Due to its larger heat exchanger, the M-WRG-II is larger than the M-WRG. Its cross-counterflow plate heat exchanger has a higher heat recovery efficiency than the counterflow plate heat exchanger in the M-WRG. The M-WRG-II also comes standard with a fine particulate filter (eMP1 60%) to filter the outside air, while the M-WRG has a coarse particulate filter (ePM10 65%) as standard (eMP1 60% optional). In addition, its constant volume flow rate function, the ability to recover moisture (M-WRG-II E series), and its suitability for use in passive houses distinguish the M-WRG-II series from the M-WRG. One M-WRG-II unit can be used to ventilate two rooms, whereas the M-WRG is a single-room ventilation solution. The M-WRG is somewhat lighter, more compact and uses slightly less power than the M-WRG-II.

Basically, both are systems for heat recovery (energy recovery) by which heat in the room is recycled. A recuperative system works by continuously and separately moving the various airflows (extract air and supply air), without ever mixing them. While push–pull ventilation always requires a pair of interconnected units for ventilation, a recuperative system manages both the extract air and supply air with a single unit. Since it is able to move the airflows simultaneously, this type of ventilation unit makes a very even and quiet sound. When they change the rotational direction of the fans (once every 60 to 80 seconds), push–pull units generate a moment of silence followed by a noise, which many feel is disruptive, especially in bedrooms. While recuperative systems supply air as describe above, push–pull units need almost twice as long, since they constantly have to switch between supply air and extract air. Our M-WRG-II and M-WRG units boast a high air throughput (up to 100 m³/h per unit), resulting in a constant volume flow rate (M-WRG-II) that is sufficient to ventilate multiple rooms with one unit. Since our ventilation units are equipped with radial fans, they are much less sensitive to changes in pressure (e.g. wind pressure) than push–pull units, which use axial fans. This pays off in terms of sound insulation against outside noise. With its longer ductwork (e.g. window reveal solution), the system is able to move air with almost no losses. Push–pull systems, on the other hand, lose air volume through pressure losses. The standard version of our M-WRG and M-WRG-II units also boast a high level of sound insulation (54 to 65 dB), without any additional insulating equipment.

Air filtering is another advantage of a recuperative system, which separately filters the outside air and exhaust air. A push–pull unit constantly moves outside air and exhaust air through the filter element, which compromises its ability to filter air. Filter service live is another area where a recuperative system stands out. For push–pull systems, it is recommended to change the filter once every three months. But the filter surface of the larger round filter cartridges used in recuperative systems only need replaced once a year (in some cases twice a year for people with a pollen allergy). On top of that, the use of filters of a high filter class, e.g. fine particulate filters ePM1≥ 50%, in push–pull ventilation units can lead to a 50% loss of pressure (air throughput losses).

Inherent noise levels always vary depending on the installation type you choose.
As an installation type, we recommend integrated into wall U².
Installed in this way, an M-WRG-II E unit has a sound pressure level at 10 m³/h of 6.5 dB and of 15.1 dB at 30 m³/h.
 

20 dB(A) – comparable to the ticking of a quiet clock, very quiet
30 dB(A) – comparable to a whisper, quiet
40 dB(A) – comparable to normal residential noises, normal
50 dB(A) – comparable to a conversation, normal
60 dB(A) – comparable to office noises, loud
70 dB(A) – comparable to a car from an approx. distance of 5 m, loud
80 dB(A) – comparable to a noisy street, very loud
90 dB(A) – comparable to the honking of a car, very loud
100 dB(A) – comparable to lorries braking, unbearable
120 dB(A) – comparable to aeroplanes flying over, unbearable

M-WRG has an element standardised sound level difference D _n,e,w of 50 dB. With improved sound insulation equipment, a D _n,e,w value of 53 dB during operation is possible. For your individual solution, it is helpful to us if you provide specific information on the sound insulation requirements for your building (sound insulation class of windows, noise level range). We are happy to provide more information!

