Indoor air mixing and heating savings

Heating, insulation, ventilation, VMC, cooling ... short thermal comfort. Insulation, wood energy, heat pumps but also electricity, gas or oil, VMC ... Help in choosing and implementation, problem solving, optimization, tips and tricks ...
Christophe
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Indoor air mixing and heating savings




by Christophe » 03/01/11, 18:53

What are the potential energy savings expected by better mixing the heated indoor air? And what would be the main drawbacks of mechanized blowing?

This topic follows on from these 2 topics:
https://www.econologie.com/forums/ameliorati ... 10292.html
et https://www.econologie.com/forums/difference ... 10239.html

The technique consists in improving on the one hand the exchanges at the level of the heat diffusers (radiator, wood stove ...) and on the other hand the uniformity of the temperature in the heated rooms. Method: place a fan, regulated or not, on a radiator or near a wood stove.

Pitmix has shown, using measurements and time curves, that its boiler was running less when it put a fan on a radiator close to its thermostat: https://www.econologie.com/forums/ameliorati ... 10292.html

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As a first approximation, I think that we can estimate a potential gain similar to that of heated floors which have the main advantage of the homogeneity of their heating (in addition to being compatible with low temperature) ... but for an investment .. .1 times lower!

Corrolaire: why the technique, so simple technologically, does not exist any more?

In terms of disadvantages, I see 2 for the moment: noise and power consumption ...

ps: we have had a ventillo near our wood stove for a few weeks. And even if it does not really reduce consumption, because there is no regulation, it improves thermal comfort on the other side of the room ...
Last edited by Christophe the 09 / 01 / 14, 16: 31, 1 edited once.
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aerialcastor
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by aerialcastor » 03/01/11, 20:25

As a first approximation, I think that we can estimate a potential gain similar to that of heated floors which have the main advantage of the homogeneity of their heating (in addition to being compatible with low temperature) ... but for an investment .. .1 times lower!



It is not at all comparable. A PC heats up by radiation, that's why it's comfortable. Moreover, the further we move away from the PC, ie the more we climb the less hot we are.



In disadvantage, you also have the mixing of the dust and the decrease in thermal comfort due to the draft.
We must systematically favor radiant heaters which are bcp more comfortable.
Unless there is a need for rapid heating.


See this discussion
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by PITMIX » 03/01/11, 20:30

Hello
This little experience encouraged me to install a double flow vmc like André in Canada. Air supply close to the heating bodies and air extraction with a lower flow rate to put the house in overpressure.
Regarding the air circulation, I installed a fan under my chimney 2 years ago to accentuate the heat exchange with the air. But you need a fan with variable speed control because otherwise it reduces the sensation of radiant heat when the ambient air is cool.
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by Christophe » 03/01/11, 23:22

aerialcastor wrote:It is not at all comparable. A PC heats up by radiation, that's why it's comfortable. Moreover, the further we move away from the PC, ie the more we climb the less hot we are.


What I compared was not the heating mode (and a PC heats by conduction as well) but the gain in temperature uniformity ... and when I said potential gain it was the maximum possible gain.

Yes for the disadvantages and with the last remark of Pitmix, on our stove I only turn on the fan when it heats up well. Otherwise the comfort is effectively reduced (and the losses on the frames probably increased) ...
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by PITMIX » 05/01/14, 14:55

Hello
I follow up on topic on the improvement of a radiator which is now a replacement by an air conditioning hacked into a water fan coil.
I bring here some figures and feelings.
Incoming water temperature 46 ° C
Discharge temperature 36 ° C
Air intake temperature 17 ° C
The blowing is from the top and I can feel the difference when I am sitting on the sofa near the fan coil compared to the standing position even 4m from the fan coil.
We feel much better standing.
Will have to reverse the direction of the fan ...
From the point of view of the energy gain I have not enough retreat but one thing is sure there is more power than before.
The temperature in my living room was colder than the bedrooms upstairs in the house, but now it's the other way around.
My thermostat being in the living room, I concluded that the temperature rise is faster so the thermostat will cut in for a shorter time.
I confirm the curves that Christophe published above but at the time I did not continue the experiment because I had no regulation on the ventilation and too much noise even at speed 1. In summary, no comfort.
There it is different I put a thermostat which activates the fan as soon as the battery reaches 27 ° C. I leave the ventilation at speed 1, which is sufficient for thermal comfort and not disturbing acoustically.

