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?
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?
Durran schrieb:
My house doesn’t meet any specific insulation standards. It’s insulated where it makes sense.
36 cm (14 inches) Poroton exterior walls with lime-cement plaster both inside and outside, resulting in a wall thickness of about 40 cm (16 inches). Cold roof on top.
Insulation between rafters with 16 cm (6 inches) of polystyrene insulation. Ceilings to the attic insulated with 20 cm (8 inches) of mineral wool.
It actually works quite well. About 1000 liters (264 gallons) of heating oil and around 6 cubic meters (212 cubic feet) of firewood are enough for me per year. Hot water is electric, with plans for a future 10 kW solar system with battery storage.
No triple glazing, no underfloor heating except in the bathroom. Instead, there are two chimneys in the house, a wood stove in the kitchen, a living room fireplace with 18 kW (61,000 BTU) output, and an oil heating system. Hot water heater. Welcome to the 1970s. 😀
S
Strahleman30 Oct 2021 07:21Since yesterday, our heating system using a ground-source heat pump has been set up and is now running. Until now, the heating was still switched off. The room temperature is currently rising, and in the living and dining area, we are now at about 21°C (70°F), which is within the target range. Other rooms are already a bit too warm; I will need to adjust those again this evening once a stable temperature has been reached.
Currently, the heating system delivers 30°C (86°F) in the flow with a temperature difference of 4°C (7°F) (so the return flow is 26°C / 79°F) at outside temperatures between 4-6°C (39-43°F). I am satisfied with this for now.
Currently, the heating system delivers 30°C (86°F) in the flow with a temperature difference of 4°C (7°F) (so the return flow is 26°C / 79°F) at outside temperatures between 4-6°C (39-43°F). I am satisfied with this for now.
Durran schrieb:
So, my house doesn’t meet any specific insulation standards. It’s insulated where it makes sense.
36 cm (14 inches) Poroton exterior walls with lime-cement plaster on both the inside and outside, resulting in a wall thickness of about 40 cm (16 inches). Cold roof on top.
Insulation between rafters with 16 cm (6 inches) of polystyrene. Ceiling to the attic insulated with 20 cm (8 inches) of mineral wool.
It basically works quite well. I use about 1000 liters (264 gallons) of heating oil and roughly 6 cubic meters of firewood per year. Hot water is powered by electricity. In the future, I plan to install a 10 kW solar system with battery storage.
No triple glazing, no underfloor heating except in the bathroom. Instead, there are two chimneys in the house: a wood stove in the kitchen, a fireplace in the living room rated at 18 kW, and an oil heating system. Hot water heater.The 6 cubic meters of firewood correspond to roughly 1800 liters (475 gallons) of heating oil (for beech wood). So you’re at about 2800 liters (740 gallons) of oil PLUS hot water.
lesmue79 schrieb:
I have already limited the heat output of the heat pump using the whisper mode, and I turn it off at night during the transitional seasons as you mentioned. This results in a ratio of about 1.5 hours of run time per compressor start. The compressor hysteresis is already set to maximum, as is the energy integral. Unfortunately, on my heat pump model, the energy integral can only be set to a maximum of 120 minutes (2 hours), whereas on other Vaillant heat pump models it can be set up to 180 minutes (3 hours). When the temperature drops to around -5°C (23°F) or below, it runs continuously 24/7. Oh man, everyone tries to adjust all the settings at once without really understanding the actual consequences.
And "tilted window ventilation" is a no-go inside the house, especially in new builds.
lesmue79 schrieb:
When the temperature drops to around -5°C (23°F) or below, it runs continuously 24/7. Ideally, this happens at the design temperature!
driver55 schrieb:
Oh man, everyone is adjusting all the settings at once again without really understanding the actual impact.
And “tilted windows” are not allowed in the house, especially in new builds.
Ideally at the design temperature! When the system runs without whisper mode, it cycles every half hour during the transition period instead of every 1.5 hours. Additionally, I noticed that if I slightly reduce the flow in the bedroom and guest room (so the bathroom gets more flow), the flow initially redistributes to other loops but unfortunately none goes to the bathroom heating loop. To achieve that, I have to reduce the flow in more loops (also the utility room, WC, and hallway), until the total flow reaches about 600 liters per hour (l/h) instead of around 750 l/h when all loops are open.
Similar topics