I’ve been planning to computerize my A/C once I buy a house. I stumbled across this simple vent mod. A $10 servo was added and controlled with some off the shelf computer servo controllers. Personally, I have visions of doing this along with several 1-wire temperature sensors. Check out the DIY zoning project for more ideas along these lines.
11 thoughts on “DIY A/C Zone Controls”
sweet… a nice cheap air handler
This is a great DIY project that has a very useful purpose. I have thought of controlling dampers in a similar way but using light sensors to determine when rooms (other than bedrooms) are vacant at night and closing the dampers to save on heating and cooling costs.
If you convert all your vents to this, you may want to add a spring to your arm to allow for pressure relief in the event you close all your ducts while the blower is running.
@3 I dont get it
@4 A spring on the arm that opens the vent, so if pressure builds up it will push the vent open rather then cause problems.
For automatically operating servos, these two voltage sensing controllers I designed may prove useful.
They’re based on the 8 pin PIC12F675 micros and the software is open source.
Hey cool and all but if you block the dampers you can create condensation in the vents which creates mold in them. Its ok for a few hours but long uses could be VERY VERY bad for your health. Figured you would wanna know. I do work for a heat and A/C company. :-)
Hey revdave (#3),
I don’t think that would be an issue in a typical residential system. I think there would probably be enough leakage in the system to compensate. And if the system calls for heat or cold at least one damper should be open.
It is a concern with large commercial systems though. When I worked in the fire alarm field, air handling shutdowns and damper control was very common for automatic smoke control however many dampers can close almost instantly and some air handlers continue to push lots of air for up to 30 seconds after it is commanded to shutdown, this can definitely lead to duct blowouts.
looking at the project documentation, as part of his DIY Zoning project the software is designed to keep at least 30-40% of the original open area through the entire system. It should be pretty rare that a single damper stays closed 100% of the time with how the system operates.
The servo’s are a great idea, but when you get a house, you’ll quickly realize that getting wiring to every vent opening will prove to be very tiresome.
It would be much easier to servo-operate the baffles you can put inline to the ductwork than go that route. All your wiring will be soooooo much easier. The baffles will already be there, most likely….
Hope to have my house fully automated in the course of he next year. Card access, temperature and humidity control, video systems, voice control, etc. Will be the culmination of many years of preperation. Can’t wait! ;)
You need to be aware of the implications of reducing. The air volume on an hvac system,if done incorrectly the heat will lockout on high temp,and the act will freeze up,leak water.it’s best done with specifically designed products for zoning.
You must disable the compressor /heat when the supply air temp gets to high/low
I would read the sequence of operations for a Honeywell zoning system and mimicking it before jumping .
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