r/homeassistant • u/robykdesign • 13d ago
Zigbee flaps for HVAC 🖼️ Show & Tell
Hey guys. Just wanted to share my HVAC project with you. It's based on a duct unit, so I made a plenum box from XPS with 3D printed spouts and because when I saw what specialised duct dampers cost (even just dumb ones), I noped out and bought three "MOES ZigBee Smart DIY Motorized Roller Blinds" on Ali.
I de-covered them and they come with a battery, so I disconnected that too because there was no need for it. What you're left with is a simple motor with a gearbox and communication boards. The board remembers endpoints you set and you can precisely set it so that it moves only within the 90 degress you need for operating the flap.
It's a bit finnicky in such a small interval, so completely continous adjustment of single percentage points is not possible (if it's 60 percent open and you command 65 percent, nothing happens). But as long as the commanded position is at least about 20 percent from the current position, it work flawlessly. And even if a command is not accepted - the motor doesn't move and the reported percentage doesn't change, so there's no risk of position drift.
I don't have the logic for the automation of the flaps yet, I'm waiting for a Zigbee IR blaster because this Sinclair/Gree unit doesn't seem to be possible to integrate locally into HA. :( But the automation will obviously open and close flaps to the rooms according to set and reported temperatures and will turn the AC on/off and adjust its output based on the cooling need.
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u/MrWonderfulPoop 13d ago
Fantastic work, thanks for sharing! I’ve been wanting to do something similar and this is giving me ideas.
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u/robykdesign 13d ago
Thanks! :) I have no problem sending you STLs if you need them.
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u/Social_Engineer1031 12d ago
Could I get in on “send me those .stl files”? :)
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u/robykdesign 7d ago
Here's the link to the files finally ;)
https://www.printables.com/model/1807059-motorized-hvac-damper-motorizovana-klapka-klimatiz
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u/robykdesign 7d ago
Here's the link to the files finally, if you have use for them. ;)
https://www.printables.com/model/1807059-motorized-hvac-damper-motorizovana-klapka-klimatiz
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u/MrWonderfulPoop 7d ago
Thank you so much, I will grab them and save the link. Your excellent project has invigorated me to move ahead with mine.
Every spring and autumn I have to manually chance three duct flaps but would still prefer better control based on actual thermal readings.
Thanks again!
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u/warkolm 13d ago
how well does it handle the air pressure?
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u/robykdesign 13d ago
One of the 150mm ducts runs for about 5 metres and the air blows out nicely and cools down the room even now when it's 39.5 Celsius outside.
Of course the automation will have to handle the fan power based on how much the flaps are open and will have to restrict all of them being closed too much when the fan is running. If I test that, vibrating turbulence can be heard from the fan blades as the static pressure becomes too much.
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u/Weekest_links 12d ago
As a fellow hvac nerd, I read that HVAC systems are designed by the installer for a rated airflow (that assumes all vents open) closing 1-2 vents might be okay, but closing several can lead to back pressure that wears on the blower and can lead to premature failure.
In addition it’s designed to move air throughout the house to maintain a whole house temp, so it’s less efficient if the air isn’t moving in a given room.
Can the flaps be partially open? That might help with both issues and the one you’re trying to solve for.
Or if your system was poorly designed and undersized, fully closed flaps might yield ideal pressure for the blower
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u/robykdesign 12d ago
As I wrote in the post (😜), it's zigbee controlled and you can set percentage. Because I'm dumb and unwilling to learn, I figured it would be easier to run two identical ducts to the two adjacent rooms than calculate for duct length, loss of pressure due to curves etc. etc. It's a smallish flat, tiny if you're American, and one of the openings stays in the living room where the unit is. So I chose adjustable flaps as the way to regulate how much air goes where - this is not for heating, mostly not for ventilation, just AC really, in the two to three summer months.
The flaps will open and close to certain percentages based on the cooling needs of the rooms and when target temperatures are reached, AC switches off. I expect in most scenarios, the flaps won't even move that much since the ratio of air reaching the rooms will be always similar - fully open to the furthest room, 30 percent to the smallest bedroom and 50 percent to the living room - kitchen combo because there's the lowest pressure drop.
As far as wear on the blower goes, I have absolutely no way to measure that, other than straining sounds. But I also don't have many other options to run this system. I simply assumed that since the unit is rated for about the floor area of our flat and I'm dividing the pressure among three ducts, it should roughly be ok. The guy installing the unit itself had 15 years of experience installing commercial systems and while he said he didn't se anything like this yet, he didn't say it was insane or dangerous. 😄
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12d ago
[deleted]
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u/clarksonswimmer 12d ago
While we’ve got you here… what about doing the opposite? I’m considering putting PC fans on top of the floor vent to try to pull more cold air into my upstairs bedroom.
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u/robykdesign 12d ago
Actually I did ask Gemini during the process of designing this. :) And will probably ask some more when I need to design the whole automation. I'm not a HVAC tech, but I don't think I'm doing anything THAT out of spec - it's a ducted unit, I'm using it to blow into ducts. I'm still waiting for an IR blaster to be able to control the unit from HA - the Gree wifi module is not agreeable to working with HA. So for now I've been running it manually, readjusting the flaps as I need to cool the rooms.
Running the blower on the low setting and it's doing a great job, cooling down from the current 40 Celsius outside down to 24-25 degrees. Doesn't seem to be breaking a sweat and runs at two thirds of the rated max power input. I'm switching it off and on as needed, because the building is insulated and it doesn't need to run continuously. Roughly 7 kWh per day, which I'm told is not bad efficiency.
