Ventbots Are Fans Of HVAC And Home Automation

Ventbot fans with 3D printed brackets and control circuit board with ESP32 breakout and multicolored 3D printed cases

[WJCarpenter] had a common HVAC problem; not all the rooms got to a comfortable temperature when the heater was working to warm up their home. As often happens with HVAC systems, the rooms farthest from the heat source and/or with less insulation needed a boost of heat in the winter and cooling in the summer too. While [WJCarpenter] is a self-reported software person, not a hardware person, you will enjoy going along on the journey to build some very capable vent boosters that require a mix of each.

Ventbot control circuit board with ESP32 breakout in a red 3D printed case

There’s a great build log on here, but for those who need more of a proper set of instructions, there’s a step-by-step guide that should allow even a beginner hardware hacker to complete the project over on Instructables. There you’ll find everything you need to build ESPHome controlled, 3D printed, PC fan powered vent boosters. While they can be integrated into Home Assistant, we were interested to learn that ESPHome allows these to run stand-alone too, each using its own temperature and pressure sensor.

The many iterations of hardware and software show, resulting in thoughtful touches like a startup sequence that checks for several compatible temperature sensors and a board layout that accommodates different capacitor lead spacings. Along the way, [WJCarpenter] also graphed the noise level of different fans running at multiple speeds and the pressure sensor readings against the temperatures to see if they could be used as more reliable triggers for the fans. (spoiler, they weren’t) There are a bunch of other tips to find along the way, so we highly recommend going through all that [WJCarpenter] has shared if you want to build your own or just want some tips on how to convert a one-off project to something that a wider audience can adapt to their own needs.

Ventbot graphing of temperature, pressure, and fan noise

See a video after the break that doesn’t show the whole project but includes footage of the start-up sequence that tests each fan’s tachometer and the customizable ramp-up and ramp-down settings.

21 thoughts on “Ventbots Are Fans Of HVAC And Home Automation

  1. What about a Roomba on Steroids. A Turret with a 2×2 Fan Array on it. A Stronger Battery. Who Rides throught all rooms and regulate the themperature.

    A Roomba build to rule the Air circulation in the Kingdom. A little in Lord of the Rings Mood today 😁

  2. I know the struggle mine was cooling not heating being in Florida. I went after various solutions, ultimately gave up on central hvac and put in ductless systems throughout house. Each room can have its own cooling.

    I applaud this effort.

    1. Are you using the Flair smart vents? I looked at them but decided it wasn’t for me, but I am curious about real-world experience from someone who actually used them.

      (For anyone not familiar, the Flair product is not a booster fan. It’s a drop-in replacement vent cover that has remote-controlled opening and closing of the louvres in the vent.)

    2. Do you use the Flair devices? I looked at them and decided they were not for me, but I would be interested in hearing the experiences of someone who actually used them.

      For anyone not familiar, the Flair devices are not booster fans. They are battery-powered vent covers that can be remotely controlled to open or close the louvres in the vent cover. There is an accompanying in-room thermostat that pairs with the vent cover to try to keep the room at a selected temperature.

  3. FWIW: These things rarely work well. Sometimes they are the only option yes and if you have the time you can of course roll your own if you don’t want to buy a commercial axial fan unit. Before going to the trouble look at the dampers (if present) in the duct system if they are accessable. These may already have 2 marks on the duct indicating summer and winter settings to address this, otherwise look up how to balance a duct system (there are system minimum airflows and you may cause damage to equipment if you arbitrarily shut off every damper but the one not working properly). Biggest issues are from older houses in northern areas where air conditioning is only a secondary thought and the system was designed for heat only. best option is to actually fix the duct (proper sizing, getting rid of “flex” duct, reducing elbows, finding that it has come apart somewhere, etc.)

    1. I think you are right that dealing with the ductwork is the ideal solution. I spent quite a bit of time standing in my basement, scratching my head, and trying to figure out if I could use inline duct fans. Alas, for me and for many people, that would require a pretty big drywall project with no guarantee of a good outcome for the upper floor.

      I agree with your advice for people to look at their existing dampers. For my upper floor, each vent location has a damper within easy reach in the duct. They were already fully open.

      1. not surprising to find those dampers open all the way, but a lot of people never look at all the rest of the dampers on the supply air lines to see if they are all open as well. closing some of them down a bit after marking their position (this is where the warning above about system minimum airflows above comes in!) and especially basement supply air vents when it’s air conditioning season, can often help a little. Sealing leaky seams can help a bit as well. Another thing I have noticed is almost no contractors that clean furnaces (they ALL need periodic cleaning)
        ever pull the blower and clean the vanes in the “squirrel cage”. I’ve seen the curved blades filled with so much dust they were basically flat and not moving nearly as much air as designed to. And those high merv 8 to 11+ rated filters are great for allergy sufferers but bad for airflow unless the system was designed for them (if you have issues with rooms – it wasn’t)
        Last things to mention make sure ALL of the return air vents (take room air back to furnace) are wide open, never blocked by rugs or furniture, and when it comes time to replace the furnace discuss the issues with the people you are getting estimates from. Most mfgers have “high static” blower options at the least and the better ones can open the walls and fix the issues where they begin if needed.

