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5.2.1 Operation of the microcontroller
The display terminal H1 consists of a 3 position
7-segment display which indicates the enclosure
internal temperature in °C or °F (changeable, see
section 5.2.2) as well as any fault codes. The
actual enclosure internal temperature is con-
stantly displayed. If a fault occurs then the fault
number is indicated in the left position. When pro-
gramming the microcontroller the program level
and parameter value is indicated on the display.
When the "TEST" button is pushed the compres-
sor and the fans will run for 5 minutes regardless
of the internal temperature or door limit switch.
This allows for a system test after an extended
shutdown period (e.g. after the winter).
5.2.2 Programming
In the EEPROM of the microcontroller various
parameters are stored which can be changed
through using the "ENTER" and "
" buttons,
9 different parameters are changeable as outlined
in table 5.1. To access the programming mode
push both the "ENTER" and "
" buttons simulta-
neously for 10 seconds. The left digit will then
indicate the program level and the LED for the
"ENTER" and "
" buttons will blink. By pushing
the "
" button the program level can be ad-
vanced to the next level. In order to access levels
5 through 9 a security code must be entered. If no
buttons are pushed for 60 seconds the display
will return to the standard mode which displays
the enclosure temperature. Programming of the
parameters is made easy with diagram 5.1 on
page 39. A description of the parameters to be
programmed can be found in table 5.1. All para-
meters are stored in the EEPROM and are retain-
ed when power is shut off to the air conditioner.
5.2.3 Fault signalling facility
All faults on the cooling unit are registered and
indicated by H1 as a fault number. The display is
by means of the left-hand number. The display
cycles through all pending fault messages in a
2 second cycle, starting with the internal tempera-
ture of the enclosure.
H1 indicates the following faults as a fault number.
1 = Enclosure internal temperature too high
(5 K above setpoint value)
2 = Current monitor, condenser
3 = Evaporator (no collective fault indication).
4 = High-pressure monitor
5 = Current monitor, condenser fan
6 = Current monitor, evaporator fan
7 = Filter mat soiled
8 = Temperature sensor cable break/short-circuit
5.2.3.1 Fault signal contact
(K1, potential-free)
The fault signal relay is pulled in at normal condi-
tion. Any faults will cause the relay to drop out
(except low-pressure monitor, fault number 3).
Any failure of the control voltage will also lead to
drop-out of the relay and can thus be registered.
The connection is made on the terminal strip X10.
For contact data and assignment, see wiring dia-
gram.
5.2.3.2 Filter mat monitoring
The specified filter mat has large pores and filters
coarse dust and lint from the air. Oil condensate is
partially separated out. Fine dust is drawn through
the filter mat and the external circuit of the unit
due to the high suction power of the fan. It does
not have any damaging effect on the function of
the unit.
Fig. 5.3 Filter mat replacement
SK 3391. . . .
SK 3394. . . .
SK 3299. . . . / 3261. . . .
Function of the filter mat monitor:
The filter mat is monitored for soiling by meas-
uring the temperature difference in the external
circulation of the cooling unit. In the event of any
filter mat soiling, the temperature difference will
increase. The setpoint value of the temperature
difference in the external circulation is adapted to
various air conditioner operating conditions. This
eliminates the need for subsequent adjustment of
the setpoint value for different operating points of
the unit. (For the setting of the filter mat replace-
ment see table 5.1 and fig. 5.1).
5.2.3.3 Door limit switch S2
(supplied by costumer)
Where a door limit switch is used and the enclo-
sure door is open (contact is closed when door is
open), the cooling unit (fans and condenser) will
switch off after approx. 10 s, thereby avoiding an
increase in condensation while the door is open.
To avoid cyclic operation, switch-on of condenser
and external fan is delayed by about 3 minutes
after the door has been closed. The internal fan
will start up immediately on closure of the door.
Connection is made at the terminal strip X10, ter-
minals 1 and 2. The extra low voltage is supplied
by the internal power pack, current is approx.
30 mA DC (no extra low safety voltage). Connect
the door limit switch free from potential only, no
external voltage! The display will flash during the
door delay time. The system message "1010" is
transmitted via the PLC interface.
5.2.3.4 PLC interface X2 (option)
The interface is used for the transmission of the
actual internal temperature of the enclosure and
any system messages of the cooling unit to the
PLC. The transmitted information can be dis-
played by means of the output facilities (e.g. plain
text display) which are connected to the PLC, or
by means of the serial interface to a higher order
computer.
Construction of the PLC interface:
The construction is potential separated via opto-
coupler (wiring diagram fig. 5.4). Connection is
made by the customer to the 15-pin socket on the
control board (fig. 5.4) to the PLC input card.
Attention!
The electrical signals at the interface are of an
extra-low voltage (not extra-low safety voltages
according to EN 60 335).
Fig. 5.4 PLC interface
9
1
2
3
4
5
6
7
8
15-pin. Sub-D
Max. loading of the outputs:
30 V/10 mA, direct current
Connection: screened 15-core control cable
The possibility exists to access this information
over the PLC interface (level 8, table 5.1 or
fig. 5.1).
a) Standard mode (Level 8 = "0")
Communication of the enclosure internal tempe-
rature and of the fault messages is made
successively in 2 s cycle. Since this is an 8-bit
parallel transmission, input signals should not
be accepted as valid in the PLC until they have
been present for 0.5 s. This ensures that no in-
valid input information will be evaluated in the
event of signal changes at the inputs.
Fig. 5.5 PLC interface X2
Pulse/time diagram (example)
0.5
0.5
0.5
Bit
2 sec.
2
2
2
7
6
5
4
3
2
1
0
Temperature
5 Fault 6
32 °C 33 °C
store cancel
Enclosure internal temperature:
Transmission with 2 digits in BCD format:
Bit 7
0
ZZZZ
EEEE
System messages:
The system messages are transferred by means
of identification (4 bit) and a fault number
(1 digit BCD). The identification is structured as
follows:
Bit 7
0
XXXX
1010
In the event of a fault XXXX (BCD), the identifi-
cation is transmitted cyclically. This information
can be used to store the fault message in the
PLC.
Bit 7
0
XXXX
1011
e.g.
+ 24 V
E x.0
E x.1
This identification is transferred once, as soon
as the fault with the number XXXX/BCD has
been rectified. This information can be used to
E x.2
delete the fault message in the PLC.
E x.3
Evaluation of the interface signals in the PLC:
Messages:
E x.4
If bit 1 and bit 3 of the input byte have a 1
signal, the transmitted information is a system
E x.5
message. In this case, the meaning of bit 0 is
either the information "store fault message" (bit
0 = 0) or "cancel fault message" (bit 0 = 1).
E x.6
Bit 4 to 7 represent the appropriate message
number (BCD).
E x.7
X2
0.5
Sub-D plug
Pin
2
8
7
6
5
4
3
2
1
Temperature
34 °C
Units
Tens
Identification
"Store fault
message"
Fault number
1 to 8
(see list)
Identification
"Store fault
message"
Fault number
1 to 8
(see list)
7
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