Heat Pump summer mode

But in summer heatwaves – as we have all experienced recently, and with more expected - you may want the house to cool down as much as possible during the cooler hours, to insulate against the highs in the daylight hours. Whilst you can switch the heat pump to hot water only mode our summer mode has a number of added benefits.

Firstly, summer mode does not disable the heating completely. This means that if the British weather behaves in its usual unpredictable fashion and we get a cold spell, it will come back on, without manual intervention. It does this by tracking average temperatures over a user-defined period (say 24 or 48 hours) so that for example, instead of coming back on if there is a nice cooling thunderstorm in the middle of a heat wave, it will only do so if there is a settled period of cooler weather.

It is also possible to adjust another parameter which relates to the thermal mass of your property. If you have a building with high thermal mass (say a very old solid stone cottage) or very high insulation levels, this can delay switching the heating on further to allow it to cool down a little further. Inversely, for buildings that lose heat quickly, it can speed up the switch on.

For systems with cooling enabled, summer mode is also the trigger for switching from heating to cooling.

You might have two hydraulic circuits (one for underfloor heating downstairs, another for radiators upstairs). The underfloor is suitable for cooling whilst the radiators are not. With the unit in summer mode a terminal is activated in the WPM heat pump controller to allow circuits to be open or closed to cooling. You may however also need a cooling input to open the valves to allow cool water to flow through the underfloor circuit.

Our FET controllers monitor humidity so that the WPM can calculate the dewpoint and keep underfloor cooling above that point to prevent condensation. It is also possible to assign an FET to each heating circuit so that if you have  fan coils that can operate below dewpoint temperatures, you can instruct the heat pump to produce the colder temperatures, while mixing it via valves for your underfloor circuits to keep it above the dewpoint and avoid condensation on floors.

The WPM can also respond to signals from third party controls via a 0-10 V input. This means that you can have a BMS boss the cooling programme if you so wish.

Our MVHR units feature a summer bypass mode that is ideal for overnight cooling. Summer Bypass Mode activates when:

• The heat exchanger is bypassed using an internal damper.
• Cooler outside air is supplied directly into the home.
• Warm indoor air is still extracted and exhausted outside.
• Heat is not transferred from the outgoing air to the incoming air.

This helps remove excess heat from the building.

On STIEBEL ELTRON units, the bypass operates automatically when several conditions are met, including:

• The outdoor temperature is lower than the indoor temperature.
• The indoor temperature is above the comfort setpoint.
• The outdoor air is warm enough that introducing it won't overcool the house.

Bypass mode can be used in conjunction with cooling from your heat pump and provides a more holistic sensation of cooling compared to either method alone, with each complementing the other.