M-WRG has an element standardised sound level difference D _n,e,w of 50 dB. With improved sound insulation equipment, a D _n,e,w value of 53 dB during operation is possible. For your individual solution, it is helpful to us if you provide specific information on the sound insulation requirements for your building (sound insulation class of windows, noise level range). We are happy to provide more information!

According to the Ecodesign for Sustainable Products Regulation (ESPR), annual power consumption includes the annual operating time, the air exchange rate per m² of heated area, whether ductwork is connected to the unit, the type of control, the specific input power of the unit, and heating energy necessary to thaw the heat exchanger e.g. with an electric heater battery. The annual power consumption of an M-WRG-II ventilation unit in continuous operation is approx. 5 kWh/(m²a), which cuts nearly in half to approx. 2.5 kWh/(m²a) in energy-efficient on-demand operation with humidity and/or CO₂ sensors (optional). You can find the annual power consumption in the corresponding ESPR product data sheet on our homepage at www.meltem.com.

A good way of comparing ventilation units is taking a look at their electrical efficiency ratio, which is a kind of equivalent coefficient of performance. While commercially available heat pumps have a coefficient of performance between 3 and 6, i.e. 3 to 5 kW of heat output with 1 kW of electricity, M-WRG-II ventilation units achieve an equivalent coefficient of performance between 7 and 12 (without ductwork connection) and between 6 and 9 (with a ductwork connection). These values have been substantiated.

A good way of comparing ventilation units is taking a look at their electrical efficiency ratio, which is a kind of equivalent coefficient of performance. While commercially available heat pumps have a coefficient of performance between 3 and 6, i.e. 3 to 5 kW of heat output with 1 kW of electricity, M-WRG ventilation units achieve an equivalent coefficient of performance between 8 and 24 (without ductwork connection). These values have been substantiated.

Yes, perfectly! After all, they don’t require any ductwork. We also offer a surface-mount unit for renovations. Only two Ø120 mm tapholes and one supply cable per unit are necessary.

Our ventilation units are not intended for use as industrial dryers! However, once a building has been completed, they can help it dry out significantly faster by providing a permanent exchange of air. We recommend running ventilation units at a higher air throughput level before anyone moves in. This will help achieve suitable humidity levels for residential spaces. After that, the air throughput should be set to the recommended or desired level.

Thanks to their frost protection feature, the ventilation unit reduces the supply air throughput while simultaneously increasing the extract air (warm air) throughput to prevent the heat exchanger from freezing.
It is recommended during heating season to keep the temperatures in the room where your units are used at a minimum between 16 and 18 °C to prevent the units from constantly switching to frost protection mode or switching off. The higher the inside temperature, the more buffer is available for operation and heat recovery.

Outdoor air can contain coarse and fine particles, insects and toxic gases (including fuels, nitrogen oxides, combustion gases). Coarse particles, such as pollen, and fine particles can cause allergic reactions, significantly reducing quality of life and leading to respiratory diseases. A fine particulate filter of filter class ePM1 ≥ 50% used on the outdoor air side of an M-WRG-II ventilation unit (standard) or an M-WRG unit (optional) cleans the air and creates a protected indoor space, not only for people with pollen allergies. Alternatively, we recommend the use of an activated carbon filter against unpleasant odours and toxic gases. At the same time, and separately, a coarse particle filter on the exhaust side of the unit cleans the room’s extract air and protects the unit’s components, such as the heat exchanger, fan and sensors, from contamination.

Operating ventilation units in rooms with a fireplace poses risks. For example, if the unit malfunctions or as a fault, negative pressure might develop in the room, drawing toxic gases from the fireplace into the room. This can be prevented with a safety mechanism that automatically switches off the ventilation unit if negative pressure is detected.

If you operate two M-WRG-II units, you can use passive cooling by using the app to control them. M-WRG-II units do not allow bypass operation. Example: On warm summer days (when the air outside is warmer than inside), you want the effect of heat recovery during the day, as the supply air is cooled by the exhaust air. At night, when the outside temperature is warmer than the inside temperature, you can set your comfort ventilation unit so that the supply air or extract air only runs at a higher level from a user-defined time, which has the effect of deactivating the heat recovery. Setting the units in this way creates cross-ventilation, allowing the cold outside air to enter your home.

