Pressure)
The MOP function limits the valve’s degree of opening as long as the evaporating
temperature measured by S1 is higher than the set MOP temperature. The function
can only be active when the injection valve function is ON. This function is common
to all injection functions.
The temperature is related to the measured S1 temperature.
OFF/ON
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The AKV valves can be closed with an external signal (the "ON" input is cut-out).
The function PXVW be used in connection with the compressor’s safety circuit, so that
there will be no injection of liquid into the evaporator when the compressor is
stopped by the safety controls.
If a defrost cycle is in progress, the forced closing status will not be re-established
until the defrost is completed.
Forced closing can also be actioned via communications from the Woodley Mk5.
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The electronic injection function may be cut out. The injection function can then be
carried out by means of a thermostatic expansion valve (like type TE). When this
application is used, a solenoid valve must be connected to the controller’s TEV
output.
This function allows the Microcool to be used as an evaporator/valve station
controller for large, pump circulation systems.
The thermostat function will now control the solenoid valve ON and OFF, so that the
required media temperature will be maintained.
The function is defined by putting the expansion valve function "Inj.Ctrl.()" in pos.
OFF and the "TEV" function in pos. ON.
OFF/ON
Expansion Valve Function
Page 16 LL01-301 (Issue C) 12.08.98 / RC8AV102 10-2001
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If a zeotrope refrigerant is used in the refrigeration appliance, a value for
temperature glide must be set. You are welcome to consult Woodley Electronics
about the correct setting.
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