  4. Also a very common overlooked aspect is return air, think of a plastic bag…you can only fill it so much and if there isn’t something open for the air to go to then you have no flow…. I have the same problem and I significantly improved my flow by cutting extra return airs above the existing ones in each room and depending on the season I cover the lower one and open the ceiling one for summer as hot air rises and opposite in the winter, then I hired a company called aero seal and they can pressurize your duct system and inject a sealant and seal all the imperfections in your system so your not losing conditioned air where you don’t want to. These 2 things improved delivery and circulation by at least 50%! Though I still would like better flow as the basement is at 18C when upstairs is at 22C but 2 story houses you can only do so much then you need boosters like this. I personally want one that’s commercially made like the flair or others but uses the full dimension for airflow and houses the sensor pack on the side along the floor as to not restrict any potential flow and possible run 3 smaller fans instead of 2 bigger ones…

    My 2 cents

    Love Canada

  5. Crappy building syndrome. Bad design, insufficient insulation, and poor ductwork, typically combined with a massively oversized HVAC to overcome. Been doing it in 99% of built homes in the US for all time. More insulation, appropriately oriented and shaded windows, and sized, sealed, and balanced ductwork and any regular home, from Miami to Fairbanks, can hold <1C throughout the conditioned space.

  6. I’ve found switching the fan to the ‘ON’ position circulates the air so all rooms are close to the same temp, even between floors. The fan doesn’t use much power, so I didn’t notice a difference in the utility bill.

  7. Commercial buildings have been using constant air flow to control temp and humidity for years, although in may slightly raise humidity levels they adjust after awhile, with almost 30 years in ac ,heat applications, the simplest is to use your fan to prevent stratification. Same works in our RV for heating and cooling fans use little power and can be replaced easily if needed

  8. The Flair product has been mentioned a couple of time. I am curious if anyone here has tried them and what your experience was? The Flair product is not a booster fan. It’s a battery-controlled vent cover replacement. In-room thermostats remotely control the louvres in the vent cover to try to achieve a desired temperature in the room.

    I looked at it a while back but decided it wasn’t for me due the combination of cost and my skepticism that it would make much difference. But if someone has tried it, they would know better than my supposing.

    1. Not Flair but a different prebuilt solution… Ive been using an AC Infinity inline duct booster for a couple years now and it absolutely does precisely what I hoped. As you noted, you need access near the trunk; my basement ceiling is unfinished so I was able to put this in pretty easily. It pushes air to a bedroom over the garage that was bad in summer and winter; totally pre-made and no diy / engineering project aspect to it but (that made it accessible to me and) I’ve been thrilled with the result. Hvac company had first looked at duct balancing (no real help) and determined that increasing physical duct capacity to the room would be in the 1000s. I run this on a mechanical timer (like a xmas light timer) for ~6pm to 6am and the speed and on/off temps are easily adjustable; mine jas temps set to keep pushing some more air after the hvac blower turns off. I also bought/installed a muffler along with it – probably would not repeat that part or st least would install closer to the trunk and not fsrther away, as it only helps in one direction. Anyhow I run the speed less than half maximum, the noise level doesnt bother anyone and the curtains in that bedroom billow toward the ceiling.

  9. I had a fan-in-a-box sitting on top of the vent in my lab last summer, with a cheap thermostat module to turn it on when the air in the duct got cold. It seemed to work pretty well for as simple as it was.

    We had a period of no heat this winter and I ended up taking it down, because it was triggering on the low temperature air that was gathering in the duct work.

    All the ducts have since been replaced, and properly balanced for the current layout of the house. So I’m not sure if it’s as needed as it was. Now that it’s summer again, I should probably put it back and see if it gets any cooler in there on average. It’s a bit warm right now with all the equipment that’s in there.

  10. anyway to mod this for use with inline duct fans? I have full access via basement to all duct work/dampers. I originally wanted to automate dampers and close lower floor dampers at night forcing air upstairs where it tends to be hotter in summer and cooler in winter. with this solution containing multiple fans where are you plugging in power? how is it routed to power?

    1. In my own installation, I run the 12v power cable through an opening in the vent cover. You can see pictures of that in Step 22 of the Instructable. It’s slightly inelegant, but all of the vents where I placed them are in locations where it’s not that noticeable.

      For inline duct fans, you could certainly use the control logic on the ESP32, but you would have to figure out some kind of physical mounting scheme if you wanted to use PC fans in that way. If I were contemplating that, I’d be likely to use off-the-shelf duct fans and a simpler scheme for controlling them.

      You might get some good ideas from this project: He does a lot of pretty cool stuff.

  11. The idea seems to make sense initially but I would warn anyone considering doing this to reconsider. This is putting a band aid on the problem; and I’m not convinced this band aid is effective at doing anything useful.

    There seems to be the assumptions that by balancing the airflow to different rooms you will achieve your comfort goals and that by using these fans by themselves you could balance the airflow. However, this doesn’t account for a myriad of variables like whether your return air ducts and vents are big enough, whether the supply ducts themselves are even capable of achieving the airflow required by the room, whether the supply registers are the correct type of registers and positioned correctly to achieve adequate throw across the room to achieve room air mixing, etc.

    HVAC systems, especially when ducted, are the most complicated appliance in most people’s homes. These fans just makes it even more complicated and introduces potentially more problems.

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