No! Air filters are essential for functionality and hygiene. According to the operating instructions (intended use), it is not permitted to operate a ventilation unit without an air filter and window cover.

For structural reasons, it is necessary to place the extract air intake and supply air outlet next to each other on the interior facade of the unit. But it is still virtually impossible for the two to mix. With ductwork connections, it is even simpler: The extract air intake and supply air outlets are generally far apart. The maximum and minimum leakage rates can be found in the corresponding ErP product fiche, which you can download from our homepage at www.meltem.com.

M-WRG units have a mixing rate of 3%, which is very low. For M-WRG-II units, this value drops to 0%. You can find the mixing rate in the corresponding ErP product fiche.

Draughts can be very subjective and different people will have different tolerances, which makes it hard to measure or compare. Studies have shown that a properly planned ventilation system does not cause draughts.

On-demand control is definitely a smart choice if you want to ventilate with greater energy efficiency and enjoy better air quality. The sensors monitor the room air and control the airflows.

Yes! Please download the ‘User control options for our comfort ventilation system’ brochure for more information.

In the ‘Devices overview’, you can select the ‘Select’ field from the menu. You can then select multiple units and control them together. This applies to both the time program and the general settings.
You can also control multiple units in several buildings or locations.

At least once every 10 minutes. If the temperature changes more than 2 degrees Kelvin, the values are updated immediately. This is also true of CO₂ and humidity values.

EXHAUST menu:

Temp.: The temperature of the room air is displayed here.

rel. humidity: The humidity of the room air is displayed here. This value may differ from those shown on weather stations. Reason: The air in the upper part of the room is sucked in and measured.

abs. humidity: The absolute humidity is the water content in one m³ of air. This is the more important humidity value, since it also reflects the temperature. This value is also used to compare the humidity of the inside and outside air.

CO₂: The CO₂ content of the room air is displayed here.

SUPPLY menu:

Temp.: The temperature of the supply air is displayed here (post heat exchanger).

rel. humidity: The humidity of the supply air is displayed here (post heat exchanger).

abs. humidity: The absolute humidity is the water content in one m³ of air. t. This is the more important humidity value, since it also reflects the temperature. This value is also used to compare the humidity of the inside and outside air.

VOC: The VOC content of the outside air is displayed here.

OTHERS menu:
Outlet temp.: The temperature of the air conveyed to the outside.

Outdoor air temp.: The temperature of the air sucked in from the outside. Depending on the flow rate, there may be deviations. This is due to the transfer of the wall to the outside air. In the low flow rate range, this effect is higher.

Operating hours: The operating hours are read out once everdy 24 hours. The displayed value indicates the time during which the ventilation unit was switched on.

This indicates the number of hours that the unit was in operation. It includes standby operation. The operating hours are updated once a day.

Ventilation level is set to low (e.g. 10 m³/h is standard). The flow rate can be changed in the settings by pressing the ‘I’ button.

Ventilation level is set to medium (e.g. 30 m³/h is standard). The flow rate can be changed in the settings by pressing the ‘II’ button.

Ventilation level is set to high (e.g. 50 m³/h is standard). The flow rate can be changed in the settings by pressing the ‘III’ button.

Use this button to manually set the ventilation level.

The unit operates in cross air OUT mode. The supply air is switched off entirely (M-WRG-II series to 0 m³/h) or mostly (M-WRG series to min. 15 m³/h). The supply air cover flaps are closed (M-WRG-II) or remain open (M-WRG). You can set the extract or supply air flow rate under ‘Settings’.

The unit operates in cross air IN mode. The extract air is switched off entirely (M-WRG-II series to 0 m³/h) or mostly (M-WRG series to min. 15 m³/h). The extract air cover flaps are closed (M-WRG-II) or remain open (M-WRG). You can set the extract or supply air flow rate under ‘Settings’.

