ᐅ Centralized mechanical ventilation with heat recovery: Are individual rooms controllable?
Created on: 23 Apr 2015 11:59
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LuciferSam
Hello community,
while researching central systems for controlled residential ventilation (controlled ventilation) with heat recovery (heat recovery), I noticed something: nobody seems to build systems where the ventilation of individual rooms can be comfortably adjusted on an ongoing basis (not just once for balancing but continuously, daily). I can neither find testimonials nor see such systems being advertised.
Why do I want this? – A central controlled ventilation system with heat recovery equalizes the temperature of all connected rooms over time. (Air is extracted from all rooms, mixed, passed through the heat exchanger; warmed fresh air reaches every room.) However, this is not always desirable. At night, I want to sleep in a cold room but still use controlled ventilation to be able to sleep with windows and doors closed. The living room, heated by underfloor heating, I do not want or need to cool down every evening. If I could turn off the ventilation in the living room at night and in the bedroom at least temporarily during the day, the problem would be solved.
Would this be difficult? – Air dampers in all pipes from the central manifold to the rooms, controlled by very expensive actuators or simple, inexpensive servos from the model building sector, could regulate the airflow. Sound attenuators would probably be needed behind them (?). Between the fan and the first central manifold, a pressure sensor could be installed to control the fan continuously. If the air pressure before the control dampers is kept constant, adjusting one damper should not significantly affect the airflow through another.
As I see it, this would be a huge advantage with reasonable extra effort. Why does nobody do this? I am still quite a beginner in this field. Have I overlooked something?
Thanks!
while researching central systems for controlled residential ventilation (controlled ventilation) with heat recovery (heat recovery), I noticed something: nobody seems to build systems where the ventilation of individual rooms can be comfortably adjusted on an ongoing basis (not just once for balancing but continuously, daily). I can neither find testimonials nor see such systems being advertised.
Why do I want this? – A central controlled ventilation system with heat recovery equalizes the temperature of all connected rooms over time. (Air is extracted from all rooms, mixed, passed through the heat exchanger; warmed fresh air reaches every room.) However, this is not always desirable. At night, I want to sleep in a cold room but still use controlled ventilation to be able to sleep with windows and doors closed. The living room, heated by underfloor heating, I do not want or need to cool down every evening. If I could turn off the ventilation in the living room at night and in the bedroom at least temporarily during the day, the problem would be solved.
Would this be difficult? – Air dampers in all pipes from the central manifold to the rooms, controlled by very expensive actuators or simple, inexpensive servos from the model building sector, could regulate the airflow. Sound attenuators would probably be needed behind them (?). Between the fan and the first central manifold, a pressure sensor could be installed to control the fan continuously. If the air pressure before the control dampers is kept constant, adjusting one damper should not significantly affect the airflow through another.
As I see it, this would be a huge advantage with reasonable extra effort. Why does nobody do this? I am still quite a beginner in this field. Have I overlooked something?
Thanks!
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nordanney23 Apr 2015 20:52nathi schrieb:
There are already centralized controlled residential ventilation systems with multi-zone control, where in summer, for example, the bedroom ventilation is brought into the house through a bypass so that it is not further heated. Isn't it normal in summer that the air is not additionally heated, but is simply ventilated?
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Sebastian7923 Apr 2015 20:53Yes and no, it should be normal, but there are still some systems without a bypass... we have one in the rental place :/
nordanney schrieb:
Isn’t it normal that in summer the air isn’t heated further, but there is “only” ventilation?Of course, the heat pump doesn’t run then, but ideally, the heat recovery is also bypassed.
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LuciferSam24 Apr 2015 07:56First of all, thank you very much for your feedback!
Generally, you’re right – it’s a huge effort to achieve a condition that is quite similar to a conventional house without a central mechanical ventilation system. I will keep thinking about it...
nordanney schrieb:Ideally 18°C (64°F), which is of course not achievable in summer. As cool as possible. But in summer I want to cool the whole house down at night anyway, so the problem is more in winter. Of course, heat is also transferred through briefly open doors, the walls, etc., but I don’t want to worsen the issue by adding an actively balancing ventilation system.
How "cold" does your bedroom need to be? Since the whole house is ventilated and you also have air exchange through the doors (or door frames, depending on your preference), the temperature will equalize throughout the house over time.
Lexmaul79 schrieb:Hmm, I can’t find a proper definition of a constant volume airflow regulator anywhere. If it does what the name suggests, then it’s rather the opposite of what I want. The air volume flow should adjust dynamically, not be kept constant.
Constant airflow system is the magic word – then regulators in front of the rooms.
nathi schrieb:Ah, okay. Thanks for the tip, I will look into that.
There are central mechanical ventilation systems with multi-zone control that, for example, in summer bring ventilated air from the bedrooms back into the house via a bypass, so it is not further heated.
Generally, you’re right – it’s a huge effort to achieve a condition that is quite similar to a conventional house without a central mechanical ventilation system. I will keep thinking about it...
I can share my experience with you... what you’re planning to do is relatively pointless. Air is a poor medium, and with a mechanical ventilation system with heat recovery, you can’t achieve acceptable cooling or heating results without additional cooling or heating units.
That’s also why you won’t find much information on this topic—it simply doesn’t make sense.
As Lex already mentioned, the bypass is only of limited use.
A mechanical ventilation system with heat recovery is neither an air conditioner nor a heater—it only provides fresh air, and temperature differences at the valve are negligible when underfloor heating is running and the sun shines into the room during the day.
That’s also why you won’t find much information on this topic—it simply doesn’t make sense.
As Lex already mentioned, the bypass is only of limited use.
A mechanical ventilation system with heat recovery is neither an air conditioner nor a heater—it only provides fresh air, and temperature differences at the valve are negligible when underfloor heating is running and the sun shines into the room during the day.
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LuciferSam27 Apr 2015 07:23Mycraft schrieb:
With a controlled residential ventilation system, neither acceptable cooling nor heating results can be achieved without additional cooling or heating...
...
A controlled residential ventilation system is neither an air conditioner nor a heater... it only supplies fresh air, and the temperature differences at the vent are negligible when the underfloor heating is on and sunlight is entering the room during the day...I tried to roughly estimate this.
Assumptions:
- In a room at T1 = 18°C (64°F), air at temperature T2 = 21.5°C (71°F) is blown in (while air at temperature T1 escapes through gaps at the door).
- Two people are sleeping in the room, with a recommended airflow of about I = 50 m³/h (29.4 ft³/min) = 50/3600 m³/s.
- The density of air is rho = 1.293 kg/m³ (0.0807 lb/ft³).
- The specific heat capacity of air (at constant pressure) is cp = 1005 J/(kg·K).
- The thermal power introduced to the room by the air exchange is A = cp × I × rho × (T2 − T1) = 63 J/s = 63 W. (Compare the first formula in the Wikipedia article on specific heat and note that 1 joule = 1 watt-second.) (Of course, this only applies as long as the room temperature remains at 18°C (64°F). The power is proportional to the difference T2 − T1 and decreases as the room warms up.)
I estimate the heat output of a sleeping adult at about 40 W to 80 W (check Google), which is quite comparable to the heat output of the ventilation.
So, although the ventilation is a poor heater compared to a radiator, it does deliver a heat output comparable to a human body and is therefore quite relevant!
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