Measuring and adjusting the ventilation system

Measurement and adjustment of the ventilation system according to the ventilation plan ensures its proper service, appropriate ventilation of each room and the correct ratio between the air flows.

A ventilation system must always be adjusted in accordance with the ventilation plan so that it will work as desired. Correct adjustment ensures appropriate ventilation in each room and the correct ratio between the supply and extract air flows. An overpressure in the building pushes moisture from the room into the structures of the external envelope, while an excessive underpressure may hinder draughts in fireplaces and the leaking air may carry impurities from outdoors or the wall structures.

The SFP figure of the supply and extract air ventilation system, i.e. the power consumption of the fans in relation to the air flow, should not exceed 1.8 kW/(m3/s) (Decree of the Ministry of the Environment on the Energy Performance of New Buildings 1010/2017). The achievement of this basically requires a ventilation unit with DC fans, in addition to thorough planning, a wide duct network and adjustment by a professional.

A competent professional can adjust the Vallox ventilation units to ensure silent, economic and efficient ventilation. In the newest ventilation unit models, each fan speed can be adjusted individually, and the ratio between the supply and extract air flow is also adjustable.

• With the MyVallox Control and MyVallox Touch control panels, the fan speed and the ratio between the supply and extract air flows are preset by using the percentage adjustment in the control panel Settings menu.
• The fan speeds can be adjusted and the entire setup carried out also conveniently on a computer. The computer can be connected to the ventilation unit with a LAN cable, without the need to install any software.

General instructions for adjustment

Air flows must be adjusted by using the lowest possible fan speed. If ventilation is adjusted by using an unnecessarily high fan speed and the air flows are choked by means of valves, this increases the noise level of the ventilation system and increases the energy consumption of the fans. In addition, low-set valves prevent the adequate boosting of ventilation.

Air flows must always be measured by using clean original filters. Heat recovery must be on, i.e. the summer damper must not be in the summer position, because in some ventilation units, the air flow can be different from the air flow in winter. A correct supply-extract ratio is particularly important in winter. Before adjustment, ensure that the outdoor grille does not have an insect net.

In below-zero weather, ensure that the heat recovery cell is free of ice. In units equipped with MC defrost automation, some ice may accumulate in the cell before the defrosting cycle starts. If there is ice in the cell, the defrosting cycle can be started manually from the service menu of the MV models or on the computer. During the defrosting cycle, the supply side of the heat recovery cell is bypassed. The duration of the cycle is at least 15 minutes. During the defrosting cycle, the speed of the fans in relation to each other does not change, but in very cold weather, the efficiency of ventilation may temporarily decrease before the electrical resistors can heat the supply air adequately. Measurements should not usually be made in very cold weather or when the humidity level is exceptionally high inside the home.

Many Vallox ventilation units have fixed air flow measuring tubes, or they are supplied with the unit and installed in the duct. The pressure difference measured from them can be used to calculate the total air flow. This is particularly convenient if the air flows measured from the valves deviate from the design values and a leak or blockage of the ducts is suspected.

Air flow adjustment

Preparing for adjustment

Adjust the valves roughly to the correct position – principally relatively wide open. If it is the Vallox MV model with the 2.0 or later software version, open the Air volume adjustment menu from the Save and restore settings menu. With older software versions, restore factory settings and select “Do you want to make expert settings?”.

Adjustment of total air flows from the unit with traditional EC or AC fans

1. Measure the pressure difference from the extraction side of the unit (between the extract air and the exhaust air ducts). See the fan curves of the unit to determine the speed at which this setting will most probably be met. Measure the pressure difference by using the fan speed that you assume to be in the correct operating range and at speeds that are 1-2 steps lower and 1-2 steps higher. In most cases, 3-4 speeds are sufficient. Depending on the ventilation unit model, the speeds of the fan curves are specified in numeric values, in efficiency (in %), or in adjustment voltage (V). If the speeds are indicated as voltages, the fan control voltage can be measured at the control panel (measuring pins – and S).
2. Mark the measured results in the extract curve of each speed in the fan curve of the ventilation unit’s technical manual and connect the dots to form a line. Fan curves can be printed in a larger scale from Vallox’s professional page. Alternatively, the facility curve can be “drawn” by using the Vallox MySelecta product selection software.
3. Draw a vertical line from the air flow axis where the planned total extract air flow is, to the line you drew and from there a horizontal line to the pressure difference axis. This will tell you how much the unit needs to increase the pressure for the total extract air flow to be correct.
4. Measure the pressure difference from the extraction side of the unit (between the extract and exhaust air ducts) and adjust by using the nearest suitable fan speed or the pressure of the “At home” mode to match the pressure requirement you just calculated. Use the fan power percentage setting of the control panel or the potentiometer of the controller for the adjustment. This setting only adjusts the fan speed in question. The total extract air flow is now correct.
5. Adjust the supply air flow correspondingly by measuring the pressure difference from the supply side (between the outdoor and supply air ducts).
6. If the supply air flow is too high, reduce the speed of the supply air fan. If the supply air flow is too low, increase the fan speed you adjusted in point 4, until an adequate pressure increase on the supply side is reached. Then decrease the power of the extract fan, until the pressure difference on the extract side is correct. This adjustment affects the supply/extract ratio at all fan speeds. Do not change the supply/extract ratio after this! The difference in power between the supply and extract fans must be less than 30%.

