Vallox 121 MC

A refrigerator cannot be installed in ventilation units afterwards, but the cooling of the outdoor air can be utilised.

The task of the heat recovery cell of the ventilation unit is to heat the air flowing in from outdoors by using the heat recovered from the extract air. When the apartment heats up too much in summer, the summer function of the ventilation unit can be taken into use. In such a case, the heat recovery cell is bypassed and the outdoor air will be blown unheated into the building. In SE models, summer automatics work when post-heating is disabled through the control panel. In MV models, the bypassing works when the outdoor temperature increases close to the set supply air temperature. In MC controlled units, summer automatics work when the supply air temperature is set to Auto or MIN. In some models, the heat recovery cell is bypassed by using the manually operated summer damper inside the unit. In older models, the heat recovery cell must be replaced with a separate summer cell. More detailed instructions can be found in the manual of the ventilation unit.

The temperature of the supply air blown into the room can be higher than the outdoor air temperature. The outdoor air heats up slightly inside the ventilation unit despite the heat recovery cell bypass due to thermal conduction inside the unit and the heating of the supply air fans. The location of the ducts in the hot attic can also increase the temperature.

When the air is hotter outdoors than indoors on hot summer days, it is recommended that the minimum ventilation speed be used, and all doors and windows be kept closed. When the supply air temperature is cooler than the room temperature, the ventilation speed can be increased for the night and the windows can also be opened. The temperature of the air coming through the valve can decrease slower than the outdoor temperature, if the ducts are located in the insulation of a hot attic.

The role of the ventilation unit in heating and cooling the apartment is very small. Changes in the indoor temperature are usually caused by other factors, such as sunshine, outdoor temperature, or the temperature load of the apartment. An example: fresh air is blown into a double bedroom at the rate of 12 l/s. If the air blown into the room is five degrees cooler than the room temperature, the cooling efficiency of the ventilation is 72 W. The temperature load of the apartment can be reduced by the same amount by covering a roughly 10 cm high section of a one-metre wide window on the sunny side of the building. Based on the same laws of physics, the apartment cannot be heated with the ventilation unit.

The most important factor in keeping the apartment cool is efficient sun protection. A separate air to air heat pump can be used for cooling and has no impact on the operation of the ventilation unit.

In some ventilation units, freeze protection of the heat recovery cell is based on the stopping of the supply air fan. When the heat recovery cell is at a risk of becoming frozen, the unit stops the supply air momentarily to allow the heat of the extract air to defrost the cell. As the extract air fan keeps on working during the defrosting process, the ventilation of the apartment is not disrupted. The frequency of stopping depends on the temperature of the outdoor air, the set efficiency of the ventilation, and the temperature and humidity of the extract air.

This is part of the normal operation of the unit and is not affected e.g. by the set supply air temperature (post-heating).

If the fan stops very often, this can be due to insufficient insulation of extract air ducts, neglected maintenance, or a technical fault. Check at least the following:

It is recommended that the temperature of the air extracted from the rooms be measured at the unit. If the temperature of the air extracted from the room has decreased by several degrees by the time it reaches the unit, the air cools down in the extract air duct, indicating that the ducts are poorly insulated. This causes the fan to stop more often. The temperature of the location where the unit is installed can also contribute to the stopping of the fan. The temperature of the installation site of the ventilation unit must be +10 °C or higher. Check the temperature also above the unit. If the vapour barrier above the unit leaks, cold air flows on top of the unit from there. Uninsulated outdoor and exhaust air ducts also cool the unit from above. These ducts must also be insulated between the unit and the vapour barrier.

Dirty filters, an incorrectly adjusted over-pressurised ventilation system, or a faulty or incorrectly adjusted freeze protection thermostat can also affect the operation of freeze protection. The default setting of the thermostat can also shift slightly over the years, causing the sensor to indicate an incorrect value. In such a case, the freeze protection thermostat can be adjusted.

If you suspect that the freeze protection is not operating correctly, the temperature of the exhaust air that is led to the roof can be measured at the unit. In very cold weather, the temperature of the exhaust air should normally be +4°C – +8°C, depending on the unit model. The colder the exhaust air, the better the efficiency rate of the unit. However, this also increases the risk of freezing of the heat recovery cell. In units equipped with the MC winter function, the temperature of the exhaust air may go several degrees below zero from time to time.