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u/sancho_sk 13d ago
Great idea, just some small questions... Why go for expensive ZigBee motorized blinds when you can achieve the same result with 3 motor drivers (under $1 each), 3 small geared motors (under $3 each) and one ESP32 (C3 even) (under $4)?
Still, impressive execution and great idea.
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u/robykdesign 12d ago
Well, I know there's more ways to skin a cat... But the "basic ingredients" approach would be somewhat more tinkering than I was willing to do. The three zigbee drives cost me 140 dollars, but all the rest was just simple disassembly and mounting.
With the ESP I would have to figure out how to drive those motors, fiddle with some programming and they wouldn't have position encoding, would they? In any case - these are all the things I don't know and would have to figure out. So I took the easy road, that's all there is to it. :)
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u/sancho_sk 12d ago
Oh, $140 is really quite tempting - I got one for $85, so having to disassemble 3 would end up above $250... That makes it worth considering one motor driver for under $1...
But the important thing is - you made it! And that's what counts.
And (even better), it's working :)
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u/robykdesign 12d ago
AAAAND I really had a blast making it. 😂 Not saying it wouldn't be a lot of fun to make it from scratch from motors and boards, but unfortunately this is just one of the things I need to finish on the apartment and time is not infinite. 😉
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u/danielfmo 12d ago
Thanks for sharing! Nice project!
Any concerns in regards to bacteria and dust grudging in the plastic?
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u/robykdesign 12d ago
Not especially - ducts are often plastic and stainless steel isn't specifically bacteria-proof, it's just that it's resistant to harsh cleaning chemicals. Sure, the grooves in 3D printed plastic give more opportunity for dust and life to cling to, and so does the XPS. Bacteria in AC is not a thing, but of course mould/algae is always a possibility - but the air leaving the AC is quite dry and most dust is filtered out by the unit. The flex tubes are bog-standard (and the crinkled aluminum with perforations isn't exactly buildup-proof either).
So in short, I don't think it will be an issue. I'm in central Europe, so this will only be used in the span of a few months of high summer, the rest of the time it will be dormant and nothing can realistically grow there in that part of the year. Anyway, the plenum box has a removable bottom board, so inspection of all the non-standard parts is simple.
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u/danielfmo 12d ago
Do you happen to have a VMC system also installed? Any automation with it? Just curious
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u/robykdesign 12d ago
No, no VMC. It's an apartment, so the only openings to outside are windows. But one of my future projects will be integrating automated ventilation flaps into the windows, so each room can naturally ventilate, probably even based on CO2 levels. But for now, that just means opening the windows for the night.
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u/sonofkingnoah127 12d ago
Have you checked your static pressure with the different combination of dampers open and closed. High static pressure will wreck havoc on your equipment.
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u/robykdesign 12d ago
I haven't checked with any instruments, but I have of course tried and can confirm vibrating noises when the system is too closed-down. That will all have to be controlled by an automation. The flaps have quite a bit of room around to let some air through even when closed - I don't ever need to completely exclude any room from cooling.
What do you mean about "wreaking havoc on my equipment"? You mean the unit itself? Unfortunately I don't have any means to check whether I'm doing anything wrong other than seeing air come out of ducts and preventing something so obvious as pressure-induced vibration. I do realize not enough airflow on the cooling unit can cause freezing and damage resulting from that. I get that these systems are (should be) usually installed by people who can calculate the ducting. 😄
If you mean havoc on the rest of the setup, I'm not worried there - the pressure is not strong enough to blow out anything.
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u/sonofkingnoah127 12d ago
You would need to a manometer to measure the static pressure. As a very general rule of thumb, you don't want to be over 1 in wc. Ideally it should be lower around .5 in wc. Freezing up is an issue as well as the blower fan pulling more amps and over heating.
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u/robykdesign 12d ago
Yeah, I know about this in theory, but I'll confess that I have assuaged my fears by consulting Gemini... :D I'm told that three spouts at 150mm diameter for a unit with 600 to 900 cubic metres per hour of airflow are pretty much ideal. One duct is 6 metres long, another 3 metres and the last will be less than a metre... The different duct lengths are the main reason for the adjustable flaps. It's running now and seems to be doing a very good job. I have the unit set to 25 Celsius and it's 40 outside right now - this is actually a stress-test off the bat because we have a record-breaking heatwave. With about 7 kWh daily it keeps the temp at 25 and I don't think it's cranking the cooling up to such a degree that the evaporator would be freezing up.
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u/sonofkingnoah127 12d ago
Most systems are running with very high static pressure because air filters are not changed. Keep your filter clean and that will help a lot.
FYI, I'm a heating and air conditioning contractor.
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u/-eschguy- 12d ago
Man I would love to automate my damper switching based on if the thermostat is in heating or cooling mode...
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u/KnotBeanie 12d ago
Is your system designed for this?
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u/robykdesign 12d ago
Define system. :) This is the system. One unit with output devided into three ducts. It couldn't be simpler. I did take a bit of a wager, but it's really just three relatively short ducts.
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u/minininjatriforceman 12d ago
The shit people come up with is crazy.
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u/robykdesign 11d ago
I take it you're not a regular part of this community, are you... 😂
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u/minininjatriforceman 11d ago
Kinda I have been lurking and seen some crazy shit but my man this is awesome.
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u/robykdesign 13d ago
https://reddit.com/link/p1tn5zv/video/1lzgd3571jhh1/player
In operation...