A very good day to the community.
I must mention beforehand that I am a novice on this topic and do not have a lot of information. I understand that the lack of details may limit your input. Nevertheless, I would be very grateful if you could share your opinion based on the available information.
Thank you in advance for your support.
The issue concerns a single-family house where underfloor heating was recently installed from the basement to the attic (i.e., basement, ground floor, first floor, attic). Previously, there were radiators, which have now been removed. The area is approximately 125 m² (1350 sq ft).
In the basement, there is a Viessmann Vitodens 200-W boiler. There is also a Viessmann hot water storage tank (if this is relevant). Each room has an individual analog room thermostat.
The current problem is as follows: The rooms only become lukewarm, even though the thermostats are set to at least 23°C (73°F). When the outside temperature is just above 0°C (32°F) in the morning, the rooms show about 19°C (66°F) according to the weather station.
Various settings have been adjusted on the Vitodens 200-W so far without success. Examples:
Additionally, a Yonos PICO plus 25/1-4 circulation pump was installed. The displayed flow rate varies depending on how many rooms are being heated. With only a few rooms (1–2) heated, the flow rate shows between 0 and 0.2 m³/h. I do not know whether this is a good or bad value.
Now the discussions have started:
All very costly in today’s times. Due to poor experiences with some heating technicians and the various opinions about what is actually necessary, I find it very difficult to decide on a direction.
Therefore, I would be very grateful if you could simply share your opinion or gut feeling based on this information.
It seems to me that too much heat is lost before it even reaches the rooms. Hence my general question: Is a Vitodens 200-W actually sufficient?
Thank you very much.
I must mention beforehand that I am a novice on this topic and do not have a lot of information. I understand that the lack of details may limit your input. Nevertheless, I would be very grateful if you could share your opinion based on the available information.
Thank you in advance for your support.
The issue concerns a single-family house where underfloor heating was recently installed from the basement to the attic (i.e., basement, ground floor, first floor, attic). Previously, there were radiators, which have now been removed. The area is approximately 125 m² (1350 sq ft).
In the basement, there is a Viessmann Vitodens 200-W boiler. There is also a Viessmann hot water storage tank (if this is relevant). Each room has an individual analog room thermostat.
The current problem is as follows: The rooms only become lukewarm, even though the thermostats are set to at least 23°C (73°F). When the outside temperature is just above 0°C (32°F) in the morning, the rooms show about 19°C (66°F) according to the weather station.
Various settings have been adjusted on the Vitodens 200-W so far without success. Examples:
- Set room temperature adjusted to 23°C (73°F) to 25°C (77°F)
- Slope increased up to 1
- Level increased up to 3
Additionally, a Yonos PICO plus 25/1-4 circulation pump was installed. The displayed flow rate varies depending on how many rooms are being heated. With only a few rooms (1–2) heated, the flow rate shows between 0 and 0.2 m³/h. I do not know whether this is a good or bad value.
Now the discussions have started:
- “A hydraulic balancing must be carried out”
- “A pump group must be installed”
- “A new gas boiler must be installed”
All very costly in today’s times. Due to poor experiences with some heating technicians and the various opinions about what is actually necessary, I find it very difficult to decide on a direction.
Therefore, I would be very grateful if you could simply share your opinion or gut feeling based on this information.
It seems to me that too much heat is lost before it even reaches the rooms. Hence my general question: Is a Vitodens 200-W actually sufficient?
Thank you very much.
rick2018 schrieb:
How are the circuits of the underfloor heating controlled? Are they open? What is your supply temperature and what about the return temperature? Try increasing the flow rate at the circulation pump.Hello rick2018, thank you very much for your quick reply. =)
I hope I understood your question correctly. There is a manifold (distribution box) on each floor. This contains the pipes (both supply and return) with the actuators and flow meters. The actuators are controlled by the individual analog room thermostats in the rooms.
Currently, the target room temperature is set to 23°C (73°F). Unfortunately, I cannot find an exact display of the supply temperature. The heating curve shows the following values:
| Outdoor temperature | Supply temperature |
| 0°C (32°F) | 47°C (117°F) |
| 10°C (50°F) | 38°C (100°F) |
| 20°C (68°F) | 27°C (81°F) |
Slope = 1
Level = 0
At the moment, according to the weather app, the outdoor temperature in my area is 7°C (45°F). However, the gas boiler shows an outdoor temperature of 10°C (50°F).
Unfortunately, I cannot provide the return temperature; it is not displayed anywhere, or I am unable to find it.
I cannot increase the flow rate of the circulation pump any further. It is already set to the maximum level for an underfloor heating system.
Thank you in advance for your feedback.
KoalasAreCute27 Mar 2023 16:24Thomas38 schrieb:
Flow rate indicated as 0–0.2 m³/hConverted, that is 0–200 L/h (0–53 gallons per hour). That sounds low to me. However, my experience is with a heat pump. In our last house (about 150 m² (1,615 ft²)), the heat pump had a flow rate of around 19 L/min (5 gallons per minute), which is about 1,000 L/h (265 gallons per hour). We had a case where the pump was broken and showed zero flow. The technician told us it should be at least around 15+ L/min (4 gallons per minute) at a supply temperature of about 35°C (95°F).Position the circulation pump higher. Regardless of what is supposedly suitable for underfloor heating, in my opinion, the flow rate is too low.
Underfloor heating is also significantly slower to respond. It takes 2-3 days to warm up. This is always the case with weather changes unless it is controlled intelligently.
Your sensor is simply in a different location, which is why there is a difference in the outdoor temperature reading.
Underfloor heating is also significantly slower to respond. It takes 2-3 days to warm up. This is always the case with weather changes unless it is controlled intelligently.
Your sensor is simply in a different location, which is why there is a difference in the outdoor temperature reading.
KoalasAreCute schrieb:
Converted, that is 0-200 L/h (0-53 gallons per hour). That sounds low to me. However, my experience is with a heat pump. In our last house (about 150 m² (1,615 sq ft)) the heat pump had a flow rate of about 19 L/min (5 gallons per minute) or approximately 1,000 L/h (264 gallons per hour).
We had a case where the pump was broken and showed 0 flow rate. The technician told us it should be at least around 15+ L/min (4 gallons per minute) at a supply temperature of about 35°C (95°F). Hello KoalasAreCute,
Thank you for your reply. Although the pump is new, it could of course be defective. For a single heated room, it indeed shows 0 m³/h (0 cubic feet per hour). When all room thermostats in the house are turned up, the flow rate displayed on the circulating pump rises but never reaches double digits. It doesn’t even show 5 m³/h (176 cubic feet per hour).
rick2018 schrieb:
Turn the circulating pump up higher. No matter what is supposedly designed for underfloor heating… in my opinion, that flow is too low.
Underfloor heating is also significantly slower to respond. It takes 2-3 days to warm up. This is always the case during weather changes unless an intelligent control system is used.
Your sensor is just in a different place, so that explains the difference in outdoor temperature measurement. I will try that. It also has a mode for radiators.
I am well aware of the slow response of underfloor heating. But even after several days—especially in the morning when it’s just above 0°C (32°F)—temperatures above 20°C (68°F) are not reached.
If, however, the sensor measures an incorrect outdoor temperature, wouldn’t that also cause an incorrect supply temperature to be generated?
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