Minimal air inlet or how to do it cheaply, quickly and qualitatively at the same time
The essence of the problem
Question: Do you need an air conditioner in your home or country house in central Russia? A strange question, you might say – the temperature in summer goes off the scale over 30 degrees!
But this question becomes less obvious when we remember that:
hot summers happen one of two ways – every other one,
ventilation of rooms is not going away – it requires opening windows, which is incompatible with the operation of air conditioners,
installation of conventional split-system air conditioners involves placing outdoor units on the walls of the house, and also (which, in my opinion, is worse) – removing condensate from the indoor units somewhere, and this means piping around the house (we don’t want to put saucepans under each unit, do we?), and sometimes installing special pumps.
The main problem is that the sun heats up, first of all, the roof and the rooms that are on the second floor or in the attic – so the air in them becomes too warm and stuffy.
The engineering minds of seasoned habr-ovchans will immediately tell you that you should use ducted supply ventilation with corresponding ducted air conditioners.
Formally, this is the most correct approach. But have you seen the price tags for ducted air conditioners? They are several times more expensive than conventional split systems (75 thousand rubles vs. 25 thousand rubles for the second half of 2024 rubles)! And if you consider that, ideally, each room needs its own air conditioner (or a multi-channel installation for a million for one and a half rubles), then the question becomes very interesting! At the same time, the question of installing an external unit does not disappear anywhere.
Landing of needs
But in general, after sunset, the air temperature in June and July drops by ten degrees, and in August – by fifteen degrees. And during the day in the summer, household members (at least mine) usually spend time in the yard or outside, where it is not so hot in the shade of trees or in the water of a pool / local pond. Therefore, the problem of heat itself is exacerbated in the evening, when the bedrooms heated during the day become hot and stuffy.
Here the thought comes to mind: are air conditioners, conventional or ducted, really necessary in our case?
Idea!
And then a rather banal thought came to mind – what if we simply install supply ventilation in each room and turn it on when the ambient air becomes slightly cooler than the air temperature in the bedrooms? It is clear that this is reinventing the wheel, but, you must admit, it is still a little different than simply buying a bicycle and learning to ride it.
So the following problem statement emerges:
you need to know the air temperature in each room that needs to be ventilated;
you need to know the temperature of the outside air that will be taken in by the supply ventilation;
Duct fans should not only be efficient and low-noise, but also remotely controlled and, it is highly desirable, have several speeds (at least two).
Project
Duct fans please with their price and capabilities – my choice fell on ERA TYPHOON 125 2SP – an inexpensive two-speed axial fan, optimal in price-performance-noise. ERA TYPHOON 100 2SP costs the same, and the performance is almost a third lower: 355 m³/h versus 250 m³/h, and the noise level according to the passport is even slightly higher – 39 dB versus 40 dB. Their older brother, ERA TYPHOON 160 2SP, is much more productive (540 m³/h), but also much noisier – according to my calculations, for a room with an area of 12-14 sq.m with a ceiling height of 2.6 – 2.7 m, even the lowest productivity will be enough, but here the issue is noise and the fact is that I already had 125 mm heat-insulated sleeves and anemostats (inlet-outlet with a screw-on mushroom) from a regular hood.
Temperature sensors can be any, but since I have been using Mi Home for a long time, the choice is clear for me – Xiaomi Mi Temperature and Humidity Monitor 2 (aka LYWSD03MMC, aka NUN4126GL, compatible with the Yandex and Sber ecosystem, by the way).
Well, and the fan control relay – Yeelight Smart Dual Control Module (aka YLAI002, compatible with the Yandex and Sber ecosystem, by the way).
I decided to use sleeves with thermal insulation, but then I thought that it was not critical – you can also get regular cheaper ones.
Anemostats (inlet-outlet with a screw-on cap) – also any.
It is obviously best to place the fans in the attic – fortunately, I have a full-fledged one above the entire ceiling, electricity, lighting, and Wi-Fi, Zigbee, and everything else that comes through there.
The question remains: where to get air?
The attic is simply not suitable – the air temperature there is the highest, and it is dusty.
Remembering the structure of my roof, I remembered that one of its advantages is that it is ventilated, that is, there is air circulation (in the first reincarnation of the roof, there was not enough ventilation and it literally started raining in the attic).
On the Internet I found a good diagram of a ventilated roof.
Accordingly, the initial idea was to bring the sleeve between the rafters into the space of the eaves overhang (marked in pink on the diagram) and pass through the soffit, and terminate it usually with a round grate so that mosquitoes and other creatures do not fly in.
Looking ahead – laziness and curiosity led to the fact that I simply brought the sleeve into the space of the eaves overhang and began to take air directly above the soffits. What this led to – I will tell you further.
I decided to install the fans on the main wall (foam block, also known as gas silicate). The question was whether a gasket was needed between the fan and the wall for vibration isolation.
Again, I'm getting ahead of myself – vibration isolation was not required, the massiveness of the wall was enough to dampen vibrations from a light fan, the noise was minimal, but more on that later.
Implementation
Let me start with the positive:
the relays fit very well into the engine boxes after removing the excess plastic casting from there – the boxes closed completely with the relays inside;
I simply installed the temperature sensors on the spotlights – I didn’t have to secure them, and I didn’t protect them from the weather because there was a roof above them (autumn will tell).
