ᐅ Where and how to install dew point sensors for underfloor heating?
Created on: 6 Oct 2023 16:45
J
JaiBee07Hello,
since I would like to have underfloor heating with a passive cooling function, it seems that I also need dew point sensors.
Where are these usually installed? Are they cast directly into the screed or mounted on the water pipes? How can they be replaced if they malfunction?
How many of these sensors are needed? One per floor?
Are there particularly effective locations for installing these sensors? For example, where the (cooling) pipe loops are laid especially close together, since that is where the greatest cooling output is delivered?
Do these cables typically connect directly to the heating system’s control unit or to the room thermostats? Do heating system manufacturers recommend specific types, or can you choose freely? Is there a well-known manufacturer that has proven reliable?
I would appreciate some answers.
since I would like to have underfloor heating with a passive cooling function, it seems that I also need dew point sensors.
Where are these usually installed? Are they cast directly into the screed or mounted on the water pipes? How can they be replaced if they malfunction?
How many of these sensors are needed? One per floor?
Are there particularly effective locations for installing these sensors? For example, where the (cooling) pipe loops are laid especially close together, since that is where the greatest cooling output is delivered?
Do these cables typically connect directly to the heating system’s control unit or to the room thermostats? Do heating system manufacturers recommend specific types, or can you choose freely? Is there a well-known manufacturer that has proven reliable?
I would appreciate some answers.
H
HeimatBauer6 Oct 2023 17:15In my underfloor heating system with a cooling function, which I absolutely love and really enjoy in summer, I have an additional sensor in the living room. It looks like a room thermostat or a small control unit but only displays some data and measures humidity and temperature. I have one sensor for the entire house. The sensor is part of the heat pump installation, so it is also from the heat pump manufacturer.
rick2018 schrieb:
A dew point sensor belongs in the floor covering.Could you be a bit more specific? Do you really mean the covering itself (I have parquet) or the floor structure? Then in the screed or somewhere else?
A
Allthewayup8 Oct 2023 11:34Opinions vary when it comes to implementation. Some install dew point monitors in the heating circuit (either the supply or return line—I’m not sure which), while others place sensors in the screed, where condensation is most likely to occur first and cause the most damage, especially if a calcium sulfate screed is used, as it cannot tolerate moisture for long or at all.
According to my heating engineer, the option with an additional dew point monitor in the supply or return line is simpler but has two disadvantages: 1. You will never know exactly how “wet” the floor construction really is or becomes during cooling, and 2. because of this uncertainty, you will always have to apply a safety margin to the supply temperature to ensure condensation does not form somewhere in the floor.
So, if you want to operate the system at maximum efficiency and without risk during cooling, you will need several sensors installed in the screed.
For us, it wasn’t worth it, so we preferred to run only 20°C (68°F) through the floor instead of 17°C or 18°C (62.6°F or 64.4°F). However, depending on the conditions, this also does not guarantee 100% protection against condensation! If the floor is already at 26°C (79°F) and you run water at 20°C (68°F), condensation could probably occur anyway.
According to my heating engineer, the option with an additional dew point monitor in the supply or return line is simpler but has two disadvantages: 1. You will never know exactly how “wet” the floor construction really is or becomes during cooling, and 2. because of this uncertainty, you will always have to apply a safety margin to the supply temperature to ensure condensation does not form somewhere in the floor.
So, if you want to operate the system at maximum efficiency and without risk during cooling, you will need several sensors installed in the screed.
For us, it wasn’t worth it, so we preferred to run only 20°C (68°F) through the floor instead of 17°C or 18°C (62.6°F or 64.4°F). However, depending on the conditions, this also does not guarantee 100% protection against condensation! If the floor is already at 26°C (79°F) and you run water at 20°C (68°F), condensation could probably occur anyway.
Hello JaiBee07
You need to approach this topic more thoroughly than with familiar heating systems.
