(SCL=2°C) or in Fahrenheit (SCL=°F). The measured temperature may be corrected with a fixed offset by assigning a value other than
0 to the parameter
OS1
. Furthermore, prior to display, the temperature is treated by an algorithm that allows the simulation of a thermal
mass directly proportional to the
SIM
value. The result is a reduction in the fluctuation of the displayed value.
The status of the compressor and auxiliary outputs is shown through the respective dots on the display.
TABLE 2
CAUTION
: upon changing the display scale SCL, it is
ABSOLUTELY
necessary to reconfigure the parameters related to the absolute (SPL, SPH,
SP) and differential (HYS, ATL, ATH, OS1) temperatures.
4. THERMOSTAT CONTROL
4.1
Thermostat control is based on comparing the temperature T1, the set point
SP
and the hysteresis
HYS
.
Example: SP= 2.0; HYS= 1.5, relay Off with T1= +2.0° and On with T1= +3.5°.
The compressor only switches On again if the minimum Off time
CRT
since the previous switchover has elapsed. Whenever a very
small hysteresis HYS must be maintained, we advise assigning a suitable value to CRT in order to reduce the number of starts/hour.
4.2
If sensor T1 fails, the output is controlled for a fixed time established with
CDC
; this determines the activation time of the output
within 10-minute cycles.
Example: CDC=06, 6 minutes On, 4 minutes Off.
5. DEFROSTING
Defrosting starts automatically when the internal timer reaches the necessary time to obtain the defrosting frequency set with
DFR
. For
example, with DFR=4 defrosting occurs once every 6 hours. With DFR=0 the timed defrosting function is cut out. When the controller
is put on a standby, the timer count is frozen.
Defrosting may also be induced manually by pressing the buttons
and
simultaneously.
The internal timer is set to zero when the instrument is switched on, at each subsequent defrost start and, if in the standby mode,
whenever standby lasts for at least the time set in
DTO
.
Defrosting occurs upon stopping the compressor and, if
OUA
=
DEF
, upon activating the defrost heater through the auxiliary relay for
the time
DTO
. During defrosting
appears on the display and remains there after the end of defrosting for the time set in
DDY
.
6. ALARMS
With LDU15 correct operation of the thermostat, sensor and the periodic warning of condenser cleaning can be checked. The alarm
warnings are given on the display with explicit indications (table 2) and, with
OAU
=
ALR
, also on the auxiliary relay (not for condenser
cleaning).
The alarm warning is removed from the display upon pressing any button for two seconds, but if the alarm persists, it reappears after
30 minutes. Operation of the various sections is given in detail below.
6.1
The parameters
ATL
and
ATH
define two differential temperatures that, referred to the set point, determine the temperature alarm
thresholds.
ATL
establishes the alarm differential for temperatures below set point,
ATH
the alarm differential for temperatures above
set point + hysteresis. Putting one or both differentials to 0 cuts out the corresponding alarm.
Example: SP= 2.0, HYS= 1.5, ATL= -5.0, ATH= 5.0; the alarm thresholds are fixed at -3.0° and +8.5°.
The alarm warning may be immediate or delayed by the time
ATD
whenever this is greater than 0. The high temperature alarm is
bypassed during defrosting.
6.2 Assigning a value greater than 0 to the parameter
ACC
enables the indication for periodic cleaning of the condenser. In other
words, when the count of compressor hours of operation reaches the equivalent in weeks set with ACC, an indication for cleaning
appears on the display (see table 2).
Example: with ACC=16 there is a warning once every 16x7(weeks)x24(hours)=2688 hours of
compressor operation
, in other words,
assuming for this an operation with 5 minutes On and 5 minutes Off - after approx. 32 weeks.
The time counter may only be cleared after the programmed time has been reached. Therefore proceed as follows: press the buttons
and
in sequence and hold them simultaneously.
7. AUXILIARY FUNCTIONS
The LDU15 controller comprises a button and an auxiliaries relay with functions that may be suitably combined through the parameters
OAU
and
BAU
. The parameter
OAU
assigns one of the following functions to the auxiliary output: alarm warning (ALR), defrost heater
control (DEF), manual control (MAN), auxiliary loads (SBY), cut-out (NON). The parameter
BAU
determines the function associated
AUX
DF
INSTRUCTIONS FOR INSTALLATION AND USE.
-
autotest (3 seconds)
HI
high temperature alarm
2.5
sensor T1 temperature
LO
low temperature alarm
DF
defrosting in progress
E1
sensor T1 failure
OFF
standby
CLN
Condenser cleaning
