5 Commencing operation and control behavior
Page 6
of
13
Rittal cooling unit assembly and operating instructions
5.1.8
Compressor: On / Off
Switching the compressor ON: press UP for more
than 3 s (when pressing the button, the display
shows ON).
Switching the compressor OFF: press UP for more
than 3 s. The d
isplay shows the message “OFF”.
In OFF status, the following functions are disabled (if
featured by the model):
compressor control
duty setting
continuous cycle
5.2
Alarm parameters
A0: Alarm temperature differential
This represents the differential used to activate the
high temperature alarm
(“AH”) .In the event of an
alarm, as seen in the figure, the value of “A0” deter-
mines the actual activation of the temperature alarm.
The value of “A0” (negative or positive) defines the
nature of alarm
“AH” (absolute or relative):
A0
≤ 0
AH expressed as absolutes
A0 > 0
AH expressed relative to the set point
Figure 4: High temperature alarm
AH: High temperature alarm
AH setting: 10 degrees is the factory setting (-50 to
99 is the lower and upper limit ). Other Factory set-
tings: Setpoint (ST) = 35°C; A0 = 2°C.
For example: If the internal temperature of the cabi-
net is Ti = 46°C, ST (35°C)+ AH (10°C) = 45°C ,
so 46°C > 45°C the display will show AH-alarm. As
long as Ti is more than 43°C the display will show
AH-alarm, because ST (35°C)+ AH (10°C) - A0 (2°C)
= 43°C. If the temperature Ti will fall to 42°C the
alarm AH will no longer be shown in the display. As
long as the temperature inside of the cabinet will not
rise over 45°C again there will be no AH-alarm dis-
played.
Temperature alarm output
Logo and buzzer on display: The information
“AH” and logo will be shown on the display and
buzzer.
The over temperature message may also be
polled via a contact on the connection clamp of
the cooling unit (system message relay with
changeover contact, see connection diagrams).
--Terminal
“
1
”
C (connection of the supply voltage
to the fault signal relay)
--Terminal
“
2
”
NO (normally open) .
Notice!
Delay for high temperature alarm when
power ON: When alarm condition is
achieved but power is ON, the timer
start to count for a specify value (Ad1).
Alarm relay becomes active when this
time is elapsed.
Notice!
The unit of parameter “Ad” is “Sec”.
The u
nit of parameter “Ad1” is “Min”.
Notice!
The contacts of the relays are normally
open (NO). If the alarm occurs the con-
tacts close (NC).
5.3
Evaluating system messages
Display
screen
Buzzer
Alarm
relay
System
message
Measures
E0
Active
Not
active
Ambient
temperature
probe bro-
ken
Check sen-
sor cable
and replace
if necessary
HI
Active
Active
High tem-
perature
alarm
Check cool-
ing capaci-
ty/check unit
5.4
Forced cooling
The continuous cycle is used to maintain refrigeration
forced cooling mode active in the cabinet or cold
room, regardless of the temperature inside the unit.
This may be useful for rapidly bringing the tempera-
ture below the set point value.
To activate or deactivate the continuous cycle from
the keypad, Press UP+DOWN for more than 3 s, the
display shows “cc” and the icon flashes (2 flashes,
pause).
The unit starts the forced cooling mode at least after
the minimum compressor off time ( 3 min.). The
forced cooling mode is activated after the start for 1 h.
After this time the unit starts normal operation.
6
Filter mats
The stainless steel filter mat available as an acces-
sory is coarse and filters large dust particles or fluff
from the air. Subject to the suction of the blower be-
ing high enough, fine dust is blown through the filter
mat and the external circuit of the unit. This does not
affect the unit's operation.
