Most of our MVHR units have an in-built summer bypass function:
The bypass opens when the extract air temperature exceeds a certain limit.
The more the fan speed, the more effective is the bypass ventilation. However the cooling effect is limited, but also low-cost, as it is passive. In contrast air conditioning can be much more powerful, but also uses a lot of electricity (it needs about 3-4 times more energy to actively cool a space than to heat it).
Solar gains can be very powerful and can bring a few kW of heat into your building, especially if there is large panels of glazing. The bypass function is not designed to counteract all solar gains, but to counteract these, as much as possible, in a passive way.
The best way to deal with excessive solar gains is
a) constructive, through thermal mass
b) through shading, such as overhangs, integral or external blinds.
c) through cross-ventilation (window opening).
Unlike air conditioning, dwellings with MVHR do not need to be kept closed, in order for the system to work. So feel free to open windows and doors, if you like. However if you don’t want to open them, the MVHR system is designed to provide good air quality without opening of windows and infiltration vents.
The bypass opens and closes usually fully automated, according to the extract air temperature readings. Ideally it is a 100% bypass, without air leakage.
With the newer PAUL units, you can see if the bypass is open or closed in the information menu/ current device status.
You can change the bypass comfort temperature for the PAUL units. The temperature is measured in the MVHR unit (the combined extract air, which reflects the average temperature in the dwelling). However the threshold temperature cannot be adjusted to less than 20 degrees C, in order to prevent unintentional conflicts with the heating. The bypass does not open, if the outside air temperatures are below 13 degrees, in order to prevent condensation on the supply ducting within the house. Your technician can lower this temperature to 12 degrees.