Tricky blog post title, mostly true, but as you know there is no such thing as free lunch 😉 Anyway, those of you following my blog know that I have a Daikin air-to-air heat pump hacked into air-to-water solution for my place. As a bonus I get domestic hot water for both heating and cooling modes by having the refrigerant pass by a heat exchange tube in my domestic hot water tank before it reaches the reversing valve. The hack is especially interesting in cooling mode as instead of dumping the heat in the outside environment, most of it gets captured in the water tank. So you get two rabbits with one shot, house is cooled and hot water tank gets hot.
This summer hasn’t been so hot, I didn’t use the cooling mode until few days ago. I wanted to share my measurements, below is an interesting chart for the few hours I had it running:
The brownish fill shows the momentary power, calculated on the base of temperature increase of a fixed water volume. You can see that it starts pretty sharp and slowly degrades, this is because condensation in the hot water tank is most efficient while the water is relatively cold. After certain point, the refrigerant simply passes on without change of state.
The orange fill shows the power consumption, it is an inverter heat pump so it can vary. Most of the time it is around 900W, which is pretty good for cooling the whole house (and heating the water tank) given that a toaster uses that much power.
I can imagine the amount of heat being dumped in the environment globally rather than being recuperated