@dylan.c I like those Honeywell dampers. I assume since you linked to larger rectangular ones that you put them in the main trunk lines? I think my system just has one trunk and the supplies go off each so I would have to do the round ones in each room that I wanted to control. Have some bedrooms that get hot, while others are cold, also want to cool the upstairs off more at night for sleeping.
Yes... my main plenum off the blower unit splits into three trunks... one for each level of the house (basement, main, and upstairs).
This is one of the things I like most. We have three bedrooms on the second floor and I can finally get them comfortable for sleeping without cooling the whole house down.
And FWIW, rather than use a bypass damper, I chose to ensure my minimum airflow was high enough to keep the system just inside of the recommended operating ranges. When only my smallest zone is "open," the other two are around 10% open and accepting some air. This keeps my discharge temperatures in safe ranges. Perhaps not as efficient, but simple and fool-proof.
The dampers I linked to work best if one of the positions is "closed" or "nearly closed." The actuators have three stops that limit how far the damper is allowed to close, with 0 being fully closed and 1, 2, and 3 being roughly 15%, 30% and 50% open. The dampers are parallel blade and once they open past 20% or so they don't work well for regulating airflow. The single-blade round dampers will have similar limitations.
This is one area where the Belimo products would be superior. They would have fully adjustable mechanical stops for both the open and closed positions. And if you want to really dial in your airflow, you could pair them with better dampers. Again, in my opinion, this would be overkill for nearly all residential applications.
Thank you for the info.
I have round ducts and I have to see how easy they are to install (because of the current installation location, not the damper itself)
Also I need to see if the current manual damper is able to be motorized.
I did find the Belimo actuator at a reasonable price: Belimo FP18-Motor
Another thread has me looking ahead to A/C season and using automation to save some energy. I'm planning to tinker with @aaiyar 's method of controlling to a dewpoint setting rather than a simple temperature. With this in mind, do you think there would there be any issues in reducing airflow through the system and pushing discharge air temp down to, say, 45F? That should help wring out more moisture while still a safe distance from freezing. Or would the actual evap coil temp be even colder and be of concern?
The actual evap temp will be lower than the supply air temperature. As long as you maintain the supply airflow at 50% +/- of the design airflow you should not have an issue with freezing the coil. You can do this by leaving some branch ducts without automatic dampers.
With 45 deg supply air you should be on the lookout for condensation on the ductwork and/or the supply grilles depending on the quality of the duct insulation and adjacent conditions.
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I hadn't considered this. Duct insulation isn't something we've done around here until very recently. Ductwork is generally all contained within the conditioned/livable spaces and so insulation wasn't generally a priority. My uninsulated ducts would seem to be prone to condensation as you've noted. Best to avoid that... thanks for the tip!
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One that you can do is tape seams and wrap exposed ductwork... That certainly helps...