In automatic mode, the ventilation unit is controlled by the rel. humidity and CO₂ parameters. This prevents too high a humidity or CO₂ level in the respective room. As a result, the unit operates in an on-demand mode that is especially energy efficient.

In the humidity program, the ventilation unit is controlled via the extract air humidity value. This prevents too high a humidity value in the respective room. As a result, the unit operates in an on-demand mode that is especially energy efficient. Depending on the humidity value, the unit automatically switches to the required ventilation level (different settings can be made under ‘Settings’).

In the CO₂ program, the ventilation unit is controlled via the extract air CO₂ value. This prevents too high a CO₂ value in the respective room. As a result, the unit operates in an on-demand mode that is especially energy efficient. Depending on the CO₂ value, the unit automatically switches to the required ventilation level (different settings can be made under ‘Settings’).

When you activate the ‘Boost’ program, the unit runs a time-limited intensive ventilation program at 100 m³/h (15 minutes is standard), before returning to the previously set ventilation program (operating time and ventilation level can be set under ‘Settings’).

When you activate the ‘Standby’ button, the ventilation unit switches to standby mode (OFF). The ventilation levels are set to zero, the supply air and extract air cover flaps are closed. Press any other button to switch the unit back on to the selected mode.

Humidity control:
Set point for the humidity (RH) control
Minimum ventilation level in normal operation
Maximum ventilation level in normal operation
 

CO₂ control:
Set point for the CO₂ control
Minimum ventilation level in normal operation
Maximum ventilation level in normal operation

Boost:
Ventilation level (factory setting 100 m³/h)
Duration (factory setting 15 minutes)

Touch pad:
Touch pad: ON/OFF
Button 1 (I) LOW: factory setting M-WRG-II 10 m³/h; M-WRG 15 m³/h
Button 2 (II) MED: factory setting M-WRG-II 30 m³/h; M-W RG 30 m3/h
Button 3 (III) HIGH: factory setting M-WRG-II 50 m³/h; M-WRG 60 m³/h
Button 4 extract air: M-WRG-II only 70 m³/h 
Button 4 supply air: M-WRG-II 70 m³/h
 

Cross air:
Cross air IN: supply flow rate (via slider in the app)
Cross air IN: extract air flow rate (factory setting M-WRG-II 0 m³/h, M-WRG 15 m³/h)
Cross air OUT: supply air flow rate (factory setting M-WRG-II 0 m³/h, M-WRG 15 m³/h)
Cross air OUT: extract air flow rate (via slider in the app)
 

CO₂ control with supply air VOC sensor (optional, WRG-II series only):
Two sensor control ON/OFF
VOC supply start control
Minimum supply air flow rate
Time delay for control

Others:
Standby operation pause time
Standby operation sampling time
Standby operation ventilation level
Standby valves closed
Buzzer for filter change indicator ON/OFF
Restore factory settings

If multiple users are using the app at the same time, they can make settings on the unit. In order to see the actual values when you open the ‘Settings’ menu, it is necessary to update the current values from the unit.

The time program makes up to 6 switching points available per day. The set program is executed at every switching point. The program runs until a new switching point becomes active or the user does something else.
Example: MON – 09.00 Humidity program ON.
The humidity program runs until a new switching point is reached or the user selects something else. On the following Monday, the ventilation unit will execute this command again. You can set up to 42 switching points per ventilation unit. Time programs can be downloaded from the unit and saves as templates in the app. This allows you to set different time programs, e.g. for summer and winter, without having to set up new times and programs.

Please note: These programs are only stored in the app on the user’s mobile device.
Select multiple ventilation units from the ‘Devices overview’ to send the time program to all of them.

In the interval program, the ventilation unit works only part of the time, at specified times or intermittently. This program includes an operating time, a pause time and the corresponding ventilation levels. The interval program runs through the times in succession.

