ᐅ Expert Assessment of Underfloor Heating in a Single-Family Home
Created on: 27 Feb 2017 23:44
C
Canca42
Hello to the experts,
we are currently caught between two opinions and would therefore appreciate an independent assessment.
On one side, the heating specialist we hired (offering a complete package for our prefab house), and on the other, a close acquaintance who is also a technician/heating installer (and a perfectionist in his field).
We are building a prefab house with underfloor heating. The heating system is a gas condensing boiler from Viessmann (Vitodens 200W, nominal heat output 2.4-13 kW, calculated heating load is sufficient) plus a 300-liter (79 gallons) solar storage tank. There is a solar system with a collector area of 5 m² (54 ft²) (Viessmann Vitosol 200F) to support hot water production. The underfloor heating is installed using plastic piping made of PE-Xa/PAM. We have two heating circuits (1x ground floor, 1x upper floor).
Now the issue — according to the quote, the heating specialist will not install a mixing circuit for the underfloor heating. When asked how the flow temperature regulation would be managed, the answer was that it is controlled via the boiler, which is apparently a common method. Additionally, there is a device to prevent overheating (I don’t remember the exact name). The design temperature is 35°C (95°F).
Our acquaintance insists that installing a mixing circuit is essential; otherwise, it would be shoddy and highly questionable. Also, there is no backflow preventer (system separator BA) installed; no explanation was given for this.
We find it difficult to evaluate the situation. Is it really possible to operate without a mixing circuit? Is this standard practice or rather a cost-saving measure that may lead to poor workmanship? Or do we need to accept the additional cost and discussion and insist on installing a mixing circuit? What advantages would this give us?
Another questionable point: we received an offer for closer spacing of the heating loops including enlargement of the heating circuits (possibly to prepare for a future heat pump). The reasoning was that this only applies as an option with the Vitodens 200 model. If we were to choose the 300W instead (still undecided), it would not be necessary. Why is that? So far no one has been able to explain this convincingly.
Thank you very much for objective professional opinions.
Best regards,
Charly
we are currently caught between two opinions and would therefore appreciate an independent assessment.
On one side, the heating specialist we hired (offering a complete package for our prefab house), and on the other, a close acquaintance who is also a technician/heating installer (and a perfectionist in his field).
We are building a prefab house with underfloor heating. The heating system is a gas condensing boiler from Viessmann (Vitodens 200W, nominal heat output 2.4-13 kW, calculated heating load is sufficient) plus a 300-liter (79 gallons) solar storage tank. There is a solar system with a collector area of 5 m² (54 ft²) (Viessmann Vitosol 200F) to support hot water production. The underfloor heating is installed using plastic piping made of PE-Xa/PAM. We have two heating circuits (1x ground floor, 1x upper floor).
Now the issue — according to the quote, the heating specialist will not install a mixing circuit for the underfloor heating. When asked how the flow temperature regulation would be managed, the answer was that it is controlled via the boiler, which is apparently a common method. Additionally, there is a device to prevent overheating (I don’t remember the exact name). The design temperature is 35°C (95°F).
Our acquaintance insists that installing a mixing circuit is essential; otherwise, it would be shoddy and highly questionable. Also, there is no backflow preventer (system separator BA) installed; no explanation was given for this.
We find it difficult to evaluate the situation. Is it really possible to operate without a mixing circuit? Is this standard practice or rather a cost-saving measure that may lead to poor workmanship? Or do we need to accept the additional cost and discussion and insist on installing a mixing circuit? What advantages would this give us?
Another questionable point: we received an offer for closer spacing of the heating loops including enlargement of the heating circuits (possibly to prepare for a future heat pump). The reasoning was that this only applies as an option with the Vitodens 200 model. If we were to choose the 300W instead (still undecided), it would not be necessary. Why is that? So far no one has been able to explain this convincingly.
Thank you very much for objective professional opinions.
Best regards,
Charly
K
Knallkörper9 Mar 2017 17:07The fact is that the mixing valve can never be a disadvantage.
I wouldn't have known that the gas condensing boiler is capable of such low temperatures!
I wouldn't have known that the gas condensing boiler is capable of such low temperatures!
The gas boiler does not produce a specific temperature but rather output power. In this case, at least 2.4 kW (2,4 kilowatt). If less power is needed due to the outside temperature, it simply cycles on and off. Once a demand of 2.4 kW (2,4 kilowatt) or more is reached, it runs steadily.
Let’s say the required supply temperature is 28°C (82°F). The boiler heats the supply water to 28°C (82°F). The water flows through the pipes and cools down to 23°C (73°F). Then the boiler reheats the water back up to 28°C (82°F). As long as this requires at least 2.4 kW (2,4 kilowatt) of power, the boiler does this continuously. Therefore, a mixing valve is completely unnecessary. Much more important is the correct design of the underfloor heating system in relation to the required heating load. The closer the pipe spacing, the lower the supply temperature can generally be. This is especially important for the efficiency of heat pumps.
If you are running only underfloor heating without towel radiators or similar, no system separation is needed.
Let’s say the required supply temperature is 28°C (82°F). The boiler heats the supply water to 28°C (82°F). The water flows through the pipes and cools down to 23°C (73°F). Then the boiler reheats the water back up to 28°C (82°F). As long as this requires at least 2.4 kW (2,4 kilowatt) of power, the boiler does this continuously. Therefore, a mixing valve is completely unnecessary. Much more important is the correct design of the underfloor heating system in relation to the required heating load. The closer the pipe spacing, the lower the supply temperature can generally be. This is especially important for the efficiency of heat pumps.
If you are running only underfloor heating without towel radiators or similar, no system separation is needed.
K
Knallkörper9 Mar 2017 18:55Joedreck schrieb:
The gas boiler doesn’t deliver temperature but power.That’s basically true, but with 2.4 kW and low flow rate, the heating circuit can already get quite warm, even without calculating it precisely. That sounds about right!
From the discussion, I gather that I don’t really need a mixing valve because, with proper design and accurate calculations, the system will always deliver the correct temperature (to put it simply). But does continuous operation not lead to more wear and tear? Or is it rather with the on/off cycling where consumption is more efficient?
They also say that when waiting at a traffic light, it’s better to turn off the car.
By the way, isn’t a system separator required by a specific DIN standard?
They also say that when waiting at a traffic light, it’s better to turn off the car.
By the way, isn’t a system separator required by a specific DIN standard?
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