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VALLOX DIGIT2 SE/VKL/MLV

DESCRIPTION OF OPERATION/MLV 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

Week-clock control

Fan speed of the ventilation unit is controlled in 8 steps using the week
clock in control panel

. 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

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

. It is also possible to select an

automatic search for the humidity content setpoint at control panel

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 at control panel

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

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

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

. The cooling function of the

MLV

radiator starts when the post-heating radiator has been switched off
and supply air temperature exceeds the setpoint for supply air.

Cascade control of supply air

The control unit directs the operation of post-heating unit

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

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

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

Controlling preheating in a liquid-circulating

MLV

radiator is different

from that in an electric preheating radiator. The liquid radiator switches
on based on the measurement data from outdoor air temperature
sensor

TE3

. The control centre of the unit starts the pump and opens

the solenoid valve when post-heating is on and outdoor air temperature
goes below the setpoint temperature for preheating. The setpoint must
be lower than the temperature of the liquid coming from the ground
collector. If the power of preheating unit

is not enough, the control

centre intermittently stops supply air fan

on the basis of the measurement

data given by temperature sensors

TE1

and

TE3

, preventing the

cell

from freezing. As soon as the risk passes, the fan restarts automatically.
The threshold temperature (-6...+15

C) and difference area

(1...10

C) for antifreeze can be set at control panel

Water radiator freezing protection

The control centre of the unit stops fans

and

, valve

remains open

and self-actuated dampers

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

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).

Overheat protection for the heating unit

Overheat protection thermostats

TS1

and

TS2

monitor the surface

temperature of heating unit

. If surface temperature exceeds the

threshold, the overheat protector trips and power supply to the heating
unit is stopped. Overheat protector

TS1

is reset automatically, whereas

overheat protector

TS2

is reset manually.

Alarms

Pressure difference switches

and

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

An extra switch

may be connected to the connection box of the

ventilation unit to work as a booster or fireplace switch. The mode of
operation of the switch is selected at control panel

. The booster

switch function raises fan speed to the set maximum 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:

0.20...1.25 VDC

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

7.75...8.25 VDC

8 8.75...10.00

VDC