Example:
Pause level: 0 m³/h
Operating time level: 30 m³/h
Pause time: 60 minutes
Operating time: 60 minutes

When you tap the Start button, the unit always starts with the operating time. In the above example, the unit ventilates for 60 minutes with a flow rate of 30 m³/h. The unit then switches to standby mode and closes the cover flaps. After a pause of 60 minutes, the unit again starts ventilating with the operating time flow rate. This is repeated until the user sets something different.

The active interval program is displayed in the device status.

In the temperature monitoring program, the unit measures the temperature of the supply air (this program requires a unit with humidity sensors). The ventilation unit switches to standby mode if the supply air temperature rises about the value set in ‘Temp. max. supply’. In standby mode, the unit switches the ventilation levels to 0 for 60 minutes and closes the cover flaps. When the 60 minutes have elapsed, the unit ventilates for 5 minutes at 20 m³/h and then checks whether the temperature allows it to return to normal operation. This program is used to prevent a room from heating up unnecessarily. If the temperature drops below the ‘Temp. min. supply’ value, the unit switches to standby mode to prevent a room from cooling down unnecessarily.

The Gateway menu allows you to change the name of devices and gateways as well as delete and add new ones.

In the Post menu, you can order air filters, fill in a form to request servicing and read the contact details or FAQs. You will be forwarded to the Meltem website.

In this menu, you can change your personal information such as your password and email address as well as unregister from the app. You can also change the language to one of the other available settings. This button also lets you access information such as the FAQs, site notice and privacy policy.

It takes a few seconds because the values are written directly to or accessed from the ventilation unit. This means that the values you see are actual feedback from the unit, rather than values displayed in the app.

There is no limit to the number of units you can control. The number depends on how many gateways are registered.

Yes. From anywhere in the world, provided your mobile device and the gateway are connected to the internet.

Yes. When you name your units, you can create groups under ‘Options’.
You can sort them into three types of group:
- Location
- Area
- Unit name

Example:
Location: Alling
Area: 1st floor
Unit name: Sales office

How the units are displayed in the app:
Alling → 1st floor → Sales office

Yes. From the Devices overview, you can do so using the ‘Select’ or ‘Select All’ menu. You can then control or set all selected units via ‘Set’.

You can edit units in the ‘Gateway’ menu.

If your ventilation unit does not have the necessary sensors, the corresponding icons are greyed out.

No. Unfortunately, this feature is not supported at this time.

When the buzzer sounds, it means that you will need to replace the air filters in the displayed units. Don’t forget to reset the filter buzzer once you have replaced the air filter (see ‘How do I reset the filter change interval?’).

The ‘Order filter’ link in the app will take you directly to our online shop. Or you visit our shop on our homepage here.

Just visit our online shop here to order filters directly in your country.

M-WRG-II series: Press and hold the I button (top button on the membrane touch pad) for 5 seconds. The unit beeps three times.
M-WRG series: Switch the 3-step switch to position I. Then switch slowly as follows: I-II-III-II-I. The unit beeps. While the unit is beeping, repeat the sequence: I-II-III-II-I. The unit beeps three times.
Follow the instructions in the operating manual, which you can download from: www.meltem.com/service/downloads/

The ventilation unit displaying the message has a fault. Switch the unit OFF, wait 5 seconds, then switch it ON again. Please contact Meltem Service if the error message has not disappeared. To do this, please use our contact form at: www.meltem.com/service/technischer-service/service-wrg/
With your consent, we can then analyse the unit and possibly fix the error.

This means that the units are either switched off or the mains supply or wireless connection to the gateway has been lost. Check your mains supply and the internet connection!

This message indicates that there is no power or no internet or wireless connection.

Your mobile device and the gateway must be on the same network.

If the unit will not connect to the gateway, you are out of range of the wireless signal or the QR code cannot be read. Try to connect the ventilation unit manually by entering the 6-digit code shown beneath the QR code.

Check the error message in the app or switch the ventilation unit off and back on.
Unplug the gateway for around 10 seconds (Micro USB and LAN connection), then plug it in again.
If the error persists, please use the ‘Service’ button to contact us or get in touch on our homepage under: www.meltem.com/service/technischer-service/service-wrg/.