In the old MUH Ilmava units, the sensor of the freezing protection thermostat is coiled at the bottom of either side of the heat recovery cell. If the sensor has been moved e.g. in connection to cleaning, this disturbs the operation of freezing protection. The minimum distance of the sensor from the cell is 20 mm.

Some Vallox unit models have a preheating radiator – either electric or one that utilises the collection circuit fluid of the geothermal heating system. If the supply air fan keeps on stopping, even when the unit has an electric preheating radiator, check from the settings of the unit that preheating has been enabled. The set preheating value must be at least 3 degrees higher than the temperature at which the supply air fan stops. Check the manual for more detailed instructions on the adjustment. Also check that the resistor warms up, but be careful not to burn your fingers. Despite preheating, the supply air fan can slow down or stop in very cold weather or when the airflow is very high.

If the unit has an MLV radiator that utilises geothermal fluid, ensure that the fluid circulates in the MLV radiator (the pump is running, the solenoid valve is open, and there is no air in the circuit). The anti-freezing properties of the fluid circulating in the collection circuit of the MLV radiator connected to the geothermal heating system must also be verified. Also check the temperature of the geothermal fluid that flows to the radiator from the collection circuit. If the temperature of the collection circuit goes down close to zero or even below freezing, the efficiency of the MLV radiator will decrease significantly. In such a case, the freezing protection of the heat recovery cell is ensured by stopping the supply air fan from time to time.

The freezing protection of a water-circulating post-heating radiator can also stop the unit from time to time. When the post-heating radiator is at a risk of becoming frozen, both fans of the unit will stop. In such a situation, check that there is a constant flow of sufficiently warm fluid to the post-heating radiator. Some geothermal heat pumps stop the heating of the building when they heat domestic water. If the post-heating radiator of the ventilation unit is connected to the same circuit as the heating of the building, the circulation is stopped to both of them. Also check that the bypass damper of the heat recovery cell is in the winter position.

The ventilation unit flows outdoor air through the heat recovery cell and heats it up with the extract air. However, in the summer it is best to by-pass the heat recovery cell and bring in outdoor air without heating it. In older models, this can be achieved by adjusting the position of the summer/winter damper, or automatically in newer models. Different units have different settings that determine when the automatic heat by-pass is allowed. NOTE! If a professional has adjusted the settings during the unit deployment, they should be in order.

Ensure that the unit has clean filters so that the unit can take fresh outdoor air.

If the problem is not solved, contact the maintenance shop.

When heat recovery is on, the exhaust air is cooler than the extract air (indoor air). You can check these temperatures on the control panel display or in the MyVallox Cloud service. On cold winter days, the temperature of the exhaust air must be a few degrees higher than the temperature of the outdoor air. During defrosting cycles, the exhaust air temperature rises; this is normal.

The heat recovery cell of the ventilation unit uses the heat of the extract air to heat up the air that is blown into the building in winter. If the temperature of the supply air (the air that is blown into the room) is, after the heat recovery cell, lower than the desired supply air temperature, the supply air can be heated more either with an electric or water-circulating post-heating radiator.

The correct temperature of the supply air that is blown into the apartment depends on a personal preference. It is advisable to keep the supply air temperature as low as possible without unpleasant drafts. This ensures that the heat adjustment of the building also works correctly when e.g. the sun or a fireplace brings heat into the building. The direction of the airflow from the valves, windows, or the heating system can also contribute to drafts.

It is not advisable to set the supply air temperature higher than the room temperature, because it is not practical to use the ventilation unit for the heating of the apartment. If the supply air temperature is increased from 16 °C to 22 °C, the energy used for post-heating will be multiplied. However, this energy is excluded from the heating energy consumption of the building.

If the air coming from the valve is unpleasantly cold (even when considering that moving air coming from the valve always feels cold on the skin when its temperature is below 37°C), it is advisable to measure the temperature of the air entering the duct at the unit and the air coming from the valve. If the air cools down by several degrees in the duct, the insulation of the duct is insufficient.

New and highly efficient cross-counter flow cells can heat the supply air to over +17°C almost throughout the year. In such a case, additional heating of the supply air is usually not needed. For this reason, small Vallox ventilation units that have a high efficiency rate always have electric post-heating. The higher procurement and installation costs of a water-circulating radiator cannot be written off within a reasonable period of time.