First of all, the most important point: a combined heating/cooling phase through the floor has, in my opinion, not proven to be effective.
The ideal, most efficient solution would be underfloor heating combined with ceiling cooling.
Please keep in mind that the temperature difference during a warm summer with high humidity can only be small. This is due to the dew point, which I mentioned earlier but occurs not within the screed, rather on the surface of the floor covering.
In the case of ceramic tiles, if this dew point is undershot during cooling, the formation of a water film can cause significant slipping hazards. Conversely, at room temperatures of, for example, 28°C (82°F) and 75% relative humidity, you should not expect significant cooling results.
Why not?
At 28°C/75% (see above), the dew point on the surface of the floor covering is around 23°C (73°F).
If you allow a safety margin of 3°C (usual value), the supply temperature of the cooling system should not be below 26°C (79°F).
Anyone can imagine that a cooling effect with only a 2°C (4°F) temperature difference between air and floor will hardly contribute to a noticeable sense of comfort through cooling.
And even if at lower humidity the supply temperature can be further reduced, you will very likely experience “cold feet.” And that during summer.
Regarding dew point sensors, this is a tricky issue.
I recall a legal case I worked on as an expert.
The sensors embedded in the screed were supposed to transmit data via an app, giving the impression of safety concerning the moisture content of the installed parquet flooring as well as the heated/cooled screed.
To be brief:
There is no universal sorption isotherm for all types of screed and parquet!
That means the sensor can display whatever it wants but cannot provide reliably specific values.
My inquiries to the manufacturer about the measurement principle remained unanswered until the end.
------------------
Conclusion:
If possible, look for another solution than a combined heating/cooling system through the floor.
You will not be satisfied and will most likely regret the costs of this unsatisfactory construction.
Better install one or more air conditioning units designed for hot summer days that can reliably handle the task.
By “air conditioning units,” I mean systems based on heat pump technology.
Best regards and wishing you a wise decision: KlaRa
You need to approach this topic more thoroughly than with familiar heating systems.
First of all, the most important point: a combined heating/cooling phase through the floor has, in my opinion, not proven to be effective.
The ideal, most efficient solution would be underfloor heating combined with ceiling cooling.
Please keep in mind that the temperature difference during a warm summer with high humidity can only be small. This is due to the dew point, which I mentioned earlier but occurs not within the screed, rather on the surface of the floor covering.
In the case of ceramic tiles, if this dew point is undershot during cooling, the formation of a water film can cause significant slipping hazards. Conversely, at room temperatures of, for example, 28°C (82°F) and 75% relative humidity, you should not expect significant cooling results.
Why not?
At 28°C/75% (see above), the dew point on the surface of the floor covering is around 23°C (73°F).
If you allow a safety margin of 3°C (usual value), the supply temperature of the cooling system should not be below 26°C (79°F).
Anyone can imagine that a cooling effect with only a 2°C (4°F) temperature difference between air and floor will hardly contribute to a noticeable sense of comfort through cooling.
And even if at lower humidity the supply temperature can be further reduced, you will very likely experience “cold feet.” And that during summer.
Regarding dew point sensors, this is a tricky issue.
I recall a legal case I worked on as an expert.
The sensors embedded in the screed were supposed to transmit data via an app, giving the impression of safety concerning the moisture content of the installed parquet flooring as well as the heated/cooled screed.
To be brief:
There is no universal sorption isotherm for all types of screed and parquet!
That means the sensor can display whatever it wants but cannot provide reliably specific values.
My inquiries to the manufacturer about the measurement principle remained unanswered until the end.
------------------
Conclusion:
If possible, look for another solution than a combined heating/cooling system through the floor.
You will not be satisfied and will most likely regret the costs of this unsatisfactory construction.
Better install one or more air conditioning units designed for hot summer days that can reliably handle the task.
By “air conditioning units,” I mean systems based on heat pump technology.
Best regards and wishing you a wise decision: KlaRa
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