Measuring of room-specific air flows

1. Set the ventilation power to the Home position or to the fan speed you adjusted in point 6 in section Adjusting total air flows at the unit. Adjust the planned room-specific basic air flows for the Home mode at the valves. If the air flow of one of the valves is not sufficient during the first adjustment round, do not increase the rotation speed of the ventilation unit. As the total air flow of the ventilation unit has been adjusted correctly, the air flow of some other valve is too high.
2. Make sure that the boosting air flows in the plan are achieved or surpassed in the Boost mode or at a fan speed suitable for boosting. If needed, adjust the fan speed of the Boost mode. Use the fan speed percentage setting of the control panel or the potentiometer of the controller for the adjustment. This adjustment only adjusts the fan speed in question. The total extract air flow is now correct. Do not make further changes to the adjustment positions or the supply/extraction ratio of the valves.
3. If the control panel has a higher adjustment position, it can usually be reserved for full speed.
4. Measure the absence air flows (for instance, 30% lower than basic ventilation) in the same way in the Away mode or at a suitable fan speed. If needed, adjust the fan speed of the Away mode. Use the fan power percentage setting of the control panel or the potentiometer of the controller for the adjustment. This adjustment only adjusts the fan speed in question. The total extract air flow is now correct. Do not make further changes to the adjustment positions or the supply/extraction ratio of the valves.
5. Record the reached valve-specific air flows and the fan speed used for the adjustment in the measurement log (including the adjustment voltage or percentage, if provided by the control panel) and the efficiency of the supply and extract air fans in percentage. In terraced houses, for example, the adjustment position of them and the valves can be used to “copy” the basic settings made in the first apartment to other similar apartments.
6. Inform the residents about the speeds that should be used in various situations. If the ventilation unit is equipped with integrated or external humidity and/or carbon dioxide sensors, inform the residents about their operation. In most cases, a ventilation unit that is equipped with both sensors can be left in the Away mode after the adjustment. Then, when the number of persons or the humidity level increases, ventilation is boosted according to need, up to the boost speed. If the unit has no carbon dioxide sensor, ensure that the ventilation in the apartment remains adequate also when the humidity sensor reduces the ventilation after the bathroom has dried by restricting the lowest fan speed either fixedly or according to the weekly programme.

Air flow adjustment for constant flow fans (CF models)

Constant flow fans keep the air flow constant regardless of the effect of wind, temperature differences, pressure loss in the duct system or other external parameters.

1. See the ventilation unit fan curves to check the fan percentages at which the required supply and extract air flows for the At home mode are achieved.
2. Set the correct supply and extract fan percentages.
3. Measure and adjust the air flows from the supply and extract air valves. Note that the total air flows always remain constant. For instance, when you reduce the air flow for one supply air valve, a similar addition takes place at other supply air valves, i.e. you cannot reduce the total air flow by throttling valves. Lock the valves after adjusting the At home air flows.
4. Measure and adjust the air flows for the Away and Boost modes and adjust their fan percentage, if required. Do not change the adjustment positions of the valves or the ratio between the supply and extract fans.

After adjustment

After measuring the air flows, the adjustment positions of the valves are locked and their adjustment positions or the location of the valves must not be changed after this. If the valve includes a “sector plate”, the blow direction of the air flow can be changed by turning the entire valve, if the air seems to be blowing into the living area. The basic fan speed settings of the ventilation unit – the supply/extract ratio in particular – must not be changed without a new air flow measurement! When the valves are cleaned, the valve is unfastened so that the adjustment position does not change. Round valves can be removed from the ceiling with their frames by turning and then cleaned. If the adjustment for a valve has been made with a magnetic tape or sticker, the number of open holes must not be changed after the adjustment.

It is important to explain to the residents how the ventilation is used.

See also: support and instructions.