I am considering adding a damper to two A/C runs. Currently each run has a manual damper in the attic.
I would consider trying to automate the existing dampers but I'm going to guess they are not designed for daily operation.
I only need two positions but I need the positions to be adjustable manually.
I don't care about it being "smart" as I have been using cc2530 Zigbee boards for some time with very good luck. I would simply add this board to a "dumb" electrically controllable valve.
I have seen Belimo offering a number of options.
All that to ask what experience other folks have had with controllable dampers?
Thanks
John
I don't have any direct experience with "smart" dampers but I am a retired mechanical engineer with over 40 years of design of HVAC systems. As such I have followed the threads on this forum on damper controls and most of the ones I have seen have been very negative with most of the problems being the life of the batteries. Do a forum search for Keen and you will see what I mean.
I can tell you that I have specified Belimo dampers and actuators on all my commercial and institutional projects and can highly recommend Belimo. I like your idea to couple a Belimo damper and actuator to a cc2530 Zigbee board. IMHO this would be the best solution. It will not be the cheapest solution but It will probably be the most trouble free in the long run. You just need to find the right Belimo damper and actuator for the job.
EDIT....Belimo makes the actuators only, not the dampers. You can find dampers with Belimo actuators as a package online or at your local AC supply house.
I have used these. They seem to be OK despite the bargain price. You just have to watch whether you want normally open (most likely this) or normally closed. And of course the size. I have it wired into my thermostat for fresh air damper, so I didn't use the included transformer or wire it into Hubitat.
My only cost here is the damper with actuator. The cc2530's are about $6 and I can get wires to my attic. I'm not a battery fan and I can run wires almost everywhere in my house. Actually I have an unused pair of #18 in the attic.
My understanding from most HVAC people is that a vent should never be 100% closed as it's not good for the system overall. For this reason I've personally avoided them. Though someone like @Sakman may have a better explanation than I could give
You do not want to restrict the airflow across the cooling coil of a direct expansion system that is used in residential applications. If you do the coil may freeze up. That is why in systems with zone control dampers you install a bypass damper controlled from duct static pressure that allows full airflow across the coil.
The OP stated that he wants to install dampers in 2 runs. I assume there will be other ducts that will not have dampers, so the airflow across the coil may not be restricted. However if the dampers close fully then the airflow at the other runs will increase.
Your suggestion to not allow the dampers to fully close is a good one.
This is a great topic. I've wanted to zone my house and have it separated by master bedroom, beds 2/3, dining, and living.
My reasoning is energy efficiency. Most of the time the whole house doesn't need to be cooled, but a zone or two do. With a variable speed system, if only one or 2 zones are requested you wouldn't need to run the system at full capacity. The only sticky widget is I haven't found a way to have full manual control of the variable speed system.
Variable speed fan alone won't do what you need. You need a modulating burner on the furnace, and a variable speed compressor on the cooling side. If you just slow the fan with the burner going full tilt, all you will do is trip the high side limits, and possibly damage the heat exchanger. On the cooling side you will ice the coil if you don't have enough airflow.
That is why most zoned systems have a place to dump the extra air. Maybe in to a basement or someplace you don't mind overheating or overcooling.
None of this will help energy efficiency. If you are trying for that, you need something like individual mini-split or some other completely separate system for each room.
My ruminations of adding zone control to an existing A/C system.
Let the built-in logic of A/C unit make all the decisions about how to control the variable speed capability of your system. It has all the logic necessary to optimize the system functions and at the same time protect the system from operational damage. If you try to manage the internal workings of the system, you may need to start managing some of the safety logic too. This is best left to a dedicated controller designed and configured for your specific A/C system.
Use an A/C zone controller to handle all the coordination of zone thermostat calls, damper position, and calls to the A/C system.. Honeywell and others make these.
You can certainly use HE to do this if you want to. My personal belief is it is best left to a dedicated controller that is designed for that purpose. Hubitat has it's place in all this. Just not here IMO.
Here is where HE plays it's part. Use Zigbee or Z-wave thermostats. This gives you connectivity to see the zones, control setpoints, and schedule setpoint changes. Using modes for is a great way to adjust temperature setpoints. I personally Like the Zen thermostats since they do not complicate the thermostat user interface with scheduling functions.
Be sure you install a properly sized bypass damper. Since you have a variable speed system, you may want to get some help with this, since the system may vary the blower speed too.
You're right @neonturbo. Adding zoning doesn't in and of itself guarantee you energy efficiency. In fact in can increase your energy use. A lot depends on your exact equipment in your system, how well the system and zoning controls work together, and how you choose to use the system. If you have dramatically use cases in parts of your home, you should probably consider a through the wall or mini split system dedicated to that space as @neonturbo suggested.
In a general case I would agree. In my case there are 6 - 8 runs each (or more) with a manual damper. I would only be closing one or two runs with a damper.
My goal is comfort and not necessarily efficiency. However I have to think if I'm not "over cooling" some section of my home there will be a decrease in energy usage albeit likely not a measurable one.
They have all kinds of sizes and round ones as well. Just do your homework and make sure you don't restrict to much airflow... it's not hard... just takes some time.
Bypass dampers are not a simple solution, either. If to much flow is allowed to short circuit right back into the return duct you could end up freezing your coil just as quickly as without. Better to just make sure you have enough open ducts to maintain minimum airflow.
P.S. I'm also an engineer and favor Belimo for commercial/industrial stuff, but consider them to be overkill for personal use.
I can post more details later... not able to at the moment.
