VALLOX 252 D
7
Control of operation
If needed, power supply to the unit can be controlled via the contactor in
the distribution panel, using a timer program, for instance. Upon starting,
the unit operates at minimum capacity. After that, capacity is controlled
on the basis of measurement data supplied by the air quality sensors
and/or through manual control on the control panel.
Fan speed adjustment
Manual control
Fan speed of the ventilation unit is controlled in 8 steps on the control
panel (
H
).
Carbon dioxide and humidity control
The fan capacity of the ventilation unit is controlled in multiple steps
depending on load, and based on the measuring results of the air quality
sensors (CO
2
and %RH sensors) located in the ventilation zone. The aim is
to keep the CO
2
and/or humidity content of the zone below the setpoint
defined on the control panel (
H
). One or more modes of control may be
used simultaneously. The dominant mode is the one demanding boosting.
Ventilation can be adjusted in a maximum of 8 steps. The basic and
maximum fan speeds for adjustment purposes can be set at the desired
level.
Voltage and current signal control
The fan capacity of the ventilation unit is controlled in 8 steps with the
voltage signal 0…10 VDC, or with the current signal 0…20 mA. How-
ever, the fan capacity cannot be raised above the preset fan speed.
The voltage or current signal control is used to control basic fan speed.
Because of this, fan speed can only be raised, but not lowered by the
manual, CO
2
and %RH controls.
Supply air temperature
Supply air temperature can be controlled using either constant temperatu-
re control or cascade control.
DESCRIPTION OF OPERATION VALLOX 252 D
Supply air constant temperature control
The control unit directs the operation of the post-heating unit (
LP2
) on the
basis of the measuring data on the temperature sensor
TE2
, aiming at
keeping supply air temperature at the temperature value set on the control
panel
H
(+10˚…+30˚C).
Supply air cascade control
The control unit directs the operation of the post-heating unit
(LP2)
on the
basis of the measuring data on the extract air sensor
TE4
, aiming at keep-
ing extract air temperature at the temperature value set on the control
panel
H
(+10˚…+30˚C).
Heat recovery bypass
When post-heating has been switched on, heat recovery is enabled all
the time. Automatic heat recovery bypass is active whenever post-heating
has been switched off and outdoor temperature is more than the preset
threshold value (range 0˚…+25˚C). In this case, the control unit directs
the operation of the damper motor (
FG
) on the basis of measuring results
given by the outdoor sensor
TE3
and the extract air temperature sensor
TE4
. The aim is to get as cool supply air to the ventilation zone as possible.
However, heat recovery is in use whenever outdoor air descends below
the preset threshold value.
Heat recovery anti-freezing
The control / regulation center of the unit directs the operation of the
preheater (
LP1
) on the basis of the measurement data supplied by the
temperature sensor
TE1
. The aim is to prevent the risk of freezing and the
stopping of the supply air fan (
TF
). If the capacity of the preheater (
LP1
) is
not sufficient, or if there is no preheater, the control center intermittently
stops the
TF
supply air fan on the basis of the measuring data on the
temperature sensor
TE1
, thereby preventing the heat recovery cell from
freezing. As soon as the risk of frosting passes, the fan restarts
automatically. The threshold temperature for defrosting (-6…+15˚C) and
the difference area (+1…+10˚C) can be set on the control panel (
H
).
Overheating protection of the heating unit
The overheat protection thermostats
TZ1
and
TZ2
monitor the surface
temperature in the
LP1
and
LP2
heating units. If surface temperature
exceeds the threshold, overheat protection is triggered and power supply
to the heating unit is stopped. The
TZ1
overheating protector is reset
automatically, and the
TZ2
protector manually.
Alarms
The pressure difference switches
PDS1
and
PDS2
monitor the pressure
difference between 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, showing as 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 maintenance reminder interval can
be set between 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:
• Alarm of high carbon dioxide content (> 5000 ppm ) switches the relay
at 1-second intervals.
• In other fault situations, such as sensor faults and filter guard ( ) alarms,
the points of the relay close.
Booster or fireplace switch function
An extra switch
S
may be connected to the connection box of the ventila-
tion unit to work as a booster or fireplace switch. The operation of the
switch is selected on the control panel
H
. The booster switch function rai-
ses fan speed to maximum speed for 45 minutes.
The fireplace switch function stops the extract air fan for 15 minutes, and
causes overpressure in the ventilation zone.
LON remote monitoring control can be implemented with the VALLOX LON converter.
Voltage values for fan speeds:
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 fan speeds:
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 signals
Code
Name
Technical details
Note!
Equipment
(factory settings in parentheses)
Parts list
CO
2
CO
2
sensor, max. 5 pcs
Adjustment range 500...2000ppm (900)
Option
Carbon dioxide control
Adjustment interval 1...15 min. (1)
FG
Damper motor
Automatic heat recovery bypass 24V, 2W, 8Nm
Standard
X
H
Control panel, max. 3 pcs
Setting, operation, display
Standard, 1 pc
X
S
Booster / fireplace switch
Functions as either a booster or a fireplace switch Standard
X
(booster switch)
LON
LON converter
Remote monitoring control
Option
LP1
Preheater
Electric radiator 2.5kW
Option
LP2
Post-heating unit
Electric radiator 2.5kW
Option
HRC1
Heat recovery cells
2-step,
η
= 70 %
Standard
X
HRC2
PDS1
Pressure difference switch
Adjustment range 0...500Pa (420)
Option
Pressure guard for supply air
PDS2
Pressure difference switch
Adjustment range 0...500Pa (420)
Option
Pressure guard for extract air
PF
Extract air fan
qv = 230 dm
3
/s (100Pa)
Standard
X
%RH
Humidity sensor, max. 2 pcs
Adjustment range 1...99% (50)
Option
Humidity control
Adjustment interval 1...15 min. (1)
SU
Filter
Supply air EU7, extract air EU5
Standard
X
TE1
Temperature sensor
Exhaust air temperature
Standard
X
Heat recovery defrosting,
Adjustment range -6˚...+15˚C (HRC)
preheating control
Adjustment range -6˚...+15˚C (preheating)
TE2
Temperature sensor
Supply air temperature
Standard
X
TE3
Temperature sensor
Outdoor air temperature
Standard
X
TE4
Temperature sensor
Extract air temperature
Standard
X
TF
Supply air fan
qv = 210 dm
3
/s (100Pa)
Standard
X
TZ1
Overheat protector
Automatic reset (+60˚C)
Included
of the heating unit
Self-resetting
in LP1 / LP2
TZ2
Overheat protector
Manual reset (+95˚C)
Included
of the heating unit
in LP1 / LP2