If the ducts have been installed on the warm side of the vapour barrier, e.g. in enclosures close to the ceiling, the supply air is heated in the ducts by the “free energy of the heat that is lost when it rises into the attic“, which enhances the comfort of living. In energy-efficient multi-storey buildings, in particular, excess heat is often a problem. The situation should not be made worse by increasing the supply air temperature too high. In most situations, 16–18°C is sufficient.

Poorly insulated ducts installed in the attic cool the supply air, reduce the efficiency of heat recovery, and increase the energy consumption of post-heating.

Here you can download a calculator for calculating the energy consumption of your ventilation unit.

All new Vallox ventilation units have the appropriate defrosting automatics that defrost the heat recovery cell when needed. This ensures a high annual efficiency of heat recovery. The automatics measure the temperatures outside the cell constantly and use this data to monitor the accumulation of ice in the cell. When the formation of ice has reached a certain point, the cell is defrosted. When the cell bypass is enabled, the ventilation unit will bypass the supply side of the heat recovery cell during the defrosting cycle, allowing the heat of the extract air to defrost the cell. As supply air flows past the cell at all times, the ratio between the supply and extract air will not change. During the defrosting cycle, the supply air is heated by using the post-heating resistor of the unit. Larger models also have an additional heating resistor, meaning that no cold outdoor air is blown into the apartment. During the defrosting cycle, the supply air temperature can drop below the set value. Supply air will be blown normally through the filters, also during the defrosting cycles. Ice may occasionally form in the heat recovery cell, and there may be condensing water at the bottom of the unit. This is part of the normal operation of the unit.

Alternatively, the stopping of the supply air fans can be selected as the defrost method. In this case, the underpressure of the building can increase during the defrosting cycle.

Defrosting settings and other important settings can be found under What are the correct settings of MV models in winter?

As the laws of physics dictate, when the outdoor air becomes cooler towards winter, the amount of water contained in it decreases, practically down to zero on the coldest days. Despite this, the relative humidity outdoors may be high. This eventually also affects the humidity of indoor air. The drying effect of outdoor air does not depend on the ventilation system. The result is the same with mechanical, natural and window ventilation. The only things that matter are the amount of air being exchanged and the water content of the outdoor air. When cold outdoor air is heated to room temperature, its relative humidity decreases. The warmer the indoor air, the lower the relative humidity,

Ventilation units cannot humidify the indoor air of the home, and no settings of the ventilation unit or the use of electrical resistors can change the amount of water contained in the outdoor air coming in. The condensing water that accumulates in the ventilation unit is water condensed from extract air in the heat recovery cell, and it would, otherwise, have been led out in the extract air. Therefore, this water is not lost from the indoor air humidity.

An evaporative air humidifier is the safest means for increasing the humidity of indoor air. When choosing the humidifier, pay attention to the evaporative power. For instance, the power of an evaporative air humidifier with an output of 4 dl per hour (9.6 litres per day) is usually adequate for a medium-sized home, even in very cold weather. The hallmark of an efficient humidifier is that it requires adding several litres of water per day. However, in winter, indoor air humidity should not be raised so high that water starts condensing in cold corners or on the inner surfaces of windows.

You can leave the bathroom door open for a while after showering, so that the humidity spreads into the other rooms and the automatic boost of ventilation decreases faster as the bathroom dries. When the home is left unoccupied, it is advisable to switch the ventilation to the Away speed. This reduces the drying effect of outdoor air.

Indoor air humidity inevitably changes according to the outdoor conditions, and in the Finnish climate, the conditions really vary a great deal. The temperature difference between seasons can be over eighty degrees Celsius. The water content of outdoor air changes accordingly. Read more about excessively humid indoor air and its effects in our blog (only in Finnish).

Not necessarily. You can choose in the fireplace profile settings of an MV unit if extract air flow is reduced and/or if supply air flow is increased, and you can also specify the amount of decrease or increase. You can freely choose the time period for the fireplace function. It is also possible to implement the fireplace function with a separate switch (push button).

The fireplace always needs to have a combustion air duct that comes directly from the outside to a location recommended by the fireplace manufacturer.

After a power cut, Vallox ventilation units and the Vallox Aito Kotilämpö air heating unit will start up with the settings that were in use when the power cut started. The ventilation unit will start at the same speed that was in use before the power cut. SE models are the only exception, as they will start up at the standard fan speed. The standard fan speed can be modified from the settings menu. If the ventilation unit is equipped with humidity and/or carbon dioxide sensors, the ventilation will be boosted with a minor delay after a power cut, if the levels are higher than normal.

