ᐅ What supply water temperatures are you currently using?

Created on: 24 Oct 2021 10:27
L
lesmue79
Just out of curiosity, to better understand the slope of the heating curve, what flow temperatures do you typically run at 0°C (32°F) outdoor temperature, given a certain indoor temperature and insulation level, when using a combination of underfloor heating and a heat pump?

Background of the question:

My logic tells me that if I want, for example, 22°C (72°F) room temperature, the flow temperature must be at least 22°C (72°F) or higher, since I learned that there needs to be a temperature difference for heat transfer to occur.

So if my heating system turns on at 12°C (54°F) outdoor temperature, my flow temperature should logically start somewhere around 22°C–25°C (72°F–77°F). Accordingly, at only 5°C (41°F) outside, it should be around 27°C (81°F), and at 0°C (32°F) close to 30°C (86°F).

The system design usually takes the location and outdoor temperature down to about –12°C (10°F). If at 0°C (32°F) flow temperature is already 30°C (86°F) according to my logic, then at –12°C (10°F) the flow temperature should be about 40°C (104°F). But most underfloor heating designs for heat pumps are based on a maximum flow temperature of 35°C (95°F).

Of course, the insulation of the house and the indoor temperatures still play a role. Or is the increase in flow temperature actually so gradual that it only rises by about 0.5–1°C (1–2°F) for outdoor temperature drops in 0–5°C (0–9°F) increments?
M
Malz1902
22 Dec 2021 10:01
Flow temperature at 31.9°C (89.4°F) with an outdoor temperature of -4.2°C (24.4°F)
Characteristic curve 0.26, offset 0
more characters again
L
lesmue79
22 Dec 2021 10:53
Current values from 5 minutes ago. Current heating curve 0.15 with a parallel offset of 1°C (1.8°F) above the setpoint temperature of 21°C (70°F). No nighttime setback, no ERR.

Blaues Display einer Heizungssteuerung zeigt Arbeitszahl Monat, Heizen, 5,7.


Blaues LCD-Display zeigt Live Monitor und Luftinlass-Temp. -1.5°C; zurück und weiter.


Blaues LCD-Display zeigt Live Monitor: Kompressor-Modulation 40,0%; Zurück/Weiter


Blau beleuchtetes Display zeigt Live Monitor und Elektrische Leistungsaufnahme 0,6 kW.


LCD-Display: Live Monitor, Kälteleistung 2,7 kW; zurück/weiter, Reset.


Blaues LCD-Display eines Geräts: Live Monitor, Energieintegral, -180 min; Zurück/Weiter.


Blaues beleuchtetes LCD-Display zeigt Live Monitor, Vorlaufsolltemp. 27,5°C; zurück und weiter.
Mahri2322 Dec 2021 10:58
So, our Vaillant air-to-water heat pump now also runs through the night. I didn’t notice any defrosting last night. It only happened once this morning.

We usually have temperatures around 0°C (32°F). Now it’s dropping below freezing. During the day, I have set the temperature to 24°C (75°F) and at night to 22°C (72°F). On average, the indoor temperature is now about 23°C (73°F) in almost all rooms.
Musketier22 Dec 2021 16:55
driver55 schrieb:

Very “questionable” values. With warm outdoor temperatures, old buildings; as it gets colder, new buildings. 🙄
True. It’s related to the comfort level of bare feet on tiles during the transitional season. 😉

With less lateral displacement and a steeper angle, it became too warm in winter.
Unfortunately, there is no intermediate setting between 0.2 and 0.3 for the angle.
However, since very little energy is used between 15-20°C (59-68°F), I simply ventilate when necessary or turn off the heating.
This is the lesser evil compared to heating unnecessarily high in winter.
OWLer22 Dec 2021 17:02
Musketier schrieb:

Women's feet

It's always the same story. I could have really built an energy marvel without my wife. The problem with that: without my wife...

Overall, no matter how you look at it, moving into a heat pump house in winter is quite concerning when you see the electricity meter.
L
lesmue79
22 Dec 2021 17:19
OWLer schrieb:

Moving into a heat pump house in winter is very worrying when looking at the electricity meter.

The first step should be to check the system settings to see if and when the electric heating element activates, and how the heating curve and related settings are configured. Heating technicians usually play it safe during handover when it comes to the heating curve, electric heater, and domestic hot water temperature, following the motto "more is better."