VALLOX DIGIT2 SE/VKL/MLV
© VALLOX • We reserve the right to make changes without prior notification.
15
DESCRIPTION OF OPERATION/VKL MODEL
Control of operation
Power supply to the unit can be controlled with a contactor in the
distribution panel if needed, e.g. with a timer programme. After
starting, the unit first operates at minimum power. After that power is
adjusted based either on the measurement data from air quality sensors
and/or on manual control at the control panel.
Fan speed adjustment
Manual control
Fan speed of the ventilation unit is controlled in 8 steps at control
panel
H
.
Week-clock control
Fan speed of the ventilation unit is controlled in 8 steps using the week
clock in control panel
H
. The week clock can be used to programme
the desired fan power option and the setpoint for supply air temperature
for each day of the week and each hour in the day.
Carbon dioxide and humidity control
The fan capacity of the ventilation unit is controlled in multiple steps
depending on loads, and based on the measurement results of the air
quality sensors (CO
2
and %RH sensors) located in the ventilation zone.
The aim is to keep carbon dioxide and/or humidity content below
the threshold set at control panel
H
. It is also possible to select an
automatic search for the humidity content setpoint at control panel
H
.
One or more modes of control may be used simultaneously – the mode
demanding boosting is the dominant one. Fan speed varies depending
on load between the base and maximum fan speeds. The base and
maximum fan speeds can be set at the desired level on control panel
H
.
Control through voltage or current signal
The fan power of the ventilation unit is controlled in 8 steps with a
voltage signal of 0...10 VDC, or with a current signal of 0...20 mA.
However, fan power cannot be raised above the set maximum fan
speed. Voltage or current signal control is used to control base fan
speed. This means that fan speed can be raised when necessary, but
not lowered, by the manual, CO
2
and %RH controls.
Supply air temperature
Supply air temperature can be controlled with either constant temperature
control or cascade control.
Constant temperature control of supply air
The control unit directs the operation of post-heating unit
R1
on the
basis of the measuring data given by temperature sensor
TE2
, aiming
at keeping supply air temperature at the temperature value (+10...+30
°
C) set at control panel
H
.
Cascade control of supply air
The control unit directs the operation of post-heating unit
R1
on the
basis of the measuring data given by extract air temperature sensor
TE4
, aiming at keeping supply air temperature at the temperature value
(+10...+30
°
C) set at control panel
H
.
Heat recovery bypass
Heat recovery is active whenever post-heating is switched on. Automatic
heat recovery bypass is active when post-heating is switched off and
outdoor air temperature exceeds the threshold set (to bet set in the
range of 0... +25
°
C). The control centre then controls the operation
of damper motor
PM
on the basis of the measurement data given by
outdoor air sensor
TE3
and extract air temperature sensor
TE4
in order
to get as cool supply air as possible in the ventilation zone. However,
heat recovery is active whenever outdoor air temperature falls below
the threshold set, or when outdoor air is warmer than extract air.
Heat recovery antifreeze
The control centre of the unit controls the operation of preheating unit
R2
on the basis of the measurement data given by temperature sensors
TE1
and
TE3
, preventing the risk of freezing and the intermittent stopping
of supply air fan
S
. If the power of preheating unit
R2
is not enough
or is not on, the control centre intermittently stops supply air fan
S
on
the basis of the measurement data given by temperature sensors
TE1
and
TE3
, preventing the
HR
cell from freezing. As soon as the risk
passes, the fan restarts automatically. The threshold temperature for
antifreeze (-6...+ 15
°
C) and the difference area (1...10
°
C) can be
set at control panel
H
. When fan
T
stops, power supply from radiator
R2
stops and post-heating radiator
R1
continues to heat.
For preheating to work, its threshold temperature has to be set by at
least one degree higher than the threshold temperature controlling the
stopping of the fan. Temperatures are adjusted at control panel
H
.
Overheat protection for the heating unit
Overheat protection thermostats
TS3
and
TS4
monitor the surface
temperature of heating unit
R2
. If surface temperature exceeds the
threshold, the overheat protector trips and power supply to the heating
unit is stopped. Overheat protector
TS3
is reset automatically, whereas
overheat protector
TS4
is reset manually.
Water radiator freezing protection
The control centre of the unit stops fans
S
and
E
, valve
V
remains open
and self-actuated dampers
SP
close based on the measurement data
given by outdoor air temperature sensor
TE3
(outdoor air < 0
°
C) and
supply air temperature sensor
TE2
(supply air < 7
°
C), reducing the risk
of water heating unit
R1
freezing. A freezing alert appears in the
display of the control panel. The fans restart automatically and dampers
SP
open as soon as the risk of freezing passes (supply air > 10
°
C).
Alarms
Pressure difference switches
P1
and
P2
monitor pressure difference on
the supply and extract air sides. If the pressure difference rises too
high because of dirty filters or clogged ducts, an alarm will be issued.
This is indicated by a symbol ( ) in the main display of the control
panel. If the unit is not equipped with pressure difference switches,
the symbol ( ) appearing in the main display of the control panel
reminds of the need of servicing the unit. The reminder interval can
be set at 1...15 months. The factory setting is 4 months. This function
is always active. The fault signal relay in the unit gives potential-free
alarm indications on the following fault conditions:
• When the antifreeze function of the water-circulating radiator is on,
the contacts of the relay close and open at a 10-second interval.
• Alarm of high carbon dioxide content (> 5000 ppm) switches the
relay at 1-second intervals.
• In other fault situations, such as sensor faults, the contacts of the
relay close.
Booster or fireplace switch function
The booster or fireplace switch function of the ventilation unit is controlled
either at control panel
H
and/or separate switch
S
, which can be
connected to the connection box of the unit. The mode of operation
of the switch is selected at control panel
H
. The booster switch function
raises fan speed to the set maximum fan speed for 45 minutes. The
fireplace switch stops the extract air fan for 15 minutes and produces
overpressure in the ventilation zone. LON remote monitoring control
can be implemented with a VALLOX LON converter. (See a separate
brochure.)
Voltage values
for each fan speed:
0
0.20...1.25 VDC
1
1.75...2.25 VDC
2 2.75...3.25 VDC
3 3.75...4.25 VDC
4 4.75...5.25 VDC
5 5.75...6.25 VDC
6 6.75...7.25
VDC
7
7.75...8.25 VDC
8 8.75...10.00
VDC
Current signal values
for each fan speed:
0 0.5...2.5 mA
1
3.5...4.5 mA
2
5.5...6.5 mA
3 7.5...8.5 mA
4 9.5...10.5 mA
5 11.5...12.5
mA
6 13.5...14.5
mA
7 15.5...16.5
mA
8 17.5...20.0
mA
Voltage and current signal values (selection in the motherboard)