If the unit reports an error after a power cut, restart the unit by unplugging it from the mains for a short while. After this, the unit will start up in the standard mode.

If the ventilation unit is equipped with a liquid radiator, its freezing protection must be ensured during power cuts, e.g., by means of dampers installed in the outdoor and exhaust air ducts. If the outdoor air duct of the ventilation unit is short, cold air can be blown inside the unit during windy weather or when the fireplace is used, even when the fans have been stopped. For this reason, it must be ensured when the fireplace is being used that its combustion air intake route is in order and unblocked. In Vallox Aito Kotilämpö, the liquid radiator is located at the bottom of the air heating unit, and, therefore, the risk of freezing is small unless the power cut continues for days and the temperature of the building decreases significantly. The temperature at the bottom part of the Kotilämpö air heating unit can be tested by opening the door and feeling the air inside. Where required, warm room air can be led to the radiator.

Download a energy consumption calculator that allows you to calculate the energy consumption of your current ventilation unit in the Finnish climate and determine how much you can save by replacing your old unit with a new energy-efficient Vallox ventilation unit.

Yes!

The purpose of the fireplace mode is not to supply air for the fire, but to make lighting the fire in the fireplace easier. When the flue is still cold, the ventilation unit is used to create a momentary overpressure in the building. Once the flue has warmed up, the draft should be effective. When the outdoor temperature is very low, the freezing protection of the ventilation unit can also turn the supply air fan off when the fireplace mode is used in order to prevent the freezing of the heat recovery cell. Therefore, the fireplace mode ensures that the ventilation unit does not create an underpressure in the apartment when the fire is lit. In SE models, the timing of the fireplace switch is 15 minutes. In MV models, the time can be set or the timing can be disabled completely if controlled by some other device.

The burning of wood requires a lot of air. In theory, wood needs roughly 3.7 m3 of air per one kilogram of wood. In practice, the air-fuel equivalence ratio or lambda (λ) is 2–2.5 in fireplaces that have a door, i.e. 7.5–10 m3 of air is needed per one kilogram of wood. In new furnaces, the ratio is lower: 2.0–2.2. In fireplaces that do not have a door, such as open fireplaces,  the air-fuel equivalence ratio is 10–30, i.e. 40–110 m3 of air is needed per one kilogram of wood. The optimal adjustment of combustion air is, however, difficult. (Source: Tehokas ja ympäristöä säästävä tulisijalämmitys, VTT)

When configured correctly, a ventilation unit does not create a major underpressure in the building, as this would disturb the draft. 5–10 % more air is extracted from the building than is supplied, i.e. the supply and extract air volumes are almost the same. The deviation of a few per cents has been added for the sake of measurement errors. This ensures that no overpressure is created inside the building, as this is always damaging to the structures of the exterior envelope. For example, in a 150 m2 building, the “surplus” caused by the ventilation unit is only 3–6 l/s. Up to tens of times more air is extracted from the building through the flue when the fire is burning efficiently. In an airtight building, this volume does not – and indeed must not – normally enter the building through the structures as leaks. Dirty filters or a blocked outdoor grille can increase the underpressure.

The ventilation unit is unable to maintain the overpressure for long periods of time in below zero temperatures. When the fireplace mode of the ventilation unit turns off the extract air fan, also the heat contained in the extract air, which would heat the heat recovery cell and the supply air, stops flowing to the unit. In such cases, freezing protection can also turn off the supply air fan. The duration of the overpressure cycle depends on the efficiency of the possible preheating, the air volume, and outdoor temperature.

An air supply duct equipped with a shut-off valve must be led directly from outdoors to all fireplaces to a location underneath the combustion chamber that is recommended by the manufacturer. In this, there are fireplace and manufacturer-specific differences. If the fireplace removes the air needed for combustion from the room, this air is replaced with outdoor air that must be heated by using the heating system of the building. If, for example, 100 l/s of air is extracted through the flue when the draught of the fireplace is high, the replacement air will come into the room from outdoors and enters the flue through the fireplace doors. When the outdoor temperature is -15°C, 4 kW of heat produced by the building’s heating system is needed to heat the combustion air, i.e. the air that is extracted through the flue, because the fireplace is still cold. For this reason, it is sensible that the combustion air is taken from outdoors directly to the fireplace and the flue without the air passing through the room.