Control; Switching The Controller On/Off; Virtual Probe; Set Point - Carel ir33+ small wide User Manual

6.1

Switching the controller On/Off

The controller can be switched ON/OFF from a number of sources;
keypad, supervisor and digital input. In this operating mode, the display
will be show the temperature selected for parameter /tI, alternating with
"OFF". The digital input can be used to switch the controller on/off , setting
parameter A4/A5 to "6". Switching on/off from digital input has priority
over the same function from the supervisor and the keypad.
Source Priority Note
Digital input 1 Disable On/Off from keypad and supervisor
Keypad 2
Supervisor 3

6.2 Virtual probe

The control output is the compressor output, which in most cases is also
associated with the evaporator fan output. The control probe is probe S1,
while probes S2, S3, S4 can be assigned functions such as product probe
(display only), defrost probe, condenser probe or frost protection probe.
For vertical display cases, the virtual probe (Sv) should be defi ned as the
control probe; this represents the half-way point between the display
case outlet and intake probes, and the reading is thus aff ected by the
environmental conditions. During the day, the display case light is on and
the curtain is open to allow customers to take out the products store, at
night the curtain is closed and the light is off . Due to the lower heat load
at night, the night-time set point is increased by the value of parameter
r4.
Par. Description
St

Set point

r4 Automatic night-time set point variation
/4 Virtual probe composition
0 = control probe S1
100 = probe S2
Parameter /4 is used to determine the virtual probe (Sv) as the weighted
average of control probe S1 and probe S2, according to the following
formula:
[( S1*(100 - /4) + S2*/4]
Sv =
DAY: set point = -13°C
S1
S2
Key
S1 Outlet probe
Sv Virtual probe
S2 Intake probe

6. CONTROL

Tab. 6.a
Def Min Max UOM
0 r1 r2
3.0 -20 20
0 0 100 -
Tab. 6.b
100
NIGHT: set point = -10°C
S1
/4=50
Sv=(S1+S2)/2
S2
Fig. 6.a
6.3 Set point
The reference output is the compressor output (CMP).
The controller can operate in 3 diff erent modes, as selected by parameter
r3:
•
direct with defrost control;
•
direct;
•
reverse.
Par. Description
St Set point
rd Diff erential
rn Neutral zone
rr Reverse diff erential
r1 Minimum set point
r2 Maximum set point
r3 Operating mode
0 = Direct with defrost control (cooling)
1 = Direct (cooling)
2 = Reverse (heating)
REVERSE
CMP
rd
°C/°F
Key
°C/°F
St Set point
Sv Virtual probe
If the second compressor output is activated (H1, H5 = 12) on the AUX
output, the compressor output is activated at St±rd/2 and the AUX
output at St±rd, as illustrated in the following fi gure.
REVERSE
AUX
CMP
rd/2
rd/2
St
Key
St Set point
Sv Virtual probe
CMP Compressor
The neutral zone is activated on the controller only if the reverse output
is activated with neutral zone control, H1 = 11. The fi gure below shows
direct operation (r3 =0, 1), with 1 compressor output (CMP) and 2
compressor outputs (CMP and AUX2).
29
Def Min Max UOM
0
2.0
4.0
2.0
-50
60
0
DIRECT
ON
ON
OFF
OFF
Sv
St
St
Fig. 6.b
rd Diff erential
CMP Compressor
DIRECT
ON
ON
OFF
OFF
ON
ON
OFF
OFF
Sv
St
Fig. 6.c
rd Diff erential
AUX Auxiliary output
ir33plus +0300028EN rel. 1.1 - 05.05.2017
ENG
r1 r2 °C/°F
0.1 20 °C/°F
0.0 60 °C/°F
0.1 20 °C/°F
-50 r2 °C/°F
r1 200 °C/°F
0 2 -
Tab. 6.c
CMP
Sv
rd
AUX
CMP
Sv
rd/2 rd/2