ᐅ Increase the supply temperature from 40°C to 35°C or not?
Created on: 5 Mar 2022 00:47
H
HoisleBauer22
Hello everyone,
My home construction company specified a flow temperature of 40 degrees Celsius (104°F) in the contract "to save money," meaning a larger pipe spacing, probably increasing from 10-15 cm (4-6 inches) to 20 cm (8 inches).
The key data for the house (planned): KfW 55 standard, Daikin Altherma 3 R ECH2O 308/508, annual performance factor around 4, living area 145 m² (1560 ft²) with the basement also heated (this was required for KfW), the basement itself has 80 m² (860 ft²) of usable/floor space, but is not considered living space according to standards due to insufficient natural light.
We have a controlled ventilation system with heat recovery. We also plan to install a photovoltaic system of about 10 kW peak on the roof at some point.
Now I’m wondering if it would be worthwhile to reduce the flow temperature from 40 degrees Celsius (104°F) to 35 degrees Celsius (95°F) given an assumed electricity price of around 45 cents per kWh. The additional costs are about €15 per m² for the upgrade. The crucial point is how much energy savings percentage is achieved per degree of reduction. It is usually assumed to be 2.5 percent per degree, which would amount to 10–12.5 percent savings at 5 degrees lower flow temperature.
Does anyone have any ideas on how to calculate this or if there is a website available for such calculations?
My home construction company specified a flow temperature of 40 degrees Celsius (104°F) in the contract "to save money," meaning a larger pipe spacing, probably increasing from 10-15 cm (4-6 inches) to 20 cm (8 inches).
The key data for the house (planned): KfW 55 standard, Daikin Altherma 3 R ECH2O 308/508, annual performance factor around 4, living area 145 m² (1560 ft²) with the basement also heated (this was required for KfW), the basement itself has 80 m² (860 ft²) of usable/floor space, but is not considered living space according to standards due to insufficient natural light.
We have a controlled ventilation system with heat recovery. We also plan to install a photovoltaic system of about 10 kW peak on the roof at some point.
Now I’m wondering if it would be worthwhile to reduce the flow temperature from 40 degrees Celsius (104°F) to 35 degrees Celsius (95°F) given an assumed electricity price of around 45 cents per kWh. The additional costs are about €15 per m² for the upgrade. The crucial point is how much energy savings percentage is achieved per degree of reduction. It is usually assumed to be 2.5 percent per degree, which would amount to 10–12.5 percent savings at 5 degrees lower flow temperature.
Does anyone have any ideas on how to calculate this or if there is a website available for such calculations?
driver55 schrieb:
KfW55 and then with 40 degrees Celsius (104°F) supply temperature. Trying to handle underfloor heating around the corner.
We are in the year 2022!
Signature signed too early! That also seems quite inconsistent to me...
40 degrees Celsius (104°F) is outrageous. And charging extra costs for just 5 degrees is just as unreasonable.
This needs to be properly designed.
I would calculate with 30/26 (degrees Celsius) (86/79°F), especially for a heat pump, as low as possible.
Even designing a gas boiler for 40 degrees Celsius (104°F) is something from the early 2000s...
bortel schrieb:
Even designing a gas boiler for 40 degrees is something from the year 2000...I can only confirm that. The old multi-family building here (350 sqm (3,767 sq ft) from 1913) was installed with gas, underfloor heating, and a supply temperature of just under 35°C (95°F) ... 12 years ago 😉. Additional wall insulation was applied only on the corners of the building facing north.D
Deliverer7 Mar 2022 19:18kbt09 schrieb:
Additional wall insulation only on the north-facing corners of the building.What does that look like, and how effective is it?D
Deliverer7 Mar 2022 20:15Ok... I can’t really imagine that this will have a significant impact on the heating load, but thanks for the picture.
No, I’m not thinking about the impact on the heating load, but rather temperature equalization, meaning the reduction of cold spots in the apartment. Also, the landlord was just here, and the back side visible here is overall also covered with a thin (about 60mm (2.4 inches)) layer of thermal insulation, since it faces north.