The temperature curve here shows that before replacing the radiator, the boiler was switched on at night for 30min for stops of 1h15 the room thermostat setpoint 19,5 ° C
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The lowest outside temperature recorded today is at 8 a.m. with 6.1 ° C
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The next day after installation of the fan coil, the boiler is activated 15min for a stop of 45min always 19.5 ° C setpoint

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Unfortunately the comparison is difficult between these two days because on 09/12/13 the minimum outside temperature fell to 0.7 ° C. But we can clearly see that despite a drop of 6 ° C outside the room temperature is reached more quickly time divided by 2 while the inertia of the house is also divided by 2.

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by PITMIX » 09/01/14, 16:09

Hello
Christophe wrote:The technique consists in improving on the one hand the exchanges at the level of the heat diffusers (radiator, wood stove ...) and on the other hand the uniformity of the temperature in the heated rooms. Method: place a fan, regulated or not, on a radiator or near a wood stove ...

... ps: we have had a ventillo near our wood stove for a few weeks. And even if it does not really reduce consumption, because there is no regulation, it improves thermal comfort on the other side of the room ...


I just got my hands on a testo 425 that had been lying around for ages in my laundry room and had never paid attention to the anemometer function in addition to the thermometer.

Image
Perfect for making a little statement on what Christophe says

Today I use the fan coil to stir the air in the room which is heated by my chimney located 4m from the fan coil. The central heating is off.
Image

It was 18.4 ° C in the living room at the level of the fan coil outlet probe before heating.
After 45min of heating I note:
-Average ambient temperature over 50m² 22 ° C
-In speed 1 at blowing 2.1m / s and 20 ° C very low noise at 1m (no sound level meter sorry)
-There are 23 ° C on the ceiling and 21 ° C on the floor on average throughout the room.
-In the kitchen at 7m I note 0.12m / sec of air at 1.55m from the floor in line with the fan coil. No unpleasant feeling from the air.

-In blowing speed 2 2.35m / sec and at 7m I also have 0.12m / sec but at 1.65m from the ground. Still no disturbance in relation to the air and the noise remains bearable for the day.

-In speed 3 at blowing 2.65m / sec and at 7m 0.20m / sec at 1.65m from the ground as well. This time the air and the noise are disturbing.

Test with fan coil stopped:
0.01m / sec of air in the room at breast height.
Convective movement on the ceiling at H2.35m causing an air flow at 0.15m / sec on average over 50m².
The radiation from the fireplace seems more noticeable.
The average room temperature is now 23 ° C.
The temperature on the ground is 22 ° C on average.
The ceiling temperature is 28 ° C on average.
The feeling of heat is more important but we can see that there are more important DTs.

Switching the fan coil back on for 20 minutes at speed 2 the chimney has been heating for 2 hours now on low heat:
The average temperature fell to 21.5 ° C in the room with 21 ° C on the floor and 22 ° C on the ceiling.
The effect of the air mixing is clearly visible with these measurements and I must say that the feeling is better with the air mixing because the temperature is more homogeneous.
No hot spot, and even around the fireplace it is less important despite the distance from the fan.
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by dirk pitt » 09/01/14, 16:31

putting a fan on a heat diffusing member will do only one thing: increase its capacity for exchange with the ambient air.
therefore the influence will only be on the transfer time of the energy from this diffuser to the ambient air. the temperature rise will be faster and the temperature distribution better in the room = thermal comfort.
but you have to ask yourself the right question: what makes the consumption of a house: it is above all its thermal losses, therefore the quantity of energy which leaves the house which must be equal to the quantity of energy that is injected into it if we want to keep a constant temperature.
this quantity is always the same with or without fan so for me, no noticeable gain. one could even say that the mixing of the air also increases the exchange with the internal walls of the house thus favors the losses.
for a wood stove, the reasoning is different because increasing heat exchange with the ambient air also means reducing the amount of heat sent to the fireplace. therefore, in this case, the consumption will actually be lower with forced convection.
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by PITMIX » 09/01/14, 17:01

Exactly but in this case I replaced a radiator with an air conditioning evaporator battery. So the exchange surface is increased by the fins and further increased by the forced ventilation.
The ventilation makes it possible to reduce the size of the exchanger compared to a static exchanger of the same power.
For the same size as a 60x80cm radiator there is a much greater power.
The advantage in terms of energy is to be able to obtain the same comfort with a lower water temperature. It remains to be seen if over time I will obtain a reduction in the bill.

As for the measurements taken above, it is just to illustrate what we already know, the mixing of the air makes the temperature more homogeneous and even more with a stove or a fireplace, with figures it is even more speaking.
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