The negative part started with the fact that it was not possible to simply attach the arm to the fan, since the usual connectors are internal, and the fans have a crosspiece at the inlet and outlet. The collective farmer did not cut out slots for it, but simply pulled the sleeves onto the outer surfaces of the inlet and outlet, and tightened them from above with a regular worm clamp, laying the outer surface of the sleeve under it (let me remind you that since it is heat-insulated, we actually have a sleeve-in-a-sleeve).
The installation process itself began with the installation of a separate 220-volt mini-electric panel in the attic with a separate circuit breaker and a place for connecting cables (I have three bedrooms upstairs). Next in the plans is the installation of a smoke alarm from the same Xiaomi.
The installation process continued with the assembly process, which consisted of the following (step by step):
the cable of the required length is pulled into a corrugated pipe according to the cable size;
installing a relay in the fan box (basically scraping out space for it) and connecting a cable of the required length to it,
pulling the sleeves of the required length onto the inlet and outlet (do not confuse the inlet and outlet – the length of the sleeves can be different, the extra length of the sleeve eats up the fan's performance!) and securing them with a clamp of the appropriate diameter, as described above.
Next we drag the resulting assembly into the attic – everything went without incident here, the most important thing in this process is not to tear the thin walls of the sleeves in the cramped space of the attic, especially where the rafters rest on the wall.
A positive good feature of ERA TYPHOON fans is that the fan barrel itself is easily separated from the installation chassis, combined with the input-output pipes. This greatly simplifies the installation of fans – the connected sleeves and the fan connected to the cable are separated.
Total:
assembled the fan assembly,
dragged her into the attic,
made a hole in the ceiling of the room and found it under the insulation in the attic,
installed an anemostat (aka diffuser),
I stuck the entrance sleeve into the space of the eaves overhang – due to the fact that the gap is slightly less than 125 mm, it worked out well and there was no need to fasten it;
I pulled the outlet sleeve over the anemostat and tightened it from above with a regular worm clamp, placing the outer surface of the sleeve underneath it (let me remind you that since it is heat-insulated, we essentially have a sleeve-in-sleeve),
where necessary, I pulled the sleeves (exits) to the rafters with mounting tape,
installed the fan in place on the wall (further away from the anemostat, screws into foam blocks),
I pulled the cable (installed it on the rafters using clips),
I pulled the cable into the panel and connected it to the machine there,
registered the relay in Mi Home,
just in case, in Mi Home I made a rule for each relay to turn off another channel when one channel is turned on.
I checked – at high mode the fan hum is audible, but not very loud.
Time expenditure: one day per room. I analyzed why it took so long, I expected it to be twice as fast. I came to the conclusion that working in the attic has its own peculiarities: the places where the fans are installed are cramped (the rafters are connected to the wall), if you forgot something from the tool or material (screws, clips, etc.) – then you have to go down from the attic to the basement and climb back to the attic, which is a bit acrobatic, since there is no direct ladder from the second floor, only a stepladder (that's how it turned out).
Acceptance and pilot operation
I turned it on from Mi Home, called my wife, demonstrated it, and received a positive conclusion: the hum is low, it blows powerfully and, most importantly, it gives the necessary cool air.
The question arose – how to control. By default – via Mi Home, but you always need to have a smartphone with you and open the corresponding application in it, which is not always convenient. We (our family) have recently become apologists for voice control.
It so happened that there is a Yandex.Station in each room (don't ask how and why this happened – that's a separate story), so all three relays were eventually pulled into Yandex Smart Home (hereinafter simply Smart Home) and the question arose of what names to assign to which channel. After much torment with compound names like “VostokPritochkaMax” and “ZapadPritochkaMin”, I suggested (and it got along) the names “Hurricane” and “Veterok” for the strong and weak modes, respectively.
But everyone forgets to turn on the supply ventilation themselves – so I set the schedule in the Smart Home to turn it on at 18-00 and 19-00 at maximum. And you don’t forget to turn it off, because by nine o’clock in the evening you feel a noticeable influx of cool air. Turning it off – by voice, the most important thing is not to forget the command (here I always remember “open sesame” 🙂 ).
I also set myself an alarm clock to turn on at 6:00 a.m. for maximum supply ventilation in the bedroom. Switching off is also done by voice.
I tried sleeping on a low setting – in the morning I felt a bit of a draft, although when I fell asleep the draft was almost unnoticeable.
It is worth noting that the included ventilation does not significantly reduce the overall temperature in the room, but it greatly refreshes the air in it and thus radically changes the situation – it becomes possible to sleep. Simply, the hood (straight-through to the roof, 125 mm, heat-insulated sleeve) is not enough for such an effect.
It doesn't suck in mosquitoes or other midges, and it doesn't suck up dust from the spotlights.
What's next?
Further, in connection with the onset of cold weather, there is a desire to make some kind of PWM depending on the room temperature and the temperature of the air taken in: for example, the ventilation works for a minute or two, and then a pause depending on the temperature of the air taken in and the air temperature in the bedroom. The problem is that the capabilities of the Smart Home do not allow you to reliably intercept events of reaching a specific temperature (tested experimentally). On the other hand, Mi Home works strangely with events upon the onset of a specific time. But Mi Home has the ability to build an infinite cycle (advanced mode via the fourth gateway – “Mijia Automation Geek Edition”) and check both the temperature and time in it yourself – the question is in monitoring that this cycle is running and restarting this cycle if it stops running.
In short, there is still something to figure out, but already in a specific IT plane. Perhaps this will encourage me to switch to Home Assistant. Or maybe I’ll get out of it again.
Surprisingly, it turned out cheap, fast and high-quality!
That's all for now!
P.S. Some photos of the result (don't judge strictly).
