Summer Bypass is a function that is available on selected units, please check your manual to determine if you have this function.
In the normal running mode a MVHR unit will recover heat from the outgoing air, this heat is then passed to the incoming fresh air which is supplied into the habitable rooms (lounge, dining room, bedrooms etc.)
The temperature of the air coming into the unit is continuously monitored, once pre-defined* temperatures are reached the unit will switch to Summer Bypass. The unit automatically triggers internal grilles and/or flaps to divert the outgoing air around the heat recovery cell, meaning that the incoming air will no longer be warmed by the outgoing air. The unit will stay in Summer Bypass until the temperatures go below the pre-defined temperatures.
NB, if the unit is required to stay in Summer Bypass for prolonged periods the unit will periodically drop out of and go back into Summer Bypass.
*Some models allow the trigger temperatures to be changed.
Whilst the air will come directly from outside, it is probable that the temperature of this air will be slightly higher than the temperature outside, due to thermal gain whilst passing through the ventilation system.
On specific units there is a function that is linked to Summer Bypass, this being SummerBoost®. If available and enabled this will increase the fans speeds to increase air movement. Please check your manual to determine if you have the function and if so how to enable.
It is important to emphasise that a MVHR is a ventilation system and not a cooling system. Summer Bypass will stop heat being recovered but does not guarantee the ambient temperature in the property will be decreased.
Where Summer Bypass is not available Summer Mode may be, please check the manual to determine if you have the function.
Summer Mode enables the Supply fan to be switched off, meaning no pre-warmed fresh air is being supplied to the habitable rooms. If this function is utilised it is important that windows are left open to provide the fresh air.