ᐅ Cooling with a heat pump through underfloor heating?

Acof1978 schrieb:

And at night, when the photovoltaic system isn’t producing energy and there are still tropical nights, do you keep the air conditioning off?

Yes. The heat doesn’t come from the warm outside air, but from the sunlight entering through the windows. Since there is no sun at night, the house doesn’t really get warmer then. We focus on reaching and maintaining the desired temperature during the day so that the bedrooms stay comfortable at night. We don’t run the air conditioning for five hours a day either. The units are quite powerful, so usually a few minutes is enough when you notice it starting to get too warm. Upstairs, we have just one split system for the entire floor, so we open the relevant doors in the afternoon and let it run for about half an hour to an hour.

RotorMotor schrieb:

Yes, run it, because that matches my numbers quite closely. You need air anyway, and with heat recovery, it's only 25W of additional heat. Manually ventilating would add much more! And your air conditioner probably cools with 3000W or more. You won’t notice the one percent difference in electricity consumption from the controlled ventilation, but you will definitely have better air quality.

How do you arrive at those 25W? The ventilation system doesn't change the temperature of the outdoor air it brings in, right? Or does it? If it’s 32°C (90°F) outside, the system just draws in 32°C (90°F) warm air into the house, doesn’t it?

kati1337 schrieb:

Would you keep the mechanical ventilation system running normally during the summer? We don’t have a summer bypass, so it operates with heat recovery. If it’s 32°C (90°F) outside and only 24°C (75°F) inside because of the air conditioning, then letting the mechanical ventilation run would make the house warmer again, right? The cooled indoor air is being vented out, and the 32°C (90°F) outdoor air comes in? Then I’d have to use extra energy to cool it down again. Or am I misunderstanding something?

The cold air flowing outside cools the incoming warm air. A heat exchanger works both ways.

kati1337 schrieb:

How do you arrive at those 25W? The ventilation system doesn’t change the temperature of the outside air it draws in, right? Or does it? If it’s 32°C (90°F) outside, the system also brings 32°C (90°F) warm air into the house, doesn’t it?

Yes, it does draw in 32°C (90°F) air, but this air is cooled down by the heat exchanger.

kati1337 schrieb:

Upstairs, we only have one split air conditioning unit for the entire floor. In the afternoon, we open the relevant doors and let it run for about half an hour to an hour.

And is that really enough?
Could you tell me how many rooms or square meters you have upstairs and what kind of air conditioning system it is, so I can understand why the 'open-door technique' is sufficient?

Ypsi aus NI schrieb:

And is that really enough?
Could you tell me how many rooms or square meters you have on the upper floor and what kind of air conditioning unit you use, so that the ‘open-door method’ is sufficient?

It might also depend on your expectations. We don’t cool the bedrooms down to 18°C (64°F).
We have a Mitsubishi air conditioning system, I’m not exactly sure of the model, probably SCM 50, with 3 indoor split units SRK 25.
A total cooling capacity of 7100 watts (24,200 BTU).
Upstairs we have the bathroom, the master bedroom, and three other rooms. None are very large. At the moment, we only open the doors for the master and one child’s bedroom. I like the bathroom warm, and the other two rooms aren’t used often enough to keep them cooled.
Our staircase is near the indoor unit, which has the effect that when the rooms upstairs are cool, the hallway downstairs is noticeably cool as well. That’s hard to avoid because cold air naturally sinks. 😉 But the air does distribute well enough this way. We were concerned about this at first. During the consultation, our contact person said that a system like this cools all the rooms in their show homes and they have quite a bit of power. So we trusted that and still believe it.

Regarding the note about colds or uncomfortable cold drafts: I’ve had those problems a few times when we were on holiday somewhere very hot and there was an air conditioner in the room. When you have your own system, you develop a feel for it over time. It has worked well for us not to set the remote control directly to 20°C (68°F) – even though it feels amazing when you’re sweating and then stand in the cool air. After the initial excitement wore off, we now usually set the unit to about 23°C (73°F) and let the rooms cool down more gradually. Also, we start cooling as soon as it gets a bit too warm (usually around 26–27°C [79–81°F]) but only for a short time until it feels comfortable again.